摘要:

ANALYST, JANUARY 1992, VOL. 117 87 Colorimetric Method for the Quantitative Determination of the Antibilharzial Drug Praziquantel and Its Application to Pharmaceutical Preparations Hanaa Saleh Faculty of Pharmacy, Zagazig University, Zagazig, Egypt J. Schnekenburger Institute of Pharmacy, Kiel University, Kiel, Germany A method for the colorimetric assay of praziquantel has been developed. For the colorimetric assay, it was necessary to hydrolyse praziquantel with 3 mol dm-3 NaOH, 6 mol dm-3 HCI and 85% phosphoric acid separately. 4-Chloro-7-nitro-2,I ,3-benzoxadiazole (NBD-CI) reacts with the basic hydrolysis product in methanolic aqueous phosphate buffer (pH 7.4), resulting in the formation of an orange product with a characteristic absorption maximum at 478 nm. The red-orange product of the interaction between the hydrochloric acid hydrolysis product and NBD-CI showed an absorption maximum at 486 nm.The colours obtained were stable for 24 h. The colour system obeyed Beer's law in the concentration range 2-15 and 2-18 pg ml-1 for the basic hydrolysis product and the acid hydrolysis product, respectively. The results obtained showed good recoveries with relative standard deviations of 0.378 and 0.47% for the basic and the acid hydrolysis product, respectively. The determination limit was found to be 0.124 and 0.150 pg ml-1 for the praziquantel basic hydrolysis product and the acid hydrolysis product, respectively. The coloured reaction products obtained with the proposed method were synthesized. The structures of these products were studied and the compounds identified.Keywords: 4-Chloro-7-nitro-2, 1,3-benzoxadiazole; colorimetry; praziquantel determination The anthelmintic activity of pyrazinoisoquinoline derivatives was first discovered by Merck (Darmstadt, Germany) and Bayer (Wuppertal, Germany) in 1972.1-3 Praziquantel is now available for the treatment of human schistosoma and other trematode infections (Biltricide).4-'9 It is also a well estab- lished veterinary cestocide, which was first launched in 1977 for oral administration2.20 and later as an injection for use as a one dose drug against tapeworms. The synthesis of praziquantel (1), 2-cyclohexylcarbonyl- 1,2,3,6,7,11b-hexahydropyrazino[2,l-~]isoquinolin-4-one, was reported in 1979.21 1 Many methods have been described for the quantitative determination of praziquantel including a fluorimetric method for the determination of praziquantel in blood plasma and urine ,21,22 gas-liquid chromatography (GLC) for the determi- nation of non-metabolized praziquantel in body fluids,23 a spectrophotometric method for the determination of macro- amounts of praziquantel,24 a derivative spectrophotometric determination in tablets25 and determination by high-per- formance liquid chromatography (HPLC) .2&28 This paper describes a colorimetric method which can be used in laboratories where modern and expensive apparatus such as that required for GLC or HPLC is not available.The proposed colorimetric method involves the hydrolysis of praziquantel with acid or base, followed by coupling of the hydrolysis products with 4-chloro-7-nitro-2,1,3-benzoxadia- zole (NBD-Cl).In the present work the structures of the acid and basic hydrolysis products and of the coloured derivatives have been studied and identified by infrared (IR) spec- trometry, proton nuclear magnetic resonance (1H NMR) spectroscopy, mass spectrometry and elemental analysis (see Scheme 1). Experimental Materials, Reagents and Apparatus Measurements with the various techniques used were carried out using the following instruments. For lH NMR spectra: Varian EM 360 A nuclear magnetic resonance spectrometer; measuring frequency, 60 MHz, and a Bruker AM 300 nuclear magnetic resonance spectrometer; measuring frequency, 300 MHz. Internal standard, tetramethylsilane; solvents, methanol, chloroform and benzene.13C NMR spectra: a Bruker AM 300 NMR spectrometer. IR spectra: a Beckman Acculab 10 IR spectrophotometer (KBr disc). Melting-points are uncorrected and were obtained using a melting-point apparatus (Biichi, Flawil, Switzerland). Elemental analyses were carried out by the Mikroanalytisches Laboratorium, Ilse Beetz Kronach (Oberfranken, Germany). Mass spectra: Atlas CH 4 spectrometer operated at 70 eV. Electronic spectra: Hewlett-Packard 8450 A ultraviolethisible (UVNIS) spectro- photometer. Fluorescence spectra: Perkin-Elmer LS-SB luminescence spectrometer. Potentiograph: Metrohm E 636 titroprocessor. Praziquantel was obtained from Merck, Darm- stadt, Germany, and Biltricide tablets from Bayer, Lever- kusen, Germany (Lot No. 964.00.00). The NBD-CI solution was prepared as follows: 100 mg of NBD-C1 were dissolved in 5 ml of warm methanol, shaken thoroughly and made up to 10 ml with methanol.Phosphate buffer solutions of pH 7 and 7.4 were prepared. Praziquantel Basic Hydrolysis Product [PBHP-HCl (2)] Praziquantel (2 g, 6.4 mmol) was mixed with 15 ml of ethanol and 15 ml of 3 mol dm-3 NaOH in a round-bottomed flask equipped with a reflux condenser. The solution was heated in an oil-bath at 70 "C for 2 h (praziquantel was dissolved in about 30 min). Ethanol was distilled off under reduced pressure and the volume made up to 30 ml with distilled water. After88 ANALYST, JANUARY 1992, VOL. 117 2 HCI CI NO2 )H 7.4 /O, WN45 \ / +coo- 5 (1) H3P04 85% COOH W H 2 C I - + 0 pH 7.4 'NnCOO- I o<No N' FjOp 6 Scheme 1 acidification to pH 2 with 6 mol dm-3 HCI the solution was extracted three times with 20 ml portions of dichlorornethane. The combined organic phase was evaporated under vacuum.For analytical purposes, the product was crystallized from acetonitrile and then dried under vacuum over phosphorus pentoxide to yield 1.6 g (68%). Melting-point (m.p.) 153- 155 "C, thin-layer chromatography (TLC), RF = 0.481. Found: C, 62.28; H, 7.42; N, 7.50. Calc. for C19H&1N203: C, 62.20; H , 7.42; N, 7.74%. The compound was also identified by its UV, lH NMR and l3C NMR spectra. Praziquantel Acid Hydrolysis Product [PAHP*2HCI (3)] A mixture of 2 g (6.4 mmol) of praziquantel and 10 ml of 6 mol dm-3 hydrochloric acid was boiled in an oil-bath under reflux for 1 h. During this time, the reaction mixture was tested for complete hydrolysis by the disappearance of the praziquantel spot in TLC.The solution was left to cool to room temperature and then extracted three times with 15 ml portions of diethyl ether. After the addition of diethyl ether a precipitate was formed. This precipitate was separated by filtration and washed with diethyl ether and then reserved to be used later. The filtrate, consisting of an ether and an aqueous phase, was separated using a separating funnel. The aqueous phase was evaporated under reduced pressure. The residue from the aqueous phase was combined with the precipitate obtained earlier, recrystallized from glacial acetic acid and dried under vacuum at 50°C over potassium hydroxide to yield 1.2 g (62%); m.p. 140-143°C; TLC, RF = 0.17.Found: C, 49.27; H, 6.30; N, 9.64. Calc. for C12H18N2C1202: C, 49.20; H, 6.20; N, 9.60%. The compound was also identified by its UV and 1H NMR spectra.ANALYST, JANUARY 1992, VOL. 117 89 Hydrolysis of Praziquantel With 85% Phosphoric Acid to Praziquantel Lactam (4) Praziquantel (2 g, 6.4 mmol) and 10 g of phosphoric acid (85%) were heated at 100°C for 24 h; the hydrolysis was followed by TLC. After cooling at room temperature, the solution was diluted to 20 ml with distilled water and extracted three times with 20 ml volumes of diethyl ether. The aqueous phase was brought to pH 9 by the addition of solid sodium carbonate, then extracted three times with 15 ml volumes of chloroform. The combined chloroform extract was evapor- ated under reduced pressure.After addition of about 2 ml of ethyl acetate, the oily residue crystallized as fine needles which were separated by filtration and dried under reduced pressure over phosphorus pentoxide. For analytical purposes, the product was recrystallized from ethyl acetate to yield 0.7 g (58%); m.p. 116-118°C; TLC, RF = 0.34. Found: C , 71.11; H, 6.93; N, 13.85. Calc. for CI2Hl4N2O2: C, 71.26; H , 6.97; N, 13.58%. The compound was also identified by its IR, 'H NMR, UV and 13C spectra. Quantitative Determination of Compound 2 With NBD-CI Compound 2 (10 mg) was dissolved in 10 ml of absolute methanol. From this solution samples of 50, 100, 200, 300 and 400 pl were transferred using a micropipette into screw-capped test-tubes. Phosphate buffer (0.4 ml) of pH 7.4 and 0.3 ml of NBD-Cl were added and the volume of each tube was made up to 1.15 ml with absolute methanol.The contents of the tubes were heated in a thermostated water-bath for 20 min at 60°C. At the end of the reaction time, the solutions were cooled to room temperature and acidified with 100 1-11 of 6 rnol dm-3 HCI. The solutions were quantitatively transferred into 25 ml calibrated flasks and made up to the mark with methanol. The absorption of the colours produced was measured from the lowest concentration up to the highest. The measurements were corrected for a reagent blank similarly treated. Absorption of the colour solution was taken as the average absorbance from 460 to 480 nm. Synthesis of the 4-Chloro-7-nitro-2,1,3-benzoxadiazolyl Derivative of Compound 2 (Compound 5) Sodium hydrogen carbonate (2.5 g, 30 mmol) and 3.65 g (10 mmol) of compound 2 were dissolved in 20 ml of distilled water, and a solution of 2 g (10 mmol) of NBD-C1 in 80 ml of methanol was added.The reaction mixture was heated at 60 "C for 2 h, left to cool to room temperature and acidified with 6 rnol dm-3 HCI to pH 2. Most of the methanol was evaporated under vacuum and distilled water was added to the residue. The precipitate was separated by filtration and dried over phosphorus pentoxide to yield 3.5 g (70%) which was purified by column chromatography. Melting-point, 150-152 "C; TLC, RF = 0.6. Found: C, 60.67; H , 5.65; N, 13.95. Calc. for The mass spectrum of compound 5 showed a molecular ion peak at m/z = 49.5; the fluorescence excitation spectrum of this compound showed a maximum at 473 nm while the emission spectrum maximum was at 540 nm.C ~ S H ~ ~ N S O ~ : C, 60.84; H, 5.51; N, 14.19%. Quantitative Determination of Compound 3 With NBD-CI Compound 3 (10 mg) was dissolved in 10 ml of methanol and SO, 100, 150, 200, 2.50 and 300 p1 volumes were transferred using a micropipette into screw-capped test-tubes. To each tube 0.4 ml of the phosphate buffer of pH 7.4 and 0.4 ml of the colour reagent were added. The volume of each tube was made up to 1.1 ml with absolute methanol. The contents of the tubes were heated at 60°C for 30 min, cooled to room temperature and then acidified with 100 pl of 6 rnol dm-3 HCI. The solution in each tube was quantitatively transferred into a 25 ml calibrated flask and made up to volume with absolute methanol.The average absorbance (from 450 to 490 nm) was measured against a blank similarly treated. Synthesis of the 4-Chloro-7-nitro-2,1,3-benzoxadiazolyl Derivative of Compound 3 (Compound 6) Sodium hydrogen carbonate (5 g, 60 mmol) and 3 g (10 mmol) of compound 3 were dissolved in 20 ml of distilled water. A 4 g amount (20 mmol) of NBD-Cl dissolved in 80 ml of methanol was added and the reaction mixture was heated at 60°C for 1 h, then cooled to room temperature and acidified to pH 2 with 6 rnol dm-3 HCI. Most of the solvent was evaporated under vacuum. With the addition of 20 ml of distilled water a coloured material precipitated. Excess of water was added until no further precipitate formed. The precipitate was removed by filtration and dried under reduced pressure.The substance obtained was purified by column chromatography. Melting-point, 165-166°C; TLC, RF = 0.72. Found: C, 52.86; H, 3.58; N, 20.37. Calc. for C24H18N808: C, 52.74; H , 3.33; N, 20.51%. The electronic spectrum showed an absorption maximum at 486 nm. The emission spectrum of the coloured product (6) showed a maximum at 534 nm, while the excitation spectrum had a maximum at 473 nm. Colorimetric Determination of Praziquantel in Biltricide Tablets Basic hydrolysis method Each tablet from one packing was weighed, ground in a mortar until homogeneous and portions of about 300 mg of the powder were weighed into 50 ml round-bottomed flasks. To each flask, 3 ml of ethanol and 1.5 ml of 3 rnol dm-3 NaOH were added. The mixture was stirred in an oil-bath at 60°C for 2 h and the resulting suspension brought to pH 7 with 6 rnol dm-3 HCI.The contents of each flask were quantitatively transferred into a 100 ml calibrated flask and made up to the mark with absolute methanol; 100 pl of the solution were used for the assay. Acid hydrolysis method From each homogenized Biltricide tablet, a portion of about 200 mg was accurately weighed into a 50 ml round-bottomed flask. The active constituent was extracted by shaking the powder with 15 ml of ethyl acetate for 10 min followed by filtration. The ethyl acetate extract was evaporated under vacuum, 3 ml of 6 rnol dm-3 HCl were added to the residue and the mixture was refluxed in an oil-bath for 1 h. The solution was neutralized with 6 rnol dm-3 NaOH to pH 7, transferred into a 100 ml calibrated flask and made up to the mark with methanol; 100 p1 of this solution were used for the assay.Results and Discussion In preliminary experiments many chromogenic reagents such as dichlone,29 1,2-naphthoquinonesulfonic acid,30 fluor- escamine31 and ninhydrin32 were tested to determine whether they gave a colour with the amino group of compounds 2 and 3. Surprisingly none of these reagents reacted to give a stable colour. There was no difference in the colour between the reference blank and the samples tested. In contrast to these results NBD-Cl proved to be a powerful reagent.334 In the present study, NBD-CI was heated in aqueous methanolic phosphate buffer. The resulting reaction product showed two absorption bands with maxima at 373 and 452 nm. These two bands may be due to the formation of 4-methoxy-7- nitro-2,1,3-benzoxadiazole (NBD-OCH3) (7) and its hydroly- sis product, 4-hydroxy-7-nitro-2,1,3-benzoxadiazole (NBD- OH) (S), respectively.In order to confirm these results NBD-OCH3 and NBD-OH