摘要:

Analyst, November, 1973, Vol. 98, p$. 811-812 811 A Solvent-saving Extraction - Evaporation Apparatus Developed for Residue Analysis of Pesticides BY G. voss AND w. BLASS (Agrochemical Division, CIBA-Geigy Ltd., Bade, Switzerland) An apparatus that simultaneously allows Soxhlet extraction of pesti- cides and concentration of the resulting extract has been designed. The evaporated solvent is refluxed into the Soxhlet flask where it is utilised again for the extraction. The major advantages of this cyclic extraction - evapora- tion system are that redistillation of solvents prior to extraction can be omitted, that manual work is reduced, as the solvent evaporation process occurs simultaneously with the extraction of the sample, and that excess of solvent is not wasted but re-utilised for extraction, which is of interest from the economic and environmental contamination points of view.A NUMBER of organic solvents have been used for extracting pesticides from various sub- strates. Owing to the accuracy of detection required for this type of compound, and also for technical reasons, the initial extracts must be concentrated to a relatively small volume by evaporation before chromatographic clean-up procedures can be applied. The evaporated portion of the solvent is lost for any further work and also contributes to air and water pollution. In order to avoid, or a t least reduce, this economic and environmental drawback, an apparatus was designed that permits the re-utilisation of evaporated solvents without complicating the extraction procedure. Because exhaustive Soxhlet extraction has recently been recommended for the analysis of all organophosphorus insecticides,l and as this procedure is well known to residue chemists, we have modified the Soxhlet apparatus as described below.14-5/23 Fig. 1. Extraction - evapo- ration apparatus designed for residue analysis of pesticides @ SAC and the authors.812 VOSS AND BLASS APPARATUS- Details of the apparatus are shown in Fig. 1. The solvent (400 to 500 ml), present in a l-litre round-bottomed flask (A), is heated and refluxed from the lower part of the condenser (B,) into the Soxhlet thimble (C). From the central part of the Soxhlet apparatus the solvent is siphoned into a 250-ml round-bottomed flask (D), from which it is continuously distilled into the upper part of the water-cooled condenser (B,) through a detachable glass tube joined at two ball and socket joints (E, and E,).The organic solvent is condensed in B, and refluxed through a second glass tube (equipped with ball joints E, and E4) back into flask A. The adjustment of the temperatures in the heating jackets (F, and F,) depends on the solvent used for extraction and is easily determined by experiment. The rates of distillation that occur in flasks A and D should be similar, thus avoiding both evaporation to complete dryness and overflow in flask D. RESULTS AND DISCUSSION Duplicate recovery experiments were carried out with a number of pesticides that differed in their chemical and physicochemical properties, and with various substrates (plant materials, meat and soil) and solvents.The present extraction - evaporation procedure was found to result in satisfactory recovery values, as summarised in Table I. TABLE I RECOVERIES OBTAINED WITH DIFFERENT MATERIALS AND PESTICIDES BY USING THE EXTRACTION - EVAPORATION APPARATUS Pesticide Material Solvent Deter- mination* Atrazine Sandy loam Methanol (4 Chlorobenzilate Apples Acetone (ii) DDT Meat n-Hexane (ii) Dichlorvos Wheat grain Methylene chloride (iii) Methidathion Orange peel Chloroform - methanol (9 + 1) (i) Monocrotophos Cotton seeds Chloroform - methanol (9 + 1) (iv) Added, p.p.m. 1.0 0-6 0.6 5-0 2-0 0.2 Recovered, per cent. 77, 87s 85, 9Sz 88, 92# l00,t 76$ 100, 1107 74, 7571 * (i). Gas - liquid chromatography with flame-ionisation detection; (ii), gas - liquid chromato- graphy with electron-capture detection ; (iii), cholinesterase inhibition ; and (iv), gas - liquid chromatography with flame-photometric detection.7 No clean-up. Column chromatographic clean-up. $ Thin-layer chromatographic clean-up. 7 Partitioning, column and thin-layer chromatographic clean-up. The major advantages of using this apparatus are as follows. Firstly, because those distilled solvent portions which actually extract the analytical material in the thimble are siphoned into flask D (Fig. 1) instead of flowing back into flask A, the often necessary re- distillation of solvents in glass prior to extraction of samples can be omitted. This advantage saves a considerable amount of manpower. Secondly, at the end of a 3 to $-hour extraction period the final extract can be recovered from flask D in a relatively concentrated form.Again, this saves time and manpower, even if further evaporation for final volume adjustment proves to be necessary. Thirdly, losses of solvents are rninimised. The initial amount of solvent placed in flask A can be used for many subsequent extractions, at least within a series of the same type of pesticide-containing sample. The advantage is of particular importance with expensive solvents. Fourthly, in most laboratories organic solvents are evaporated by streams of air, Kuderna- Danish evaporators, or rotating evaporators attached to water pumps, thus contributing to the contamination of air and water. This disadvantage is avoided by the process of recycling the solvents in the system between flasks D and A. In our experience the apparatus can DC operated in the open laboratory and a fume hood is not required. REFERENCE X. Beroza, M., and Bowman, M. C., in Tahori, A. S., Editov, “Pesticide Terminal Residues,” Butter- Received April 9t6, 1973 Accepted April 26th, 1973 worths, London, 1971.

ISSN:0003-2654    

DOI:10.1039/AN9739800811

出版商:RSC    

年代:1973

数据来源: RSC

摘要:

Analyst, November, 1973, Vol. 98, @@. 813-815 813 Fractionation and Identification of Commercial Hydrocolloid Stabilising Agents Part II.* Identification of the Components of Guar Gum - Locust Bean Gum and of Pectinate - Gum Tragacanth Mixtures BY R. G. MORLEY, G . 0. PHILLIPS, D. BE. POWER (Department of Chemistry and Applied Chemistry, University of Salford, Salford, Lancashire, M6 4WT) AND R. E. MORGAN (The Medical Center, University of Alabama, Birmingham, Alabama, t ..A.) The limitations of a method for the identification of mixtures of stabilising agents described previously have been overcome. The method now facilitates positive identification of pectinate and tragacanth in admixture and of guar gum and locust bean gum in admixture. A METHOD for the fractionation and identification of the components of stabiliser mixtures has been described previously.112 The method suffers from two limitations, namely that guar gum and locust bean gum cannot be positively identified when they occur in admixture, and that the identification of pectinate and tragacanth in admixture requires experience in assessing the extent to which the precipitate redissolves on addition of excess of iron(II1) chloride.These limitations have now been overcome. EXPERIMENTAL The detailed experimental procedure has been described previous1y.l The clear liquid retained after precipitation with 1 N hydrochloric acid in the original procedure1 is neutralised with sodium hydroxide solution (but not made alkaline). Ethanol (3 volumes) is then added and the precipitate that forms is redissolved in water to give a 0-5 per cent.solution, which is divided into three portions. Two portions are treated as des- cribed previous1y.l The third portion (1 volume) is added to 2 M potassium hydroxide solution (1 volume) and the solution centrifuged. Formation of a precipitate indicates the presence of pectinate. The supernatant liquid is then made just acidic to litmus by the dropwise addition of glacial acetic acid. Lead acetate solution (i volume) is added and the white, curdy precipitate formed is dispersed by the dropwise addition of glacial acetic acid. The presence of a gel on centrifugation indicates the presence of gum tragacanth. PECTINATE - GUM TRAGACANTH FRACTIONATION- GUAR GUM AND LOCUST BEAN GUM FRACTIONATION- Amberlite IR-45 resin (exchange capacity 2 mequiv ml-l of wet resin) is regenerated in the hydroxide form by stirring it with 4 per cent.sodium hydroxide solution for 1 hour. The resin is then washed free from excess of sodium hydroxide, stirred with 5 per cent. boric acid solution for 30 minutes and packed in a 30 x 2-cm column. The column is washed with boric acid solution and the excess of borate finally removed with water. Finally, 250 ml of 4 per cent. cetylpyridinium chloride solution is percolated through the column and the eluate is lyophilised to give cetylpyridinium borate. The clear liquid from the 1 per cent. cetylpyridinium chloride precipitation step in the original method,l containing the neutral stabilisers, is divided into three portions. Two portions are treated as described in the original procedure.To the third portion (1 volume) acetic acid is added so that on addition of cetylpyridinium borate (1 volume) a pH of 4.6 is obtained. Sodium hydroxide solution (10-1 M) is then added until a pH of 8 is attained. I t is important to monitor the pH continuously during these operations and to stir the solution. * For details of Part I of this series, see reference list, p. 815. I@ SAC and the authors.Stock solution (agar 1, alginate 2, arabic 3, carboxymethylceliulose 4, carrageenan 5, guar gum 6, locust bean gum 7, methylcellulose 8, pectate 9, pectinate 10, tragacanth 11 1. Add 1 volume 1% cetyl pyridinium chloride; allow to clarify; centrifuge I Supernatant (discard ) Precipitate ( 1,3,10,1 1 1. Re-dissolve in HzO; divide into three portions I I Precipitate (1,2,3,4,5,9,10,11).Dissolve in 2 volumes 4~ NaCI; centrifuge 1 I Precipitate. Supernatant CONFIRMS LOCUST BEAN GUM I Supernatant (6,7,8). Add 3'volumes ethanol; centrifuge 1 I I I Precipitate (5). Supernatant (1,2,3,4,9,10,11~. CONFIRM CARRAGEENAN Add 3 volumes ethanol; centrifuge Precipitate (1,2,3,4,9,10,1 1). Wash with 80% ethanol; re- dissolve in 1 volume H20; add 1 volume 1 N HCI; centrifuge I Supernatant (discard) I Supernatant (8). CE L LU LOSE I Precipitate (6,7). divide into two portions Dissolve in minimum volume HzO; CONFIRM METHYL- I 1 2nd portion. Add 1 volume cetylpyridinium borate and acetic acid to pH 4.5; titrate with 0 . 1 ~ NaOH to pH 8 I 1st portion. CONFIRM GUAR GUM OR LOCUST BEAN GUM I Precipitate (2,4,9).Re-dissolve in dilute NaOH to pH 7; add 1/5 volume trichloroacetic acid; centrifuge I Supernatant (1,3,10,11~. Adjust to just pH 7; add 3 volumes ethanol; centrifuge I I I Precipitate. CONFIRMS GUAR GUM Supeinatant. Titrate to pH 8.4 I I I r I I I I 1 I st portion. Add IM CuSOd 2nd- portion. Add FeC13 3rd portion. Add ZM KOH Precipitate. Superhatant. Precipiiate. Superinatant. Precip'itate. supernatant. CONFIRMS CONFIRM INDICATES CONFIRM CONFIRMS CONFIRM PECTINATE ARABIC PECTINATE AGAR PECTl NATE TRAGXANTH AND/OR T RAG ACANTH I I 1 I 1 Precipitate (2,9). Re-dissolve in dilute NaOH just to pH 7; divide into two portions I 1 Supernatant (4). Adjust to just pH 7; add 3 volumes ethanol; centrifuge I 1st portion. 2nd portion. Precipitate. CONFIRM CONFIRM Dissolve in H20.PECTATE ALGlNATE CONFIRM CARBOXYMETHYLCELLULOSE U U M Z Fig. 1. The fractionation schemeNovember, 19731 COMMERCIAL HYDROCOLLOID STABILISING AGENTS. PART 11 815 The formation of a precipitate indicates the presence of guar gum. The precipitate is removed by centrifugation and the addition of sodium hydroxide solution is continued until a pH of 8.4 is attained. The formation of a further precipitate at this pH indicates the presence of locust bean gum. The guar gum - cetylpyridinium borate precipitate is yellow whereas the locust bean gum - cetylpyridinium borate precipitate is white. The new fractionation scheme, modified on the basis of the results presented here, is shown in Fig. 1. DISCUSSION The fractionation scheme described (Fig.1) facilitates the separation and identification of gum tragacanth in admixture. Moreover, the procedure allows guar gum and locust bean gum to be separated readily and identified when they occur in admixture. The procedure outlined in Fig. 1 represents the first successful chemical separation of these hydrocolloids. The precise pH at which guar and locust bean gum precipitate varies slightly with the nature of the sample. Thus, solutions of different samples of guar gum have been found to precipitate between pH 7.7 and 8.3; solutions of locust bean gum alone precipitate in the pH range 8.6 to 9.3. When both hydrocolloids are present in the solution, guar gum precipitates in the pH range 7.8 to 8.3 and locust bean gum in the pH range 9.2 to 9.4. However, it is important to stress that in every instance, with all samples tested, a clear separation of guar and locust bean gum was achieved.The analysis scheme (Fig. 1) is still subject to certain minor criticisms, because although K-carrageenan samples give a positive methylene blue test, X- and p-carrageenan fractions do not. In practice, however, this observation does not constitute a difficulty as all commercial samples of carrageenan so far encountered do contain K-carrageenan and will accordingly form a blue - black fibrous precipitate in the methylene blue confirmatory test for carrageenan. The confirmatory test for agar described in the original paper1 depends on the presence of the anionic fraction. Industrial samples of agar normally contain this anionic fraction and consequently show a positive reaction. The fractionation scheme has been successfully used for the analysis of stabiliser mixtures isolated from food products, particularly frozen desserts. We thank the Dari-Tech Corporation, Atlanta, Georgia, who supported this investigation, and Drs. M. T. E. Evans and J. Petty, Unilever Research Laboratory, for an independent assessment of the method under industrial conditions. REFERENCES 1. 2. Morley, R. G., Phillips, G. O., Power, D. M., and Morgan, R. E., Analyst, 1972, 97, 316. Morley, R. G., Ph.D. Thesis, University of Salford, 1972. NOTE-Reference 1 is to Part I of this series. Received April 6th, 1973 Accepted June ZIst, 1973

