摘要:

252 Analyst, April, 1968, Vol. 93, pp. 262-268 Fumigant Residues in Wheat and Flour: Solvent Extraction and Gas-chromatographic Determination of Free Methyl Bromide and Ethylene Oxide BY S. G. HEUSER AND K. A. SCUDAMORE (Agvicultural Research Council, Pest Infestation Laboratory, London Road, Slough, Bucks.) Methods are described for the cold solvent extraction and analysis of traces of the fumigants methyl bromide and ethylene oxide present in flour and wheat after treatment, and for determining the efficiency of extraction, in which a combination of gas-chromatographic and chemical techniques is used. Results are given showing the loss of fumigant caused by reaction with cereal constituents before recovery, and a method for correcting this is described. Recoveries generally of 96 per cent., or more, were obtained with a lower detection limit of about 0.3 p.p.m. The application of the method to other volatile compounds is indicated. THERE is a growing awareness of the need for methods to monitor all types of pesticide residues in foods.lJ2 Most attention has naturally been given to the problem of the highly persistent insecticides, but when a substantial proportion of the national consumption of a commodity may be treated with a less persistent pesticide, for example, methyl bromide, as a fumigant for imported grain, it is important that the most minute amount of such a toxic agent should be detectable and its significance assessed.3 Ethylene oxide, which is sometimes used for flour fumigation, and methyl bromide are alkylating agents. Winteringham, Harrison, Bridges and Bridges* studied the methylation of wheat constituents, such as protein amino-acids, by methyl bromide.Ethylene oxide has been shown to produce hydroxy-ethylated derivatives of similar substances and also of celluloses and sugars in dried f r ~ i t . ~ In addition, ethylene oxide has been shown to react with inorganic chloride in foods to form ethylene chlorohydrin.6 The reaction products of methyl bromide were considered by Winteringham' not to constitute a hazard in normal dietary requirements. The extent of ethylene chlorohydrin formation by ethylene oxide in flour under normal fumigation conditions is at present being studied. These reactions and the volatility of the fumigants indicate that most of any residual methyl bromide or ethylene oxide will quickly disappear after treatment and during subse- quent processing.To show whether this disappearance reaches completion, more efficient and more sensitive methods are required than have hitherto been available.3 Classical methods have included grinding and dry aeration to remove volatile fumigant,8 steam- distillation or aeration of solvent extracts,8 and indirect determination from the difference in total bromide before and after solvent extra~tion.~ Recoveries of added fumigant have generally been low, partly because of incomplete removal from the substrate, as in dry aeration, and partly because of reaction of the added fumigant with grain constituents, either in the dry state or during recovery, for example, during steam-distillation.lO The authors obtained almost 100 per cent.recovery of ethylene chlorohydrin and ethylene dibromide from flour and wheatlo by cold extraction with a mixture of acetone and water (5 + 1 v/v), followed by direct injection of 2 to 10-pl aliquots of the supernatant liquor into a gas chromatograph. During the chromatography of such extracts from wheat flour, in which ethylene chlorohydrin had been produced in situ by reaction of naturally occurring inorganic chloride with ethylene oxide, the presence of ethylene oxide in the solvent was detected by flame ionisation as an early peak emerging from the column before acetone and water. It appeared that if precautions were taken to prevent losses by premature volatilisation from the extracts, substances more labile than ethylene dibromide and ethylene chlorohydrin should also be recovered with high efficiency. 0 SAC; A.R.C.Copyright Reserved.HEUSER AND SCUDAMORE: FUMIGANT RESIDUES IN WHEAT AND FLOUR 253 EXPERIMENTAL DETERMINATION OF PERCENTAGE RECOVERY OF KNOWN AMOUNTS OF FUMIGANT- To determine the rate of recovery by a candidate-extraction method by establishing a precisely known content of a volatile and reactive substance, such as ethylene oxide or methyl bromide, in cereals, in the form in which it would be present in practice, presents problems caused by reaction losses of the added fumigant and the difficulty of complete removal by aeration of the fraction more firmly held by sorption. Field samples received for analysis will have received some aeration in the course of normal handling. It is, therefore, necessary in experiments involving laboratory application to remove the loosely held vapour by preliminary aeration, as this might be extracted with high efficiency, whereas the more firmly held residue, which is of concern, might tend to give a lower recovery by the method under investigation. During the necessary exposure period for the application of the vapour phase and the preliminary aeration, some of the initially applied fumigant will have been lost by reaction, and with ethylene oxide, because of the complexity of the reaction products, the starting amount can no longer be fully accounted for.If now, however, a second aeration of the material is carried out, and the vapour is collected in bubblers and chemically analysed, the amount of vapour removed PZzcs that which has reacted with the material during this aeration period will represent the change in content of the free fumigant.Let the amount in milligrams of fumigant collected in bubblers per gram of material aerated be a ; the amount of fumigant, in milligrams per gram, reacted with unit weight of material during aeration be r ; the amount of fumigant, in milligrams per gram, recovered by the method under test, calculated from representative samples taken before and after aeration, be g, and g2, respectively; and the percentage recovery of fumigant by the method under test be x. Then .. .. .. 100 a + r = - (g,-gg,) * * X and hence and the percentage recovery by the candidate method can be calculated if r is known.While the measures outlined are necessary in evaluating a proposed analytical procedure, only g, is required to be found when determining residual unchanged fumigant subsequently when the percentage recovery is known. ANALYTICAL PROCEDURE EXTRACTION AND DETERMINATION OF FREE FUMIGANT (e.g., g, and g2)- About 10 g of wheat or 5 g of flour are quickly weighed and transferred into a stoppered flask containing 30 ml of a mixture of analytical-reagent grade acetone and water (5 + 1 v/v), and allowed to stand for at least 1 hour at 20" C, with occasional shaking. At suitable intervals (see Fig. l), 2-4 aliquots of the clear supernatant liquor are quickly withdrawn with a lo-$ Hamilton syringe and injected into a vaporising U-tube, as described by Heuser and Scudamore,lo for introduction into the carrier-gas stream of a gas - liquid chromatograph (Perkin-Elmer 452).Alternatively, the injection may be made directly into the injection block if it is fitted with a removable glass liner, e.g., a Perkin-Elmer F11. With these highly volatile components in solution it is advisable, before injection, to withdraw the liquid from the needle into the barrel of the syringe after filling it to the required volume. Reproducibility of peak heights from duplicate injections is generally & 1 per cent. With a 2 metre x 4-6-mm i.d. stainless-steel column containing 15 per cent. w/w poly(propy1ene glycol) ("Ucon" oil LB-550-X) on 60 to 80-mesh Chromosorb W, dry helium carrier at 80 ml per minute, flame-ionisation detector, injection U-tube or block at 125" C and column oven at 85" C, ethylene oxide is eluted at 42 seconds and methyl bromide at 45 seconds.(In the unlikely event that the two fumigants are required to be determined simultaneously, a lower column temperature would be preferable.) They are eluted as sharp peaks before the solvent peaks, giving a highly stable base-line. High amplification can thus be used, and ultimate sensitivity is about 2 x 10-log for ethylene oxide and 5 x 10-log254 HEUSER AND SCUDAMORE: FUMIGANT RESIDUES IN WHEAT AND FLOUR [Analyst, Vol. 93 for methyl bromide. About 12 minutes must be allowed to elapse for complete removal of water from the column before another sample is injected, as traces of water temporarily lower the sensitivity of the detector.Standard solutions of methyl bromide and ethylene oxide were prepared for calibration purposes by adding drops of chilled liquid fumigant to a previously weighed volume of chilled acetone - water (5 + 1 v/v) in a calibrated flask, re-weighing and making up to volume at 20" C. By using the flame detector, a linear relationship between peak height and weight was obtained in the range Dry flour added to solutions of ethylene oxide or methyl bromide of known strength in acetone - water (5 + 1 v/v) , and held in sealed flasks, did not lower the amount of fumigant determined by gas chromatography in the supernatant liquor, after allowing it to stand for periods up to 4 hours at 20°C. This shows that no adsorption of fumigant from the solvent takes place; that there is no measurable loss of volatile fumigant from the solutions into the head space; and that no reaction with cereal constituents takes place under these conditions, and hence that reaction of sorbed vapour on treated flour is halted by solvent extraction.g to g, with a standard injected volume (2 or 10 ~ 1 ) . PREPARATION OF SAMPLES FOR DETERMINATION OF g, AND g2- Known weights of ethylene oxide or methyl bromide were introduced as vapour into 250-ml cylindrical separating funnels, fitted with 2-mm bore stopcocks at each end and containing 10 to 100 g of wheat or flour, by using the method with a gas pipette, as described by Heuser.,, After allowing them to stand for a set period (Tables I and II), a preliminary aeratioqof 15 minutes' to 2 hours' duration at 100 ml per minute was carried out to remove loosely held fumigant.A small proportion of the flour or wheat was then quickly weighed out for solvent extraction of fumigant and determination of g,, as described above, and the aeration then continued for several hours, during which the fumigant removed was collected in two sintered- glass bubblers in train. For ethylene oxide, the absorbent reagent used was a 50 per cent. w/v solution of anhydrous magnesium bromide in 0.1 N sulphuric acid, and for methyl bromide a mixture of monoethanolamine and dioxan (1 + 1 v/v). Determination of the weight of ethylene oxide absorbed in the bubblers was carried out as described by Lubatti,l2 and that of methyl bromide as described by Winteringham, Bridges and Harrison.13 After the second aeration, further portions of flour or wheat were similarly analysed for their free fumigant content to evaluate g2.EVALUATION OF ?'