were synthesized according to the method used by Dal-monte90 0.500 0.450 0.400 ~ 0.350 0.300 5 0.250 0 2 0.200 0.150 0.100 0.050 0 - ANALYST, JANUARY 1992, VOL. 117 - - - - - - - - - - 1 1 1 I I I 1 I I et aZ.34 The absorption spectra of these compounds in methanol showed maxima at 372 and 462 nm, respectively. The addition of HCl to NBD-OH caused a hypsochromic shift of the absorption band from 462 to 387 nm. The shift may be due to protonation of the dissociated hydroxy group of NBD-OH.This assumption was confirmed by neutralization of the above acidic solution with NaOH, the absorption maximum at 387 nm showing a red shift to 460 nm. Therefore, it was necessary to acidify the coloured solution to pH 2 before spectrophotometric measurements were carried out. At this pH the reagent blank did not show any significant absorption between 450 and 500 nm. OCH3 OH 7 a The reaction of compound 2 with NBD-C1 gave an orange product that had a characteristic absorption maximum at 478 nm (molar absorptivity = 23340 dm3 mol-1 cm-1) (Fig. 1). The absorbance of the coloured solution remained constant for at least 24 h. The optimum reaction conditions for the quantitative determination of compound 2 with NBD-CI were attained when 0.4 ml of phosphate buffer of pH 7.4 was used, 22 pmol of NBD-CI were reacted with 595 pg per 25 ml of PBHP (1.6 pmol) and the reaction solution was heated to 5MO"C for 20 min.A calibration graph was constructed using standard solutions of PBHP. Under the experimental conditions, a linear relationship existed between the absorption and the concentration of compound 2 in the concentration range 2-20 pg ml-1 according to the equation: A = 0.00265~ + 0.0099 (c Table 1 Reproducibility of the colour development of replicate PBHP samples containing 127 pg per 25 ml Experiment No. 1 2 3 4 5 6 7 8 9 Average : SD : RSD: Absorbance 0.3451 0.3428 0.3432 0.3429 0.3440 0.3460 0.3434 0.3442 0.3435 PBHP found/pg per 25 ml 126.49 125.62 125.77 125.66 126.07 126.83 125.84 125.39 125.88 125.93 0.476 0.378% in pg per 25 ml of measuring solution), r* = 0.9991, r = 0.9995 (Fig.2). The precision of the colorimetric method was evaluated in terms of relative standard deviation (RSD). Nine independent assays on samples each containing 127 pg per 25 ml gave a mean concentration of 125.93 pg per 25 ml. The SD and RSD were found to be 0.476 and 0.378% , respectively. The results indicated that the method was precise and gave reproducible results as shown in Table 1. The sensitivity was expressed as the amount of PBHP corresponding to an absorption value equal to twice the absorption value of the reagent blank treated similarly. It was found that as little as 0.124 pg ml-1 of PBHP can be determined by the proposed method. An orange-red product was obtained as a result of the interaction between compound 3 and NBD-Cl in an aqueous phosphate buffer medium and gave a broad peak with a maximum at 486 nm and a shoulder at 454 nm (molar absorptivity = 31 890 dm3 mol-1 cm-1) (Fig. 3).The colour obtained was stable for at least 24 h. When the coloured solution was left for more than 24 h, the colour changed gradually from orange-red to deep yellow with a concomitant hypsochromic shift to 456 nm. In addition, the absorption intensity of the coloured solution decreased. The same results were obtained when the pure synthesized coloured substance was dissolved in methanol and left at room temperature for 5 d. Moreover, if the stock solution of compound 3 in methanol was left for about 20 h and then reacted with NBD-CI, the coloured solution obtained showed an absorption at 486 nm with a decrease in absorption intensity.The absorption spectra of the coloured solutions resulting from the reaction of the above methanolic stock solution of PAHP with NBD-CI and that of the NBD derivative of lactam 4 were compared. Both have identical Table 2 Reproducibility of the colour development of PAHP with NBD-CI Absorption 0.3880 0.3900 0.3917 0.3933 0.3908 0.3880 0.3975 0.3894 PAHP found*/ pg per 25 ml 102.15 102.69 103.15 103.34 102.91 102.13 104.71 102.53 Absorption 0.7775 0.7751 0.7780 0.7802 0.7842 0.7715 0.7773 0.7786 Average: 102.95 SD : 0.827 * Amount taken, 103 pg per 25 ml. I Amount taken, 206 pg per 25 ml. RSD: 0.8% PAHP found?/ pg per 25 ml 207.14 206.49 207.27 207.87 208.94 205.52 207.08 207.43 207.28 0.993 0.47% 1 .o 0.8 0.6 42 8 13 a 0.4 0.2 0 72.2 144.4 216.6 288.8 361 [PBHP]/pg per 25 mi Relation between absorbance of the coloured derivative and Fig.2 PBHP concentrationANALYST, JANUARY 1992, VOL. 117 91 Table 3 Determination of praziquantel in Biltricide tablets using the proposed colorimetric method, n = 2 Basic hydrolysis method Acid hydrolysis method PraziquanteYyg per 25 ml PraziquanteVpg per 25 ml Tablet No. Taken Found Recovery (% ) Taken Found Recovery (YO) 1 2 3 4 5 6 Average: SD : RSD: 232.9 231.70 99.48 233.3 230.60 98.94 229.2 231.60 101.05 220.5 222.64 100.97 233,5 237.60 101.75 231.2 231.80 100.25 100.39 1.088 1.08% 123.0 123.53 100.43 123.5 122.56 103.60 122.4 126.81 103.60 126.30 128.19 102.89 125.74 129.38 102.89 110.1 112.77 102.42 101.67 1.62 1.60% Table 4 Recovery of praziquantel added to Biltricide tablets using the proposed colorimetric method, n = 2 Basic hydrolysis method Acid hydrolysis method Praziquantel/yg per 25 ml PraziquanteUpg per 25 ml Added Found Recovery (YO) Added Found Recovery (YO) 75.64 74.00 140.32 140.00 206.64 206.6 294.24 294.23 402.54 399.1 Average: SD : RSD : 99.15 99.77 99.98 99.99 99.14 99.60 0.374 0.375% 75.64 140.32 206.64 294.24 402.54 75.2 140.6 206.9 293.8 404.0 99.41 100.19 loo.12 99.85 100.36 99.98 0.347 0.347% 0.80 :::: i' 0.30 0.20 1 0.10 400 420 440 460 480 500 520 540 560 580 600 Wavelengthhm Fig. 3 Absorption spectrum for the colour produced on reaction of compound 3 with NBD-C1. (PAHP = 240 yg per 25 ml). The absorbance at 486 nm is 0.9188 and is indicated by + spectra with maxima at 456 nm.A probable explanation of this behaviour is as follows. Compound 3 is cyclized to form compound 4 in methanolic solution at room temperature in about 24 h; however, the NBD derivative of compound 3 when allowed to stand in methanolic solution for 1 week is also cyclized to form the NBD derivative of 4, presumably with loss of an NBD-OH molecule as shown in Scheme 1. Therefore, it is recommended that the coloured solution from PAHP be measured within the first 24 h after colour development. Moreover, the methanolic solution of PAHP should be freshly prepared. The optimum reaction conditions for the quantitative determination of compound 3 with NBD-CI were achieved by using 0.4 ml of phosphate buffer of pH 7.4; 20 pmol of NBD-CI were required for 460 pg per 25 ml (1.5 pmol) of compound 3 and the reaction solution was heated at 60°C for 30 min.The intensity of the colour produced from the reaction of PAHP with NBD-CI was found to be proportional to the concentration of PAHP. A typical calibration graph was 2.0 1 I 1.6 1 2 q 1.2 I I I 1 0 90 180 270 360 450 [PAHP]/pg per 25 ml Relation between absorbance of the coloured derivative and Fig. 4 PAHP concentration obtained according to the equation: A = 0.00371~ + 0.0090 (c in pg per 25 ml), r2 = 0.9994, r = 0.9997 (Fig. 4). The precision was calculated from eight replicate measure- ments of 0.1 and 0.2 ml aliquots of standard PAHP containing 103 and 206 pg per 25 ml, respectively. The proposed method gave mean recoveries of 102.95 and 207.28 pg per 25 ml with RSDs of 0.8 and 0.47%, respectively, as shown in Table 2.The sensitivity was determined according to the concentra- tion of PAHP corresponding to an absorption value equal to twice the absorption value of the reagent blank. It was found that as little as 0.15 pg ml-1 of PAHP could be detected by the proposed colorimetric method. The validity of the proposed colorimetric method was tested by determining praziquantel in Biltricide tablets. Both acid and basic hydrolysis processes were applied, followed by coupling with the NBD-CI reagent. The concentration of praziquantel in each tablet was calculated from the appro- priate calibration graph. It was found that the hydrolysis of praziquantel with 3 mol dm-3 NaOH could be performed in the presence of the tablet matrix.There was no shift in the absorption maximum due to the presence of other constituents of the Biltricide tablets. On the other hand, heating of Biltricide tablets with 6 mol dm-3 HCI at 130-140°C led to the92 ANALYST, JANUARY 1992, VOL. 117 Table 5 Statistical analysis of the results obtained by applying the colorimetric method to Biltricide tablets Basic hydrolysis Acid hydrolysis method method X 100.39 101.67 n 6 6 Variance 1.174 2.63 F-value (p = 5%) 2.25 (5.05)* t-value (p = 5%) 1.60 (2.27)t significance level. significance level. * Value in parentheses represents the tabulated F-value at the 5% t Value in parentheses represents the tabulated t-value at the 5% Table 6 Statistical analysis of the results obtained by addition of known amounts of praziquantel to Biltricide tablets, applying the colorimetric method Basic hydrolysis Acid hydrolysis method method X 99.60 99.98 n 4 4 Variance 0.140 0.120 F-value (p = 5%) 1.16 (9.27)* 1.49 (3.18)T t-value (p = 5%) significance level. significance level.* Value in parentheses represents the tabulated F-value at the 5% t Value in parentheses represents the tabulated t-value at the 5% development of a brown colour which may have been due to the interaction between HCI and the ingredients of the tablet matrix. This brown colour led to inaccuracies in the absorption assay. Therefore, it was necessary to extract the active constituent from the Biltricide tablets before using the acid hydrolysis method. For this purpose ethyl acetate was chosen as the solvent because of its excellent solvent properties for praziquantel.After evaporation of the organic solvent, the acid hydrolysis process was performed. Results obtained are given in Table 3. Comparing the experimental data after acid and basic hydrolysis, it was observed that there was relatively good correlation, both methods giving reliable recoveries. However, the determination of praziquantel in Biltricide tablets by basic hydrolysis is recommended because of its simplicity compared with the acid hydrolysis procedure. Known concentrations of pure praziquantel were added to accurately weighed amounts of powdered Biltricide tablets. After hydrolysis of the samples with 3 mol dm-3 NaOH or 6 mol dm-3 HCI, the pH of the solution was adjusted to 7.The hydrolysis products were reacted with NBD-CI. The recoveries of the added praziquantel were calculated from the appropriate calibration graphs. The results presented in Table 4 indicate the accuracy of the method. The results obtained are reproducible and quantitative. Results given in Tables 5 and 6 reveal that there is no significant difference in the accuracy and precision achieved by applying the colorimetric method using hydrolysis in acid or base. However, the basic hydrolysis is recommended for the reasons mentioned above. 1 2 3 4 5 6 7 8 9 10 11 References Seubert, J., Pokhlke, R., and Loebich, F., Experienria, 1977, 33, 1036. Thomas, H., and Gonnert, R., Z. Parasitenkd., 1977,52, 117. Gonnert, R., and Andrews, P., 2. Parasitenkd., 1977,52, 129.Shao, H.-S., Pan, S.-R., and Ling, X. N., Zhongguo Yaoli Xuebao, 1981,2, 49. Chavasse, C. J., Brown, M. C., and Bell, D. R., Z. Para- sitenkd., 1979,58, 169. Becker, B.. Mehlhorn, H., and Andrews, P., Z. Parasitenkd., 1980,63, 113. Webbe, G., and James, C., Z. Parasitenkd., 1977,52, 169. Pellegrino, J., Lima-Costa, F. F., Carlos, M. A., and Mello, R. T., Z . Parasitenkd., 1977, 52, 151. James, C., Webbe, G., and Nelson, G. S., Z. Parasitenkd., 1977, 52, 179. Wegner, D. H. G., Arzneim. Forsch., 1981, 31, 566. Katz, N., Rocha, R. S., and Chaves, A., Rev. Inst. Med. Trop. S6o Paulo, 1981, 23, 72. 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 McMahon, J. E., Arzneim. Forsch., 1981, 31, 592. Smith, D. H., Highton, R. B., and Roberts, J.M., Arzneim. Forsch., 1981, 31, 594. Ranque, P., Konate, S., Karemberi, B., and Kone, D., Arzneim. Forsch., 1981, 31, 597. Diallo, P. S., Victorius, A., Diouf, F., Ndir, O., Dieng, Y., and Bah, I. B., Arzneim. Forsch., 1981,31, 574. McMahon, J. E., Arzneim. Forsch., 1981,31, 579. Oyediran, A. B., Kofie, B. A., Bammeke, A. O., and Bamgboye, E. A., Arzneim. Forsch., 1981,31, 581. McMahon, J. E., and Koistrup, N., Br. Med. J., 1979,2, 1396. Xu, Z.-Y., Zhonghua Neike Zazhi (Beijing), 1981,20. 385. Thomas, H., and Andrews, P., Tropenmed. Parasitol., 1977,28, 275. Putter, J., Eur. J. Drug Metab. Pharmacokinet., 1979, 3, 143. Putter, J., and Held, F., Eur. J. Drug Metab. Pharrnacokinet., 1979, 4. 193. Diekmann, H. W., Eur. J. Drug Metab. Pharmacokinet., 1979, 3, 139. Yuan, X., Yaowu Fenxi Zazhi, 1982, 2, 356; Chem. Abstr., 1985, 98, 166973t. Yuan, X., Yaowu Fenxi Zazhi, 1985, 5 , 120, Chem. Abstr., 1985, 103, 27405t. Xiao, S.-H., Catto, B. A., and Webster, L. T., J. Chromatogr., 1983,275, 127. Xu, P., Ren, Z., Li, Y., Lu, M., Xu, H., andZhao, M., Yaoxue Xuebao, 1983, 18, 401; Chem. Abstr., 1984, 100, 29286s. Katori, N., Shibazaki, T., and Uchiyama, M., Iyakuhin Kenkyu, 1985, 16, 1407; Chem. Abstr., 1986, 104, 136149d. Abou-ouf, A. A., Taha, A. M., and Saidhom, M. B., J. Pharm. Sci., 1973, 62, 1700. Nehring, H., and Hock, A., Pharmazie, 1971, 26, 616. Toome, V., and Manhart, K., Anal. Lett., 1975, 8, 441. Ruhemann, S., J. Chem. SOC., 1910,97, 1438. Boulton, A. J., Ghosh, P. B., and Katritzky, A. R., J. Chem. SOC. B , 1966, 1004. Dal-monte, D., Sandri, E., and Mazzaracchio, P., Boll. Sci. Fac. Chim. Ind. Bologna, 1968,26,165; Chem. Abstr.. 1969,70, 115074q. Gosch, P. B., J. Chem. SOC. B , 1968,334. Lawrence, J. F., and Frei, R. W., Anal. Chem., 1972,44,2046. Klimisch. H.-J., and Stadler, L., J. Chromatogr., 1974,90, 141. Wolfram, J. H., Feinberg, J. I., Doerr, R. C., and Fiddler, W., J. Chromatogr., 1977, 132, 37. Roth, M., Clin. Chim. Acta, 1978, 83, 273. Krol. G. J., Banovsky, J. M., Mannan, C. A., Pickering, R. E., and Kho, B. T., J. Chromatogr., 1979, 163, 383. Paper 1 I01 6 76 H Received April 11, 1991 Accepted July 4, 1991