ISSN:0003-2654    

DOI:10.1039/AN9739800813

出版商:RSC    

年代:1973

数据来源: RSC

摘要:

816 Analyst, November, 1973, Vol. 98, pp. 816-818 Determination of Nicotinamide in Some Injections of B-complex Vita-mins by Thin-layer Chromatography BY SAAD A. ISMAIEL AND DAWOUD A. YASSA (Research Department, Sociktk Misr pour Z’lndustrie Pharmaceutique, 92 El-Mataria Street, Post El-Zeitoun, Cairo, Egypt) Nicotinamide in some injections of B-complex vitamins can be separated on a thin layer of silica gel G by using a solvent mixture of ethanol (98 per cent.) - chloroform (25 + 60 V / V ) , eluted from the scraped off area with 0-1 N hydrochloric acid and the solution measured spectrophotometrically at 26 1 nm. Results obtained by use of the proposed method are compared with those obtained with the ammonia distillation method of the British Pharmacopoeia 1968. NICOTINAMIDE in injection solutions of B-complex vitamins alone, or in the presence of liver extract, cannot be determined by direct measurement of the light absorption in 0.1 N hydro- chloric acid1 because of the interference of the other B-complex vitamins and liver extract, while use of the ammonia distillation method of the British Pharmacopoeia2 gives high results owing to the interference of the volatile titratable bases formed by the action of sodium hydroxide on the other constituents of the injection during the distillation.If the cyanogen bromide method of the United States Pharmacopoeia3 is used, nicotinic acid, when present, will interfere. Trials with the thin-layer chromatographic method of Sunshine4 to separate nicotinamide from the other constituents of the injection resulted in incomplete separation of nicotinamide from riboflavine. The thin-layer chromatographic method of Ismaiel and Yassa5 successfully separated nicotinamide from riboflavine; however, Rg values were found to be 0-6 and 0.46, respectively, thus making the careful scraping of the area containing nicotinamide alone difficult.In this paper a method is proposed that depends on the thin-layer chromatographic separation of nicotinamide from the other constituents of the injection solution with use of a solvent mixture of ethanol (98 per cent.) - chloroform (25 + 60 V / V ) , followed by elution with 0-1 N hydrochloric acid and measurement of the absorption at 261 nm. Use is made of the Ei:& value reported by Clarke and Ber1e.l The proposed method can be used to determine nicotinamide in the presence of other B-complex vitamins, liver extract and nicotinic acid.EXPERIMENTAL MATERIALS- and Y a ~ s a . ~ is preferable to use freshly distilled solvents. SAMPLES- Silica gel G plates-These plates are the same as those used in the method of Ismaiel Solvent mixtare-The mixture is ethanol (98 per cent.) - chloroform (25 + 60 V / V ) , It Hydrochloric acid, 0.1 N. The formulations of the samples under test are shown in Table I. PROCEDURE- Apply, by means of a tuberculin syringe in portions of 0.2 to 0.5 ml, the injection solutions (containing from 15 to 40 mg of nicotinamide, as stated on the label) to the plate as a trans- verse line about 6 ciii long, evaporating the solvent after each application by using a hot stream of air; allow the plate to cool to room temperature.Separate the nicotinamide from the otlier constjttlents by allowing the solvent front to travel at least 12 cm, then remove the plate and dry it in air. Scrape off the silica gel G containing the iiicotinamide (3 mrn from 0 SAC and thc authors.ISMAIEL AND YASSA 817 TABLE I COMPOSITION OF SAMPLES Sample r 7 I I1 111 I V v VI VII VIII IX 100 100 100 100 100 100 250 100 60 A 2 - 2 1 2 1 5 1 0.5 Constituent Thiamine hydrochloride/mg Riboflavine-5-phosphate Riboflavinelmg . . .. .. (sodium salt)/mg . . .. Nicotinamidelmg .. .. Nicotinic acid/mg .. * . Pyridoxine hydrochloride/mg . . Calcium pantothenatelnig . . Sodium pantothenate/mg . . Cyanocobalaminlpg . . .. Biotinlpg .. .. .. Benzyl alcohol/mg .. . . methylphenol) /mg . . . . use/mg . . .. . . . . Water for injection . . .. Chlorocresol(4-chloro-3- Dry liver extract for parenteral Liver injection crude (U.S.P. XV) - 2 - 200 200 200 10 10 10 1 1 6 - 100 20 20 20 - - - - - - - - - - - - - - 100 160 50 30 40 - 10 5 10 50 - 5 - - 7 - - - 100 - - 5 - - 20 20 20 140 - - - - - - 100 50 10 5 5 10 5 5 - - 100 5 - 20 20 - 2-5 2.5 2.5 2.6 2.6 2.5 - 2.5 2.5 - - - - 100 - 10 - - to to - to to to to to to l m l l m l l m l 1 ml 1 ml l r n l l m l l m l - - t o l m l - - - - - - the margin of the riboflavine spot to 1 cm away from the solvent front) and transfer it to a lOO-ml, wide-mouthed, calibrated flask. Add about 50 ml of 0.1 N hydrochloric acid, shake the flask for 2 minutes, then dilute to volume with 0-1 N hydrochloric acid and centrifuge (or filter through a dry Whatman No.1 filter-paper, rejecting the first 10-ml portion of the filtrate). Transfer a volume containing about 0.75 to 1.2 mg of nicotinamide to a 100-ml calibrated flask and dilute to the mark with 0.1 N hydrochloric acid. Finally, measure the extinction a t 261 nm by using 0.1 N hydrochloric acid as a blank. The results obtained are given in Table 11. For calculation purposes use 454 as the value of Ei:h. TABLE I1 COMPARISON BETWEEN THE RESULTS BY THE PROPOSED METHOD AND THE AMMONIA DISTILLATION METHOD Sample* 1 .. .. I1 .. I11 .. .. IV .. .. v .. .. VI .. .. V I I . . .. VIII .. IX .. .. .. . . .. .. .. .. .. .. . . Stated 200 200 200 100 160 50 30 100 60 Amount of nicotinamidelmg ml-1 A I Found by r 3 ammonia distillation proposed methodt method: A 196.4 (& 1.22%) 218.88 196.1 (f 1.92%) 224-5 194.2 (f 1.35%) 220 99.2 (4 1.4%) 1 12-94 157-6 (f 1.62%) 173.5 30.8 (&2.12y0) 32.9 101.2 (f 1.8%) 109.8 48.9 (A I -62°/o) 54.1 50.9 (f 1.43%) 63.7 * Authentic sample. t Mean of 6 experiments; values in parentheses are the mean standard deviations of individual results $ Slightly high results due to the interference of volatil~ titratable bascs formed by the actioll of sodium hydroxide on the other constituents of the injection cluris ig the distillation.The separation of nicotinamide from the other ingredients of the injection was attempted by use of mixtures of ethanol (95 and 98 per cent.) - chloroform - water and ethanol (95 and 08 per cent.) - chloroform in different proportions, bzt the mixture ethanol (98 per cent.) - chloroform (25 + GO VjV) gave the best separation.It is interesting to note that higher proportions of chloroform than that used in the method separated riboflavine into two spots,818 ISMAIEL AND YASSA --- I I Fig. 1. Developed chromato- gram showing the separation of nicotinamide from the other B- complex vitamins contained in the injection after treatment with cyanogen bromide and aniline. (a) Nicotinamide reference stand- ard; (b) sample V; and (G) nicotinic acid reference standard. Spots 1 and 6 represent nicotinamide, spots 4 and 7 nicotinic acid, spot 5 ribo- flavine, spot 2 thiamine and spot 3 pyridoxine with tailing from the upper spot reaching the lower one on the starting line.This effect occurs because of a decrease in the solubility of riboflavine on increasing the proportion of chloroform. The RF values of the spots on the developed chromatogram, as shown in Fig. 1, are thiamine 0-00, pyridoxine 0-015, riboflavine 0.26, nicotinamide 0.51 and nicotinic acid 0.23. It is also shown that the RF value of nicotinic acid is affected by the presence of the other vitamins, especially nicotinamide. Liver extract , if present, however, will give three brown spots, with R, values of 0.00, 0.02 and 0.98. The nicotinamide spot can be made visible by leaving the developed chromatogram in a closed jar containing two small beakers, the first of which contains cyanogen bromide solution and the second aniline, deep orange spots representing nicotinamide or nicotinic acid being obtained within 1 hour.This method was used to determine the boundary of the area containing nicotinamide to be scraped off for the determination. The absorption spectrum of the measured solution showed that nicotinamide was separated with a purity sufficient for accurate measurement at 261 nm. Recoveries of the products studied ranged from 94.6 to 103.6 per cent., and the standard deviation ranged from &1*22 to &2-12 per cent. (n = 6). REFERENCES 1. 2. 3. 4. Clarke, E. G. C., Editor, assistedby Berle, J., “Isolationand Identificationof Drugs in Pharmaceuticals, Body Fluids and Post-mortem M;terial,” The Pharmaceutical Press, London, 1969, p. 440. “The British Pharmacopoeia 1968, “The United States Pharmacopoeia,” XVIIIth Revision, Mack Co., Easton, Pa., 1970, p. 446. Sunshine, I., Amer. J . Clin. Path., 1963, 40, 576, cited in Clarke, E. G. C., Editor, assisted by Berle, J . , “Isolation and Identification of Drugs in Pharmaceuticals, Body Fluids and Post-mortem Material,’’ The Pharmaceutical Press, London, 1969, p. 46. Received Jamary 25th, 1973 Accepted June 18th, 1973 The Pharmaceutical Press, London, 1968, p. 652. 5. Ismaiel, S. A. , and Yassa, D. A., Analyst, 1973, 98, 1.