- An estimate of the value of r in equation (2) for the second aeration period can be obtained by measuring the disappearance of free fumigant in wheat or flour, under sealed conditions. This is related to the initial fumigant content of the material under test, and it can be shown that after several hours' exposure, the rate of reaction thus measured (milli- grams per hour per gram of material) does not differ greatly from that in material that has been partially aerated after the initial exposure. This suggests that it is the more firmly adsorbed fumigant that reacts and not that which is easily removable by aeration. As the amount of reaction is small compared with the total amount of fumigant removed by aeration, little error is introduced by assuming that r is the same under both sets of conditions if the temperature remains the same for the period being considered. The amount of reaction taking place in a portion of the partially aerated material, held in a sealed flask, was, therefore, determined by extraction of total free fumigant from 6 g of flour or 10 g of grain with 30 ml of acetone - water (5 + 1 v/v), before and after allowing it to stand at constant temperature for a period equivalent to the second aeration period.The solvent was introduced into the flask through a stopcock, after rapidly cooling to reduce internal pressure to avoid loss of free vapour. The fumigant content of the extracts was determined by gas chromatography, as already described.Let the total amounts of fumigant determined per unit weight of material before and after standing be g, and g,, respectively, and the percentage recovery of fumigant by the method under test be x. Therefore y = - k 3 -g4) * * .. .. . . (3). 100TABLE I OXIDE AND METHYL BROMIDE FROM PARTIALLY AERATED FLOUR Experi- ment number 1 2 3 4 6 6 RECOVERY Initial exposure , Fumigant hours GH4O 1 16 CHsBr 16 19 66 OF FREE ETHYLENE Pre- liminary Main aeration, aeration, hours hours t 3 3 i 4 2 2 2 4 t 2 w, g 6.9 6.9 14.5 10.4 10.3 6.2 Initial dose, mg 22.6 82.3 57.0 86.6 85.2 88.3 Recovered in bubblers from w g (=awl, mg 2-87 7-97 5.05 2.16 3.26 6.00 TABLE I1 g, wJ mg 4.67 11.87 13.00 9.60 8.48 12-60 g'w, mg 1.86 4.02 7.85 7.38 4-90 7.50 gas g4 I 0.683 0.675 1.714 1.697 0.889 0.868 0.922 0.908 0-821 0.783 2-025 1.985 mg Per g mg Per g RECOVERY OF FREE METHYL BROMIDE FROM PARTIALLY AERATED WHEAT GRAINS YW, mg =p 0.09 + 0.24 0.32 =p0*18 0-40 0.25 x, per cent.96.0 95.6 95.8 94.9 97.5 97.0 M v, g2w E 24-hour gs, g, J Pre- Recovered in g1W Experi- Initial liminary Main Initial bubblers from 24-hour ment exposure, aeration, aeration, W , dose, gJ (extraction*) , (extraction*), mgper g mgper g r mg W, per X . cent. 2 M number hours hours hours g mg mi3 mg mg 7 18 2 4 60.6 135.6 3.89 7.89 3.28 0.128 0.118 0.60 103.0 % 2 4 70.3 141.1 3.86 11.53 6.89 0.167 0.166 0.76 100.5 + 4 15.1 83.1 1.35 3-75 2.29 0.244 0.235 0.14 97.8 Z U 8 9 r c: w * See Fig. 1.s256 HEUSER AND SCUDAMORE: FUMIGANT RESIDUES IN WHEAT AND FLOUR [Analyst, VOl. 93 CALCULATION OF THE VALUE OF x- weight of the same material, from equation (1)- By incorporating this value for r in the result from an aeration experiment on an aliquot L hence .. . . (6). 100 x = ,[k1--g3 - (9.--83] - * RESULTS The amounts of each fumigant recovered from W grams of white flour by aeration and by extraction, with the calculated value for r to obtain x , the percentage recovery for the extraction method, are shown in Table I. In experiments 1 , 2 and 4 the differences in value between g, and g, are within the limits of experimental error for the reproducibility of chromatogram peak heights (& 1 per cent.). Here r has been calculated as not greater than 2 per cent.of g., and hence the percentage recoveries for these experiments given in the last column of Table I are minimum values. The percentage recovery of methyl bromide from wheat grains, without grinding, by extraction for 24 hours, is shown in Table 11. With this result as a final estimate, the amounts of methyl bromide extracted into the supernatant liquor in shorter periods were calculated as a percentage of the maximum and plotted in Fig. 1 to show the rate of extraction of methyl bromide from the wheat grains. The greater part of the residual free fumigant appears in the supernatant liquor within 6 hours. Time, hours Fig. 1. Rate of extraction of methyl bromide from wheat grains by acetone - water (6 3- 1'lV) With flour, extraction of about 95 per cent.of the methyl bromide or ethylene oxide is obtained in a few minutes. DISCUSSION It could be argued that the percentage recovery by extraction might still be lower after the second aeration than before it and that equation (1) should be re-written thus- .. .. . * (6) 100 100 a + r = where x1 and x , are the percentage and after aeration and x1 is greater than x,.April, 19681 HEUSER AND SCUDAMORE: FUMIGANT RESIDUES IN WHEAT AND FLOUR 257 If equation (6) is multiplied through by x1 and re-arranged thus- each set of experimental results shown in Table I can be incorporated in equation (7), and a straight line drawn for calculated values of x1 plotted against-', the ratio of the extraction efficiencies, for values of, say, 1.3 to 0.9 (Fig. 2). X x2 Fig. 2. Values of x1 plotted as a function of xl/xz in equation (7) by using results from experiments 1 to 6 (Table I) : graph A, experiment 1; graph B, experi- ment 2; graph C, experiment 3; graph D, experiment 4; graph E, experiment 5; graph F, experiment 6 The convergence of these lines when x1 is about 1-0 indicates clearly that the results from the various experiments can be correlated to give a working value for x1 when x1 is equal to x2, and not otherwise, hence equation (1) is shown to be valid.In experiments 1 to 6, different periods of exposure were chosen to vary the proportion of reacted fumigant, and different aeration periods were used so that the remaining free fumigant was more or less firmly held by adsorption or solution, or both. Despite these variations the recovery of free fumigant appeared to be consistent.Because each percentage recovery calculation is based upon five separate analyses the variability is greater than in the single extraction subsequently required to determine the free fumigant content of a sample. Reproducibility of results from separate extractions and gas - liquid chromatographic analyses of the same material was +Z per cent. for flour and +3 per cent. for wheat grains. These results are similar to those obtained in the recovery of the more stable ethylene chlorohydrin and ethylene dibromidelO by the same method and suggest that the actual extraction of fumigant into the supernatant liquor is remarkably constant and complete. The uniformly high rate of recovery of these volatile aliphatic compounds with boiling- points ranging from 3.6O to 131.6" C, and other widely differing physical characteristics, indicates that a range of similar compounds with intermediate boiling-points should be recoverable in the same way.258 HEUSER AND SCUDAMORE The technique of controlled partial aeration described, and the accompanying calculations, may be generally applicable to the determination of the percentage recovery, by alternative methods, of other volatile substances, for which complete aeration is either tedious or impracticable. REFERENCES 1.2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. Meeting Report of the Food and Agriculture Organisation No. PL/1965/10/1 and World Health Moore, N. W., J. Appl. Ecol. (SuppZ.), 1966, 3, 261. Meeting Report of the Food and Agriculture Organisation No. PL/1965/10/2 and World Health Winteringham, F. P. W., Harrison, A., Bridges, R. G., and Bridges, P. M., J. Sci. Fd Agric., Gordon, H. T., Thornberg, W. W., and Werum, L. N., J. Agric. Fd Chem., 1959, 7 , 196. Wesley, F., Rourke, B., and Darbishire, O., Fd Res., 1965, 30, 1037. Winteringham, F. P. W., J. Sci. Fd Agric., 1966, 6, 268. Lubatti, 0. F., J. SOC. Chem. Ind., Lond., 1944, 63, 133. Shrader, S. A., Beshgetoor, A. W., and Stenger, V. H., Ind. Engng Chem. Analyt. Edn, 1942, 14, 1. Heuser, S. G., and Scudamore, K. A., Chern. 6. Ind., 1967, 1557. Heuser, S. G., J. Sci. Fd Agric., 1959, 10, 90. Lubatti, 0. F., J. SOG. Chem. Ind., Lond., 1936, 54, 424T. Winteringham, F. P. W., Bridges, R. G., and Harrison, A., J. Sci. Fd Agric., 1950, 1, 186. Organisation Food Additives/27, Rome, 1965. Organisation Food Additivesl28, Rome, 1965. 1965, 6, 251. Received July loth, 1967