ISSN:0003-2654    

DOI:10.1039/AN9921700087

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

ANALYST, JANUARY 1992, VOL. 117 93 Rapid Ultraviolet Spectrophotometric Assay of Benzoyl Metronidazole in an Oral Suspension Asis K. Sanyal University College of Science, Department of Biochemistry, Microbiology Laboratory, 35 Ballygunge Circular Road, Calcutta-700 0 19, India A procedure is described for the rapid determination of benzoyl metronidazole in an oral suspension which is based on measurement of the change in absorbance at 276 nm during alkaline hydrolysis of the compound in 2 mol dm-3 NaOH. The change in absorbance follows a linear relationship with concentration in the range 3-18 pg m1-l. Results of the determination of benzoyl metronidazole in an oral suspension and of the recovery experiments performed on this formulation, and also on various individual excipients and other additives, confirmed the applicability of the proposed method to complex formulations.Keywords: Benzoyl metronidazole determination; oral suspension; ultravioiet spectrophotometry The hydrolysis of 5-nitroimidazoles depends on their struc- tural configuration. The C-N bond at position 5 of the 5-nitroimidazoles is susceptible to alkaline hydrolysis which takes place readily when position 1 in the heterocyclic ring is substituted.' Metronidazole and benzoyl metronidazole, which have CH2CH20H and CH2CH200CC6HS substitu- ents, respectively, at position 1, liberate nitrite ions on hydrolysis with the formation of 2-(2-methylimidazol-l-yl)- ethanol and 2-(2-methylimidazol-l-yl)ethyl benzoate, res- pectively. A method for the assay of metronidazole in pharmaceuticals based o n the colorimetric determination of the liberated nitrite ions has been reported previously.' In subsequent studies it was found that the process of alkali hydrolysis itself causes a change in the ultraviolet (UV) absorption of metronidazole at 276 nm.This might be used for the determination of metronidazole or benzoyl metronidazole by direct spectrophotometry without the need to employ the second colour reaction. The spectrophotometric assay' of metronidazole at 274 nm is often very difficult owing to interference by UV absorbing pharmaceutical ingredients4 such as methyl, ethyl or propyl paraben and vanillin that are generally present in pharmaceut- ical preparations. The proposed method is based not on measuring the absolute absorbance of metronidazole but on measuring the relative change in absorbance at 276 nm due to hydrolysis of this compound.This property was found not to be shared by the various additives usually present in phar- maceutical formulations. This selectivity allows the method to be applied to the analysis of complex formulations. In this paper the applicability of the method to the assay of benzoyl metronidazole in an oral suspension, which is the most complex of the dosage forms of this drug, is demon- strated. There is n o officially accepted assay method at present for this formulation. Experimental Apparatus and Chemicals A Hitachi Model U-3210 spectrophotometer was used. Authentic samples of metronidazole and benzoyl metron- idazole were obtained from May & Baker (UK).Flagyl suspension (May & Baker, India) was purchased locally. Preparation of Standard About 30 mg of metronidazole were accurately weighed and dissolved in 30 ml of methanol. The solution was diluted to an exact volume (50 ml) with the same solvent. For use in the assay, 5 ml of the solution were diluted to 100 ml with water. Preparation of Samples Ben z oy 1 metronida zole An accurately weighed amount of the sample, equivalent to about 30 mg of metronidazole, was dissolved in 30 ml of methanol and the solution diluted to an exact volume (50 ml) with the same solvent. For use in the assay, 5 ml of the solution were diluted to 100 ml with water. Oral suspension The contents of the bottle were shaken vigorously before adding a measured volume (containing the equivalent of about 30 mg of metronidazole) to 30 ml of methanol contained in a calibrated flask (50 ml).The mixture was diluted to volume with methanol after which the flask was stoppered and shaken vigorously for 2 min. The undissolved excipients were then allowed to settle. For analysis, 5 ml of the clear supernatant were diluted to 100 ml with water. Determination Hydrolysis of metronidazole and benzoyl metronidazole Solutions of the standard or test samples (3 ml) were mixed with an exactly equal volume of 4 mol dm-3 NaOH in glass-stoppered tubes which were then immersed in a boiling water-bath for exactly 15 min. The tubes were removed, cooled in an ice-water bath and the contents acidified with 3 ml of 5 mol dm-3 HCI. In the control reaction (no hydrolysis), 3 ml of 4 mol dm-3 NaOH were acidified with 3 ml of 5 1 .o 0.8 al (D 2 0.6 + 8 2 0.4 0.2 0 200 250 300 350 400200 250 300 350 400 Wavelengthhm Fig.1 Ultraviolet absorption spectra of ( a ) metronidazole and ( h ) benzoyl mctronidazole in acidic solution A, before and B. aftcr hydrolysis94 ANALYST, JANUARY 1992, VOL. 117 Table 1 Recovery of metronidazole from authentic samples Experiment Added/mgper lOOml Recovery* (YO) 1 1 .0 99.4 2 2.0 99.8 3 3.0 100.3 4 4.0 99.9 5 5.0 101.1 Average k standard deviation 100.1 +- 0.6 * Each recovery is the average of three determinations. Table 2 Assay of benzoyl metronidazole in authentic samples Amount of benzoyl Amount determined using metronidazole taken metronidazole as reference 20 20.2 -t 0.12 30 29.9k0.15 40 39.8 k 0.22 for assay*/mg standardt/mg * Samples were dissolved in SO ml of methanol and processed as t Each result is the mean of ten independent assays t standard described under Experimental. deviation.mol dm-3 HCI and the mixture was cooled to room tempera- ture prior to the addition of 3 ml of the standard or sample solutions. Measurement of absorbance The absorbance of the standard or test samples that had not been hydrolysed (controls) was measured at 276 nm against the corresponding hydrolysed solutions. Calculations The content of metronidazole in the oral suspension and of benzoyl metronidazole in the raw material was calculated by using the following equations: Content of metronidazole (mgper5 ml) = (U/S) x c X (5/V) X D Content of benzoyl metronidazole (%) = (U/S) X c X (100/m) X (1001100 - X) X 1.61 X D where S and U are the differences between the absorbances of the non-hydrolysed and hydrolysed drug at 276 nm for the standard and sample, respectively, cis the concentration of the standard preparation (mg ml- I ) , m the mass of sample taken for analysis (mg), V the volume of sample taken for analysis (ml),x the moisture content of the sample (%) and D the sample dilution. The raw material is determinedon an anhydrous basis: 1 mg of metronidazole is equivalent to 1.61 mg of benzoyl metronidazole.Results and Discussion The UV absorption spectra of the acidic solutions of metron- idazole and benzoyl metronidazole before and after the hydrolysis are shown in Fig. 1. The peak at 276 nm disappeared almost completely when the drugs were hydro- lysed.The reaction reached equilibrium within 15 min in a boiling water-bath when the alkali concentration was 2 mol dm-3. Under the conditions standardized in the proposed method, a plot of metronidazole concentration versus decrease in absor- bance was linear in the concentration range 3-18 pg ml-1. A similar linear relationship was also obtained for benzoyl metronidazole in a concentration range equivalent to that obtained for metronidazole. The recoveries obtained from authentic samples demonstrate the high degree of accuracy and precision of the proposed method (Table 1). The use of a Table 3 Determination of metronidazole in a raw material and an oral suspension Nitrite-colorimetric Proposed method* method" Concen- Found Concen- Found tration (YO of label tration (YO of label Sample found claim) found claim) Benzoyl metronida- zole (raw material) 99.9 k 0.71 - 99.7k0.61 - Flagyl oral suspen- sion 199.5It2.63 99.8+ 1.3 200.1 *2.8$ 100.1 * 1.4 * Each result is the mean of ten independent determinations k f Value in YO m/m.Content ofbenzoyl metronidazole iscalculated on 3 Value in mgper5 ml. Label claim: 200mgofmetronidazole per5 ml. standard deviation. an anhydrous basis. Table 4 Recovery of added metronidazole from an oral suspension Metronidazole equivalent of benzoyl metronidazole added per5 mloforal Experiment suspension*/mg Recovery? (Y ) 1 30 99.5 * 1 .s 2 60 99.3 t- 1.6 3 90 99.7 * 1 .5 4 120 100.8 + 1.4 equivalent per 5 ml. standard deviation. * Flagyl oral suspension containing 199.8 mg of metronidazole t Each result is the average of six independent determinations k separate reference standard for benzoyl metronidazole is not required during the assay of this drug (Table 2).Results for the determination of benzoyl metronidazole using metron- idazole as the reference standard correspond well with the amount of authentic sample taken for assay. Results for the determination of the metronidazole content of an oral suspension and of benzoyl metronidazole in a raw material using the proposed method (Table 3) agree well with the declared amounts of the drugs and are comparable to the results obtained using the nitrite-colorimetric method.' Known amounts of benzoyl metronidazole were spiked with the oral suspension sample containing a known amount of metronidazole equivalent.Quantification of the added metronidazole indicated a 99.3-100.8% recovery of the drug from this complex mixture (Table 4). In order to investigate the interference of excipients, a series of recovery experiments were performed with thedrug together with various individual excipients and other additives at stated concentrations (Table 5 ) . As the concentrations of different excipients and additives might be different in different commercial formulations their amount in the binary mixture was selected on the basis of the type of material taken. The results show a satisfactory recovery of metronidazole from various preservatives, suspending, colouring, sweetening and flavouring agents commonly present in the oral suspension. Strongly UV absorbing phenolic compounds such as methyl paraben, propyl paraben and vanillin were found not to interfere with the proposed assay.The author thanks Professor A. B. Banerjee, Department of Biochemistry, Calcutta University, for his invaluable sugges- tions during the course of this work.ANALYST, JANUARY 1992, VOL. 117 95 Table 5 Recovery of metronidazole from exeipients. preservatives and other pharmaceutical additives Addedlmg per 50 ml of methanol" Excipient, preservative or add i t ive Acacia Agar Sodium alginate Carboxymethyl- Gelatin Povidonc S i I ico n d io x ide Bentonite Dextrose Fructose Mannitol Sorbi to1 Sucrose GI yccrol Saccharin sodium Aspartame Methyl paraben Propyl paraben Benzoic acid Peppermint oil Menthol Raspberry (concentrated juice) Strawberry (concen t ra ted juice) Pineapple Ice cream soda Van i 11 in Sunset Yellow Tartrazinc Carmoisine cellulose (concentrate) Excipient.preservative or additive added 30 30 30 30 30 30 30 30 30 30 30 30 30 0.05$ 3 3 3.8 3.8 3.8 0.0lt 1 .s 0.013 0.01$ 1 .5 0.01 $ 1 .s 0.5 0.5 0.5 Metronidazole equivalent of' benzoyl metron- idazole added 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 * The mixture was processed as described under Oral suspension prior to analysis. -t Each result is the mean of five independent determinations _+ standard deviation. :i: Volume added (ml). Metronidazole recoveredtlmg 30.03 ? 0.20 29.94k0.24 29.97 t 0.19 30.00t 0.20 29.96 t 0.23 30.06 t 0.21 30.15 t 0.22 29.79 t 0.19 30.03 k 0.18 29.95 t 0.21 29.91 t 0.23 30.06 t 0.21 30.1 5 t 0.1 8 29.88 t 0.24 30.04 t 0.19 29.85 ? 0.22 29.82 rt 0.20 30.09 t 0.21 30.00 t 0.19 29.98 t 0.20 29.76 +- 0.2 1 30.16 k 0.23 30.04 2 0.2 1 29.85 t 0.21 30.18 k 0.23 29.82 t 0.20 29.92 k 0.23 30.02 rt 0.18 30.00 k 0.22 Recovery? (%) 100.1 s 0.7 99.8 t 0.8 99.9 t 0.6 100.0 t 0.7 99.9 t 0.8 100.2 k 0.7 100.5 k0.7 99.3 t 0.6 100.1 t 0.6 59.8 k 0.7 99.7 t 0.8 100.2 k 0.7 100.5 t 0.6 99.6 * 0.8 100.1 s 0.6 99.5 ? 0.7 99.4 t 0.7 100.3 t 0.7 100.0 k 0.6 99.9 t 0.7 99.2 k 0.7 100.5 t 0.8 LOO. 1 t 0.7 99.5 t 0.7 100.6 k 0.8 99.4 t 0.7 99.7 f 0.8 100.1 t 0.6 100.0 t 0.7 References 4 United Stutes Pliurmucopeiu, X X t l Revision. Mack. Easton, PA. 1990, p. 1857. 1 Lau. E., Yao. C., Lewis, M.. and Senkowski, B. Z . . J . Plzurm. Sci.. 1969,58,55. 2 Sanyal, A. K . . J . AJJOC. Off. And. Cliem.. 1988.71.849. 3 Wearley, L. L . . and Anthony, G. D.. Anulyticul Profiles o f Drug Subsrunces. Academic Press, Ncw York. 1976. vol. 5 . p. 328. Paper 0105699E Received December 18, 1990 Accepted July 31, I991