ISSN:0003-2654    

DOI:10.1039/AN9739800816

出版商:RSC    

年代:1973

数据来源: RSC

摘要:

Analyst, November, 1973, Vol. 98, $p. 819-822 819 Determination of Balsamic Acids and Esters by Gas = Liquid Chromatography BY K. J. HARKISS AND P. A. LINLEY (Postgraduate School of Studies in Pharmacy, University of Bradford, Bradford, BD7 1DP) A gas - liquid chromatographic method for the determination of balsamic acids and esters in crude drugs is described. Methylation of free acids is followed by a single-stage separation and quantitative determination of methyl and benzyl esters of benzoic and cinnamic acids. Results are pre- sented for the column parameters and reproducibility of the method. The analysis of a commercial sample of tolu balsam is reported; the interpretation of the results may offer additional information to that obtained from official standards. OFFICIAL methods for the evaluation of balsamic drugs rely upon the determination of total balsamic acids, together with acid, ester and saponification values, which are normally calcu- lated with reference to the dry alcohol-soluble matter.lS2 These standards yield limited information on the drug and do not enable sophisticated products to be readily detected.Additionally, the determination of total balsamic acids presents practical difficulties owing to the resinous nature of these drugs,394 and the analysis of individual acids can be achieved only after bromination of the cinnamic acid fraction. More recent procedures based on thin-layer chromatography do not permit the satis- factory resolution of acids and esters on a single system and are difficult to make quanti- tati~e.~-' Gas - liquid chromatography is a convenient method for the evaluation of the free acids and esters, but the separation of free benzoic and cinnamic acids is difficult owing to tailing, as found by Monard and Grenier,' although more efficient separations can be achieved by esterification of these acids.*s9 This paper describes the development of a gas - liquid chromatographic method for the determination of free balsamic acids as their methyl esters together with the benzyl esters in a commercial sample of tolu balsam.EXPERIMENTAL REAGENTS AND MATERIALS- verified by gas - liquid chromatography on the system described below. was used. All reagents and standards were of general laboratory grade, and their purities were Diazomethane-A solution in ethyl acetate was prepared from nitrosomethylurea.lO Internal standard solution-A 0.6 per cent. mlV solution of n-hexadecane in ethyl acetate APPARATUS- Gas chromatograph-A Pye, Model 104, gas chromatograph was used, with a flame- ionisation detector maintained at the temperature of the column.GZass column-The column, of dimensions 2-7 m x 3 mm i d . , packed with 10 per cent. E301 on Diatomite C (acid washed and dimethyldichlorosilanised, 90 to 100 mesh, supplied by J. J. Chromatography Ltd.), was conditioned at 300 "C for 24 hours before use. In order to prevent blockage of the column by resin from the balsam, the injection port was lightly plugged with glass-wool, which was replaced daily. Integrator-Peak areas were determined by means of a Honeywell digital integrator.Operating coutditions-The initial column temperature was 175 "C for 1 minute, pro- grammed at the rate of 9 "C min-l to a final temperature of 240 "C for 8 minutes. The initial injection block temperature was 220 "C and the final temperature 260 "C. The carrier gas was nitrogen at the flow-rate of 80 ml min-1. The amplifier attenuation was 2 x 10-*A (full scale). For the integrator, a threshold value of 3 per cent. was found to be necessary owing to slight baseline drift that occurred at the higher temperature. @ SAC and the authors.820 HARKISS AND LINLEY: DETERMINATION OF BALSAMIC ACIDS AND [Analyst, Vol. 98 SAMPLE PREPARATION- Standard solutions-Methylation of benzoic (25 to 120 mg) and cinnamic acids (25 to 160 mg) was achieved by the careful addition of diazomethane solution at 0 "C.The products were transferred into a 100-ml standard flask, known amounts of benzyl benzoate (40 to 220 mg) and benzyl cinnamate (50 to 450 mg) were added together with 25 ml of internal standard solution, and the volume was made up with ethyl acetate. ToZu balsam solzztion-Approximately 1 g of tolu balsam was accurately weighed into a 50-ml beaker and diazomethane solution slowly added until effervescence ceased. The mixture was stirred continuously during the methylation process so as to facilitate dissolution of the resinous material and to ensure efficient release of the free acids contained in the sample. After allowing the beaker to stand for 15 minutes, the contents were transferred into a 100-ml standard flask, 25ml of internal standard solution added, and the mixture was diluted to volume with ethyl acetate.GAS CHROMATOGRAPHY- For calibration, G pl of standard solution were injected and the temperature programme was started simultaneously; this volume gave approximately 80 per cent. of full-scale deflection for the peak due to the internal standard. Areas under the peaks were measured and standard ratios were calculated with reference to the internal standard. These solutions were used to check the linearity of the system. For the analysis of balsam, one standard solution was adopted and single injections of this solution were interspersed between duplicate 6-p1 injections of balsam test solution. Test ratios for acids and esters in the balsam were calcu- lated with reference to the internal standard peak.Contents of free acids and esters were calculated from the following equation: x 100 Test ratio Standard ratio Mass of standard in 100 ml (g) Mass of sample (g) Content (1.x cent.) = RESULTS AND DISCUSSION Typical gas - i quid chromatograms for a standard solution and a balsam solution are shown in Fig. 1. 'I emperature programming was found to be necessary for adequate resolution of the methyl benzoate peak from the solvent peak and at the same time permitting the determination of the major components in a single analysis. Additionally, the peaks were A I I L 16 14 12 10 8 6 4 2 0 Tirne/m inu tes B 16 14 12 10 8 6 4 2 0 Time/rninutes Fig. 1. Chromatogram .4, commercial sample of tolu balsam ; chromatogram B, standard solution.(a), Methyl benzoate; ( b ) , methyl cinnamate ; (c) , n-hcxadecane ; ( d ) , benzyl bcnzoatc; and (c), benzyl cinnamateNovember, 19731 ESTERS BY GAS - LIQUID CHROMATOGRAPHY 821 resolved more satisfactorily than was found to be possible with isothermal operation, eliminat- ing interference from minor components in the balsam sample. Several stationary phases of different polarity groups were investigated; in general, relatively non-polar packings were found to be more suitable and of these the E301 silicone elastomer gave the optimum resolution on a 2.7-m column. Column parameters are given in Table I. TABLE I COLUMN PARAMETERS Retention timelminutes Methyl benzoate . . .. .. 2.2 Methyl cinnamate . . .. .. 4.9 Benzyl benzoate . . .. .. 9.7 n-Hexadecane .. .. .. .. 7.7 Benzyl cinnamate . . .. .. 15.5 Benzoic acid . . .. .. . . 2.4 Cinnamic acid . . .. . . .. 5.4 Efficiency (No. of theoretical plates) 1940 7430 12 460 16 640 10 680 - The conversion of the free acids into their methyl esters was found to be advantageous, giving high column efficiencies and a marked increase in detector sensitivity, without the tailing that is commonly associated with organic a c i d ~ . ~ ~ ~ ~ Diazomethane was selected in preference to other methylating reagents because of the simple procedure required for its use in esterification, the absence of interfering products and the obviation of the needfor solvent extraction of the reaction mixture, so reducing the possible sources of experimental error in the quantitative determination.Difficulties in the use of this reagent lay chiefly in the preparation and storage of the starting material, although these difficulties were minimised by storing batches of the reagent in a deep-freeze for several weeks. The complete- ness of the reaction was checked by the absence of peaks for benzoic and cinnamic acids (Table I). However, it was found that a large excess of diazomethane in the final solution caused a secondary reaction with methyl cinnamate, producing a compound with a retention time of 10.0 minutes, and hence gave unreliable values for the cinnamic acid content of the balsam. The use of boron trifluoride in methanol12 was investigated ; although gas chromatography could be carried out directly on the diluted reaction mixture, the presence of even a slight excess of methanol caused severe tailing of the solvent peak and loss of resolution of methyl benzoate.The reproducibility of the instrument was verified by repeated injections of a single standard solution; standard ratios (peak area for the solute to peak area for the internal standard) were calculated (Table 11). Calibration graphs prepared by using several standard solutions of different concentrations showed that correlation coefficients for each component were between 0-990 and 0.998, indicating that a linear relationship between amount of substance and detector response existed within the ranges indicated above. As standard solutions were prepared from the free acids, the linearity of the response for their methyl esters showed the methylation reaction to be complete.In order to ascertain whether The nature of the secondary reaction is under investigation. TABLE I1 PEAK-AREA RATIOS OBTAINED FROM REPEATED INJECTIONS OF A STANDARD SOLUTION WITH RESPECT TO n-HEXADECANE AS INTERNAL STANDARD Amount Mean Standard Coefficient of Component in solution presen t/mg ratio* deviation variation, per cent. Benzoic acid . . . . . . 118.3 0.585 f 0.004 0.75 Cinnamic acid . . .. .. 96.5 0-966 f 0-005 0.49 Benzyl benzoate . . . . 166.5 1.37 &0*01 0.76 Benzyl cinnamate . . , . 416.6 3.25 f 0.05 1.64 * Values obtained from ten injections of the solution.822 HARKISS AND LINLEY methylation of the acids contained in the balsam, in which the matrix is resinous, was also complete, nine replicate amounts of a commercial sample of tolu balsam were analysed.The results are summarised in Table 111. TABLE I11 ANALYSIS OF A COMMERCIAL SAMPLE O F TOLU BALSAM Replicate No.* 1 2 3 1 5 6 7 8 9 Over-all mean Benzoic acid, per cent, r C o e f f i c i e n t Mean of variation 7.7 2.6 7.4 1.6 7.9 2.9 7.8 0.8 7.5 0.8 7.8 0.7 7.8 2.1 7.7 0-8 7.7 1.3 7.8 1.3 Cinnamic acid, per cent. -ent Mean of variation 10.5 1.0 11.3 1-6 10.9 1.0 11.3 1.2 11.2 0.7 11.2 1.2 11-1 0.6 10.3 0.3 11.4 2.0 11.0 1.1 Benzyl benzoate, per cent. r Mean 11-4 11.5 11.4 11-3 11.5 11.7 11.4 11.3 11.4 11.4 -I Coefficient of variation 1.6 1.9 0.8 1.2 0.9 3.1 2.4 0-5 3-1 1.7 * Results calculated from four determinations on each replicate amount. The sample of tolu balsam used in this work was found to contain only a trace amount of benzyl cinnaniate, so that an accurate quantitative determination of this component could not be made without amending the experimental conditions.This finding agrees with constitumts listed in the official monograph for Tolu Balsam B.P.C.13 However, current investigations indicate that measurable amounts of this ester occur in authentic museum samples of the drug and can be determined by this method. The results given in Table I11 show the method to be reliable and reproducible for the analysis of tolu balsam. The chromatographic determination of free balsamic acid and ester components of the drug offers a significant advantage over the official standards, particularly as the latter include the acid and ester components of the resin, which have little or no therapeutic value.A detailed study of several samples of the drug and comparison with official values is the subject of current work and will be reported later. In addition to benzyl cinnamate, other trace constituents can be determined simul- taneously, and may be important in detecting sophistication of the drug. Preliminary studies indicate that the method can readily be applied to the analysis of other balsamic drugs. The authors express their thanks to Mrs. N. Dale for valuable technical assistance. 1. 2. 3. 4. 5 . 6. 7. 8. 9. 10. 11. 12. 13. REFERENCES “The British Pharmacopoeia 1968,” The Pharmaceutical Press, London, 1968. “The Pharmacopoeia of the United States of America, 18th Revision, 1970,” United States Pharma- copoeial Convention Inc., Washington, D.C., 1970. Cocking, T. T., Q. ,JZ Pharm. Pharmac., 1931, 4, 330. Garratt, D. C., “The Quantitative Analysis of Drugs,” Third Edition, Chapman and Hall, London, 1964, p. 643. Jork, EI., Dt. ApotkZtg, 1962, 102, 1263. Van Severen, R., Delaey, J. A., and Jacobs, J.. Pharm. Tijdschr. Belg., 1967, 44, 17. hlonard, A., and Grenier, A., “Fifth International Symposium on Chromatography and Electro- ICarlsen, J., and Svensend, A. B., Meddr Nowk Farm. Sels., 1965, 27, 91. Kaltagawa, S., and Tsuda, S., Osaka Furitsu Kogyo Shoreikan Hokoka, 1966, No. 38, 52; Chem. Eistert, B., in Foerst, W., Editor, “Newer Methods of Preparative Organic Chemistry,” Intcr- Clarke, E. G. C., Humphreys, D. J., and Stoilis, E., Analyst, 1972, 97, 433. Brian, B. L., Gracy, R. W., and Scholes, V. E., J . Chramat., 1972, 66, 138. “British Pharmaceutical Codex 1968,” The Pharmaceutical Press, London, 1968, p, $53. Received May 30th, 1973 Accepted June 19tk, 1973 phoresis,’’ Ann Arbor/Humphrey Science Publishers, Ann Arbor, Mich., 1969, p. 529. Abstr., 1966, 65, i9337a. science Publishcrs, New York, 1948, Volume I, p. 561.