ISSN:0003-2654    

DOI:10.1039/AN9689300252

出版商:RSC    

年代:1968

数据来源: RSC

摘要:

Afialyst, April, 1968, Vol. 93, $9. 259-261 259 The Determination of Quebracho in Mixtures with Some Other Tannin Extracts and Related Materials BY K. FIELD AND B. E. KENT (Mhistry of Technology, Labovatory of the Government Chemist, Cornwall House, Stamfwd Street, London, S . E. 1) A spectrophotometric method is described for the determination of The A method is quebracho in mixtures with other tannin extracts and related materials. accuracy of the method is to within a range of f l 0 per cent. also described for the identification of quebracho. IN recent years attention has been given to problems dealing with the elucidation of com- position and structure of the many complex components present in vegetable tannin materials. Much of this work has been reviewed by Haslarn.1 In the present paper emphasis is given to the identification and determination of a particular vegetable tannin extract in the presence of other tannin extracts and related materials.This work was undertaken in connection with a proposed extension of a drawback scheme at present in operation for the payment of draw- back on soluble quebracho made from the insoluble and duty paid imported variety. Under the proposed provisions of the scheme it is necessary to be able to identify and determine the amount of quebracho in admixture with other tannin materials of vegetable origin, e.g., mimosa, myrobalan and mangrove, with other tanning agents, sulphite cellulose and sulphite lye, and with other added materials, such as lignite and Vandyke brown. Vegetable tannins can be divided into two categories, namely the “condensed” or “catechol” type and the “hydrolysable” or “pyrogallol” type.Sohn2.S has shown that these two general classes of vegetable tannin extracts can be distinguished by their ultraviolet absorption spectra. White* has shown that an ultraviolet-absorption technique can be adapted to permit the determination of any one vegetable tannin extract in a limited range of binary blends of the materials, provided that certain conditions are observed. One condition is that the identities of the components of a blend are known and another is that at a specified wavelength sufficient difference exists between the absorption of solutions of the separate components when prepared under identical conditions. White415 established the identity of the components by a paper-chromatographic technique.Maranville and Goldschmidts used a differential ultraviolet-absorption technique for the determination of the phenolic hydroxyl content of lignin preparations in which the absorption of solutions of equal concentration in acidic and alkaline media are compared. We have found that by a combination of the methods of these workers it has been possible to determine the quebracho content of a range of binary and tertiary blends of the specified materials. For the determination of the quebracho content of any blend, it is essential that samples of the blend and of its components are available. A thin-layer chromatographic method is used to establish the identity of the quebracho by comparing the characteristic distribution of fluoresence of the blend with that of the quebracho ingredient. Under the conditions specified, the other vegetable tannin extracts and related materials have relatively little or no fluorescence.For the quantitative determination of quebracho extract, it has been found that by using the differential ultraviolet-absorption technique to be described, the catechol and pyrogallol-type tannin extracts have absorption maxima at about 290 and 320 mp, respectively. In Table I, optical densities are shown for 0.008 per cent. WIV aqueous solutions of the vegetable tannin extracts and related materials, recorded at the peak maximum of about 290 mp, and it can be seen that White’s condition relating to differences in optical density is satisfied.0 SAC; Crown Copyright reserved.260 FIELD AND KENT: DETERMINATION OF QUEBRACHO IN MIXTURES [Analyst, Vol. 93 For quebracho - myrobalan mixtures measurements can also be made of the absorption maximum at about 320mp. Measurement at this wavelength is more accurate when the quebracho content falls below 37.5 per cent. The optical densities recorded for 0.008 per cent. w/v aqueous solutions of quebracho and myrobalan at 320mp are about 0-090 and 1-40, respectively. TABLE I OPTICAL DENSITIES OF 0.008 PER CENT. W/V AQUEOUS SOLUTIONS OF VARIOUS TANNIN MATERIALS AT 290 mp Extract Mimosa . . .. .. .. Quebracho .. .. .. Mangrove . . .. .. .. Myro balan .. .. .. Sulphite cellulose .. ,. Suiphite lye . . .. .. Lignite . . .. .. .. Vandyke brown .. .. .. Optical density 0.780 to 0.860 0.410 to 0.440 0.530 to 0,550 0.320 to 0-360 0 t o 0.070 0 to 0.060 0 to 0.010 0.200 to 0.250 METHOD APPAR.4TUS- Recording sfiectrophotometer.Chromatographic tank, and plates, 20 x 20 em. Camag adjustable spreader. Hydrochloric acid, 0401 N. Borate bufler, PH 10-Dissolve 6.184 g of boric acid, 7-45 g of potassium chloride and Kieselgel G. Ethyl methyl ketone. PROCEDURE- Prepare separately 0.1 per cent. w/v aqueous solutions of the blend and of the two components (A and B) of the blend (i.e., solutions A and B). Centrifuge portions of the solutions, if necessary, and transfer, by pipette, aliquots of 0, 1, 2, 3 and 4 ml of solution A and 4, 3, 2, 1 and 0 ml of solution B into 50-ml graduated flasks, so that for each the total concentration of the solution, when diluted to volume with 0-001 N hydrochloric acid, is 0@08 per cent.w/v. Prepare another series of solutions of the same strengths but dilute to volume with borate buffer. Transfer by pipette 4 ml of the 0.1 per cent. w/v solution of the blend into each of two separate graduated flasks and make one up to volume with OW1 N hydro- chloric acid and the other with buffer. Record the ultraviolet absorption of the alkaline series of 0@08 per cent. w/v solutions over the wavelength range 260 to 330mp, in 1-em quartz cells, with the corresponding acidic solution for each reference. Plot a calibration graph relating optical density, measured at the wavelength corresponding to the absorption maximum of the solution containing only quebracho extract, to concentration of quebracho.Read off from the calibration graph the composition of the blend. In order to avoid possible hydrolysis of the tannin materials, it is advisable to record the spectra of the solutions as soon as possible after preparation. RESULTS REAGENTS- 87.8 ml of N sodium hydroxide in 2 litres of carbon dioxide free water. The quebracho contents found for a series of binary blends are given in Table 11. It