ISSN:0003-2654    

DOI:10.1039/AN9921700093

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

ANALYST, JANUARY 1992, VOL. 117 97 Proficiency Testing of Analytical Laboratories: Organization and Statistical Assessment Analytical Methods Committee* Royal Society of Chemistry, Burlington House, Piccadilly, London WI V OBN, UK Proficiency testing is becoming an integral feature of laboratory accreditation, which itself is now being advocated as a result of the development of the European Community Certification and Accreditation Policy. In analytical science, proficiency testing involves the regular circulation of test materials for analysis in the participating laboratories, and the subsequent assessment of the resulting data by the organizing body. It plays a vital role in the achievement and maintenance of appropriate data quality, in combination with the use of certified reference materials, validated methods and data quality control.In this report the technical background and organization of proficiency testing are presented, together with statistical methods for interpreting the results. Because of the rapid proliferation of proficiency testing schemes, it is recommended that anlytical chemists move towards a unified approach t o the presentation of results from trials, so that the meaning of the results of all schemes is immediately apparent. This is best achieved by the use of standard elementary statistics. Specific recommendations are given and a specimen protocol is appended. Keywords: Proficiency testing; accreditation; data quality The Analytical Methods Committee has received and has approved for publication the following report from its Statistical Sub-committee.Report The constitution of the Sub-committee responsible for the preparation of this report was: Dr. M. Thompson (Chairman), Dr. W. H. Evans, Mr. M. J. Gardner, Dr. E. J. Greenhow, Dr. R. Howarth, Dr. E. J. Newman, Professor B. D. Ripley, Mrs. K. Swan and Dr. R. Wood with Mr. J. J. Wilson as Secretary. The Analytical Methods Committee acknowledges the financial support from the Ministry of Agriculture, Fisheries and Food. The views expressed and the recommendations made in this paper are those of the Analytical Methods Committee and not necessarily those of the Ministry of Agriculture, Fisheries and Food. Introduction Tests are carried out in analytical laboratories in order to make important decisions. It is essential, therefore, to operate a scheme to monitor the reliability of data originating from these laboratories.Such a scheme reinforces an interest in quality control and provides the basis for review and correc- tive action in those laboratories where data do not meet criteria of acceptability. The continuing assessment of labora- tory competence provides a record of any improvements that have been achieved or, conversely, may alert a laboratory to declining performance and so prompt the introduction of remedial measures before the deterioration has become serious. This type of scheme is known as proficiency testing and a number of such schemes already exist for particular areas of interest such as clinical biochemistry, food analysis and environmental monitoring.A proficiency scheme tests the competence of a group of participating laboratories by a statistical evaluation of the data they obtain on analysing distributed materials. Each laboratory is then provided with a numerical indicator of its performance, together with informa- j: Corrcspondencc should be addressed to the Secretary, Analytical Methods Committec. Analytical Division. Royal Society of Chcm- istry, Burlington House, Piccadilly, London W1V OBN, UK. tion on the performance of the group as a whole, enabling proficiency relative to the group to be compared and evaluated. Proficiency testing is becoming an integral feature of laboratory accreditation, which itself is now being advocated as a result of the development of the European Community Certification and Accreditation Policy. Proficiency testing schemes usually operate a few rounds of tests each year. They are managed by a central body which is responsible for the design of the scheme, the preparation and validation of test materials, the production and distribution of instructions and test materials to the participating labora- tories, the collection and statistical analysis of the data obtained from the tests and feedback of the results to the participants.The main aspects of proficiency testing are considered in this paper. Approaches to the analysis of test data are discussed and presented, and an example of an outline protocol for a proficiency test is given. 1. Role of Proficiency Schemes in Quality Assurance 1.1. General Context of Proficiency Testing Proficiency testing is the use of results generated in interlaboratory test comparisons for the purpose of a continuing assessment of the technical competence of participating testing laboratories.1 Alternative terms used for proficiency testing are ‘quality assessment’ and ‘external quality assessment’. Proficiency testing is distinct from other interlaboratory tests, such as collaborative trials (used for validating a standard method) , certification trials (used to establish the true value of an analyte concentration in a reference material) or co-operative trials (used for laboratory assessment on a one-off basis). Numerous schemes for proficiency testing are already in use in several types of analytical laboratory. In the current climate of intense and widespread interest in the improvement of data quality, it seems likely that proficiency test schemes will proliferate greatly.A defect already apparent in existing schemes as a whole is the diversity of performance indices in use. It is therefore difficult rapidly to appreciate the meaning of an index in an unfamiliar scheme. In order to avoid a further deterioration of this situation, the universal use of a harmonized method for the assessment of proficiency schemes is greatly to be desired. At the present time the International Union of Pure and Applied Chemistry (IUPAC), the Inter-98 ANALYST, JANUARY 1992, VOL. 117 national Organization for Standardization (ISO) and the Association of Official Analytical Chemists (AOAC) are jointly pursuing such a harmonization.2 Proficiency testing must be seen in the general context of accreditation and quality assurance.In order to gain accreditation, an analytical laboratory has to demonstrate an effective quality assurance system, which includes participation in relevant proficiency testing schemes and the routine use of a properly designed quality control system. Proficiency testing takes place periodically, and is organized by a central authority. It is distinct from data quality control, which is an activity organized on a routine basis within individual laboratories. At the present time, however, it is clear that not all laboratories employ adequate quality control. One of the main purposes of proficiency testing is therefore strongly to encourage the proper use of quality control and to incorporate an external reference to guard against bias.The type of proficiency test envisaged in this paper is one where samples of test materials are distributed, on a regular basis, to the participating laboratories for unsupervised analysis within a short period from receipt. This is appropriate for trial measurements of the concentration or amount of analyte on a quasi-continuous scale, with which this paper is solely concerned. Other types of proficiency test could be employed in this context and indeed may be useful in conjunction with the type of test described here. 1.2. Aims of Proficiency Testing Two distinct aims of proficiency tests can be formulated: ( a ) to encourage good performance generally, and especially to encourage the use of proper routine quality control measures within individual laboratories; to provide feedback to the laboratories and encourage remedial action where shortcom- ings in performance are detected; (b) to provide a rational basis for the selection or licensing of laboratories for a specific task and likewise to disqualify laboratories from a specific task should their performance fall below a certain standard.These two aims are somewhat divergent, but the motivation is the same: the identification of laboratories that produce data of unacceptable quality. Within the scope of either of these two aims, a successful proficiency test must provide certain types of information for the participants and for the organizers: (i) it must enable a laboratory to compare its performance at a particular time with an appropriate external standard of performance; (ii) it must enable a laboratory to compare its performance at a particular time with its performance in the past; (iii) it must enable a laboratory to compare its performance with that of other laboratories at a particular time; (iv) it must enable the organizers to identify participants whose performance is unsatisfactory; and (v) it must enable the organizers to see whether there is general improvement in performance with time.It is also highly desirable that a uniform method of assessing the results of proficiency tests should be applied, so that the results from different schemes, involving various test materials, analytes and analyte concentration levels, are strictly comparable on an international basis and readily understood by analytical chemists everywhere.For the above-mentioned requirements to be achieved, it is clear that the assessment of proficiency must be expressed in terms of a score that can be readily interpreted in terms of well-known statistical measures. In order to create a scoring system that is harmonized from one proficiency scheme to another, it is essential that arbitrary scaling factors are not introduced and the statistics are used in their standard form. An appropriate degree of training in statistics must be presumed in professional analytical chemists for a harmonized approach to be achieved. 1.3. Limitations of Proficiency Tests Proficiency tests are not in themselves sufficient to ensure the production of high quality data.Firstly, it is clear that the interpretation of data from proficiency tests is subject to statistical uncertainty, and the criteria on which decisions will be based are to some degree arbitrary. Secondly, there is the possibility that not all of the data will be valid. For example, laboratories faced with the prospect of exclusion from a commercial market might be tempted to improve their performance index in unprofessional ways, for example by treating the test samples with special care or by collusion with other laboratories. Some of these practices would be difficult to eliminate. Thirdly, the scope of proficiency testing is necessarily limited by costs. In most laboratories this will mean that only a small proportion of the many different determinations con- ducted can be subjected to a proficiency test.Obviously, a test method can be chosen so that it can be considered representa- tive of a class of test materials or of analytical methods. Nevertheless, there is little alternative but to assume that the proficiency demonstrated in a relatively small number of tests will be representative of the behaviour of the laboratory in a much wider range of activities. All of these circumstances lead to the same conclusion: proficiency tests, useful though they may be, cannot be the exclusive basis for action beyond exhortation to remedial activity. Decisions to disqualify laboratories should be based on further, perhaps more comprehensive, trials and on inspections of quality control records, analytical protocols and the laboratory environment.In addition to the foregoing, it must be recognized that proficiency testing is only applicable to certain classes of analytical task. Broadly, it is restricted to analyses where a determination is carried out as a matter of routine, in a group of laboratories, and where comparability and/or trueness is important. Even where these conditions prevail, there may be technical difficulties (for instance related to the nature of the test materials) that prevent the execution of proficiency testing. 2. General Organization of Proficiency Tests The organizing body is responsible for drawing up the protocol, operating the scheme, taking any appropriate action as an outcome of the scheme, reviewing on a regular basis the effectiveness of the scheme, and, where necessary, amending the protocol.Advice on the drafting of the protocol and implementation of the scheme should be sought from a technical panel consisting of: (i) a manager, with responsibility to the organizing body for running the proficiency test, distribution of the results, any follow-up action that is required and record keeping; (ii) a statistical expert; (iii) representa- tives of government bodies, commercial firms or accreditation agencies with a legitimate interest in the conduct of the tests; and (iv) representatives of professional bodies. Members of the technical panel must be familiar with the methodology of proficiency testing and be suitably qualified. It is desirable that only a minority of members have commercial interest in the outcome of the scheme.The manager must conduct the scheme in such a way that privileged information is not divulged to members of the technical panel. Information that should be so restricted includes: (a) the identities of the participating laboratories; and ( b ) the exact composition of samples distributed to participants in advance of the reporting deadline. Where the technical panel needs to review individual results, laboratories must be identified only by a code number.ANALYST, JANUARY 1992. VOL. 117 99 2.1. Stages of a Proficiency Test Proficiency tests are organized in a sequence of clearly defined stages. ( i ) The organizing body lays down a protocol for the conduct of the tests, the interpretation of the data and any sub- sequent intervention.(ii) The protocol is circulated to intending participants. (iii) The organizers prepare and validate the test materials. Then, for each round of the test: (iv) The materials are distributed to the participating labora- tories in accordance with the protocol. ( v ) The laboratories analyse the materials by appropriate methods and return the data by the prescribed date. ( v i ) The data are analysed by the specified statistical methods. (vii) Each participant is in- formed of the outcome of the statistical analysis. (viii) The organizing body takes any action required by the protocol. (ix) The organizing body reviews its effectiveness and future strategy in the light of the results and comments from the participants. 2.2. Protocol The protocol is the definitive statement of the aims of a proficiency test and the steps taken in its execution.The protocol must be sufficiently detailed to allow no alternative interpretations. Statistical methods to be used must be specified exactly so that values of the calculated statistics from a data set can be reproduced exactly. Criteria for decisions must be stated exactly, together with the outcome of the decisions. Laboratories must be fully aware of the protocol, its aims and consequences, before they participate in the scheme. Provision must be made for participants to be briefed on the protocol initially and for the feedback of views during the operation of the scheme. An outline specimen protocol illustrating the requirements for an imaginary situation is given in Appendix 1.This is not intended as a model protocol for general use. 2.3. Preparation and Validation of Materials 2.3. I . Choice and preparation of materials The prime consideration in the choice of material is that it should be as far as possible representative of the type of material that is normally analysed, in respect of composition of the matrix and the concentration range or loading of the analyte. This is most easily accomplished with some manufac- tured materials (such as steels for example), where a range of analyte concentrations in appropriate matrices can be readily obtained. Stability of material between preparation and analysis must be ensured. Natural materials (e.g., flour) can usually be obtained in large bulk. However, a difficulty is liable to arise with natural materials in that they are easily obtainable at ‘normal’ concentrations of analyte, but much more difficult to obtain at elevated levcls.I t is often the latter situation that is the focus of attention of analytical methods. Where no satisfactory alternative exists, natural materials can be fortified by spiking with analyte. Fortification is relatively easy for some materials (for example, trace metals in water) but much more difficult to execute satisfactorily for others (trace additives in animal feedingstuffs) where the achicvement of homogeneity is a problem. Some limitations of spiking are discussed subsequently (Section 3.1.). Spiking is a valuable method where the analytical measure under consideration is the amount of analyte rather than its concentration.This is particularly true when the spike can be added to an inert and analyte-free matrix such as a filter. Certified reference materials will usually not be suitable for use in proficiency tests. 2.3.2. Quality of test material Materials need to be tested before distribution for mean level of analyte and for homogeniety. The mean level determina- tion is merely a check that the material is appropriate for the needs of the proficiency test and is distinct from the establishment of the true value. However, the assumption of effective homogeneity underlies all interptetation of test data and so must be established for each separate batch of test material. These tests are most effectively carried out in a single competent laboratory.The experimental design for such a test is a replicated randomized trial. After a bulk material is subdivided for distribution, a random selection of 10-20 of the containers should be taken and the contents of each subjected to replicate analyses. This enables the between-sample variance to be estimated by analysis of variance. This variance ideally should be small in comparison with the magnitude of the target variance of reproducibility used in the subsequent proficiency test (Section 3.2.). After validation, the materials should be stored and distributed under conditions that minimize the effects of any instability of the sample. 2.4. Distribution of Samples There is no experimentally established optimum frequency for the distribution of samples. Informed opinion is that the minimum frequency should be four rounds per year.Tests that were less frequent would probably be ineffective in reinforcing the perceived need for maintaining quality standards or for following up marginally poor performance. A frequency of one round per month for any particular type of analysis is the maximum that is likely to be effective. Postal circulation of samples and results would impose an absolute minimum of about 2 weeks for a round to be completed and it seems unlikely that a laboratory would have time to respond to the results of one round if another followed within a 2 week period. Over-frequent rounds might have the counter-produc- tive effect of discouraging laboratories from conducting independent routine quality control. If the organizers have at their disposal just one large batch of a particular test material, the participants will become aware of the consensus value after the first round and the credibility of the results in successive rounds would be compromised. Therefore, the organizers should procure several batches of nominally similar materials, for example from different suppliers, and with small differences in the analyte level.These could be distributed in a random manner, so that the participants would have no advance information of the true concentration of the analyte. An extension of this idea would render very difficult any possible collusion between laboratories within a single round of the test. If laboratories were to receive either of two similar test materials, selected at random by the organizing body, they would have no logical basis for adjusting their results, because they would not know whether they have samples from a common source or not.The amount of material distributed to each laboratory must be sufficient for normal analytical practice. 2.5. Collection and Analysis of Data A detailed consideration of the statistical treatment of data is deferred until Section 3 of this paper. However, some preliminary considerations are recorded here. It is assumed that the data for statistical analysis are on a quasi-continuous scale, i.e., that the digital resolution of the data is at least one order of magnitude smaller than the inherent variability of the measurements. Hence in this paper range-data, such as might be obtained by visual comparison, are not considered.It is the responsibility of the organizers to instruct the participants how to report the data by the provision of results sheets. It is considered that attempts to measure repeatability in proficiency tests are superfluous. Repeatability could be100 ANALYST, JANUARY 1992, VOL. 117 monitored by duplication within a laboratory, but the infor- mation gained would be suspect unless the duplication were blind and the pairing not obvious from the analytical results. This would require extra effort on the part of the laboratories and organizers, effort that might be better spent on a wider variety of analyses. Moreover, numerous trials have shown that repeatability is usually small compared with variation between laboratories.Even laboratories reporting wildly inaccurate results can usually get their blind duplicates to agree satisfactorily. Finally, it would be virtually impossible to prevent laboratories reporting the means of many individual results in an attempt to improve their repeatability. Replica- tion is therefore not recommended in the general situation, but could be allowed if particular circumstances suggest it. 2.6. Feedback to Participants Participants need to be informed of the outcome of a round of the trial as soon as possible after the closing date for the reporting of results. They need to have information on their Performance in relation to performance targets and on the general performance of all other laboratories. This should be presented in the form of a pre-defined common scoring system that can be applied to any type of analysis and in the form of readily understandable graphical output.An output should show the participant’s raw data as originally entered into a computer system by the organizers, so that the participant can check for transcription errors in data entry and, if necessary, ask for a revised assessment. Participants must be informed of the method used to estimate the true value. An example output that might be sent to a participant is shown in Appendix 2. 3. Approaches to Data Analysis in Proficiency Testing 3.1. Estimates of True Value The first stage in producing a score from a result x (a single measurement of analyte concentration in a test material) is obtaining the estimate of the bias, thus: bias = x - X where X is the true concentration or amount of analyte.The efficacy of any proficiency test depends on using a reliable value for X . Severa! methods are available for establishing a working estimate (X) of X for natural or artificial materials. (i) The addition of a known amount or concentration of analyte to a base material containing none. This method is completely satisfactory in many instances, especially when it is the amount of analyte rather than concentration that is subject to testing. However, problems arise in other situations, namely: (a) it is necessary that the base material is in fact effectively free from analyte; ( b ) it may be difficult to mix the analyte homogeneously into the base material where this is required; and ( c ) the speciation of the analyte added may be different to that found in actual test materials where the analyte may be chemically bound to the matrix.Hence the use of a material containing the analyte in its natural (or normally occurring) form is preferred where this is possible. (ii) The use of a consensus value produced by a group of expert or referee laboratories using best possible methods. This is probably the closest approach to true values for representative materials under practical circumstances. There are obvious reasons for using such a value if it is available. There are also arguments against using it, namely: ( a ) it may be expensive to execute; and (b) there might be lingering doubts about the validity of the consensus value, especially among the participants.