ISSN:0003-2654    

DOI:10.1039/AN9739800819

出版商:RSC    

年代:1973

数据来源: RSC

摘要:

Analyst, November, 1973, Vol. 98, $9. 823-829 ‘823 Analytical Methods Committee REPORT PREPARED BY THE ESSENTIAL OILS SUE-COMMITTEE Application of Gas - Liquid Chromatography to the Analysis of Essential Oils Part III.* The Determination of Geraniol in Oils of Citronella THE Analytical Methods Committee has received the following report from its Essential Oils Sub-committee. The Report has been approved by the Analytical Methods Committee and its publication has been authorised by the Council. REPORT The constitution of the Essential Oils Sub-committee responsible for tlie preparation of this Report was: Mr. A. M. Humphrey (Chairman), Mr. J. H. Greaves, Mr. R. E. Kent, Mr. W. S. Matthews, Mr. R. G. Perry, Mr. J. Ridlington, Mr. R. A. Stocks and Mr. G. Watson, with Mr. P.W. Shallis as Secretary. INTRODUCTION Geraniol, a primary alcohol (C,,H,,O), occurs widely in essential oils and is the major constituent of oil of palmarosa. It is usually associated with trace amounts of its geometric isomer, nerol, and with other terpenic alcohols. This factor has made its determination in essential oils a difficult procedure. In the case of oil of citronella the geraniol content is of particular importance as this content is used as a basis for the determination of the quality and commercial value of the oil. The alcohols in an essential oil are usually determined by acetylation, but in the case of oil of citronella the citronellal is also affected by acetylation and gives rise to a falsely high result for the true geraniol content. This difficulty has been recognised for many years and to express this apparent “alcohol” content the term “total geraniol” has been adopted.Consistent values for this “total geraniol” are obtained only by the most careful work, as a slight variation in the acetylation procedure affects the degree of acetylation of the citronellal, and although procedures have been suggested for tlie subtraction of the citronellal contribution there is still a further unknown contribution from other alcohols known to be present, e.g., nerol, linalol, isopulegol and citronellol. In view of this unsatisfactory situation, the Essential Oils Sub-Committee decided to examine the possibility of using gas - liquid chromatography for the determination of the true geraniol contents of oils of citronella.HISTORICAL REVIEW In 1896, Umneyl was the first to propose that the geraniol content of oil of citronella could be related to its quality. The method used for its determination was the Liebermann acetylation procedure2 with acetic anhydride and sodium acetate. The most favourable conditions for this determination were established by Messrs. Schimmel & C O . ~ and are ostensibly the same as those in current US^.^,^ However, in 1909, SemmlerG showed that citronellal behaves towards acetic anhydride as a substituted vinyl alcohol, and according to him forms citronellal enol acetate, which is subsequently converted into isopulegyl acetate. He also noted the formation of a diacetate, which was confirmed by de Jong in 191g7 and further confirmed by Keclaire and Spoelstra8 in 1927.The latter workers further noted the variability of the results obtained by the acetyIation procedure and attributed this variability to the non-stoicheiometric reaction of the acetic anhydride with the citronellal. In their paper they suggested that the true geraniol content could be determined after the citronellal had been converted into its oxime by the method of Dupont and Labaune,”lo in which aqueous hydroxylamine solution is used. * For particulars of Part I1 of this series, see Analyst, 1973, 98, 616. @ SAC.824 A.M.C. : APPLICATION OF GAS - LIQUID CHROMATOGRAPHY [ATZa&St, VOl. 98 The situation was reviewed in 1932 by Zimmermann,ll who showed that the oximation procedure was not quantitative and further that some hydrolysis of the oxime occurred during the saponification of the acetylated oil.His work confirmed .the formation of mono- and diacetates of citronella1 and he suggested that the true geraniol content could be deter- mined by a phthalisation procedure.12 It was left to Sabetay and Naves in 193913 to publish details of a modified procedure in which phthalic anhydride and pyridine are used. However, the method is seldom used for commercial analyses. As an alternative to the acetylation method the use has been proposed of the "hot formylation" method of Glichitch,l* but it was shown by Holnessls that this procedure also suffered from anomalies similar to those of the acetylation procedure when applied to oil of citronella. Having reviewed the complexities of the previous work on this subject, the Essential Oils Sub-committee undertook a preliminary examination of the gas - liquid chromatography of oil of citronella with a view to ascertaining the feasibility of applying the method so as to obtain more specific results for the geraniol content.EXPERIMENTAL A sample of oil of Java citronella was circulated to members of the Sub-committee for gas-chromatographic examinations and seven members submitted results. Each partici- pant was asked to devise his own conditions for the test. All except one used the method of internal standards, and in all instances the instrument was calibrated by using one or more mixtures of internal standard and high-purity geraniol. A summary of the conditions used by participating laboratories is shown in Table I.It will be seen that a wide variety of instruments and conditions were used. In some instances, the homogeneity of the geraniol peak component was checked by trapping and testing it by infrared spectroscopy or thin-layer chromatography.16 TABLE I GAS-CHROMATOGRAPHIC CONDITIONS USED BY COLLABORATING LABORATORIES Laboratory . . . . A Instrument* . . . . Pye 104 Column length . . . . 9 feet Support .. . . Celite, 100 to 120 mesh Stationary phase . . Apiezon L Stationary phase loading 10% + Column temperaturelOC 120 1% FFAP Injection teiiperature/OC On-column Sample sizelpl . . . . 0.1 Chart speed/in h-l . . 6 Internal standard . , Diphenyl- methane B P.E. F-11 2 m Celi t e , 60 to 80 mesh Carbowax 20M 6% 130 220 0.2 ' 12 2-Phenyl- ethanol C P.E. 880 6 feet Chromo- sorb W, 80 to 100 mesh Carbowax 20M 16% 140 200 2.0 (dilute) 12 Nonet D Pye 104 9 feet Chromo- sorb W, 80 to 100 mesh Silicone DC 710 7-6 yo 176 On-column 0.16 60 Butyl benzoate E P.E.F-11 8 feet Chro mo - sorb W, 80 to 100 mesh Butane-1,4- diol succinate 10% 115 140 0.1 12 2-Phenyl- ethanol F Pye 104 7 feet Gas- Chrom Q Poly- ethylene gl ycol-adipate 10% 136 On-column 0-2 16 Eugenol * With flame-ionisation detector in each instance. t External standardisation used. RESULTS The results obtained in six participating laboratories by use of various methods of peak measurements are summarised in Table 11. These results show that the sample of oil of citronella probably contained between 22 and 25 per cent. of geraniol, a much lower figure than may be implied from the usual results of chemical analysis by an acetylation procedure, The variation between laboratories provides a useful guide to the differences that may be expected between laboratories that use gas - liquid chromatography, but without any st andardisat ion of conditions.November, 19731 TO THE ANALYSIS OF ESSENTIAL OILS.PART I11 TABLE I1 DETERMINATION OF GERANIOL IN OIL OF JAVA CITRONELLA Geraniol found, per cent. m/m, by*- 825 r 1 (4 24.5 22.4, 22.4, 22.6 22.6, 22.6, 22.6 23.0, 234, 22.9 - 25.1, 24-5, 24.0 - - - E F 23.0 23.3 23.6 - (4 25.4 (b) 21.8 Laboratory (4 - - 24-a,24.8 24.8, 24.8 24.8, 24.8 - 22.8, 22.2, 23.6 21.7, 23.8, 22.8 21.7, 23.6, 22.6 2 3 * Method of calculating peak "area"- (a) Integration; (b) Peak height x width a t half-height; (G) Peak height x retention distance; (d) Peak height only. t Each result is the mean of five determinations.$ Results obtained by a method of external standardisation. It was concluded that gas - liquid chromatography could serve as a basis for a reliable determination of geraniol in oil of citronella and it was also evident that a variety of instru- ments, columns and conditions could be used for this determination. Consideration of the results obtained thus far led to the adoption of a standardised procedure in which Carbowax 20M is used as a stationary phase and 2-phenylethanol as the internal standard. The homogeneity of the geraniol peak component so obtained was again checked by infrared spectroscopy, mass spectrometry and coupled thin-layer and gas - liquid chromatography.Several samples of different oils of citronella were circulated to the collaborating members, who were asked to determine the geraniol contents according to the following method. Preparation of calibration mixture-Accurately weigh about 1 g of geraniol and 1 g of 2-phenylethanol and dilute to 100ml with ethyl acetate. The geraniol used should be at least 99 per cent. pure. Preparation of sample-Accurately weigh 4 g of the oil under examination and 1 g of 2-phenylethanol and dilute to 100 ml with ethyl acetate. Gas-chromatographic conditions-Column length, 6 feet ; column packing, 15 per cent. Carbowax 20M on Chromosorb W, 85 to 100 mesh, acid washed and dimethyldichlorosilanised ; flow-rate for &-inch column, 40 ml min-l; carrier gas, nitrogen; isothermal temperature, 140 "C; and sample size, 1 to 5 pl, to suit attenuation setting.From the peak height x retention distance, determine a mean response factor, f, for geraniol to 2-phenylethanol by using the equation- 2-phenylethanol response x mass of geraniol = geraniol response x mass of 2-phenylethanol and use this factor to calculate the percentage of geraniol in the samples by using the equation- geraniol response x mass of 2-phenylethanol x 100 2-phenylethanol response x mass of sample Geraniol, per cent. =f x NOTE- The results in Table I1 support the evidence provided in Part I" of this series on the suitability of this method of measurement of relative peak response. Six different oils were circulated: two samples of Ceylon oil, two of Formosan and one each of Java and Chinese.A summary of the results obtained is given in Table 111. Each of the collaborating members in this exercise reported a good precision, but criticised the use of 2-phenylethanol as an internal standard when applied to the sample of Ceylon oil B, owing to the presence of an interfering peak. An