can be seen that the quebracho content found is within a tolerance of & 10 per cent., which is acceptable in this type of analysis. The use of the method can be extended to cover the analysis of ternary blends containing quebracho extract and two other vegetable tannin extracts. In this method it is necessary in preparing the calibration graph to fix the concen- tration of one of the components in the solutions while varying the concentration of the other two components. The quebracho content of a blend incorporating quebracho - mimosa - myrobalan (1 + 1 + 1) was found to be 36 per cent.In this particular experiment the concentration of the myrobalan in the reference solutions was fixed at 339 per cent., and the measurements were recorded at 290 mp.April, 1968] WITH SOME OTHER TANNIN EXTRACTS AND RELATED MATERIALS TABLE I1 RESULTS OF QUEBRACHO DETERMINATIONS IN BINARY BLENDS Quebracho found, per cent. Composition of blend as given by supplier 47% soluble quebracho + 63% mimosa 48 64% soluble quebracho + 3696% myrobalan 69 17*6y0 insoluble quebracho + 8206% mimosa 16 76% soluble quebracho + 26% mangrove 78 50% soluble quebracho + 60% sulphite cellulose 63 60% soluble quebracho + 40% sulphite cellulose 62 60% soluble quebracho + 40% lignite 61 60% soluble quebracho + 40% Vandyke brown 66 76% soluble quebracho + 25% sulphite cellulose 74 86’8% soluble quebracho + 14.2% sulphite lye 85 261 Identijcation of quebracho-Prepare 10 per cent.w/v aqueous solutions of the blend and of the quebracho extract used for preparation of the blend. Prepare the carrier plates in the usual way with Kieselgel G (150 p thick) as substrate. Divide the plate into two parts and transfer a portion of the blend solution (100 pl), spotwise, on to one half of the plate along an origin line 1.5 cm from one edge of the plate and parallel to it. Apply the quebracho solution (equivalent to the amount of quebracho present in the blend) in a similar manner to the other half of the plate.Develop the plate by ascending chromatography in a suitable tank, with ethyl methyl ketone, until the solvent front has travelled about 15 cm. Remove the plate from the tank, allow the solvent to evaporate, and examine the plate under ultra- violet light. The presence on both parts of the plate of a pattern of fluorescent compounds of similar distribution and intensity may be taken as positive identification of the quebracho present in the blend. A method for the identification and determination of quebracho present in blends has been described. The accuracy of the method is to within a range of +lo per cent. We thank the British Leather Manufacturers Research Association for their advice and assistance in checking the method, and the British Tannin Extract Manufacturing Associa- tion for their interest and for supplying the samples. We also thank the Government Chemist for permission to publish this paper. REFERENCES 1. Haslam, E., “Chemistry of VegetabIe Tannins,’’ Academic Press, London, 1966. 2. Sohn, A. W., Angew. Chem., 1960, 639. 3. - , Ledev, 1951,2, 4. 4. King, H. G. C., and White, T., “Symposium on Chemistry of Vegetable Tannins,” Society of 6. White, T., Kirby, K. S., and Knowles, E., J . SOL Leath. Trades Chem., 1962, 36, 148. 6. Maranville, L. F., and Goldschmidt, O., Analyt. Chem., 1964, 26, 1423. Leather Trades’ Chemists, Croydon, 1966, p. 31. Received November lsf, 1967

ISSN:0003-2654    

DOI:10.1039/AN9689300259

出版商:RSC    

年代:1968

数据来源: RSC

摘要:

262 Afid'st, April, 1968, VO~. 93, p$. 262-263 A Simple Device for Delivering an Approximately Metered Amount of a Powdered Catalyst Mixture into a Sample Boat BY M. ELLISON (Fiscms Ltd., Cambridge Division, Chesterfovd Park Research Station, Near Saflron WaEde.11, Essex) A device for delivering a metered amount of a powdered catalyst mixture The design of the dispenser ensures that the into a sample boat is described. hygroscopic mixture is stored and dispensed under clean conditions. DURING the preparation of a sample for combustion in an F. & M. 185 CHN Analyzer it is necessary to introduce an oxidising catalyst mixture into a sample boat. This catalyst mixture (in fine powder form) is normally heated to about 500°C before use, to ensure a low carbon, nitrogen and water content.After a sample boat, containing catalyst, is placed in the cool portion of the Analyser combustion tube, a waiting period of 4 to 5 minutes is necessary before the combustion procedure is carried out. Tube retaining cap w Rubber foot (at each corner), , - - _ _ - - - (a) Plan view angle - 30" Base-plate Tweezer Tube holder slots (i) Tube mounting (ii) Sample boat slot (b) Plan and side view Fig. 1. 0 SAC and the author. Details of the catalyst dispenser: (a) plan view; (b) plan and side view; all measurements are in inchesELLISON 263 During this time, moist helium carrier gas is passed through the apparatus and over the sample boat, and, because of the hygroscopic nature of the catalyst, a small but significant amount of water is retained.During combustion this entrained water is driven off and appears as a blank on the resulting chromatogram. Two factors influence the reproducibility of this blank, the time the catalyst is exposed to moist carrier gas, and the amount of catalyst mixture in the sample boat. The former can readily be standardised but the latter would require weighing the mixture before each determination. To overcome this problem a dispenser was constructed, the details of which are shown in Fig. 1. METHOD OF OPERATION- Make sure that the boat is sunk flush with the top surface of the base-plate, i.e., the boat is sitting on the countersunk steps [see Fig. 1, detail ( b i i ) ] . Then move the arm controlling the catalyst-tube holder from side to side over the sample boat. Two or three passes are usually sufficient to fill the boat. Insert the forcep points in the slots provided and carefully transfer the boat to a prepared sample-rod holder. EXPERIMENTAL With the aid of forceps place a sample boat in the boat slot in the base-plate. CONCLUSIONS The use of a dispenser for the catalyst eliminates the need for a spatula, and also reduces the possibility of contamination, both to the sample and catalyst. The dispenser provides a convenient and virtually sealed store for the catalyst; one tube filling will last for 2 or 3 days. It also ensures that a constant weight of catalyst is added to the sample boat, within +3 per cent.; this total weight depends on particle size and constituents of the catalyst but is normally between 0.1 and 092g. The whole of the pre-combustion procedure is simplified by using the dispenser for the catalyst mixture. Received August 30#h, 1967