(iii) The use of a consensus value, produced in each round of the proficiency test, and based on the results obtained by the participants. The consensus is usually estimated as the mean of the observations remaining after outliers have been detected and eliminated, but other possible estimators include the robust mean and the modal value. The consensus of partici- pants is clearly the cheapest estimator to obtain. Objections that can be levelled against such a value are: ( a ) there may not be a real consensus among the participants; and ( b ) the consensus may be biased because of the general use of faulty methodology. Neither of these conditions is rare in the determination of trace constituents. The choice between these methods of evaluating &depends on circumstances.It is usually advisable to have one other estimate in addition to the consensus of participants. Any significant deviations observed between the estimates must be carefully considered by the technical panel. The choice between a consensus either from expert labora- tories or from the participants depends, in part, on whether the aim of the proficiency test is to encourage the production of true results or merely to obtain conformity among the participants. In spite of the extra cost, it is felt that considerably more attention should be paid to trueness than has been hitherto. In an empirical method, e . g . , the determination of ‘fat’, the true result (within the limits of measurement uncertainty) is produced by a correct execution of the method.Empirical methods are used when the analyte is ill-defined chemically. It is clear that in these circumstances the analyte content is only defined if the method is simultaneously specified. Empirical methods can give rise to special problems in proticiency trials when a choice of such methods is available. If X is obtained from expert laboratories and the participants use a different empirical method, a bias may be apparent in the results even when no fault in execution is present. Likewise, if participants are free to choose between empirical methods, no valid consensus may be evident among them. Several recourses ?re available to overcome this problem: (i) a separate value of Xis produced for each empirical method used; (ii) participants are instructed to use a prescribed method; or (iii) participants are warned that a bias may be the result of using a different empirical method.3.2. Formation of a z-Score Most proficiency testing schemes proceed by comparing the estimate of the bias with a standard error. An obvious approach is to form the z-score given by z = (x - */o where CJ is a standard deviation. The value of o could be chosen either as an estimate of the actual variation encoun- tered in a particular round ( 5 ) of a trial or a target representing the maximum allowed variation consistent with valid data. In the former situation, ( S ) should be estimated from the results of the laboratories after outlier elimination, or by robust methods,3 for each analyte/material/round combina- tion. A value of j: will therefore vary from round to round (hopefully steadily decreasing). In consequence, the z-score for a laboratory could not be compared directly from round to round.However, the bias ( x - X ) for a single analyte/material combination could be usefully compared round by round for a laboratory and the corresponding value of S would indicate general improvement in ‘reproducibility’ round by round. A fixed target value for o is greatly preferable, however, and can be arrived at in several ways. (i) o could be fixed ar- bitrarily, with a value based on a perception of how laboratories should perform. The problem with this criterion is that perceptions change with time, and laboratory perfor- mance may improve with advances in analytical technology. The value of o may therefore need to be changed occasionally, disturbing the continuity of the scoring scheme.However, there is some evidence that laboratory performance responds favourably to a stepwise increase in performance standards. (ii) o could be an estimate of the precision required for a specific task of data interpretation. This is the most satisfac-ANALYST, JANUARY 1992, VOL. 117 101 tory type of criterion, it if can be formulated, because it relates directly to the required information content of the data. (iii) Where a standard method is prescribed for the analysis, CY could be equated with oR, the standard deviation of reproduci- bility obtained during a collaborative trial. (iv) o could be derived from a model of precision, such as the Horwitz curve.4 However, although this model provides a general picture of reproducibility, substantial deviation from it may be experi- enced for particular methods.It should be used only with considerable caution for the present purposes, if no other information is available. A fixed value for o has the advantage that the z-scores derived from it can be compared from round to round to demonstrate general trends for a laboratory. 3.3. Interpretation of z-Scores If 2 and CI are good estimates of the population mean and standard deviation (or are known to be true), then z will be approximately normally distributed with a mean of zero and a unit standard deviation. Analytical results can be described as ‘well behaved’ when they comply with this condition. An absolute value of z (lzl) greater than three suggests poor performance in terms of accuracy.This judgement depends on the assumption of the normal distribution, which, outliers apart, seems to be justified in practice. Because z is standardized, it is comparable for all analytes, test materials and analytical methods. Because of this com- parability, values of z obtained from diverse materials and concentration ranges can, with due caution (see below), be combined to give a composite score for a laboratory in one round of a proficiency test. Moreover, the meaning of z-scores can be immediately appreciated, i.e., values of lz1<1 would be very common and values of lz1>3 would be very rare in well behaved systems. 3.4. Alternative Score An alternative type of scoring, which here is called Q-scoring, is based not on the standardized value but on the relative bias, namely Q = ( x - ?)/A where x and 2 have their previous meaning.This type of score is used when the participants in a proficiency test have diverse standards of performance and there is no basis for a commcy value of o. Q is centred on zero with a standard error of S/X. Whereas relative bias is an obvious measure, its statistical significance depends on the value of S/X. Methods suitable for trace amounts of analyte are likely to show much larger standard errors than are the more precise methods for major constituents. Therefore, values of Q from different sources may not be comparable or capable of valid combination unless the assumption that the SIX values are comparable can be justified.This would be a reasonable assumption for a single analyte/material/method combination where the range of analyte concentrations in the different materials fell above about 20 times the system detection limit for the analyte.5 In favourable situations the assumption could be extended to include several analytes determined by a common method. Where it is possible, the use of z-scores is recommended in preference to the use of @scores. 3.5. Combination of Several z-Scores I t is common for several different analyses to be required within each round of a proficiency test. Although each individual test furnishes useful information, many participants want a single figure of merit that will summarize the over-all performance of the laboratory within a round.This approach may be appropriate for the assessment of long-term trends. However, there is a danger that such a combination score will be misinterpreted by non-experts, especially outside the context of the individual scores. Therefore, the general use of combination scores is not recommended, but it is recognized that they may have specific applications if used with due caution. It is especially emphasized that there are limitations and weaknesses in any scheme that combines z-scores from dissimilar analytical methods. If a single score out of several produced by a laboratory were significant, the combined score may well be not significant. In some respects this is a useful feature, in that an occasional lapse in a single method is downweighted in the combined score.However, there is a danger that a laboratory may be consistently at fault only in a particular method and frequently report an unacceptable value for that method in successive rounds of the trial. This factor may well be obscured by the combination of scores. Of the various methods used to combine z-scores, the following are statistically well-founded and can be used within the limitations discussed above. (i) The sum of scores, SZ = X z . (ii) The sum of squared scores, SSZ = 2 ~ 2 . (iii) The sum of absolute values of the scores, SAZ = ClzI. These statistics fall into two classes. The first class (contain- ing only SZ) uses information about the signs of the z-scores, whereas the alternative class (SSZ and SAZ) provides information about only the size of scores, i.e., the magnitude of biases.Of the latter, the sum of the squares is more tractable mathematically and is therefore the preferred statistic although it is rather sensitive to single outliers. The SAZ method may be especially useful if there are extreme outliers or many outlying laboratories, but its distribution is complicated and its use is not, therefore, recommended. 3.5.1. Sum of scores, SZ The distribution of SZ is zero-centred with variance m, where m is the number of scores being combined. Hence SZ could not be interpreted on the same scale as the z-scores. However, a simple scaling restores the unit variance, giving a rescaled sum of scores RSZ = Zz/v%z, which harmonizes the scaling, i . e . , both z and RSZ can be interpreted as standard normal deviates.The SZ and RSZ methods have the advantage of using the information in the signs of the biases. Hence if a set of z-scores were (1.5, 1.5, 1.5, 1.5), the individual results would be regarded as non-significant positive scores. However, re- garded as a group, the joint probability of observing four such deviations together would be small. This is reflected in the RSZ value of 3.0, which indicates a significant event. This information would be useful in detecting a small consistent bias in an analytical system, but would not be useful in combining results from several different systems, where a consistent bias would not be expected and is unlikely to be meaningful. Another feature of the RSZ is the tendency for errors of opposite sign to cancel.In a well-behaved situation (i.e., when the laboratory is performing without bias according to the designated 0 value) this causes no problems. If the laboratory were producing badly behaved results, however, the possibil- ity arises of the fortuitous cancellation of significantly large z-values. Such an occurrence would be very rare by chance. These restrictions on the use of RSZ serve to emphasize the problems of using combination scores derived from various analytical tests. When such a score is used, it should be considered simultaneously with the individual scores. 3.5.2. Sum of squared scores, SSZ This combination score has a chi-squared (~2) distribution with m degrees of freedom for well-behaved results. Hence there is no simple possibility for interpreting the score on a common scale with the z-scores.However, the quantiles of the102 ANALYST, JANUARY 1992, VOL. 117 x 2 distribution can be found in most compilations of statistical tables. The SSZ method takes no account of the signs of the z-values, because of the squared terms. Hence, in the example considered previously, where the z-scores are (1.5, 1.5, 1.5, 1 S ) , it is found that SSZ = 9.0, a value that is not significant at the 5% level and does not draw sufficient attention to the unusual nature of the results as a group. However, in proficiency tests, concern is directed much more towards the magnitude of deviations than their direction, hence SSZ seems appropriate for this use. Moreoever, the problem of chance cancellation of significant z-scores of opposite sign is elimi- nated.Hence the SSZ has advantages as a combination score for diverse analytical tests and is to an extent complementary to RSZ. 3.6. Running Scores Although the combination scores discussed above give a numerical account of the performance of a laboratory in a single round of the proficiency test, for some purposes it may be useful to have a more general indicator of the performance of a laboratory. Although the value of such indicators is questionable they can be constructed simply and give a kind of average impression of the scores over several rounds of the test. For example, a running SSZ covering the current (nth) round and the previous k rounds could be constructed as follows: where zij is the z-score for the ith material in the jth round. In a well-behaved system, RSSZ would have the distribution xzrn(k + 1 1 , which could be used to set action limits on the experimental values.The running score has the alleged advantage that instances of poor performance restricted to one round are smoothed out somewhat, allowing an over-all appraisal of performance. On the other hand, an isolated serious deviation will have a ‘memory effect’ in a simple running score that will persist until ( k + 1) more rounds of the trial have passed. This might have the effect of causing a laboratory persistently to fail a test on the basis of the running score, long after the problem has been rectified. Two strategies for avoiding undue emphasis on an isolated bad round can be formulated. Firstly, individual or combined scores can be restrained within certain limits.For example, a rule such as: if IzI > 3 then z’ = +3 could be applied, the sign being the same as that of z , where z is the raw value of a z-score and the modified value z’ is limited to the range k3. The actual limit used could be set in such a way that an isolated event does not raise the running score above a critical decision level for an otherwise well-behaved system. As a second strategy for avoiding memory effects, the scores could be ‘filtered’ so that results from rounds further in the past would have a smaller effect on the running score. For example, exponential smoothing uses: m calculated by 2, = (1 - a)zn + air, - 1 where a is a parameter between 0 and 1, controlling the degree of smoothing.3.7. Classification, Ranking and Other Assessment of Pro- ficiency Data 3.7.1. Classification If the frequency distribution of a proficiency score is known or can be assumed, significance can be attributed to results according to the quantiles of that distribution. For example, in a well-behaved analytical system, z-scores or values of RSZ would be expected to fall outside the range -2 < z < 2 only in about 5% of instances and outside the range -3 < z < 3 only in about 0.3%. In the latter situation the probability could be interpreted as so small for a ‘well-behaved’ system that it almost certainly represents badly behaved results. Hence a classification based on z-scores could be made: IZJ d 2 Satisfactory 2 < I z 1 < 3 l z 1 2 3 Unsatisfactory The same classification could be applied to scores such as SSZ and RSSZ that have x 2 distributions (Appendix 3).Care is required in practice because our knowledge of the relevant probabilities rests pn two questionable assumptions: (i) that appropriate values X and o are being used; and (ii) that the underlying distribution of analytical errors is normal, apart from outliers. In addition, the division of a continuous measure into a few named classes has little to commend it from the scientific point of view. Questionable 3.7.2. Ranking Laboratories participating in a round of a proficiency trial can be ranked on their combined score for the round or on a running score. Such a ranked list could be used for encourag- ing better performance in poorly ranked laboratories by providing an invidious comparison among the participants.However, ranking is not recommended as it is an inefficient use of the information available. A histogram is a more effective method of presenting the same data. 4. Recommendations 4.1. Proficiency tests make an important contribution to the accuracy of analytical data and should therefore be im- plemented wherever it is appropriate and technically feasible. Proficiency tests must be conducted by a properly constituted organizing body, advised by a technical panel, according to a written protocol. The protocol prescribes the conduct of the test and the consequences of participation and must provide for adequate feedback of information to the participants. 4.2. Proficiency tests must be designed to provide informa- tion on the performance of a laboratory in relation to that of other laboratories; in relation to prescribed standards of performance; and in relation to its own past performance. In addition, proficiency tests must provide information on changes in the level of performance of individual laboratories or groups of laboratories.Emphasis should rest on trueness as the main requirement in analysis rather than simple consis- tency amongst laboratories. 4.3. Proficiency tests should be conducted not less than quarterly. 4.4. The agreement and general use of a harmonized scoring system for the appraisal of the results of proficiency tests is an important target for the immediate future. To this end, the scores used must be standard statistics in their basic form, without arbitrary scaling factors. The z-score is recommended as the basic score for proficiency tests.4.5. Care must be taken in the selection and interpretation of combination scores. Where applicable, the combination scores and running scores described in sections 3.5 and 3.6 should be used. 4.6. The use of alternative batches of materials is recom- mended as a precaution against the reporting of falsified data.ANALYST, JANUARY 1992, VOL. 117 103 4.7. Proficiency testing schemes have inherent limitations and their findings need to be considered alongside wider evidence for decisions relating to licensing and accreditation. APPENDIX 1 Example of an Outline Protocol for a Proficiency Test This is intended to be an example of a hypothetical scheme: numerical details have been specified for the purpose of illustration only.Real schemes will have to take account of factors specific to their area. 1. Name of the Scheme The scheme will be called FLPTS (Food Laboratory Pro- ficiency Testing Scheme). 2. Distribution of Materials and Return of Results There will be four distributions of materials per year, dispatched by post on the Monday of the first full working week of January, April, July and October. Results must reach the, organizers by the last day of the respective month. A statistical analysis of the results will be dispatched to partici- pants within 2 weeks of the closing dates. 3. Analyses Required The four analyses required in each round will be: ( i ) aflatoxin in peanut butter; (ii) lead in milk powder; (iii) fat in a dried meat product; and (iv) Kjeldahl nitrogen in a cereal product.4. Methods of Analysis Fat shall be determined by BS4401: Part 4 (1970): Method B. No particular methods are prescribed for the other analytes, but they should be the methods used in routine analysis. Participants must provide an outline of the method actually used or give a reference to a documented method. Participants must report a single result, in the same form as provided for a client. 5. Number of Batches of Material The organizers will employ several similar batches of each material simultaneously, so that: (i) within a round, labora- tories do not all receive samples from the same batch; and (ii) a laboratory does not, except by chance, receive samples from the same batch in successive rounds.6. Assignment of Reference Values Estimates of true analyte concentration 8will be arrived at for each batch of material as the robust mean (see below) of the results of six expert laboratories. Reference values for the standard deviation of reproducibility (a) will be derived as follows: ( i ) a1 = 1 + 0.381 pg kg-1 (ii) (52 = 0.2 +A0.0582 pg g-1 (iii) 03 = 0.04X2 % m/m ( Z V ) 04 = 0.015X4 % m/m 7. Statistical Analysis in the nth Round of the Trial 7. I . Robust means and standard deviations For each of the materials calculate: x* = 3 / 0 2 t = v%(/((x" - XI)/$ where f and 9 are the appropriate robust means and standard deviations, respectively, calculated by the method recom- mended by the Analytical Methods Committee, X and o are the reference values defined in Section 6 above and L is the total number of laboratories returning results.The organizers will compare the values of x* ?nd t with reference distributions to check that the values of X and o are sensible. 7.2. Z-Scores Each individual result ( x ) is standardized by conversion into a z-score thus: z = ( x - */a 7.3. Sum of squared z-scores (SSZ) For each laboratory, the z-scores for the round are combined to give an over-all score for the round: ssz = zz2 This score will be used only for the purpose of compiling long-term trends. 7.4. Rescaled sum of z-scores (RSZ) For each laboratory, the z-score for an individual type of material is combined with the corresponding values for the previous three rounds to give a rescaled running score for that material. Hence RSZ = Z z / a 8. Decision Limits Remedial action will be recommended when any of the z-scores or RSZ fall outside the range -3 to 3. APPENDIX 2 Example Output That Might be Sent to a Participant Laboratory FOOD LABORATORY PROFICIENCY TESTING SCHEME ROUND NO. 14 JANUARY 1991 LABORATORY NO. 31 REPORTED ASSIGNED ASSIGNED ANALYTE RESULT VALUE SIGMA 2-SCORE RSZ AFLATOXIN (TOT) 10.7 14.4 5.32 -0.70 -2.14 (PPB) LEAD (PPM) 0.0 0.41 0.22 - 1.86 0.03 FAT (% M/M) 9.78 9.50 0.38 0.74 0.88 NITROGEN (% M/M) 2.61 2.55 0.038 1.57 1.30 SSZ FOR ROUND 6.96104 ANALYST, JANUARY 1992, VOL. 117 ~ FLPTSROUNDNO 14 ' JANUARY 1991 AFLATOXIN Z-SCORES LABORATORY NO 31 = X LOWER LIMIT FLPTS ROUND NO 14 JANUARY 1991 FAT Z-SCORES LABORATORY NO LOWER LIMIT 31 = X FLPTS ROUND NO 14 JANUARY 1991 LEAD Z-SCORES LABORATORY NO LOWER LIMIT 31 = X APPENDIX 3 Points of the 22 Distribution Values of the critical point for scores resulting from combining n z-scores. A combined score is satisfactory if its magnitude is less than A, questionable between A and B, and unsatisfactory over B. The values are upper 4.55% and 0.27% points of the x 2 distribution corresponding to two-sided Z values of 2 and 3" n 2 3 4 5 6 7 8 9 10 A 6.18 8.02 9.72 11.31 12.85 14.34 15.79 17.21 18.61 B 11.83 14.16 16.25 18.21 20.06 21.85 23.57 25.26 26.90 n 11 12 13 14 15 16 17 18 19 20 A 19.99 21.35 22.70 24.03 25.35 26.66 27.96 29.25 30.53 31.80 B 28.5 1 30.10 31.66 33.20 34.71 36.22 37.70 39.17 40.63 42.08 References 1 IS0 Guide 43-1984 (E), Development and Operation of Labor-a- tory Proficiency Testing. ISO, 1984. 2 Proceedings of the Third International Symposium on the Har-monisarion of Quufiry Assurance Systems in Chemical Analysis. Washington, DC, 1989 (ISO/REMCO 184). Analytical Methods Committee. Anulysr 1989. 114, 1693. Boyer, K. W.. Horwitz. W.. and Albert. R., Anal. Cliem.. 1985, 57, 454. Analytical Methods Committee. Analyst 1987. 112. 199. 3 4 5 Paper /I045160 Received August 29, 1991 * The values were calculated by Professor B. D. Ripley