alternative internal standard was sought, and n-dodecanol was found to be suitable. The exercise was repeated, replacing the 2-phenylethanol by n-dodecanol and restricting the determinations to two oils only,826 A.M.C. : APPLICATION OF GAS - LIQUID CHROMATOGRAPHY [A?Z&!ySt, VOl. 98 vix., Ceylon B and Java B oils. In Table IV is a summary of the results obtained, which includes details of the columns used. Again, each of the collaborating members reported a good precision and there were no difficulties in the use of the n-dodecanol as the internal standard.TABLE I11 DETERMINATION OF GERANIOL (PER CENT.) IN VARIOUS OILS OF CITRONELLA Internal standard : 2-phenylethanol A 16.8 16.9 17.6 21.5 19.9 21.8 C 17.9 18.5 17-9 21.0 20.2 22.1 D 18.0 18-6 18.0 20.9 21.3 22-4 E 17.3 17.0 17.4 22.2 21.6 22.9 F 17.9 18.2 18.1 21.1 20.9 23.1 G 17.5 17.9 18.0 21.3 21-2 23.1 Laboratory Ceylon A Ceylon B Formosan A Formosan B Java H Chinese Typical traces for the four different types of oils are shown in Figs. 1 to 4. These two sets of results can be compared with the corresponding results in Table I11 but it is to be noted that they should not be compared with the results in Table I1 as these applied to a different sample of oil of Java citronella.IDENTIFICATION OF THE GERANIOL PEAK- An initial identification of the peak was made by the use of retention data followed by the comparison of an oil with a sample of the same oil spiked with geraniol. There was no apparent increase in the peak width compared with its height, thus confirming the retention data. The actual identity of the peak was confirmed by mass spectrometry with a Perkin- Elmer RMU-5 mass spectrometer, which also confirmed its homogeneity. This observation was further confirmed by applying a coupled thin-layer and gas-chromatographic technique.l6 A sample of fortified oil was assayed for geraniol and comparison of the results with the original oil showed a recovery of 94 per cent. VARIATIONS IN LABORATORY WORKING CONDITIONS- In the final stages of the exercise it can be seen that some variation in the operating conditions still existed (see Table IV).These variations are due primarily to the different constructional details of the gas chromatographs used and may be grouped under four headings. TABLE IV DETERMINATION OF GERANIOL (PER CENT.) IN TWO OILS OF CITRONELLA Internal standard : n-dodecanol Laboratory A B C D E F G H Ceylon B 16.2 17.3 18.4 17.8 17.8 18.3 17.8 18-3 Java B 20.0 19-8 21.5 2 0 4 20-6 20.7 21.4 20.9 Stationary phase loading, per cent. 15 15 15 5 15 10 10 15 Flow-rate/ ml mi1i-l 60 22 p.s.i. 40 40 20 p.s.i. 50 40 40 Column diameter1 inch Injection On-column Flash, 220 "C Flash, 200 "C On-column Flash, 150 "C On-column Flash, 200 "C Flash, 150 "C ' Stationary phase Zoading-Although specified in this collaborative work at 15 per cent., the availability of columns with a different loading may make them an attractive alternative. In the case of laboratory D, the lower loading was used in order to reduce the retention time.This laboratory was using a &-inch glass column and the flow-rate of 40 ml min-l gave unduly high retention times with a 15 per cent. loading. Laboratory H also reported long retention times, but managed to achieve results with a 10 per cent. loading. Laboratory A was able to use a 15 per cent. loading with a $-inch glass column because of the higher flow-rate.Vovember, 19731 TO THE ANALYSIS OF ESSENTIAL OILS. PART I11 827 Ger n-Dodecanol 01 2-Phenyl -et ha no1 I Geraniol / I Fig.1. Typical chromatogram of Ceylon citronella oil, with n-dodecanol as internal standard. Total analysis time 30 minutes Fig. 2. Typical chromatogram of Java citron- ella oil, with 2-phenylethanol as internal standard. Total analysis time 30 minutes Geraniol s i Geraniol Fig. 3. Typical chromatogram of Chinese citronella oil. Total analysis time 30 minutes Fig. 4. Typical chromatogram of Formosan citronella oil. Total analysis time 30 minutes828 A.M.C. APPLICATION OF GAS - LIQUID CHROMATOGRAPHY [Analyst, VOI. 98 Carrier jow-rate-This can be optimised for any particular column in order to give the maximum resolving power, but it is often altered so as to give the desired retention time, particularly if it is undesirable to alter the temperature.Measurement of the flow-rate is not always easy or convenient and some laboratories give the inlet pressure. Column diameter-This is usually fixed by the design of the instrument and it is often found that glass columns are a inch in external diameter whereas stainless-steel columns are Q inch in external diameter. Other variations are also known to exist. The wider-bore columns have a lower pressure drop and require higher flow-rates than an equivalent column of smaller diameter in order to achieve similar retention times. Injection system-This can either be “on column” or “flash” and the results did not show that either method was inferior to the other. In general, it was found that the variations shown in Table IV did not affect the results, but it must be borne in mind that the stationary phase loading, the flow-rate and the column dimensions are all inter-related so far as the retention time is concerned, and widely different variations of these factors may adversely affect the resolution.There was no evidence that an injector temperature of 200 “C had any adverse effects and no degradation was apparent from the use of stainless-steel columns. The use of acid- washed, dimethyldichlorosilanised Chromosorb W was found to be satisfactory and no attempts were made to use more sophisticated supports. CONCLUSIONS The quantitative determination of geraniol in commercially available samples of oils of citronella can be satisfactorily achieved by a gas - liquid chromatographic procedure. Based on experience with a range of oils and operating conditions, the Sub-committee recommends the procedure given in the Appendix, which should provide accurate results for the determination of the geraniol content with an acceptable level of precision, and should reduce variations, both within and between laboratories, to a satisfactory level.Appendix RECOMMENDED METHOD FOR THE DETERMINATION OF GERANIOL IN OILS OF CITRONELLA BY GAS - LIQUID CHROMATOGRAPHY OPERATING CONDITIONS- as constant as practicable. its linear range1* : It is essential that throughout a determination the operating conditions are maintained It is also essential to use the detector - amplifier system within Detector . . .. .. Stationary phase . . Stationary phase loading Column . . .. .. Column temperature . . Internal standard .. Support . . . . . . Injection .. .. Chart speed . . .. Flame ionisation Carbowax 20M Chromosorb W, acid washed, dimethyldichlorosilanised, SO to 100 mesh About 10 per cent. m/m 5 to 9 feet. Outside diameter .Q to & inch, glass or stainless steel Isothermal, 140 “C On-column or flash between 150 and 200 “C 6 in h-1 (minimum) n-Dodecanol. Purity by gas - liquid chromatography not less than 99 per cent. Geraniol . . .. Sample size . . Peak heights . . Gas fiow-rates . . . . To give satisfactory instrument performance Solvent . . .. . . Ethyl acetate . . . . . . Purity by gas - liquid chromatography not less than 99 per cent. Such that the internal standard and geraniol peaks fall within the linear Internal standard and geraniol, within 40 to 76 per cent.of full-scale range deflection DETERMINATION OF THE FACTOR, f, FOR THE INTERNAL STANDARD (GERANIOL = 1)- Make all weighings to an accuracy of 0.2 mg. Weigh about 1.0 g of geraniol and 1.0 g of n-dodecanol (or such other amounts as will give approximately equal heights for the two peaks), and dissolve them in about 100 ml of solvent. Inject 1.Op1, or such other volume of the solution as will ensure response within the linear range, and calculate to three decimal places the factor, f, from the equationNovember, 19731 TO THE ANALYSIS OF ESSENTIAL OILS. PART 111 829 h x d W , f = 1 2 , x x X W where he is the height of the geraniol peak, d, the retention distance of the geraniol peak, h the height of the n-dodecanol peak, d the retention distance of the n-dodecanol peak, W the amount of n-dodecanol and W, the amount of geraniol.Repeat the operation twice on the same solution, and use the average of the three values off in the calculation of the geraniol content of the sample. DETERMINATION OF THE GERANIOL CONTENT OF THE SAMPLE- Weigh about 4 g of sample and an amount of n-dodecanol (usually about 1 g) that will give approximately equal heights for the two peaks of interest and dissolve them in about 100ml of solvent. Inject l.Opl, or such other volume as will ensure response within the linear range, and calculate the geraniol content of the sample to two decimal places from the equation H , H x D W, D, x w x 100 Geraniol, per cent. = f x where H , is the height of the geraniol peak, D, the retention distance of the geraniol peak, H the height of the n-dodecanol peak, D the retention distance of the n-dodecanol peak, W the amount of n-dodecanol, W, the amount of sample and f the average response factor. Repeat the operation twice with the same solution, and report the average of the three results to one decimal place. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. REFERENCES Umney, J. C., Pharm. J., 1896, 3, 199 and 256. Liebermann, L., Bey. dt. chem. Ges., 1888, 21, 435 and 1172. Schimmel & Co., Technical Leaflet, 1923, p. 18. Jolly, S. C., Editor, “Official, Standardardised and Recommended Methods of Analysis,” The Society for Analytical Chemistry, London, 1963. British Standards Institution, B.S. 2073 : 1962. Semmler, F. W., Ber. dt. chem. Ges., 1909, 42, 2016. de Jong, A. K. W., Kon. Akad. Wetenach., Amsterdam, 1919, 21, 576P. Reclaire, A., and Spoelstra, D. B., Perfum. Essent. Oil Rec., 1927, 18, 130. Dupont, G., and Labaune, J., Amer. Perfumer, 1924, 19, 257. Zimmermann, J., Ibid., 1932, 23, 128. Schimmel & Co., Technical Leaflet, 1912, October, p. 39. Sabetay, S., and Naves, Y . R., Annls Chim. Analyt., 1937, 19, 285. Glichitch, L. S., Bull. SOC. Chim. Fr., 1923, 33, 1284. Holness, D., Alzalyst, 1961, 86, 231. Humphrey, A. M., J . Chromat., 1970, 53, 375. Analytical Methods Committee, Analyst, 1971, 96, 887. Primavesi, G. R., McTaggart, N. G., Scott, C. G., Nelson, F., and Wirth, M. M., J . Inst. PetroZ., NOTE-Reference 17 is to Part I of this series. , , Perfum. Essent. Oil Rec., 1924, 15, 363. -- 1967, 53, 367.