ISSN:0003-2654    

DOI:10.1039/AN9689300262

出版商:RSC    

年代:1968

数据来源: RSC

摘要:

264 Analyst, April, 1968, Vol. 93, $$. 264-265 Accurate Dispensing of Small Volumes of Volatile Liquids with a Micro Syringe and Aluminium Capillary Tubes BY M. ELLISON (Fiscms Ltd., Cambridge Division, Chesterfwd Park Research SM'on, Near Saflron Walden, Essex) A device for delivering and sealing accurate volumes of volatile liquids into aluminium capillary tubes is described. THE need for dispensing liquids within fairly close limits of weight arises from the more recent use of automatic analysers, with which elements in organic compounds are determined on small sample weights, viz., less than 1 mg. More specifically, with an F. & M. 185 CHN Analyzer it is important that during opera- tion sample weights must be kept within certain limits. The design of this instrument also requires that a sample container must not be greater than 1-5 cm in length, thus making a scaled-down version of the well known semi-micro sealed-tube technique difficult, if not impracticable, to carry out.Open-ended glass capillaries holding about 1 p1 can be used for liquid samples, but this simple technique of filling by capillarity can be tedious if a weight within 50 pg is required, and even more difficult with a volatile compound. EXPERIMENTAL APPARATUS- Fig. 1 shows a sealed-tube liquid dispensing device for overcoming this particular problem. Essentially, a 1-pl Hamilton micro syringe is mounted through two sliding supports; the rear or right-hand support carries a screw clamp so that the syringe may be held rigidly when required. The front or left-hand support consists of a length of glass tubing with a capillary just large enough to allow movement of the syringe needle.This glass tube is rigidly supported at both ends, and radial movement of the needle for aligning purposes is carried out with three radially mounted worm screws on the left-hand support. A tube-crimping device is shown in Fig. 2. It consists of a grooved platform to hold aluminium capillaries (0.d. 0.025 inch, i.d. 0-020 inch). A short length of rod is mounted vertically through a hole over this recess and, during operation, a capillary is crimped by pressure on this rod. The sample holder shown in the diagram is L-shaped and has five holes in one face, into which melting-point tubes containing samples can be inserted. ALIGNMENT OF THE MICRO SYRINGE- following adjustments before use.out of this tube by about half an inch when the syringe is moved fully to the left. position. can be carried out. As individual syringes differ slightly in dimensions it is necessary to carry out the Put the needle-guide tube into position longitudinally so that the syringe needle protrudes Place an aluminium capillary in the crimper groove and slide the crimper into load Check the radial position of the needle, as described earlier, so that free capillary entry 0 SAC and the author.Fig. 1. Sealed-tube liquid dispensing device [To face page 264ELLISON 265 (a) Plan view Countersunk slot Countersunk groove 0.02 deep x 0.025 wide ' Soft rubber base (b) Side view Details of crimper, sample holder and needle guidc.Fig. 2. Construction material was Tufnol, except where indicated; all measurements arc in inches PROCEDURE FOR WEIGHING A SAMPLE- Fill a melting-point sample tube three quarters full with sample and place the sample- holder tube in position. The holder is then put into position as shown in Fig. 2 (side view). Slide the syringe fully forward and pump the syringe piston several times. When the air has been expelled from the needle draw the piston back to the required volume (this can be calculated from the sample density if it is already known), then draw the syringe back until the needle is clear of the sample tube, and withdraw the piston a further 0.1 pl. Remove the sample holder from the stage, place a tared aluminium capillary in the crimper groove and slide the crimper into load position. Slide the syringe fully forward and inject sample into the capillary, then depress the crimping rod. Withdraw the syringe and carefully reverse the capillary in the crimper groove with forceps; seal the capillary tube by depressing the crimping rod. The capillary tube can then be transferred to a balance for weighing. Received August 30th, 1967

ISSN:0003-2654    

DOI:10.1039/AN9689300264

出版商:RSC    

年代:1968

数据来源: RSC

摘要:

266 Analyst, April, 1968, Vol. 93, p p . 266-268 Book Reviews ANNUAL REPORTS ON THE PROGRESS OF CHEMISTRY FOR 1966. Volume LXIII. Pp. XVi + 834. London: The Chemical Society. 1967. Price 100s. The “Annual Reports on the Progress of Chemistry for 1966,” published by the Chemical Society, occupy 762 pages of text. Of these, 31 pages are devoted to Analytical Chemistry. The authors of this section of the report, Messrs. Anderson, Pierce, Stoddart and Wilson, have sought, within these 31 pages, to give a balanced account of the most significant developments in analytical chemistry in 1966. They feel that they have dealt with about 5 per cent. of the analytical papers published in the year and, in their selection, which cannot be free from personal bias, have dealt with items under the following main headings : Qualitative Analysis, Quantitative Organic Analysis, Electrochemical Methods, Radiochemistry, Spectroscopic Analysis, Methods of Separation, Gravi- metric Analysis, Titrimetric Analysis, Reaction-Rate Methods and Thermal Methods.In the view of the reviewer, who carried out similar work for 3 years, and who is well aware of some of the difficulties involved, the task is becoming almost impossible to perform satisfactorily. In 31 pages, 453 references to original papers and other reviews have been covered; the average for each reference is less than 24. lines of text. The analytical chemist seeking new ideas will be well advised to read this report very carefully indeed and try to find very brief notes that will lead him to original papers worthy of intensive study.He will, however, find himself beset with difficulties because of the large amount of ground that has had to be covered, for example, on page 678 it is said, with reference to a particular paper, “Reaction products from the oxidation or reduction of organic compounds in acetic acid may be isolated from the acetic acid by extraction with carbon disulphide.” How many analytical chemists will be led to the original paper without knowledge of the chemical nature of the organic compounds that are being oxidised or reduced? Similar examples of difficulty could be quoted, not as criticisms, but as evidence of the task that the authors have been set and with which they have tried admirably to cope. The introductory part of this report gave the present reviewer the most pleasure because here the authors try to point out the trends in analytical work as a result of their study of in- numerable papers. They draw attention to the procedures that are being used less frequently and to those that are developing fast, to the importance of automation of analytical methods and to the very welcome changes that are taking place in the attitudes adopted by commercial man- facturers to the instruments they sell.J. HASLAM COLORIMETRIC METHODS OF ANALYSIS INCLUDING PHOTOMETRIC METHODS. By FOSTER DEE SNELL, Ph.D., Sc.D., and CORNELIA T. SNELL, Ph.D. Volume IVA. Pp. x + 645. Prince- ton, New Jersey, Toronto and London: D. Van Nostrand Company Inc. 1967. Price 140s. If you are in need of a colour reaction with which to determine a particular organic compound or group of compounds, your first action will almost certainly be to consult Snell.The six books that make up the third edition of “Colorimetric Methods of Analysis,” by Foster D. Snell and Cornelia T. Snell offer the analyst a quick and reliable means of making a first search for suitable colour reactions, and every competent organic analyst must surely be familiar with them. Volume IV, which was published in 1954, contained sixteen chapters, each one covering a compact group of compounds, mostly nitrogenous in composition: Volume IVA is a supplement to the first six chapters of volume IV (the authors, in their preface, say, seven, but this appears to be an error) and its effect is both to up-date and to expand considerably the material given in the earlier volume.The information given is, of course, taken directly from the literature, and although the reviews are accompanied in all cases by detailed instructions for carrying out the determinations, no claim is made that they have been confirmed by the authors, and the reader must recognise that the responsibility for examining the methods critically falls upon his shoulders. Nevertheless, it is clear from the references, which are given at the foot of each page, that the authors have cast their net widely in their search for up-to-date and dependable analytical methods. The first chapter covers nitrites, nitrates and nitro compounds, and includes methods for determining several nitrobodies that are commonly used for preservation and pest control in agricultural products.In the subheadings, these are named with their chemical and with their commercial names, but their constitutional formulae do not appear, and although it is generally possible to write them down after a moment’s thought, I am sure that most people would welcome the inclusion of structural formulae for the compounds that are described.BOOK REVIEWS 267 Chapter 2 is devoted to aliphatic amines and amides, and includes methods for distinguishing between primary, secondary and tertiary amines. Sometimes the text is difficult to follow; for example, on p. 74, dibeprin, 8-( lO-dioxodiinden0[3,2-b : 2’,3’-e]pyrid-ll-yl)-l-naphthoyl chloride, is described as “a reagent for primary amines: the reagent is yellow, but gives a blue - violet colour with unsubstituted and monosubstituted amides in ethanolic alkaline solution.Esters and di- substituted amides do not give the colour.” And on page 77, in the working instructions for carrying out the determination of primary amines by reaction with dibeprin, the important step of adding the reagent has been omitted. The latter part of this chapter has a decidedly biochemical flavour, through the inclusion of several drugs, amino-acids and metabolites. Chapter 3 deals in a much more detailed way with amino-acids, allotting 92 pages to this group of substances, and Chapter 4 is devoted to the determination of proteins, such as globulin, albumin , lipo- and muco-proteins, fibrinogen and gelatin in tissues, serum, cerebrospinal fluid and other biological or natural products. The fifth chapter reverts to the subject of primary, secondary and tertiary amines and amides, this time of the aromatic series, and the final chapter covers a selection of azo compounds, hetero- cyclics (barbiturates, pyridine derivatives and indoles) , purines and vitamin BIZ.One cannot say much that is original about a volume of this kind; those who frequently use this work will probably have the previous volumes of the third edition, and will wish to keep the series complete. Colorimetric methods of determination have, of course, declined in import- ance as a result of the revolution in spectroscopy and chromatography that has taken place in recent years, but there are some fields of analysis that are, as yet, only lightly touched by these powerful techniques, and one has only to remember the successes that have been achieved in the mechanisation of clinical analysis to recognise the important part that colorimetry still plays in modern analytical science.DUNNSCHICHT-CHROMATOGRAPHIE. EIN LABORATORIUMSHANDBUCH. Edited by EGON STAHL. Second Edition. Pp. xx + 979. Berlin, Heidelberg and New York: Springer-Verlag. 1967. Price DM 98; $24.50. The expansion from the first to this revised (German) edition of Stahl’s book fittingly marks recent advances in thin-layer chromatography. The compendium is a credit to the thoroughness of editor, publisher and printer. The many authors contribute authoritative chapters on twenty-six topics, physical, organic and inorganic ; the classification is based, with little overlap, on chemical features (essential oils, steroids, lipids, alkaloids, indole derivatives, amines, amino-acids, nucleo- tides and nucleic acids, sugars and inorganic ions), and on biological action or technical utility (vitamins, synthetic drugs and dyestuffs, antibiotics, foodstuffs and additives, fine chemicals and hydrophilic plant substances).Materials and apparatus are fully described, as well as special methods, electrophoresis, gas-chromatographic adjuncts, documentation, quantitative methods, application of isotopes and clinical tests (forensic methods are not gathered into one chapter). The literature is covered into 1965, which dates the volume on preparative chromatography and on the ready-made plates now on sale.The volume ends with an updated list of 246 spray reagents, a glossary of terms in English, French and German, an international list of suppliers of equipment and a copious index. It is well produced and illustrated, but some of the pages have the shiny surface that marred those of the first edition. The modern analyst works with pure standard samples and is regaled with a spate of com- mercial literature; with a little wit and resource he can solve many of his problems and establish the sensitivity of his methods in less time than it takes to consult the literature or a compendium. Much of the effort devoted to this book may, therefore, be lost to the average user of the methods. The authority of Stahl’s book reiterates the significance of the composition of layers and of factors in methods of detection.Ultraviolet examinations may strain the eyes of observers unless they stand behind a suitable screen and wear glasses. Some spray reagents contain highly toxic substances; all spraying should be camed out in a fume-cupboard. Layers may contain dangerous constituents, such as uranyl salts, and the silica and alumina presumably form dangerous dusts (the tenacious layers now on sale reduce this hazard). It is surprising that more progress has not been made on mass-spectrographic examinations of substances volatilised direct from the area of the layer in which they have been detected. Stahl’s new “Diinnschicht-chromatographie’J is described, like its predecessor, as a laboratory handbook, although it has grown into a tome costing over &8.It is an eligible compendium for libraries. ALAN LONG What about the amines then? H. E. STAGG268 BOOK REVIEWS [Analyst, VOl. 93 RAMAN SPECTROSCOPY, THEORY AND PRACTICE. Edited by HERMAN A. SYZMANSKI. Pp. x + 256. This book consists of seven chapters, each by different authors. The Preface makes interesting reading; the preparation of the book was obviously not trouble-free! Its intention, as stated on the dust cover, is to act both as an introduction for the beginner and to assist established workers in the field. Such divergent duality is always difficult to achieve satisfactorily in any relatively short, single work. The General Introduction by L. A. Woodward is elegantly composed and presented. It discusses the nature of the Raman effect and the necessary underlying theory, as well as pointing out applications as they naturally arise at the various theoretical phases of the chapter.I cannot see many readers, previously unfamiliar with group theory, being able to apply it to vibrations from the condensed presentation here, but it will surely act as an incentive to the reader to look further afield; it is a pity that the reference suggested for further study is not pitched at a more elementary level. There is one unfortunate printing error on page 24 where transitions appears in place of translations. The section, Advances in Raman Instrumentation and Sampling Technique, by J. R. Ferraro, considers most of the recording Raman spectrometers, about which details have been published, but does not, unfortunately, manage to give much detail of the recently praised APC Laser Raman Model 81.The second half of the chapter is mainly devoted to sampling techniques for investigating solids, and is marred by some appalling photographic illustrations and an annoying lack of phase between the text and the diagrams. Laser Raman Spectroscopy, by J. A. Konigstein, presents a comparison between laser and Toronto-arc spectra, and then describes a variety of experiments in which laser sources have been used, some of them specifically requiring laser properties. The article is well written, but one feels that many of the comments are out of date. Raman Intensities and the Nature of the Chemical Bond, by R. E. Hester, gives a usefully detailed theoretical introduction and discusses results that have been published on the relationship between Raman intensity and bond nature. The data are critically assessed, and experimental and theoretical dangers exposed, the final section on intermolecular interaction in liquids being patticularly useful in this respect.Ionic Melts, by G. J. Janz and S. C. Wait, jun., and Observed Resonance Raman Spectra, by J . Behringer, provide excellent up-to-date specialist reviews. Raman Spectroscopy of Complex Ions in Solution, by D. E. Irish, is curious in that it is written at a much more elementary level than the rest of the book. For this reason, and because it refers to the most commonly used aspect of the Raman effect, it would have been better placed as the earliest applications chapter. This book has a place in a chemical library, but it is not indispensable at the work bench; at its high price it cannot be recommended to students. ULTRA VIOLET AND VISIBLE SPECTROSCOPY. CHEMICAL APPLICATIONS. By C. N. R. -0, DSc., Ph.D., F.R.I.C., F.A.Sc. Second Edition. Pp. xiv + 200. London: Butterworths. 1967. Price 50s. The first edition (1961, reprinted 1964) of t h i s monograph met a need, and the opportunity has now been taken to revise the work thoroughly. The section on quantitative analysis has been much enlarged and the treatment of far ultraviolet spectra has been extended. The chapter on fluorescence has been modified and the treatment of charge-transfer spectra is now more com- prehensive. There is a new chapter on the absorption spectra of amino-acids, proteins and related compounds. Although the revision has made the book more up to date, the very real merits of the first edition have been retained and the treatment has been kept concise. New York: Plenum Press. 1967. Price $12.60. This section is not constructive or critical enough in the reviewer’s opinion. PETER L. GOGGIN R. A. MORTON