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DOI:10.1039/AN9921700097

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年代:1992

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ANALYST. JANUARY 1992, VOL. 117 105 Subcellular Biochemistry. Volume 16. lntracellular Trans- fer of Lipid Molecules Edited by H. J. Hilderson. Pp. xix + 412. Plenum Press. 1990. Price $89.50. ISBN 0-306-43443-1. Lipid molecules form a variety of structures in aqueous media, collectively termed lyotropic mesophases, but the concentra- tion of single lipid molecules in equilibrium with mesophases is extremely small (-10-1°-10-13 mol dm-3)). Thus the move- ment of lipid molecules from the point of biosynthesis (mainly the endoplasmic reticulum and Golgi apparatus) to their destination in the cell requires both a sorting mechanism and a transport mechanism, which are specific for each type of lipid. This ‘trafficking’ of lipids in the cell is a major problem in cell biology and it is now believed that the process is most probably protein mediated. The purpose of this volume is to present an up-to-date account of the field of lipid transfer proteins, their specificity, characterization, function and general application in the field of membrane studies.The 12 chapters cover the protein-mediated transfer of phospholipids, glycolipids, fatty acids, dolichol, sterols and retinoids in a range of cellular systems. The introductory chapter (Spener and Mukherjea) is a useful, concise overview of the subject matter, which is treated in more detail by the individual specialists in subsequent chapters. The book is not only for the cell biologist or biochemist interested in lipid movement and compartmentation; there is much here of interest to membranologists in general.Specifically, the chapters dealing with fluorescent phospholipid analogues (Somerharju, van Paridon and Wirtz), the use of phospholipid transfer proteins to probe the structure of membranes (Crain) and the spontaneous transfer of lipids between membranes (Brown) should have a general appeal to all interested in membrane phenomena. Whereas the chapter on phospha- tidylinositol (Helmkamp) covers not only the transfer proteins but also aspects of membrane organization, metabolism and turnover. The book is well balanced, although perhaps it would have been useful to see a short chapter dealing with the fundamental principles of ligand binding, e . g . , the measure- ment of lipid binding and the kinetic and thermodynamic aspects. The chapter on fatty acid binding proteins (Paulussen and Veerkamp) is partially absolved in this respect and presents a comprehensive table of affinity constants for different ligands.As the editor points out, although there is an increasing body of information on protein-mediated lipid transfer in vitro the function of transfer proteins in vivo is not yet clearly defined. However, this volume represents a significant step forward, in that it collects together a very substantial body of knowledge on transfer proteins in a clear and coherent manner. The volume is well produced, well referenced and has a good index; it should become a standard reference work on the topic for some time to come. Malcolm N . Jones Radionuclide X-ray Fluorescence Analysis with Environ- mental Applications J.Tolgyessy, E. Havranek and E. Dejmkova. Wilson and Wilson‘s Comprehensive Analytical Chemistry. Volume XXVI. Pp. xv + 254. Elsevier. 1990. Price $120.50; Df 1235.00. ISBN 0-444-98837-8. This book has the subheading ‘Environmental Applications’, rather as an afterthought. However, do not be misled into thinking that this aspect plays a subordinate role in defining the scope of this book. It does not! Indeed, environmental applications [by radionuclide X-ray fluorescence (XRF)] are covered in a comprehensive (and non-parochial) manner and represent an area of strength in this book. The authors are all based in universities in Bratislava, Czechoslovakia, and begin their book with a brief comparison of analytical method- ologies (9 pp.). Chapter 2 discusses in 52 pp.the physical basis of radionuclide XRF instrumentation-this is the technique in which samples are excited by a suitable radioactive source and the fluorescence X-ray spectrum is measured on an energy dispersive detector [normally Si(Li)]. However, this introduc- tion serves as a prelude to the main scope of this book: environmental applications. Sources of pollution and their interaction with the human environment are reviewed in Chapter 3 (15 pp.). Sampling procedures for air, water, soil, sludges and biological materials are covered in a comprehen- sive manner in Chapter 4 (20pp.), followed by sample preparation techniques prior to analysis in Chapter 5 (1 1 pp.). The final two chapters (1 19 pp.) then review the application of radionuclide XRF to the analysis of almost every category of environmental sample imaginable, the more obvious applica- tions (air, water, soil and sediment) being complemented by more exotic examples, including welding fumes, fuel, hair, teeth (including a photograph of a child undergoing a direct dental measurement!), space research and archaeology. Each chapter includes tabulated data, where appropriate, and a large number of clear line diagrams, including spectral scans. The text is fully referenced, amounting to some 589 entries, a significant proportion of which originate from the 1970s. For an analytical point of view, I found most interest in the section on sampling and sample collection. However, this work clearly represents a useful and comprehensive review of modern applications in environmental analysis and can be recommended to those unfamiliar with this field. My main reservation concerns any imbalance that might have risen from limiting the applications to only radionuclide X-ray fluorescence. Phil Potts

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DOI:10.1039/AN9921700105

出版商:RSC    

年代:1992

数据来源: RSC

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106 ANALYST, JANUARY 1992, VOL. 117 ERRATUM Analytical Applications of Oxocarbons Part 3.* Specific Spectrophotometric Determination of Oxalic Acid by Dissociation of the Zirconium(iv)-Chloranilate Complex Anne-Marie Dona and Jean-FranGois Verchere Analyst, 1991, 116, 533 The authors of this paper have asked that we publish the following information as a correction to their paper. ‘Most concentrations of solutions of the analyte and interferents were incorrectly calculated, especially those used in Fig. 4. This error does not alter significantly the analytical value of the method and the conclusions. However, the reported sensitivities and the detection limit for oxalate should be corrected as follows. The detection limit is 0.23 ppm instead of 0.035 ppm. Revised values for the sensitivities are S = 87 1 g-1 (oxalic acid), 7.8 I g-1 (tartaric acid) and 1.8 I g-1 (D-gluconic acid) for [H2C] = 5 x 10-5 mol dm-3, q = 0.33, pH = 2, h = 335 nm and 1 = 1 cm. When [HzC] = 5 x 10-4 mol dm-3 and 1 = 1 mm, S = 8.4 1 g-* for oxalic acid’.

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DOI:10.1039/AN9921700106

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年代:1992

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ANALYST, JANUARY 1992, VOL. 117 CUMULATIVE AUTHOR INDEX JANUARY 1992 Analytical Methods Committee, Aydin, Hasan, 43 Boomer, Dave, 19 Bourgoin, Bernard P., 19 Cacho, Juan, 31 ChCnieux, Jean-Claude, 77 Coker, Raymond D., 67 Dinesan. Maravattickal K., 61 Edgar, Duart, 19 Evans, Don, 19 Ferreira, Vicente, 31 Gaind, Virindar S., 9 Haswell, Stephen J., 67 Hendrix, James L., 47 97 Hirayama, Kazuo, 13 Kageyama, Susumu, 13 Kalpana, G., 27 Koshy, Valsamma J., 27 Levillain, Pierre, 77 Lu, Jianmin, 35 MilosavljeviC, Emil B., 47 Momin, Saschi A., 83 Montagu, Monique, 77 Narayanaswamy, Ramaier, 83 Nawaz, Sadat, 67 Nelson, John H., 47 Nerin, Christina, 31 Nikolic, Sneiana D., 47 Norris, John D., 3 Novozamsky, Ivo, 23 Padalikar, Sudhakar V., 75 Patil, Vitthal B., 75 Peddy, Rao V. C., 27 Petit-Paly, Genevikve, 77 Plambeck, James Alan, 39 Powell, Mark J., 19 Preston, Brian, 3 Ransirimal Fernando, Angelo, Rideau, Marc, 77 Ross, Lynn M., 3 Rusterholz, Bruno, 57 Saleh, Hanaa, 87 Sanyal, Asis K., 93 39 107 Schnekenburger, J., 87 Seiler, Kurt, 57 Sevalkar, Murlidhar T., 75 Simon, Wilhelm, 57 Staden, Jacobus F.van, 51 Syed, Akheel A., 61 Taha, Ziad, 35 Temminghoff, Erwin J. M., 23 Unohara, Nobuyuki, 13 Wang, Joseph, 35 Wang, Kemin, 57 Willie, Scott, 19 Wu, Weh S., 9 Yahaya, Abdul Hamid, 43108 ANALYST, JANUARY 1992, VOL. 117 Sixth Biennial National Atomic Spectroscopy Symposium will be held at Polytechnic South West, Plymouth, UK 22-24 July I992 The symposium will provide a forum where interesting and useful applications of atomic spectros- copy can be reported and discussed.In addition to plenary, invited and submitted lectures, a particu- lar feature of the meeting will be the presentation of posters. There will also be an exhibition and a social programme for delegates and their guests. Scientific programme will include: Plenary Lecturers- M.W. Blades (Vancouver, BC, Canada) B.V. L’vov (Leningrad, USSR) J.W. McLaren (Ottawa, Ontario, Canada) K. Niemax (Dortmund, Germany) B.L. Sharp (Lmghborough, UK) Invited Lecturer- J. s. Crighton (Sunbury-on-Thames, UK) H. Falk (Kleve, Germany) S.J. Hill (Plymouth, UK) D. Littlejohn (Glasgow, UK) C. McLeod (Shefield, UK) G. Schlemmer (Uberlingen, Germany) P. Stockwell (Sevenoah, UK) J.F. Tyson (Amherst, MA, USA) J.G. Williams (Egham, UK) A.M. Ure (Glasgow, UK) This meeting is organized by the Atomic Spectroscopy Group, Analytical Division of The Royal Society of Chemistry. Further information can be obtained from the Chairman of the organizing committee: Dr S. J. Hill, Department of Environmental Sciences, Polytechnic South West, Drake Circus, Plymouth, Devon PL4 8AA, UK.