ISSN:0003-2654    

DOI:10.1039/AN9739800823

出版商:RSC    

年代:1973

数据来源: RSC

摘要:

1330 Analyst, November, 1973, Vol. 98, pp. 830-837 Recommended Methods for the Evaluation of Drugs ’ PREPARED BY THE JOINT COMMITTEE OF THE PHARMACEUTICAL SOCIETY AND THE SOCIETY FOR ANALYTICAL CHEMISTRY ON RECOMMENDED METHODS FOR THE EVALUATION OF DRUGS The Chemical Assay of Cascara Bark and Cascara Dry Extract IN 1968, Panel 3 of the Joint Committee of the Pharmaceutical Society of Great Britain and the Society for Analytical Chemistry published recommended methods for the chemical assay of cascara dry extract, cascara tablets and cascara bark.l Subsequently, the European Pharmacopoeia2 has included a modified version of the method recommended by the Joint Committee for the assay of cascara bark. In consequence, the Joint Committee set up a Panel to compare the two different methods and to report its findings.The work carried out by this Panel and the conclusions it has drawn are given in this report. The Constitution of the Panel was: Dr. D. C. Garratt (Chairman), Dr. C. Daglish, Mr. J. D. Edmond, Professor J. W. Fairbairn, Mr. S. C. Jolly, Dr. P. A. Linley, Mr. N. Nix, Mr. C. A. Macdonald, Mr. M. H. Ransom, Mrs. S. Richens and Mr. F. H. Tresadern, with Mr. P. W. Shallis as Secretary. Cascara Bark EXPERIMENTAL The method recommended by the Joint Committee is based on that described by Fair- bairn and S i r n i ~ . ~ In this method preliminary extraction of the dry powdered bark is carried out with 70 per cent. ethanol, from which the free anthraquinones are extracted with carbon tetrachloride and the aloins and cascarosides are partitioned between ethyl acetate and water.The aloins are then recovered from the ethyl acetate phase, oxidised with iron(II1) chloride, the product is extracted with carbon tetrachloride, transferred to sodium hydroxide solution, and the resulting aglycones are determined by measuring the extinction at the maximum at about 500 nm. The cascarosides are determined in a similar way in the aqueous phase, and the concentrations of aloins and cascarosides present in the sample are calculated, as cascaroside A, from an established Eizm value at 500 nm of the red solution obtained from pure cascaroside A under the same conditions. The method included in the European Pharmacopoeia2 differs from the Joint Committee’s method in two main respects. First, the preliminary extraction is carried out with hot water instead of with 70 per cent.ethanol, and secondly, the transfer of the final product to sodium hydroxide solution is made by evaporating the carbon tetrachloride solution to dryness and dissolving the residue in 1 N sodium hydroxide, whereas in the Joint Committee’s method the product is extracted from the carbon tetrachloride with 1 N sodium hydroxide. The Panel decided to carry out a collaborative comparison of the two methods, and this comparison was extended to include the other two possible combinations of the methods of preliminary extraction with the alternative methods of final transfer of the product to sodium hydroxide solution. The requirement of the European Pharmacopoeia method that the extinction of the final coloured solution should be measured within 1 hour of making the sodium hydroxide solution up to volume was thought by members of the Panel to be a possible source of major variations, as in the original work of Panel 3 the final coloured solution had been found to be unstable in daylight.In consequence, it was decided that in the collaborative work extinctions should, for the purposes of comparison, be made within 5 minutes of adjusting the final solution to volume and again after 1 hour. In order to indicate possible contamination of the solutions containing aloins and cascarosides, both methods under investigation incorporate an additional extinction measure- ment at 440 nm; the ratio of the extinction at 440 nm to that at 500 nm is then taken as an indication of the validity of the assay result.The lower limiting values for this ratio given in the Joint Committee’s method are 1.7 for the determination of aloins and 1-8 for the determination of cascarosides. The European Pharmacopoeia had originally decided that 1-8 should be the limiting ratio value for both determinations. The Panel therefore decided to record all ratio values in its collaborative comparison of the methods in order to ascertain whether this higher value for the determination of aloins was justified. @ S.IC.THE CHEMICAL ASSAY OF CASCARA BARK AND CASCARA DRY EXTRACT 83 1, The assay included in the European Pharmacopoeia makes use of standardisation against 1,s-dihydroxyanthraquinone, whereas in the Joint Committee’s method the assay results are calculated from an established E i k value for pure cascaroside A.Members of the Panel were of the opinion that, as no established reference sample of 1,s-dihydroxyanthraquinone was available, differences between samples of this material could give rise to errors greater than those normally associated with spectrophotometric measurement. It was therefore decided that, for the purposes of the collaborative test, assay results would be calculated by using the known E1”& value of 125 for cascaroside A under the same conditions. A common sample of powdered cascara bark was distributed to all collaborators and assays were carried out in duplicate by both methods and the other two possible combinations of the conditions. The assay results and the individual values for the ratios of the extinctions at 440 nm and at 500 nm are given in Tables I and 11, respectively.TABLE I COMPARISON OF RESULTS FOR THE ASSAY OF CASCARA BARK BY FOUR DIFFERENT METHODS Methods- 1 : Joint Committee’s meth0d.l 2 : European Pharmacopoeia method.2 3 : Toint Committee’s method, but with evaporation of final carbo!i tetrachloride solution before transfer to sodium hydroxide solution. 4: European Pharmacopoeia method, but with solution with 1 N sodium hydroxide. Aloins, as cascaroside A, per cent. & Method Laboratory 5 niinutes 1 Mean . . .. . . Standard deviation . . Coefficient of variation, per cent. . . .. 1-Hour means* .. 2 A B C D E F G Mean .. .. .. Standard deviation . . Coefficient of variation, per cent. . . .. l-Hour mcans* ..3-40 3.54 3.56 3.55 3.82 3.90 3-72 3-55 2-72 3-22 3-17 3-05 3.85 3.67 3.48 0.337 9.68 100 3-51 3.43 2.54 2.61 3.67 3.9 1 3.29 3-15 3-10 3-04 3-32 3-21 3-32 3.24 0.378 11.67 100 1 hour 2.99 3.15 3.53 3.33 3.69 3.85 3-57 3.48 2.68 3.08 3.00 2.90 3.77 3.52 3-32 0.359 10.80 95.4 3.43 3.34 2.48 2.57 3.54 3-50 3.2 1 3.08 3.08 3-03 3.07 2.94 3-22 3.11 0.321 10.33 96.0 extraction of final carbon tetrachloride Cascarosides, as cascaroside A, per cent. 5 Ainutes 6.12 6-13 5-62 6.07 6.47 6.34 6.47 6-55 4.53 5.64 5.63 5-61 6.16 6.1 1 5.96 0.529 8-87 100 6.38 6.39 6.5 5-79 7-04 7-04 7.18 7.43 6.80 6-22 6.18 6.26 6.85 6.62 0-475 7.17 100 1 hour 5.90 5-94 5.5 6.06 6-29 6-24 6-07 6.28 4.43 5.52 5.31 5-41 6.08 6.09 5.79 0.514 8-87 5-33 5.29 6-21 5-89 6-84 6.70 6-72 7.08 6.76 6.52 5-47 5-48 6.54 6.14 0.663 97-1 10.80 92.7 Total glycosides, as cascaroside A, per cent.& 5 minutes 9.52 9-67 9.18 9.62 10.29 10.24 10.19 10-10 7-25 8-86 8.80 8.66 10.01 9-78 9-44 0.837 8.87 100 9.89 9-82 9.04 8.4 10.71 10-95 10.47 10.68 9.90 9.26 9.50 9-47 10.17 9-86 0.727 7-38 100 1 hou-r 8-89 9.09 9.03 9.6 9.98 10.09 9.64 9.76 7.11 8-60 8-31 8.31 9-85 9.61 9-13 0-834 9.13 8-76 8.63 8-89 8.46 10.38 10.20 9.93 10.16 9.84 8.56 8.64 842 9.76 9-34 0.760 8.13 [continued 96.7 94-7832 THE CHEMICAL ASSAY OF CASCARA BARK Method Laboratory 3 A B c; D E F G Mean . . .. .. Standard deviation . . Coefficient of variation, per cent. . . .. l-Hour means* .. 4 A B c D E F G Mean . . .. .. Standard deviation . . Coefficient of variation, per cent. . . .. 1-Hour means* ..TABLE I (continzled) Aloins, as cascaroside A, per cent. & 5 minutes 3.54 3.60 3.45 3.33 3.84 3.74 3.54 3.48 3.49 3-28 3-28 3-17 3-91 3-72 3.53 0.220 6-25 100 3.49 3.45 2.57 2-59 3-12 2.98 3-43 3.36 2.72 3.72 3-41 3.41 3.30 3-20 0.370 11.59 100 1 hodr 2.99 3-06 3.3 3-15 3-79 3.65 3.40 3.40 3-43 2-92 3-05 2.98 3-8 1 3.58 3.32 0.306 9.20 94.1 3.40 3-36 2-5 2-59 3-04 2.90 3-34 3.28 2-72 3-69 3-18 3.24 3.23 3.11 0.347 11-14 97.2 Cascarosides, as cascaroside A, per cent. & 5 ininutes 6-10 5-93 5-38 6-32 7-18 6.65 6-47 6.70 6-34 5-81 5-73 5.63 6.10 6-10 6-17 0.479 7-76 100 6.50 6-45 6.09 6-08 6.86 7-19 7.11 7-26 7-04 5.68 5.66 5-75 6-91 6-60 0.598 9.19 100 1 hour 6.07 5.83 5.30 6.27 7.11 6-57 6.09 6.47 6.20 5-36 5-41 5-31 5.90 5-87 5.98 0.532 8.89 5.73 5.79 6.9 5-72 6.69 6.63 6-69 6.98 7.06 5-21 5-10 6-18 6.75 6-11 0.716 96.9 11-72 94-0 [Analyst, Vol.98 Total glycosides, as cascaroside A, per cent. & 5 minutes 9.64 9.53 8-83 9.65 11-02 10-39 10.0 1 10.18 9-83 9.09 9.01 8-80 10.01 9.82 9.70 0-628 6.47 100 9.99 9-90 8-66 8.67 9-98 10-17 10.54 10.61 9.76 9.40 9.07 9.16 10.21 9.70 0.655 6-76 100 1 hour 9.06 8.89 8.6 9.42 10.90 10.22 9.49 9-87 9.63 8-28 8.29 9.71 9.45 9.30 0.762 8.20 8.46 95.9 9-13 9.15 8.4 8.3 1 9.73 9.53 10.03 10.26 9.78 8.90 8.28 8.42 9-98 9.22 0.714 7-76 95.1 * These figures are the mean values for the results after 1 hour relative to the values obtained for the reading after 5 minutes. RESULTS AND DISCUSSION It can be seen from Table I that the results by both methods and the other two com- binations of conditions are very similar, and it is apparent that no advantage is to be gained from the alternative combinations of preliminary extraction and final transfer to sodium hydroxide solution.There is no significant difference between the results by both methods, although it can be seen that the European Pharmacopoeia method gives slightly higher figures for cascarosides and total glycosides. The European Pharmacopoeia method was, however, found to offer certain advantages over the Joint Committee’s method in speed and ease of manipulation at some stages. Within-laboratory agreement between results of the duplicate assays is for the most part good and inter-laboratory variations are considered to be no greater than would be expected for a method of this type. The results for total glycosides based on extinction readings taken 1 hour after the final solution had been made up to volume were on average 6 per cent. lower than those based on readings made within 5 minutes, thus indicating that some degradation of the coloured solution had occurred, but no significant differences resulted.The values for the ratios of extinctions a t 500 and 440 nm are given in Table 11, and indicate that a limiting value of 1.8 for the determination of cascarosides is satisfactory. However, the Panel is of the opinion that the values for the extinction ratios obtained inNovember, 19731 AND CASCARA DRY EXTRACT 833 the collaborative work point conclusively to the retention of a limiting value of 1.7 for the determination of aloins, rather than the figure of 1.8 originally proposed by the European Pharmacopoeia.Method TABLE I1 RATIO OF EXTINCTIONS AT 500 nm TO THOSE AT 440 nm FOR THE The key to the methods is as given in Table I READINGS TAKEN WITHIN 5 MINUTES Aloins Cascarosides w - 500nm 440 nm Ratio 500nm 440nm Ratio 1 Mean* . . .. .. , . 0.351 0.193 1.83 0.601 0.297 2.03 Standard deviation .. .. 0.09 0.08 Coefficient of variation, per cent. 5.04 4-12 2 Meant .. . . .. . . 0.326 0.175 1.86 0.655 0.315 2.09 Standard deviation . . .. 0.10 0.12 Coefficient of variation, per cent. 5-47 5.61 3 Mean* . . .. .. . . 0.356 0.192 1.86 0.623 0-301 2-08 Standard deviation .. .. 0.09 0.10 Coefficient of variation, per cent. 4.60 4.7 1 4 Meant . . .. .. . . 0.321 0.177 1-82 0.655 0.319 2.06 Standard deviation ... . 0.08 0.09 Coefficient of variation, per cent. 4.22 4.28 * Values are for 14 determinations by 7 laboratories. t Values are for 13 determinations by 7 laboratories. One member of the Panel noticed that originally in the European Pharmacopoeia method no instruction was given regarding the method of heating to be used when evaporating the final carbon tetrachloride solution to dryness before dissolving the residue in sodium hydroxide solution. In the Joint Committee’s method excessive heating of the final solution is avoided by carrying out the evaporation on a bath of boiling water. To test the effect of the method of heating used for the evaporation of the carbon tetrachloride solution to dryness, the member subjected portions of the carbon tetrachloride solution of an aloins fraction and a cascarosides fraction to heating on a bath of boiling water and on an electric hot-plate.The residue from each was then dissolved in 1 N sodium hydroxide and the extinction measured at 500 nm; the results were as follows: Water-bath Hot-plate Aloins fraction .. .. . . 