ISSN:0003-2654    

DOI:10.1039/AN9689300266

出版商:RSC    

年代:1968

数据来源: RSC

摘要:

April, 19681 NOTICE TO AUTHORS 269 Notice to Authors THE Society publishes papers on all aspects of the theory and practice of analytical chemistry, fundamental and applied , inorganic and organic, including chemical , physical and biological methods. Such papers may describe original work or may present in review form a critical evaluation of the existing state of knowledge on a particular facet of analytical chemistry Papers may be submitted for publication by members of the Society or by non-members. Every paper will be submitted to at least two referees, by whose advice the Editorial Committee of .The Analyst will be guided as to its acceptance or rejection. Papers that are accepted must not be published elsewhere except by permission of the Committee. Submission of a manuscript will be regarded as an undertaking that the same material is not being considered for publication by another journal.C~PYRIGHT- The whole of the literary matter (including tables, figures, diagrams and photo- graphs) in The Analyst is copyright and may not be reproduced without permission from the Society for Analytical Chemistry (SAC) and the author(s), or such other owner of the copyright as may be indicated on the first page of each paper. Regional Advisory Editors-For the benefit of potential contributors outside the United Kingdom, a Panel 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 Panel, which a t present consists of- Mr.S. E. Q. ASHLEY, Major Appliances Laboratories, General Electric Company, Appliance Park, LOUISVILLE, Kentucky 40225, U. S. A. Professor G. CHARLOT, Facult6 des Sciences de Paris, Laboratoire de Chimie Analytique, 10 rue Vauquelin, PARIS Ve, FRANCE. Professor L. GIERST, Universit6 Libre de Bruxelles, Facult6 des Sciences, Avenue F.-D. Roosevelt 50, BRUXELLES, BELGIUM. Professor Dr. R. HERRMANN, Abteilung fur Med. Physik. a.d. Univ.-Hautklinik, 63 GIESSEN, Gaffkystrasse 14, GERMANY. Professor Axel JOHANSSON, Institutionen for analytisk kemi, Tekniska Hogskolan, STOCKHOLM 70, SWEDEN. Professor W. E. A. MCBRYDE, Dean of Faculty of Science, University of Waterloo, WATERLOO, Ontario, CANADA. Dr. W. Wayne MEINKE, Analytical Chemistry Division, Room A-309, Chemistry Building, National Bureau of Standards, WASHINGTON, D.C.20234, U. S. A. Professor J. MINCZEWSKI, Department of Analytical Chemistry, Institute for Nuclear Research, WARSAW-ZERAN, Dorodna 16, POLAND. Dr. D. D. PERRIN, Department of Medical Chemistry, The John Curtin School of Medical Research, The Australian National University, Box 4, G.P.O., CANBERRA, A.C.T. , AUSTRALIA. Dr. A. STRASHEIM, National Physical Research Laboratory, P.O. Box 395, PRETORIA, SOUTH AFRICA. Professor K. UENO , Department of Organic Synthesis, Faculty of Engineering, Kyushu Manuscripts of papers and correspondence relating thereto, and proofs, should be sent DIRECT to the Editor, The Analyst, 9/10 Savile Row, London, W.l, England. Manuscript-Papers should be typewritten in double spacing on one side only of the paper.Three copies (top and two carbon copies) should be sent to the Editor, and a further copy retained by the author. Title and synopsis-The title should be brief but descriptive, and must pin-point the original features of the work. All papers must be accompanied by a short synopsis of about 100 to '250 words; this should give the principle of the method, draw attention to its novel features and indicate its scope and sensitivity. University, FUKUOKA, JAPAN.270 NOTICE TO AUTHORS [Afialyst, VOl. 93 Proofs-The address to which proofs are to be sent should accompany the paper. Proofs should be carefully checked and returned within 48 hours of receipt. Reprints-Twenty-five reprints, or a maximum of fifty if there is more than one author, are Additional reprints may be obtained at cost if ordered directly from the printers, Details are sent to supplied free.W. Heffer & Sons Ltd., Hills Road, Cambridge, at the time of publication. authors with the proofs. NOTES ON THE WRITING OF PAPERS FOR The Analyst Manuscripts should be in accordance with the style and usages shown in recent copies of The Analyst.* Conciseness of expression should be aimed at: clarity is increased by adopting a logical order of presentation, with suitable paragraph or section headings. Descriptions of new methods should be supported by experimental results showing accuracy, precision and selectivity. The recommended order of presentation is as indicated below- (a) Synopsis. (b) Statement of object of investigation and, if nccessary, historical introduction and account of preliminary experimental work: these need be no longer than is necessary for the understanding of the new material.(c) Description of method. When working details are given, they should, if possible, be given in the imperative mood. (d) Presentation of results. (e) Statistical analysis of results. Any statistical evaluation of results should be in accordance with accepted practice. (f) Discussion of scope and validity. (g) Summary and conclusions. S I Units-In 1960, the Confkrence Gkn6rale des Poids et Mesures formally approved the Its main features are Well known procedures must not be described in detail. metric system of units known as SI (Systkme International d’Unitt5s).(1) that there are six basic units- physical name symbol quantity of unit for unit length metre m time second S mass kilogramme kg electric current ampere A thermodynamic temperature degree Kelvin “K luminous intensity candela cd (2) that the unit of force, the newton (kg m s-~) is independent of the Earth’s gravitation, so that the introduction of g into equations is no longer necessary; (3) that the unit of energy is the joule (newton x metre) and of power the joule per second (watt), so that the variously defined calories, the kilowatt-hour, the B.t.u. and the horse-power are all superseded; (4) that “electrostatic” and “electromagnetic” units are replaced by SI electrical units; and (5) that multiples of units are normally to be restricted to steps of a thousand and fractions similarly to steps of a thousandth.In SI there are two supplementary dimensionless units, plane angle (radian, rad) and solid angle (steradian, sr) . The following derived SI units have special names- name of unit joule newton watt coulomb volt ohm symbol physical fobr unit quantity J energy N force W power C electric charge V electric potential Q electric resistance difference definition of unit kg m2 5-2 kg m s-2 = J m-1 kg m2 s-3 = J s-1 A s kg m2 s-3 A-1 = J A-1 s-1 * Rules for nomenclature in “Handbook for Chemical Society Authors 1961” (price 21s. from the The Shorter Oxford English Dictionary Chemical Society, Burlington House, London, W. 1) are followed. is followed for spelling, and some of the alternative spellings are used.April, 19681 NOTICE TO AUTHORS name symbol physical of unit for unit quantity farad F electric capacitance weber Wb magnetic flux henry H inductance tesla T magnetic flux density lumen Im luminous flux lux Ix illumination hertz Hz frequency degree Celsius "C customary temperature, t Examples of other derived SI units are- physical quantity SI unit area square metre volume cubic metre 27 1 definition of unil A2 s4 kg-1 m-2 = A s V-1 kg m2 s-2 A-1 = V s kg m2 s-2 A-2 = V s A-1 kg 5-2 A-1 = V s m-2 cd sr cd sr m-2 cycles per second t/OC = T/"K - 273.15 symbol foor unit m2 m3 density kilogramme per cubic metre kg m--3 velocity metre per second m s-l angular velocity radian per second rad s-1 acceleration metre per second squared m s - ~ pressure newton per square metre N m-2 magnetic field strength ampere per metre A m-1 luminance candela per square metre cd m-2 Certain units will be allowed in conjunction with SI, uiz.