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DOI:10.1039/AN9921700107

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

ANALYST, JANUARY 1992, VOL. 117 The Analyst INSTRUCTIONS TO AUTHORS 109 The Analyst publishes original research papers on all aspects of the theory and practice of analytical chemistry, fundamental and applied, inorganic and organic, including chemical, physical, biochemical, clinical, pharmaceutical, biological, automatic and computer-based methods. Papers on new techniques and instrumentation, detectors and sensors, and new areas of application with due attention to overcoming limitations and to underlying principles are all equally welcome. All contributions are judged on the criteria of ( i ) originality and quality of scientific content and (ii) appropriateness of the length to content of new science. Thus, papers reporting results which would be routinely predicted or result from application of standard procedures or techniques are unlikely to prove acceptable in the absence of other attributes which themselves make publication desirable.Although short articles are acceptable, the Society strongly discourages fragmentation of a substantial body of work into a number of short publications. Unnecessary fragmentation will be a valid reason for rejection of manuscripts. Papers may be submitted for publication by members of The Royal Society of Chemistry or by non-members. There is no page charge for papers published in The Analyst. The following types of papers will be considered. Original research papers. Communications, which must be on an urgent matter and be of obvious scientific importance. Rapidity of publication is enhanced if diagrams are omitted, but tables and formulae can be included.Communications receive priority and are usually published within 5-8 weeks of receipt. They are intended for brief descriptions of work that has progressed to a stage at which it is likely to be valuable to workers faced with similar problems. A fuller paper may be offered subse- quently, if justified by later work. Although publication is at the discretion of the Editor, communications will be examined by at least one referee. Reviews, which must be a critical evaluation of the existing state of knowledge on a particular facet of analytical chemistry. However, original work may be included. Simple literature surveys will not be accepted for publication. It is desirable that potential review writers should contact the Editor before embarking on their work.Copyright. The whole of the literary matter (including tables, figures, diagrams and photographs) in The Analyst is Royal Society of Chemistry copyright and may not be reproduced without permission from the Society or such other owner of the copyright as may be indicated. Papers that are accepted must not be published elsewhere except by permission. Submission of a manuscript will be regarded as an undertaking that the same material is not being considered for publication by another journal in any language. US Associate Editor. Papers from North America can be submitted to Dr. J. F. Tyson, Department of Chemistry, University of Massachusetts, Amherst, MA 01003, USA. To enhance the speed of processing of manuscripts, these papers will usually be refereed in the United States or Canada.Regional Advisory Editors. For the benefit of potential contributors outside the United Kingdom and North America, a Group of Regional Advisory Editors exists. Requests for help or advice on any matter related to the preparation of papers and their submission for publication in The Analyst can be sent to the nearest member of the Group. Currently serving Regional Advisory Editors are listed in each issue of The Analyst. Manuscripts. Papers should be typewritten in double spacing on one side only of the paper. Copies of any related, relevant, unpublished material and raw data should be made available on request. Three copies of text and illustrations should be sent to the Editor, The Analyst, The Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge CB4 4WF, or directly to the US Associate Editor, and a further copy retained by the author.Administration and Publication Procedure. Receipt of a contribu- tion for consideration will be acknowledged immediately by the Editorial Office. The acknowledgement will indicate the paper reference number assigned to the contribution. Authors are particu- larly asked to quote this number on all subsequent correspondence. All papers (including conference presentations submitted for special issues) are sent simultaneously to at least two referees, whose names are not disclosed to the authors. On the basis of the referees’ reports, the Editor decides whether the paper is suitable for publication, either unchanged or after appropriate revision.This decision and relevant comments of the referees are communicated to the author. Differences of opinion are mediated by the Editor, possibly after consultation with further referees, or, in the last resort, by the Editorial Board. When rejection of a paper is recommended, the Editor informs the author, and returns the top copy of the manuscript. Authors have the right to appeal to the Editorial Board if they regard a decision to reject as unfair. Authors will receive formal notification when papers are accepted for publication. Proofs. The address to which proofs are to be sent should accompany the paper. Proofs should be carefully checked and returned immediately (by Air Mail from outside Europe).Particular attention should be paid to numerical data both in the tables and text. Reprints. Fifty reprints of each paper are supplied free on request. Additional reprints can be purchased if ordered at the time of publication. Details are sent to authors with the proofs. Notes on the Writing of Papers for The Analyst Manuscripts should be in accordance with the style and usage shown in recent copies of The Analyst. Conciseness of expression is expected: clarity is increased by adopting a logical order of presentation, with suitable paragraph or section headings. Spellings should be in accordance with the Oxford English Dictionary. To facilitate abstracting and indexing by Chemical Abstracts Service, and other abstracting organizations, it would be helpful if at least one forename could be included with each author’s family name.The corresponding author should be clearly indicated. Descriptions of new methods should be supported by experimental results showing accuracy, precision and selectivity. The recommended order of presentation is as indicated below: Title. This should be as brief as is consistent with an adequate indication of the original features of the work. The title should usually include the analyte being determined or identified, the matrix and the analytical method used. Summary. A summary of about 250 words, giving the salient features and drawing attention to the novel aspects, should be provided for all papers. It should be essentially independent of the main text and include relevant quantitative information such as detection limits, precision and accuracy data.Keywords. Up to 5 keywords or key phrases, indicating the topics of importance in the work described, should be included after the summary. Aim of investigation. A concise introductory statement of the novel features of the work and the object of the investigation with any essential historical background, followed, if neces- sary, by a brief account of preliminary experimental work with relevant references. Description of the experimental procedures. Working details must be given concisely. Analytical procedures should pre- ferably be given in the form of instructions; well known operations should not be described in detail. Suppliers of equipment and materials, and their locations, should be mentioned.ANALYST.JANUARY 1992, VOL. 117 Results and Discussion. Results are best presented in tabular or diagrammatic form (but not both for the same results), followed by an appropriate statistical evaluation, which should be in accordance with accepted practice. For example, a new procedure for multi-element determinations which produced results for which the concentrations of 8 out of 10 of the elements determined in a standard reference material were statistically indistinguishable from the certificate values should be described in those terms and not referred to as ‘excellent agreement’. This is particularly important in the summary. Any discussion should comment on the scope of the method and its validity, followed by a statement of any conclusions drawn from the work.A separate conclusions section is not encouraged but, if included, it should not simply duplicate statements in the discussion. Acknowledgements. Contributors other than co-authors, com- panies or sponsors may be acknowledged in a separate paragraph at the end of the paper. Titles may be given but not degrees. References. References should be numbered serially in the text by means of superscript figures, e.g., Foote and Delves,’ Burns et aL2 or Hirozawa,3 and collected in numerical order under ‘References’ at the end of the paper. They should be listed, with the authors’ initials, in the following form (double-spaced typing) : Yerian, T. D., Christian, G. D., and RGiiEka, J., Analyst, 1986, 111, 865. Sharp, B. L., Barnett, N. W., Burridge, J.C., Littlejohn, D., andTyson, J. F., J. Anal. At. Spectrom., 1988, 3, 133R. Committee for Analytical Methods for Residues of Pesticides and Veterinary Products in Foodstuffs and the Working Party on Pesticide Residues of the Ministry of Agriculture, Fisheries and Food, Analyst, 1985, 110, 765. Hara, H., Horvai, G., and Pungor, E., Analyst, 1988,113,1817; Anal. Abstr., 1989, 51, 6H57. Norwitz, G., and Keliher, P. N., Analyst, 1987, 112, 903 (and references cited therein). L’vov, B. V., Polzik, L. K., Romanova, N. P., and Yuzeforskii, A. I., J. Anal. At. Spectrom., in the press. O’Connor, A., Sigma, St. Louis, MO, personal communication, 1989. Appelqvist, R., Ph.D. Thesis, University of Lund, Sweden, 1987. Klinger, J. A., and Harrison, W. W., paper presented at the 1990 Winter Conference on Plasma Spectrochemistry, St.Petersburg, FL, USA, January 8th-l3th, 1990. Journal titles should be abbreviated according to the Chemical Abstracts Service Source Index (CASSI). For books, the edition (if not the first), the publisher and the place and date of publication should be given, followed by the page number. Harrison, W. W., and Donohue, D. L., in Treatise on Analytical Chemistry, eds. Kolthoff, I. M., and Winefordner, J. D., Wiley, New York, 2nd edn., 1989, pt. 1, vol. 11, ch. 3, pp. 189-235. Gutscht, C. D., Calixarenes, The Royal Society of Chemistry, Cambridge, 1989. British Pharmacopoeia 1988, HM Stationery Office, London, 1988, vol. 1, p. 140. RiiiiEka, J., and Hansen, E. H., Flow Injection Analysis, 2nd edn., Wiley, New York, 1988, pp.299-304. Moody, G. J . , and Thomas, J. D . R . , in Zon Selective Electrodes in Analytical Chemistry, ed. Freiser, H., Plenum Press, New York, 1978, ch. 4. Beauchemin, D., and Craig, J. M., in Plasma Source Mass Spectrometry. The Proceedings of the Third Surrey Conference on Plasma Source Mass Spectrometry, University of Surrey, July 16th-l9th, 1989, eds. Jarvis, K. E., Gray, A. L., Jarvis, I., and Williams, J. G., Royal Society of Chemistry, Cambridge, 1990, pp. 25-42. Official Methods of Analysis of the Association of Official Analytical Chemists, ed. Horwitz, W., Association of Official Analytical Chemists, Arlington, VA, 13th edn., 1980, sect. 20.104. Authors must, in their own interest, check the lists of references against the original papers; second-hand references are a frequent source of error.References to conference abstracts which have not been published in the open literature are not acceptable. The number of references must be kept to a minimum. Nomenclature. Current internationally recognized (IUPAC) chemical nomenclature should be used. Common trivial names may be used, but should first be defined in terms of IUPAC nomenclature. A listing of all relevant IUPAC nomenclature publications appears in the January issue. Symbols and units. The SI system of units, as recommended by IUPAC, should be followed. Their basis is the ‘Systkme Internation- ale d’UnitCs’ (SI). A detailed treatment is given in the so-called Green Book: Quantities, Units and Symbols in Physical Chemistry (Black- well Scientific Publications, Oxford, 1988 edn.).The following will be the guidelines used: (a) A metric system will always be used in preference to a ( b ) SI will be the standard usage. (c) The units used to record the definitive values of ‘critical data’ or quantitities measured to a high degree of accuracy will be SI. These units are summarized in the Appendix. non-metric one. The effect on current style of papers for The Analyst includes the following: dimensions should preferably be given in metres (m) or in millimetres (mm); temperatures should be expressed in K or “C (not OF); wavelengths should be expressed in nanometres (nm) (not mp); frequency should be expressed in Hz (or kHz, etc.), not in c/s or c.P.s.; rotational frequency can be denoted by use of s-1; in mass spectrometry, signal intensity should be expressed in counts s-1 and not in Hz; radionuclide activity will be expressed in becquerels (Bq) or curies (Ci); 1 Ci = 3.7 X 1010 Bq; the micron (p) will not be used; 10-6 m will be 1 pm.When non-SI units are used they must be adequately explained unless their definition is obvious (e.g., degree Celsius, mmHg). The derivation of derived non-SI units should be indicated. Abbreviations. Abbreviational full stops are omitted after the common contractions of metric units (e.g., ml, g, pg, mm) and other units represented by symbols. Abbreviations other than those of recognised units should be avoided in the text except after definition. Upper case letters without points should be used for abbreviations for techniques and associated terms, e.g.., HPLC, AAS, XRF, UV, NMR, SCE.Other common abbreviations and contractions require full points, e.g., eqn., m.p., Dr., except when sub- or super-script, h,,, for example. The abbreviations Me, Et, Pr”, Bun, Bui, BUS, But, Ph, Ac, Alk, Ar and Hal can be used; others should be defined. Carboxy groups are written COzR, not COOR. Substituents should be indicated by R (one) or by R1, R2, R3 . . . (more than one). Percentage concentrations of solutions should be stated in inter- nationally recognized terms. Thus the symbols ‘m’ instead of ‘w’ for mass and ‘v’ for volume are to be used. The following show the manner of expressing these percentages together with an acceptable alternative given in parentheses: % m/m (g per 100 g); % m/v (g per 100 ml); Yo v/v.Further implications of the use of the term ‘mass’ are that ‘relative atomic mass’ of an element (A,) replaces atomic weight, and ‘relative molecular mass’ of a substance (M,) replaces molecular weight. Concentrations of solutions of the common acids are often conveniently given as dilutions of the concentrated acids, such as ‘dilute hydrochloric acid (1 + 4)’, which signifies 1 volume of the concentrated acid mixed with 4 volumes of water. This avoids the ambiguity of 1 : 4, which might represent either 1 + 4 or 1 + 3. Dilutions of other solutions can be expressed in a similar manner. Molarity is generally expressed as a decimal fraction (e.g., 0.375 mol dm-3). Tables and diagrams. Table column headings should be brief. Tables consisting of only two columns can often be arrangedANALYST, JANUARY 1992, VOL.117 111 horizontally. Tables must be supplied with titles and be so set out as to be understandable without reference to the text. Either tables or graphs may be used but not both for the same set of results, unless important additional information is given by so doing. The information given by a straight-line calibration graph can usually be conveyed adequately as an equation or statement in the text. Column headings and graph axis labels should be in accord with SI conventions. Thus, the expression of numerical values of a physical quantity should be dimensionless, i.e., the quotient of the symbol for the physical quantity and the symbol for the unit used, e.g., platm, or some mathematical function of a number, e.g., Inblatm).Further examples are vlcm-l, Ucm, mass of substancelg and flow-rate/ml min-1. For units which are already dimensionless, i.e., ratios such as % or ppm, the type of ratio is indicated in parentheses, e.g., c (%) or c (ppm). The diagonal line (solidus) will not be used to represent ‘per’. In accordance with the SI system, units such as grams per millilitre are already expressed in the form g ml-I. It should be noted that the ‘combined’ unit, g ml-l, must not have any ‘intrusive’ numbers. To express concentration in grams per 100 millilitres, the word ‘per’ will still be required: Concentration/g per 100 ml. It may be preferable for an author to express concentrations in grams per litre (g I-l) rather than grams per 100 ml. Most diagrams will be retraced and lettered in order to achieve uniform line thicknesses and lettering size and style.However, all diagrams should be carefully and clearly drawn on good quality paper and should be carefully and clearly lettered. If possible, chromato- grams and spectra, complicated flow charts, circuit diagrams, etc., should be supplied as artwork for direct reproduction in order to avoid time-consuming and expensive redrawing. The clearest copy should be without lettering. Three complete sets of illustrations should be provided, two sets of which may be made by any convenient copying process for trans- mission to the referees. All diagrams should be accompanied by a separately typed set of captions. Wherever possible, extensive identifying lettering should be placed in the caption rather than on lines on graphs, etc.Photographs. Photographs can be submitted if they convey essential information that cannot be shown in any other way. They should be submitted as glossy or matt prints made to give the maximum detail. Colour photographs will be accepted only when a black-and-white photograph fails to show some vital feature and can be supplied either as prints or transparencies. Appendix The SI System of Units In the SI system there are seven base units- Physical Name Symbol quantity of unit for unit length metre m mass kilogram kg time second S electric current ampere A thermodynamic temperature kelvin K amount of substance mole mol luminous intensity candela cd There are two supplementary dimensionless units for plane angle (radian, rad) and solid angle (steradian, sr).Some derived SI units that have special names are as follows- Physical quantity energy force power electric charge electric conductance electric potential difference electric resistance electric capacitance frequency magnetic flux density radionuclide activity presssure, stress energy, work, heat inductance (magnetic induction) Name of unit joule newton watt coulomb siemens volt ohm farad hertz tesla becquerel pascal joule henry Examples of other derived SI units are- Physical quantity area volume Symbol for unit J N w C S V 52 F Hz T Pa J H Bq SI unit square metre cubic metre density kilogram per cubic metre velocity metre per second angular velocity radian per second acceleration metre per second squared magnetic field strength ampere per metre kgs-zA-l= Vsm-2 S-1 m-1 kg s-2 (= N m-2) m2kgs-2(= Nm = Pam3) m2 kg s-2 A-2 (= VA-1 s) Symbol for unit m2 m3 kg m-3 m s-1 rad s-1 m s-2 A m-1112 ANALYST, JANUARY 1992, VOL. 117 Certain units will be allowed in conjunction with the SI system, e.g. Physical quantity time plane angle volume magnetic flux density temperature, t radionuclide activity energy pressure mass (magnetic induction) Name of unit minute degree litre gauss degree Celsius curie electronvolt bar unified atomic mass unit Symbol for unit min 1 G "C Ci eV bar 0 U Definition of unit 60s (~1180) rad 10-3 m3 = dm3 10-4 T 1.6021 x 10-19 J tl°C = TIK - 273.16 3.7 x 1010Bq l o 5 Pa 1.66054 x 10-27 kg The other common units of time (e.g., hour and day) will continue to be used in appropriate contexts. Decimal multiples and submultiples have the following names and symbols (for use as prefixes)- 10-3 10-9 1 0 4 5 10-24 10-6 10-12 10-18 10-21 milli micro nano pic0 femto atto zepto yocto m CL n P f a Y Z Compound prefixes (e.g., mpm) should not be used; 10-9 m = 1 nm. The Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge CB4 4WF, UK 103 109 1015 1024 106 1012 1018 1021 kilo mega tera peta exa zetta yotta gigs k M G T P E Z Y Telephone 0223 420066; Fax 0223 423623 (Group III); E-mail RSCl @UK.AC. RL.GB (JANET)