0-386 0.300 Cascarosides fraction . .. . . 0.721 0.513 From these results the Panel concluded that, as the method of heating used for the evaporation of the carbon tetrachloride could have a profound effect on the extinction of the final alkaline solution, heating on a bath of boiling water should be specified. The Panel’s observations on the European Pharmacopoeia method were passed to the Commission’s Group of Experts No. 13 (Pharmacognosy) for consideration.This Group accepted the retention of the ratio value of 1.7 for the determination of aloins and also the requirement that heating of the flask on a bath of boiling water should be specified as the method for evaporation of the carbon tetrachloride solution to dryness. It did not, however, accept that the assay should be standardised against an established Ei%m value for pure cascaroside A. The Panel is opposed to the introduction of the additional step necessitated by the standardisation of the assay against 1,8-dihydroxyanthraquinone, and is of the opinion that it could be justified only if a reference sample of the standard were made available. Cascara Dry Extract The Panel, having accepted the modifications of the originally recommended method for the assay of cascara bark1 detailed above, decided that it would be advisable to investigate the possibility of incorporating these modifications in the recommended method for the assay of cascara dry extract.In the Joint Committee’s published recommendations the method834 THE CHEMICAL ASSAY OF CASCARA BARK [Analyst, VOl. 98 for the assay of cascara dry extract differed from that for the assay of cascara bark only in the mass of sample taken and in the volume of water-saturated ethyl acetate used for extraction at the partition stage. EXPERIMENTAL A sample of cascara dry extract was circulated to all the participating laboratories for assay by the procedure as modified to incorporate initial extraction with hot water and transfer of the final product to sodium hydroxide solution after evaporation of the carbon tetra- chloride solution to dryness.All laboratories found during the extraction of the free aglycones with carbon tetrachloride that an emulsion formed at the interfacial layer. This emulsion was either impossible or, at best, extremely difficult to break. Attempts to break down the emulsion by the addition of sodium chloride were entirely unsuccessful, continuous centri- fugation met with partial success in some laboratories and in one laboratory heating it gently after the addition of a small volume of water afforded some success, but in no instance was all the emulsion broken down by these means. Another laboratory found it possible to avoid the formation of emulsion after initial extraction with hot water by shaking 10 ml of the water extract with 2 drops of 1 N hydrochloric acid, 5 ml of 95 per cent.ethanol and 40 ml of carbon tetrachloride, allowing the layers to separate, extracting the aqueous layer with a further 40 ml of carbon tetrachloride and then proceeding with the ethyl acetate extraction of the aqueous phase in the usual manner. The Panel, however, considered that there was little to choose between this approach and the Joint Committee’s original recommendation of an initial overnight extraction with 70 per cent. ethanol. A further collaborative test involving two samples of cascara dry extract was then carried out. On this occasion the initial extraction was carried out with 70 per cent. ethanol, after which the modified procedure was applied except that the carbon tetrachloride extrac- tion, before the partitioning with ethyl acetate, was carried out with two 40-ml portions of carbon tetrachloride instead of two 20-ml portions, and the volume of ethyl acetate used in the partitioning stage was reduced from 300 to 120ml.In this work, two laboratories encountered some trouble from the formation of emulsions, which was surprising as this effect had not been evident in the original work carried out for the Joint Committee. The erriulsions formed on this occasion were not, however, troublesome, and could be broken down without difficulty. The method as used in this work was considered to be satisfactory and was applied collaboratively to a sample of spray-dried dry extract so as to ensure that the method was satisfactory for the material prepared by different processes.The results obtained on three samples of cascara dry extract are shown in Table 111. DISCUSSION The modified procedure for the assay of cascara bark involving initial extraction with hot water gave rise to the formation of intractable emulsions in a subsequent stage of the assay when applied to samples of cascara dry extract. The Panel found that this problem could be overcome by reverting to the use of 70 per cent. ethanol for the initial extraction, as originally recommended. The modified procedure for the transfer of the final product to sodium hydroxide solution was, however, found to be satisfactory for the assay of cascara dry extract and offered some advantage in that it was easier and quicker to perform.RECOMMENDATION The Panel recommends that the methods for the assay of cascara bark and cascara dry extract previously published by the Joint Committee1 should be replaced by the methods given in Appendixes I and I1 to this Report. Appendix I RECOMMENDED METHOD FOR THE ASSAY OF CASCARA BARK REAGENTS- Carbon tetrachloride. Iron(lI1) chloride, mhydrous, or iron (111) chloride solution, 60 per cent. m/V.November, 19731 AND CASCARA DRY EXTRACT 835 Hydrochloric acid, 36 per cent. m/m and 1 N. Methanol. Sodium hydroxide, 1 N. Ethyl acetate, water saturated-Shake 150 rnl of ethyl acetate with- 15 ml of water for 3 minutes, and then allow the layers to separate. TABLE I11 ASSAY OF THREE SAMPLES OF CASCARA DRY EXTRACT BY THE hlETHODS GIVEN IN APPENDIX I1 Sample Laboratory 1 A C D E F G H Mean .. . . .. Standard deviation . . Coefficient of variation, per cent. . . .. 2 A C D E F G H Mean . . . . .. Standard deviation . . Coefficient of variation, per cent. . . .. A C D E G Mean . . . . . . Standard deviation . . Coefficient of variation, per cent. . . .. Aloins, as cascaro- side A, per cent. 6.48 6.57 8.83 6-95 8.68 8.84 8.90 8-80 8.75 8.67 8.20 9.52 9.42 8.35 1.02 12-22 5-97 6.00 7.57 7.10 7.92 8-30 9.04 8.96 7-87 8.03 7.50 8-74 8-72 7-82 1.01 12.86 5.30 5.14 5.56 5.56 5.10 4.76 4.92 4.80 4-76 4.87 5.47 5-51 5.1 1 5.14 0.3 1 6-04 Ratio (&OO to E440) 1.98 1.98 1.86 1-92 2.02 1.98 1.93 1.94 2.00 1.98 2.05 1-80 1-85 1.95 0.07 3.77 2.01 2.05 1.86 1.94 2.16 1.94 1-73 1.74 2-03 1.99 2.05 1-88 1.88 1.94 0.12 6.42 1.92 1.91 1.87 1.93 1-81 1 -89 1.70 1 a 7 0 l*SO 1.84 1 6:) 1.6% 1 6 6 1-80 0.11 6-00 Cascarosides, as cascaro- side A, per cent.3.62 3.68 4.55 5.99 4.53 4.10 4.60 4.70 4.63 4.56 4-30 4-18 4.28 4.44 0.58 13.07 4.65 4.54 6.10 6.17 6.54 5.70 5-76 5.62 6.08 6-49 5.70 5-64 5-59 5.74 0.60 10-45 9.50 9-48 9.08 9.08 9.02 9.64 8.58 9 50 8.7 1 8.9.) 9.13 8.711 8.94 9.11 0.33 3-65 Ratio (E5"O to E 4 4 J 2.03 1.99 1.92 1.45 1.92 1.94 2.00 2.09 1.90 2.0 1 2.06 2-01 1.86 1.94 0.16 8-28 1.93 2.18 2-08 2.04 2.09 1 *92 1.98 2.01 2.12 2.1 1 2.1 1 2.06 2.08 2.05 0.08 3.70 2.05 2.04 2.07 2-07 2.13 2.00 2.02 J -92 1-99 2.16 2.00 2 07 2.10 2 Or, 0.06 3 05 Total gl ycosides, per cent. 1@10 10.25 13-38 12-94 13.21 12.94 13.50 13.50 13.38 13.23 12.80 13.70 13.70 12.79 1.21 9.45 10.62 10.64 13-67 13.27 14-46 14.00 14.80 14-58 13-95 14.52 13.20 14.38 14.31 13.56 1.41 10.40 14.80 14-62 14-64 14.64 14.12 14-40 13.50 14.30 13-47 13.86 11 60 14 30 14.05 14.2.i 0.44 3.06836 THE CHEMICAL ASSAY OF CASCARA BARK [Analyst, Vol.98 PROCEDURE- Weigh accurately 1 &- 0.05 g of sample, and add it, with stirring, to 100 ml of boiling water in a beaker. Continue boiling and stirring for 5 minutes. Cool, transfer the mixture to a 100-ml calibrated flask, dilute to the mark with water, shake the mixture well, and filter it through a Whatman No. 4 or other suitable filter-paper. By pipette, transfer 10.0 ml of the filtrate to a separating funnel, add 2 drops of 1 N hydrochloric acid, and extract with two 20-ml portions of carbon tetrachloride. Wash the combined carbon tetrachloride extracts with 5 ml of water, and return the washings to the aqueous layer. Discard the washed carbon tetrachloride extracts.Extract the aqueous layer with four 30-ml portions of freshly prepared water-saturated ethyl acetate, on each occasion allowing separation to take place until the solvent layer is clear. Combine the four ethyl acetate extracts, and reserve both layers for further work. Determination of aloins-Transfer the combined ethyl acetate extracts to a suitable flask, distil off the solvent, and evaporate just to dryness. Dissolve the residue in 0.3 to 0.5 ml of methanol, rinse the solution out with warm water into a 50-ml calibrated flask, cool, and dilute to the mark with water. Transfer 20.0 ml of the solution to a 100-ml round-bottomed flask containing 1-2 g of anhydrous iron(II1) chloride [or 2 ml of a 60 per cent.m/V solution of anhydrous iron(II1) chloride] and 12 ml of hydrochloric acid (36 per cent. m/m). Attach a water-cooled double-surface condenser to the flask, place the flask in a bath of continuously boiling water (so that the water level is above that of the liquid level in the flask), and heat it for 4 hours. Then set it aside to cool, transfer the solution to a separating funnel, and rinse out the flask successively with 3 to 4 ml of 1 N sodium hydroxide solution and 3 to 4 ml of water, adding these rinsings to the contents of the separating funnel. Extract the contents of the separating funnel with three 30-ml portions of carbon tetrachloride. Wash the combined carbon tetrachloride layers with two 10-ml portions of water.Discard the washings, and dilute the carbon tetrachloride layer to 100.0ml with the same solvent. Transfer 20.0 ml of this solution to a suitable flask, and evaporate carefully to dryness on a bath of boiling water. Dissolve the residue in 10.0 ml of 1 N sodium hydroxide solution, and within 5 minutes measure the extinction of this solution at 440 nm and at the maximum at about 500 nm in a 1-cm cell against 1 N sodium hydroxide solution. Calculate the percentage of aloins present, as cascaroside A, on the assumption that E:3m at 500 nm of the red solution obtained from cascaroside A is 125. If the ratio of the extinction a t 500nm to that a t 440nm is less than 1.7, reject the result. Determination of cascarosides-Dilute the aqueous layer reserved from the preliminary extraction to 50-0 ml with water.Treat 20.0 ml of this solution as described under Deter- mination of aloins. Calculate the percentage of cascarosides present, as cascaroside A, on the assumption that E:%m at 500 nm of the red solution obtained from cascaroside A is 125. If the ratio of the extinction a t 500 nm to that a t 440 nm is less than 1.8, reject the result. Appendix I1 RECOMMENDED METHOD FOR THE ASSAY OF CASCARA DRY EXTRACT REAGENTS- As described in Appendix I with the addition of the following reagent. Ethanol, 70 per cent. VlV. PROCEDURE- Weigh accurately 0.5 -& 0.05 g of powdered extract and place it in a 100-ml calibrated flask with 80ml of 70 per cent. ethanol. Shake the mixture occasionally, allow it to stand overnight, make the volume up to 100 ml with 70 per cent. ethanol, shake the mixture well, and filter it through a Whatman No. 4 filter-paper. By pipette, transfer 10.0 ml of the filtrate to a separating funnel, add 10 ml of water and 2 drops of 1 N hydrochloric acid, and extract with two 40-ml portions of carbon tetrachloride. Wash the combined carbon tetrachloride extracts with 5 ml of water, and return the washings to the aqueous layer. Discard the washed carbon tetrachloride extracts. Extract the aqueous layer with four 30-ml portions of freshly prepared water-saturated ethyl acetate, on each occasion allowing the solvent layerNovember, 19731 AND CASCARA DRY EXTRACT 837 to become clear before running off the aqueous phase. Combine the four ethyl acetate extracts, and reserve both layers for further work. Continue with the determination of aloins and cascarosides as described in Appendix I. REFERENCES 1. 2. 3. Joint Committee of the Pharmaceutical Society and the Society for Analytical Chemistry, Analyst, “European Pharmacopoeia,” Volume 11, Maisonneuve S.A., Sainte Ruffine, France, 1971, p. 355. Fairbairn, J. W., and Simic, S., J . Phavm. Phavmac., 1964, 16, 450. 1968, 93, 749.