- physical name symbol definition qua ntz ty of unit for unit of unit area barn b 10-28 m2 volume litre 1 10-3m3 = dm3 pressure bar bar 106 Nm-2 mass tonne t lo3 kg = Mg kinematic viscosity, stokes St 10-4 m2 s-1 dynamic viscosity poise P 10-1 kg m-1 s-1 hectare ha 104 ma diffusion coefficient magnetic flux density gauss G 1 0 - 4 T radioactivity curie Ci 37 x 100s-1 (magnetic indication) energy electronvolt eV 1.6021 x 10-la J The common units of time (e.g., minute, hour, year) and the angular degree (") will continue to be used in appropriate contexts.Fractions and multiples have the following names and symbols (for use as prefixes)- 10-3 milli m 103 kilo k 10-6 micro P 1 06 mega M 10-9 nano n 1 OD gigs G 10-12 pic0 P 1 012 tera T 10-15 femto f 10-18 atto a In addition the fractions 10-1 (deci, d) and (centi, c), and multiples 10 (deka, da) and 102 (hecto, h) are available, but their use should be avoided if possible.Until such time as a new name may be adopted for the kilogramme, the gramme will continue to be used, both as an elementary unit (g) to avoid the absurdity of mkg, and in association with prefixes, e.g., pg. Compound prefixes (e.g., mpm) should not be used; metre = 1 nm. The effect on current style of papers for The Analyst includes the following- (a) dimensions should preferably be given in metres or in mm, although cm will be permitted in special cases; (b) temperatures should be expressed in "C (NOT O F ) ; (c) wavelengths should be expressed in nm (which equals 10 and replaces mp) ;272 NOTICE TO AUTHORS [Analyst, Vol.93 (d) frequency should be denoted in Hz (or kHz, etc.), NOT in c/s or c.P.s.; rotational frequency can be denoted by use of s-1; (e) radioactivity will continue to be expressed in curies (or millicuries or microcuries), but the symbol will be Ci (mCi; &I), NOT C; (f) the micron (p,) will NOT be used; m will be 1 pm. A bbreviations-SI units as recommended by The Royal Society Conference of Editors should be used, with exceptions as already indicated. Normality and molarity are generally expressed as decimal fractions (e.g., 0-02 N, 0.375 M ) . Abbreviational full stops are omitted after the common contractions of metric units (e.g., ml, g, p,g, mm) and other units represented by symbols; litre and metre, when without prefixes, are printed in full.Abbreviations other than those of recognised units should be avoided in the text; symbols and formulae are not used instead of the names of elements and compounds in the text, but may be used in addition to names when they are necessary to avoid ambiguity, e.g., to specify crystalline composition, as in CuS04.5H,0, to show structure or in equations. Percentage concentrations of solutions should be stated as “per cent. w/w” (alternatively “g per 100 g”), as “per cent. w/v” (alternatively “g per 100 ml”) or as “per cent. v/v.” Concen- trations of solutions of the common acids, however, are often conveniently given as dilutions of the concentrated acids, such as “diluted 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 be equivalent to either 1 + 4 OY 1 + 3. Column headings should be brief. No lines should be ruled in tables in the manuscript. Tables must be supplied with titles and be so set out as to be understandable without reference to the test. Tables or graphs may be used, but not both for the same set of results, unless important additional information is given by so doing. In general, graphs should have a reasonable number of co-ordinate lines, and not only the two main axes. The information given by a straight-line calibration graph can usually be conveyed adequately as an equation in the text.Diagrams and graphs should be drawn in Indian ink on Bristol board, stout paper or tracing cloth, not larger than foolscap size and with at least 1-inch margins all round. The use of squared paper should be avoided. All lettering should be inserted lightly in black lead pencil at the appropriate place in the diagram, and will be replaced by type in block-making. All lines in Indian ink should be firmly drawn and sufficiently thick to stand reduction. Drawings should be specially prepared for submission to The Analyst, as they cannot normally be returned and may be modified or cut in the course of block-making. Three sets of illustrations should be provided, two sets of which may be photographic or dyeliiie copies of the originals, or pencil sketches, for transmission to the referee; there is no need to prepare Indian-ink duplicates.Photographs-Photographs should only be submitted if they convey essential information that cannot be shown in any other way. They should be submitted as glossy prints made to give the maximum detail. Colour photographs can only be accepted when a black-and-white photograph fails to show some vital feature. References-References should be numbered serially in the text by means of superscript and collected in They should be listed, with the Tables, diagrams, &.-The number of tables should be kept to a minimum. Tables consisting of only two columns may often be arranged horizontally. figures, e.g., Wilson and Duff,l Mendoza, Wales, McLeod and McKinley2 or numerical order under “REFERENCES” at the end of the paper. authors’ initials, in the following form (doubled-spaced typing)- 1. 2. 3 . Wilson, H. N., and Duff, G. M. S., Analyst, 1967, 92, 723. Mendoza, C. E., Wales, P. J., McLeod, H. A., and McKinley, W. P., Ibid., 1968,93, 173. Jolly, S. C., Editor, “Supplement to Official, Standardised and Recommended Methods of Analysis,” The Society for Analytical Chemistry, London, 1967, p. 77. For books, the edition (if not the first), the publisher and the place and date of publication should be given, followed by the volume or page number, or both if required. The entry of “personal communications” in the reference list is not justified; full acknowledg- ment of such unpublished sources should be made in the text or in the acknowledgments at the end of the paper. Authors must, in their own interest, check their lists of references against the original papers; second-hand references are a frequent source of error. The number of references must be kept to a minimum.

ISSN:0003-2654    

DOI:10.1039/AN9689300269

出版商:RSC    

年代:1968

数据来源: RSC