ISSN:0003-2654    

DOI:10.1039/AN9921700109

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

ANALYST, JANUARY 1992, VOL. 117 113 IUPAC Publications on Nomenclature and Symbolism 1 .O Compilations 1.1 Nomenclature of Organic Chemistry, a 550-page hardcover volume published in 1979, available from Pergamon, Oxford. Section A: Section B: Section C: Section D: Section E: Section F: Hydrocarbons Fundamental heterocyclic systems Characteristic groups containing carbon, hy- drogen, oxygen, nitrogen, halogen, sulphur, selenium, and tellurium Organic compounds containing elements not exclusively those referred to in the title of Section C Stereochemistry General principles for the naming of natural products and related compounds Section H: Isotopically modified compounds 1.2 Nomenclature of Inorganic Chemistry, a 278-page hardcover volume published in 1990, available from Blackwell Scientific Publications, Oxford.Chapter 1: General aims, functions and methods Chapter Chapter Chapter Chapter Chapter Chapter Chapter Chapter 2: Grammar 3: Elements, atoms, and groups 4: Formulae 5: Names based on stoichiometry 6: Neutral molecular compounds 7: Names for ions, substituent 8: Oxoacids and derived anions 9: Co-ordination compounds radicals, and salts groups and Chapter 10: Boron hydrides and related compounds 1.3 Biochemical Nomenclature and Related Documents, a 220-page softcover manual published in 1978 by The Biochemical Society for IUB, and available from the Biochemical Society Book Depot, PO Box 32, Commerce Way, Colchester, Essex C 0 2 8HP. The contents are as follows: General Nomenclature of organic chemistry. Section E: Stereo- chemistry (1974) Nomenclature of organic chemistry.Section F: Natural products and related compounds (1976) Nomenclature of organic chemistry. Section H: Isotopically modified compounds (1977) Isotopically labelled compounds: common biochemical practice Recommendations for measurement and presentation of biochemical equilibrium data (1976) Abbreviations and symbols for chemical names of special interest in biological chemistry (1965) Abbreviations and symbols: a compilation (1976) Citation of bibliographic references in biochemical journals (1971) Amino acids, peptides and proteins Nomenclature of x-amino acids (1974) Symbols for amino-acid derivatives and peptides (1971) Rules for naming synthetic modifications of natural peptides (1 966) Abbreviated nomenclature of synthetic polypeptides or polymerized amino acids (197 1) A one-letter notation for amino-acid sequences (1968) Abbreviations and symbols for the description of the conformation of polypeptide chains (1969) Nomenclature of peptide hormones (1974) Recommendations for the nomenclature of human im- munoglobulins Protein data bank.A computer-based archival file for macromolecular structures (1977) Nomenclature of multiple forms of enzymes (1976) Nucleotides and nucleic acids Abbreviations and symbols for nucleic acids, polynuc- leotides and their constituents (1970) Lipids Nomenclature of lipids (1976) Nomenclature of steroids (1967) Nomenclature of quinones with isoprenoid side chains (1973) Tentative rules for the nomenclature of carotenoids (1970). Amendments (1974) Nomenclature of tocopherols and related compounds (1973) Carbohydrates, etc.Tentative rules for carbohydrate nomenclature. Part 1 (1 969) Nomenclature of cyclitols (1973) Phosphorus- con t ain ing compounds Nomenclature of phosphorus-containing compounds of biochemical importance (1976) Miscellaneous Trivial names of miscellaneous compounds of importance in biochemistry (1965) Nomenclature and symbols for folic acids and related compounds (1965) Nomenclature for vitamins B-6 and related compounds (1973) Nomenclature of corrinoids (1973) 1.4 Compendium of Analytical Nomenclature, a 280-page hardcover volume published in 1987, available from Blackwell Scientific Publications, Oxford. The contents are as follows: Presentation of the Results of Chemical Analysis Solution Thermodynamics (activity coefficients, equilibria, PW Recommendations for Terminology to be used with Precision Balances Recommendations for Nomenclature of Thermal Analysis Recommendations for Nomenclature of Titrimetric An- alysis Electrochemical Analysis Analytical Separation Processes (precipitation, liquid- liquid distribution, zone melting and fractional crystallis- ation, chromatography, ion exchange) Spectrochemical Analysis (radiation sources, general atomic emission spectroscopy, flame spectroscopy, X-ray emission spectroscopy, molecular methods) Recommendations for Nomenclature of Mass Spec- trometry Recommendations for Nomenclature of Radiochemical Methods Surface Analysis (including photoelectron spectroscopy)114 ANALYST, JANUARY 1992, VOL.117 1.5 Compendium of Macromolecular Nomenclature, a 172- page hardcover volume published in 1991, available from Blackwell Scientific Publications, Oxford. The contents are as follows: Basic Definitions of Terms Relating to Polymers Stereochemical Definitions and Notations Relating to Polymers Definitions of Terms Relating to Individual Macro- molecules, their Assemblies, and Dilute Polymer Solutions Definitions of Terms Relating to Crystalline Polymers Nomenclature of Regular Single-strand Organic Polymers Nomenclature for Regular Single-strand and Quasi-single- strand Inorganic and Coordination Polymers Source-based Nomenclature for Copolymers A Classification of Linear Single-strand Polymers Use of Abbreviations for Names of Polymeric Substances 1.6 Compendium of Chemical Terminology: IUPAC Recommendations, a 456-page volume published in 1987, available in hardcover and softcover from Blackwell Scientific Publications, Oxford.1.7 Quantities, Units, and Symbols in Physical Chemistry, a 134-page hardcover volume published in 1988, available from Blackwell Scientific Publications, Oxford. 2.0 Documents not included in the compil- ations 2.1 Nomenclature and symbolism for amino acids and peptides (Pure Appl. Chem., 1984, 56, 595; Eur. J. Biochem., 1984, 138, 9). Guide to trivial names, trade names, and synonyms for substances used in analytical chemistry (Pure Appl. Chem., 1978, 50, 339). Nomenclature of inorganic boron compounds (Pure Appl. Chem., 1972,30,681). Conformational nomenclature for five- and six-membered ring forms of monosaccharides and their derivatives (provisional) (Pure Appl.Chem., 1981, 53, 1901; Eur. J. Biochem., 1980, 111, 295). Abbreviated terminology of oligosaccharide chains (provis- ional) (Pure Appl. Chem., 1982, 54, 1517; J. Biol. Chem., 1982, 257,2347). Polysaccharide nomenclature (provisional) (Pure Appl. Chem., 1982,54, 1523; J. Biol. Chem., 1982,257, 3352). Nomenclature of unsaturated monosaccharides (provisional) (Pure Appl. Chem., 1982,54,207; Eur. J. Biochem., 1981,119, 1; errata Eur. J. Biochem., 1982,125, 1). Nomenclature of branched-chain monosaccharides (provis- ional) (Pure Appl. Chem., 1982,54, 21 1; Eur. J. Biochem., 1981, 119, 5; errata Eur. J. Biochem., 1982,125, 1). Symbols for specifying the conformation of polysaccharide chains (provisional) (Pure Appl.Chem., 1983, 55, 1269; Eur. J. Biochem., 1983,131, 5). Nomenclature for cyclic organic compounds with contiguous formal double bonds (Pure Appl. Chem., 1988,60,1395). Recommendations for the names of elements of atomic number greater than 100 (Pure Appl. Chem., 1979,51, 381). Nomenclature of Elements and Compounds 2.1.1 Amino acids and Peptides 2.1.2 Analytical Reagents 2.1.3 Boron Compounds 2.1.4 Carbohydrates 2.1.5 Delta Convention 2.1.6 Elements 2.1.7 Enzymes Enzyme Nomenclature (1984), published by Academic Press in hardcover and softcover editions. Nomenclature and symbols for folic acid and related compounds (Pure Appl. Chem., 1987,59, 833; Eur. J. Biochem., 1987,168,251). Nomenclature of glycoproteins, glycopeptides, and peptido- glycans (Pure Appl.Chem., 1988,60,1389). Revision of the extended Hantzsch-Widman system of nomenclature for heteromonocycles (Pure Appl. Chem., 1983, 55,409). Names for hydrogen atoms, ions, and groups, and for reactions involving them (Pure Appl. Chem., 1988,60, 11 15). Nomenclature of inorganic chemistry. Part 11. 1. Isotopically modified compounds (Pure Appl. Chem., 1981,53,1887). Treatment of variable valence in organic nomenclature (Pure Appl. Chem., 1984,56,769). Nomenclature of hydrides of nitrogen and derived cations, anions, and ligands (Pure Appl. Chem., 1982,54,2545). Abbreviations and symbols for the description of conformations of polynucleotide chains (provisional) (Pure Appl. Chem., 1983, 55, 1279; Eur. J. Biochem., 1983, 131,9). Extension of Rules A-1.1 and A-2.5 concerning numerical terms used in organic chemical nomenclature (Pure Appl.Chem., 1986, 58, 1693). See 1.5. Nomenclature of polyanions (Pure Appl. Chem., 1987,59,1529). Nomenclature of prenols (Pure Appl. Chem., 1987,59,683; Eur. J. Biochem., 1987,167, 181). Nomenclature of retinoids (provisional) (Pure Appl. Chem., 1983,55, 721; Eur. J. Biochem., 1982, 129, 1). Nomenclature of steroids (Pure Appl. Chem., 1989,61, 1783). Nomenclature of tetrapyrroles (Pure Appl. Chem., 1987, 59, 2.1.8 Folic Acid 2.1.9 Glycoproteins 2.1.10 Heterocyclic Compounds 2.1.1 1 Hydrogen 2.1.12 Isotopically Modified Compounds 2.1.13 Lambda Convention 2.1.14 Nitrogen Hydrides 2.1.15 Nucleotides 2.1.16 Numerical Terms 2.1.17 Polymers 2.1.18 Polyanions 2.1.19 Prenols 2.1.20 Retinoids 2.1.21 Steroids 2.1.22 Tetrapyrroles 779).2.1.23 Tocopherols Nomenclature of tocopherols and related compounds (Pure Appl. Chem., 1982,54,1507; Eur. J. Biochem., 1982,123,473). Nomenclature of Vitamin D (provisional) (Pure Appl. Chem., 1982,54, 1511; Eur. J. Biochem., 1982,124,223). Chemical nomenclature and formulation of compositions of synthetic and natural zeolites (Pure Appl. Chem., 1979, 51, 1091). 2.1.24 Vitamins 2.1.25 Zeolites 2.2 Terminology, Symbols, and Units, and Presentation of Results Glossary of terms used in physical organic chemistry (Pure Appl. Chem., 1983,55,1281). Glossary of atmospheric chemistry terms (Pure Appl. Chem., 1990,62,2 167). English-derived abbreviations for experimental techniques in 2.2.1 GeneralANALYST, JANUARY 1992, VOL.117 surface science and chemical spectroscopy (Pure Appl. Chem., 1991,63, 887). Nomenclature, symbols, units, and their usage in spectro- chemical analysis. Part VII, Molecular absorption spectroscopy, UV and visible (Pure Appl. Chem., 1988, 60, 1449). Part X, Preparation of materials for analytical atomic spectroscopy (Pure Appl. Chem., 1988,60,1461). Recommendations for publication of papers on a new analytical method based on ion exchange or ion-exchange chromato- graphy (Pure Appl. Chem., 1980,52,2555). Recommendations for presentation of data on compleximetric indicators. 1 . General (Pure Appl. Chem., 1979,51, 1357). Recommendations for publishing manuscripts on ion-selective electrodes (Pure Appl. Chem., 1981,53, 1907). Recommendations on use of the term amplification reactions (Pure Appl.Chem., 1982,54,2553). Recommendations for the usage of selective, selectivity, and related terms in analytical chemistry (Pure Appl. Chem., 1983, 55, 553). Nomenclature for automated and mechanised analysis (Pure Appl. Chem., 1989,61, 1657). Nomenclature for sampling in analytical chemistry (Pure Appl. Chem., 1990,62,1193). Physicochemical quantities and units in clinical chemistry with special emphasis on activities and activity coefficients (Pure Appl. Chem., 1984,56, 567). Quantities and units in clinical chemistry (Pure Appl. Chem., 1979,51,2451). Quantities and units in clinical chemistry: nebulizer and flame properties in flame emission and absorption spectrometry (Pure Appl. Chem., 1986,58, 1737).List of quantities in clinical chemistry (Pure Appl. Chem., 1979, 51,248 1). Proposals for the description and measurement of carry-over effects in clinical chemistry (Pure Appl. Chem., 1991,63, 301). Definitions, terminology, and symbols in colloid and surface chemistry. I (Pure Appl. Chem., 1972, 31, 577). 11, Hetero- geneous catalysis (Pure Appl. Chem., 1976, 46, 71). Part 1.14: Light scattering (provisional) (Pure Appl. Chem., 1983,55,93 1). Reporting experimental pressure-area data with film balances (Pure Appl. Chem., 1985,57,621). Reporting physisorption data for gas/solid systems with special reference to the determination of surface area and porosity (Pure Appl. Chem., 1985,57,603). Reporting data on adsorption from solution at the solid/ solution interface (Pure Appl.Chem., 1986,58,967). Manual on catalyst characterization (Pure Appl. Chem., 1991, 63, 1227). Nomenclature for transfer phenomena in electrolytic systems (Pure Appl. Chem., 198 1,53, 1827). Electrode reaction orders, transfer coefficients, and rate constants-amplification of definitions and recommendations for publication of parameters (Pure Appl. Chem., 1980,52,233). Classification and nomenclature of electroanalytical techniques (Pure Appl. Chem., 1976,45, 81). Recommendations for sign conventions and plotting of electrochemical data (Pure Appl. Chem., 1976,45, 131). Electrochemical nomenclature (Pure Appl. Chem., 1974,37,499). Recommendations on reporting electrode potentials in non-aqueous solvents (Pure Appl. Chem., 1984,56,461). Definition of pH scales, standard reference values, measurement of pH and related terminology (Pure Appl.Chem., 1985,57,53 1). Interphases in systems of conducting phases (Pure Appl. Chem., 1986,543,437). The absolute electrode potential: an explanatory note (Pure Appl. Chem., 1986,58,955). 2.2.2 Analytical 2.2.3 Clinical 2.2.4 Colloids and Surface Chemistry 2.2.5 Electrochemistry 115 Electrochemical corrosion nomenclature (Pure Appl. Chem., 1989,61, 19). Terminology in semiconductor electrochemistry and photo- electrochemical energy conversion (Pure Appl. Chem., 199 1,63, 5 69). Nomenclature, symbols, definitions and measurements for electrified interfaces in aqueous dispersions of solids (Pure Appl. Chem., 1991,63,895). Symbolism and terminology in chemical kinetics (provisional) (Pure Appl.Chem., 1981,53,753). Recommended standards for reporting photochemical data (Pure Appl. Chem., 1984,56,939). Glossary of terms used in photochemistry (Pure Appl. Chem., 1988,60, 1055). Expression of results in quantum chemistry (Pure Appl. Chem., 1978,50, 75). Nomenclature for organic chemical transformations (Pure Appl. Chem., 1989,61,725). System for symbolic representation of reaction mechanisms (Pure Appl. Chem., 1989,61,23). Detailed linear representation of reaction mechanisms (Pure Appl. Chem., 1989,61, 57). Selected definitions, terminology, and symbols for rheological properties (Pure Appl. Chem., 1979,51, 1215). Recommendations for publication of papers on methods of molecular absorption spectrophotometry in solution (Pure Appl. Chem., 1978,50, 237).Recommendations for the presentation of infrared absorption spectra in data collections. A, Condensed phases (Pure Appl. Chem., 1978,50,23 1). Definition and symbolism of molecular force constants (Pure Appl. Chem., 1978,50, 1709). Nomenclature and conventions for reporting Mossbauer spectroscopic data (Pure Appl. Chem., 1976,45, 21 1). Recommendations for the presentation of NMR data for publication in chemical journals. A, Proton spectra (Pure Appl. Chem., 1972,29,625). B, Spectra from nuclei other than protons (Pure Appl. Chem., 1976,45,217). Presentation of Raman spectra in data collections (Pure Appl. Chem., 1981,593, 1879). Names, symbols, definitions and units of quantities in optical spectroscopy (Pure Appl. Chem., 1985,57,105). A descriptive classification of the electron spectroscopies (Pure Appl. Chem., 1987,59, 1343). Presentation of molecular parameter values for IR and Raman intensity (Pure Appl. Chem., 1988,60, 1385). Recommendations for EPR/ESR nomenclature and conven- tions for presenting experimental data in publications (Pure Appl. Chem., 1989,61,2195). Nomenclature, symbols, units and their usage in spectro- chemical analysis - VIII. Nomenclature system for X-ray spectroscopy (Pure Appl. Chem., 1991,63,735). Recommendations for nomenclature and symbolism for mass spectroscopy (Pure Appl. Chem., 1991,63, 1541). A guide to procedures for the publication of thermodynamic data (Pure Appl. Chem., 1972,39, 395). Assignment and presentation of uncertainties of the numerical results of thermodynamic measurements (Pure Appl. Chem., 1981,53, 1805). Notation for states and processes; significance of the word ‘standard’ in chemical thermodynamics and remarks on commonly tabulated forms of thermodynamic functions (Pure Appl. Chem., 1982,54, 1239). 2.2.6 Kinetics 2.2.7 Photochemistry 2.2.8 Quantum Chemistry 2.2.9 React ions 2.2.10 Rheological Properties 2.2.1 1 Spectroscopy 2.2.12 Thermodynamics

ISSN:0003-2654    

DOI:10.1039/AN9921700113

出版商:RSC    

年代:1992

数据来源: RSC

摘要:

i Announcement and Call for Papers Nineteenth Annual Meeting of the Federation of Analytical Chemistry and Spectroscopy Societies September 20-25, 1992 Adams Mark Hotel, Philadelphia, Pennsylvania, USA The nineteenth annual meeting of the Federation of Analytical Chemistry and Spectroscopy Societies (FACSS) will be held at the Adams Mark Hotel. FACSS is considered by many to be the premier annual technical analytical meeting. This year's conference will provide an expanded technical program with an emphasis on emerging technologies in analytical, spectroscopic, and chromatographic sciences. The deadline for submission of your title and a preliminary 100 word brief is March 4. 1992. A title submission form appears on the next page. For information concerning the scientific program, please contact Barry Lavine, Program Chairman, Dept.of Chemistry, Clarkson University, Potsdam, NY 13676. Nominations are requested for the Tomas Hirschfeld Student Awards, which will be presented at the conference for the most outstanding papers submitted by graduate students. The student nominees will give their papers at the FACSS conference. To be considered for these awards, students must submit the title of their paper, two letters of nomination including one from their graduate advisor, any preprints/reprints, and a 250 word abstract to the FACSS National Office by March 4, 1992. Contributed papers are solicited in all areas of analytical chemistry including atomic and molecular spectroscopy, chromatography, laser spectroscopy, mass spectrometry, nuclear magnetic resonance, process analysis, computers and software, environmental analysis, and biotechnology.The scientific program will also include various award symposia. For general information please contact: Matthew Klee, General Chairman, Hewlett Packard Corp., P.O. Box 800, Avondale, PA 1931 1. For other information please contact the FACSS National Office: FACSS, P.O. Box 278, Manhattan, KS 66502 or phone (301)-846-4797.1992 FACSS Meeting Title Submission Form Preliminary 100 word brief: Please note: No Fax’s will be accepted Title Deadline: w c h 4. 1992 Topic Codes Please print clearly or type ( maximum of 3 from Topic Code List) Title: Authors: Corresponding Author Information: First Name M.I. Last Name Corn pany/University Address City State Zip Code country Phone ( ) Fax ( ) Preferred Format *: Talk [7 Poster 0 Either * Actual format may be determined by space availability and format of similar talks in your topical area.ToDic Codes; A B C D E F G H J Atomic Spectroscopy K Other Analytical Biomed /Biological /Pharmacological Analyses L Other Sessions: Chromatography L1 Fundamentals/Theory Electroanalytical L2 Applications Lasers L3 Instrumentation Mass Spectroscopy Molecular Spectroscopy Process Control/Computers/Chemometrics Solid State/Surfaces /MaterialsFederation of Analytical Chemistry and Spectroscopy Societies Nominations for the Tomas Hirschfeld Student Awards 1992 FACSS Conference September 20-25, 1992 A d a m Mark Hotel, Philadelphia, PA Nominations are requested for the Tomas Hirschfeld Student Awards, which will be presented at the nineteenth annual FACSS Conference. Awards are given for the most outstanding papers submitted by graduate students in the field of analytical chemistry. The student nominees will present 20 minute papers at the 1992 FACSS Conference. To be considered for these awards, students must submit the title of their paper, two letters of nomination, including one from their graduate advisor, any reprints/preprints and a 250 word abstract to: Diane Landoll, FACSS National Office, P.O. Box 278, Manhattan, KS 66502. The deadline for submission of all materials is March 4. 1992. The awardees' travel will be arranged and paid for by FACSS. For further information concerning the Tomas Hirschfeld Student Awards contact either of the Student Award Co-chairs: F. Monte Evens Conoco Inc. P. 0. Box 1267 Ponca City, OK 74603 Ivan L. Glaze American Cast Iron Pipe Co. P.O. Box2727 Birmingham, AL 35202 (405)-767-38% (205)-325-8979 ... 111

ISSN:0003-2654    

DOI:10.1039/AN992170000i

出版商:RSC    

年代:1992

数据来源: RSC