ISSN:0003-2654    

DOI:10.1039/AN9739800830

出版商:RSC    

年代:1973

数据来源: RSC

摘要:

838 Book Reviews [Analyst, Vol. 98 THIRD INTERNATIONAL CONGRESS OF ATOMIC ABSORPTION AND ATOMIC FLUORESCENCE SPECTRO- L’AVANCEMENT DES M~THODES PHYSIQUES D’ANALYSE (GAMS), LE COMMISSARIAT k L’ENERGIE ATOMIQUE, LA FACULTB DE PHARMACIE DE PARIS. 69 PAPERS PRESENTED AT THE CONGRESS. Edited by M. PINTA. Volume 1, Pp. xviii + 398; Volume 2, Pp. xviii + 399-924. London: Adam Hilger. 1973. Price i 8 the set. With the exception of the plenary lectures, most of the papers presented at the Third Inter- national Congress on Atomic Fluorescence and Absorption Spectrometry (ICAFAS) , held in Paris in September, 1971, appear in these two official volumes. The nine plenary lectures were pub- lished in the journal Mkthodes Physiques d’AnaZyse (GAMS, Paris) in a special issue in September, 1971, and in the March, 1972, issue (Vol.8, No. 1). Volume 1 begins with the Congress opening address by Proiessor M. L. Girard, in which the development of atomic-absorption and atomic-fluorescence spectroscopy are discussed, and the two previous Conferences held in Prague and Sheffield, respectively, are briefly referred to. There- after, the subject headings of this volume (number of papers in parentheses) are as follows: Theory and Methodology (lo), Apparatus (lo), Atomic Fluorescence (3) and Rocks, Soils and Minerals (9). Volume 2 has about the same number of main headings and contributions, vzz., Water, Agriculture and Kelated Subjects (ll), Biology (lo), Metals ( 5 ) and Miscellaneous (11); it also includes a cumulative Author Index. The section covering Metals deals with, for example, the determination of trace amounts of platinum metals, versatile applications of atomic-absorption spectroscopy in the steelworks industry, typified by the analysis of raw materials, the determination of atmospheric pollutants and trace amounts of aluminium in silicon-bearing steels. The latter and the deter- mination of iron in fruit drinks are both described in detail in this section.Incidentally, the paper on The Application of “Difference Atomic Absorption” to the Accurate Determination of Major Concentrations, in the Biology section, should, more appropriately, appear under Metals. Of the 69 papers contained in this two-volume lithographic publication, one is in German, the remainder being about equally divided between the French and English languages and, with the exception of the Presidential Address, which is in French, each of the technical contributions has summaries in each of these three languages.These two companion volumes present a panoramic view of the status of atomic-absorption and atomic-fluorescence (to a lesser extent flame-emission) spectroscopy up to the time of the Congress but, despite the commendable efforts made by those responsible for the early release of these papers in book form, it is almost inevitable that information in these rapidly advancing fields soon becomes out-dated, even though only about 2 years have elapsed since the Congress was held. W. T. ELWEEL METRY. PARIS, 27 SEPTEMBER-1 OCTOBER 1971. ORGANIZED BY LE GROUPEMENT POUR ION-SELECTIVE ELECTRODES.SYMPOSIUM HELD AT MATRAFURED, HUNGARY, 23-25 OCTOBER, 1972. Edited by Professor E. PUNGOR. Technical Editor I. BuzAs. Pp. 283. Budapest: Akadbmiai Kiad6. 1973. Price fj3.50. This book, produced by offset lithography from double-spaced, typewritten copy in English, is based on the Proceedings of the Symposium on Ion-selective Electrodes held a t Mhtrafiired in October, 1972. The first two thirds of the book is devoted to the seven invited plenary lectures, which were centred mainly on fundamental aspects of electrode design, behaviour and applications. One of these lectures was directed to the applications of ion-selective electrodes in continuous analysis. The remaining third of the book is given to the ten contributed lectures followed by a short summary of the symposium discussion. Not unnaturally, most of the contributed lectures were based on silicone rubber matrix membrane electrodes, although some attention was also given to Crytur solid-state electrodes as well as to liquid membrane and coated wire systems. Regarding the analytical viewpoint, appropriate conditions for using the electrodes are described, but the range of illustrative applications is necessarily limited.Thus, although some sections will be helpful to the analyst, the volume, being a record of symposium proceedings, is likely to be of more specialised interest to those in the ion-selective electrode field. J. D. R. THOMASNovember, 19731 BOOK REVIEWS 839 SELECTED ANNUAL REVIEWS OF THE ANALYTICAL SCIENCES. Edited by L. S. BARK. Volume 1.Pp. vi + 269. 1971. Volume 2. Pp. vi + 149. 1972. London: Society for Analytical Chemistry. Price jt15 per volume. This review is concerned with the first two volumes of a series of annual reviews to be pub- lished by the Society for Analytical Chemistry. The purpose of the series is to assist scientists with an interest in analysis to keep abreast of developments in the subjects covered. Each volume contains several comprehensive discussions of significant developments in a selected subject area during the preceding four or five years. The contents of Volume 1 (1971) are as follows: Molecular-sieve Chromatography, by D. M. W. Anderson, I. C. M. Dea and A. Hendrie; Photoluminescence and Chemiluminescence in Inorganic Analysis, by L. S. Bark and P. R. Wood; Recent Developments in Activation Analysis, by T.B.Pierce ; Atomic-absorption Spectroscopy, by P. Platt ; and Catalytic Methods in Analytical Chemistry, by G. Svehla. Volume 2 (1972) contains : The Techniques and Theory of Thermal Analysis Applied to Studies on Inorganic Materials with Particular Reference to Dehydration and Single Oxide Systems, by D. Dollimore; Developments in Ion Exchange, by F. Vernon ; and Thermometric and Enthalpi- metric Titrimetry, by L. S. Bark, P. Bate and J. K. Grime. The treatment of the subject matter of this series differs significantly from that of other reviews with which most analytical chemists are familiar. The subjects are more specific than general, and the authors have been given free rein to select material in order to present a state- of-the-art coverage in a systematic manner. Sufficient discussion is included to make the reviews self-contained in most instances.The reader will, of course, consult the references, as well as those of other bibliographic reviews for technical details. The reviews contained in the present volumes are well presented and should prove to be very valuable to analytical chemists working in the subject fields or in related areas or for those who require only a current awareness of progress in analytical science. It is hoped that the series will continue and expand to hasten the coverage of the broad field of modern analytical chemistry. JOHN K. TAYLOR ATLAS OF SPECTRAL DATA AND PHYSICAL CONSTANTS FOR ORGANIC COMPOUNDS. Edited by Cleveland, Ohio: The Chemical Rubber Co.It is now generally recognised that the vast amount of available scientific data can be managed only by the employment of sophisticated computerised information storage and retrieval systems. The success of such systems, however, depends greatly on the quality and type of data stored; the production of this Atlas represents the first step towards the creation of a data-bank of sufficient quality to act as the basis of a computerised system for the chemical literature. In order to be of maximum utility, a base of “hard” data of sufficient magnitude and potential was required. It was decided that the first section of the data-bank to be compiled would consist of the spectral data and physical properties for approximately 8000 compounds presented in printed format in the present volume.For the first time, comprehensive data including name, synonyms, empirical and structural formulae, Chemical Abstracts Registry Number, Wiswesser line notation, boiling- point, melting-point, density, refractive index, specific rotation, solubilities, relative molecular mass, literature references, and infrared, ultraviolet, nuclear magnetic resonance and mass spectral data are all combined for these compounds into a single volume for desk-top use. The spectral data are coded with emphasis on the selection of values characteristic of compound structure, not necessarily striving for a complete representation of the original spectra. The physical constants given for each compound are abridged from the Tables of Physical Constants of Organic Compounds section in the Chemical Rubber Company’s “Handbook of Chemistry and Physics.” It is planned to review and update these values in each edition of the Atlas.The inclusion of the Wiswesser line notation for each compound is an innovation; for those willing to expend a small effort in order to become familiar with this concise and unambiguous representation o€ chemical structure, however, it is a powerful aid in compound searching and identification. The Atlas can be used to obtain information, including spectral data, on the compounds covered or, conversely, to identify an unknown compound from some characteristic physical constant or from spectral data. A set of comprehensive indexes is given and their application is explained in the foreword to each.JEANNETTE G. GRASSELLI. 1973. Price L50. Pp. xii + 1747. The volume is well laid out and the material is presented concisely.540 BOOK REVIEWS [Analyst, Vol. 98 The publication of this Atlas represents the culmination of several years of dedicated effort on behalf of the Editor and her associates. It is a staggering production, even if judged only from its physical proportions. It comprises almost 1800 oversized pages and contains well over one million items of evaluated data. The expertise and courage required in order to organise and complete the production of the Atlas is indeed impressive. As part of an immense design to create a computerised data-bank of virtually unlimited capability for information storage and retrieval, this volume should certainly be made available in library facilities as a first edition and cornerstone of the system.G. F. KIRKBRIGHT ANNUAL REPORTS ON NMR SPECTROSCOPY. Volume 5a. Edited by E. F. MOONEY. Pp. xii Volume 5 in this well established series is divided into two parts in an effort to keep the price down. Volume 5b deals with the nuclear magnetic resonance parameters of phosphorus compounds. The present volume (5a) starts with a general review of proton magnetic resonance by T. hT. Huckerby, and is a critical survey of the 1970 literature. There follow chapters on fluorine-19 nuclear magnetic resonance spectroscopy (R. Fields) and on nuclear magnetic resonance spectro- scopy in the study of carbohydrates and related compounds (T. D. Inch) ; the former is a somewhat uncritical review of the literature for 1970, the latter an updating, covering 1968-70.Both chapters will have some general appeal although they are more for the specialist. A chapter on hetero- nuclear double resonance (W. McFarlane) updates an earlier review (1968), as does a chapter on nitrogen nuclear magnetic resonance spectroscopy (M. Witanowski and G. A. Webb). Both will be useful but it is a pity that virtually no literature later than 1970 is quoted. There follows a. chapter on nuclear magnetic resonance spectroscopy in liquids containing compounds of aluminium and gallium (J. W. Akitt), a specialist topic but welcome because it reviews all the literature to 1970 and includes some references for 1971 and 1972. The final chapter deals with the application of Fourier transformation to high-resolution nuclear magnetic resonance spectroscopy (D. G. Gillies and D. Shaw). Activity in this last field is high and is being sustained by the application of the technique to the carbon-13 nucleus. I t is a timely review but it does meet with some competition. I t is a pity that, where rcle\~~nt, the literature was not surveyed to a later date. The book would be even more useful if it had been produced earlier. W. I. STEPHEN + 696. London and New York: Academic Press. 1972. Price Q3. This is a well produced book, but a t L13 is probably suited only to library purchase.

ISSN:0003-2654    

DOI:10.1039/AN9739800838

出版商:RSC    

年代:1973

数据来源: RSC

摘要:

540 BOOK REVIEWS [Analyst, Vol. 98 Errata JUNE (1973) ISSUE, p. 447, line 26. Fov “100 ml” read “1000 ml.” SEPTEMBER (1973) ISSUE, p. 682, Table 1711, 4 lines from the bottom. For “170.6” yead “70.6.”

ISSN:0003-2654    

DOI:10.1039/AN9739800840

出版商:RSC    

年代:1973

数据来源: RSC