ISSN:0003-2654    

DOI:10.1039/AN95479FX005

出版商:RSC    

年代:1954

数据来源: RSC

摘要:

No. 18 February, 1954 THE SOCIETY FOR ANALYTICAL CHEMISTRY BULLETIN FORTHCOMING MEETINGS Annual General Meeting of the Society, March 3rd, 1954 THE Annual General Meeting of the Society will be held at 4.30 p.m. on Wednesday, March 3rd,* 1954, in the Meeting Room of the Royal Society, Burlington House, Piccadilly, London , W.1. This will be followed at about 5 p.m. by the Bernard Dyer Memorial Lecture, entitled “The Contribution of Public Analysts and Other Analytical Chemists to Public Welfare,” to be given by E. B. Hughes, D.Sc. , F.1C.I.C. * The date of this meeting has been altered since the Programme of Meetings for the Session was printed. Informal Dinner of the Society THE Society will hold an Informal Dinner at the Trocadero Restaurant, Piccadilly Circus, London, W.1, on Wednesday, March 3rd, 1954, at 7 p.m.for 7.30 p.m. Guests, particularly ladies, will be welcome. Ordinary Meeting of the Scottish Section, March llth, 1954 AN Ordinary Meeting of the Scottish Section will be herd at 7.15 p.m. on Thursday, March llth, 1954, at the George Hotel, George Street, Edinburgh, 2. At this meeting a lecture entitled “Applications of Infra-red Spectroscopy” will be given by H. A. Willis, BSc. Ordinary Meeting of the Physical Methods Group, March 9th, 1954 THE Forty-fourth Ordinary Meeting of the Physical Methods Group will be held at 6.30 p.m. on Tuesday, March 9th, 1954, in the Meeting Room of the Chemical Society, Burlington House , Piccadilly, London, W. 1. The subject of the meeting will be “Refractometry and Interferometry,” and the following papers will be presented- “Differential Refractometers: Theory and Construction,” by G.H. F. Seiflow, M.A., A.1nst.P. “An Application of Differential Refractometry,” by R. Hill, B.Sc. , A.R.I.C. “Interferometric Refractometry: a Survey of the Methods,” by H. G. Kuhn, M.A., D.Phi1. “The Use of a Rayleigh Interferometer for Estimating Trichloroethylene,” by R. E. Jahn, M.A.PAPERS ACCEPTED FOR PUBLICATION IN THE ANALYST THE following papers have been accepted for publication in The Analyst, and are expected to appear in the near future. It is not possible to enter into correspondence about any of them. “The Polarographic Determination of Fluoride. Part I : Basic Principles of the Method : Application to the Cathode-ray Polarograph,” by B. J.MacNulty, G. F. Reynolds and E. A. Terry. Modern interest in traces of fluoride has revealed the need of more sensitive methods of fluoride determinaticn. In this paper a method of great sensitivity for determining fluoride polarographically is described. The method is based on the depression by fluoride of the polarographic step given by the reduction of the aluminium - Solochrome Violet R.S. complex. The step depression is shown to be linearly related to amount of fluoride down to 0.001 pg per ml. The use of this method with the cathode- ray polarograph is described. “The Determination of Glucosamine,” by R. Belcher, A. J. Nutten and Miss C. M. Sambrook. The colorimetric method for the determination of glucosamine based on the reactions with acetylacetone and p-dimethylaminobenzaldehyde has been systematically examined.Severa.1 improvements have been made in the method, which has been applied to the determination of glucosamine in N-acetyl-a-methylglucosaminide and h.eparin. The method has been adapted for use with commercially available instruments. “Colorimetric Determination of Iridium and Rhodium,” by A. D. Maynes and W. A. E. McBryde. A procedure for the colorimetric determination of iridium has been developed in which the sulphate is oxidised. by ceriumIv sulphate to produce a red solution. The tin11 chloride procedure for the colorimetric determina- tion of rhodium has been examined with special attention to the effect of the presence of iridium. A procedure has been worked out for the applica- tion of these methods in sequence to the: analysis of solutions containing iridium and rhodium together, without the necessity of a prior separation.Some data are presented to show that the :mixed perchloric - phosphoric acid procedure for the colorimetric determination of iridium may lack precision. “The Spectrophotometric Determination of Magnesium with Thiazol Yellow Dyes,” by T. A. Mitchell. A critical examination of the Thiazol yellow method for the colorimetric determination of magnesium has shown the following: (i) The fading of the Thiazol yellow - magnesium hydroxide complex is caused by “ageing” of the magnesium hydroxide. This change in the structure of the colloid, which takes place both in the presence and the absence of Thiazol yellow, is inhibited by the addition of glycerol and concentrated sodium hydroxide.(ii) The solubility of magnesium hydroxide and hence of the coloured complex is greatly increased by the colloid protectors, starch and polyvinyl alcohol. Starch, however, is preferable to polyvinyl alcohol for this purpose, because, unlike the alcohol, it does not itself affect the colour of the dye or dye-complex. (iii) Numerous cations and organic compounds interfere, and neither their removal by precipitation nor the use of “compensating solutions” satisfactorily controls this effect. A method is accordingly proposed in which the magnesium itself is precipitated from solution as magnesium ammonium phosphate, the pre- cipitate is redissolved and the colorimetric determination is carried out on the resulting solution, starch being used as the protective colloid and glycerol as the colour stabiliser.The absorptions of the solutions are measured at a fixed brief interval after colour development.“An Improved Apparatus for the Micro-determination of Unsaturation in Organic Com- pounds by Catalytic Hydrogenation,” by A. F. Colson. A description is given of an improved form of the apparatus devised by Johns and Seiferle for the micro-determination of unsaturation by catalytic hydrogenation. The improved apparatus can be used for the hydrogenation of solid or volatile liquid samples at temperatures ranging from 0°C (or lower) to about f-50” C . The final measurement of the volume of hydrogen absorbed has been made more accurate and precise by simple modification of the original apparatus, and by housing the entire assembly in a constant temperature cabinet.The procedure for making a determination is described in detail, and some results for pure organic compounds are given. The maximum relative error to be expected in routine determinations is about f2 per cent. “The Assay of Penicillin in Compound Feeding Stuffs,” by S. A. Price and Kay A. Boucher. A large-plate method is described for the assay of penicillin in feeding stuffs. The primary standard solution is prepared by dilution in methanol of a buffered aqueous solution of crystalline sodium penicillin G. Final dilutions for assay are made in an unfortified extract of the feeding stuff under test. Both sodium penicillin G and procaine penicillin are found to be unstable when dissolved in aqueous methanol, unless phosphate is also present.Samples are extracted with methanol and the methanolic solutions are taken up on paper discs essentially as described by Esposito and Williams. The dried discs are applied to the medium in a randomised Latin square assay design. With the method as described, the limits of error (P = 0-95) are of the order of 90 to 11 1 per cent. in an 8 x 8 assay of two samples with 8 replicates per dose, or 85 to 117 per cent. if four samples are accommodated and the number of replicates is reduced to 4. Bacillus subtilis is used as the test organism. “The Absorptiometric Determination of Traces of Copper in Highly Purified Water,” by E. N. Jenkins. A method is described for the determination of copper in highly purified water at the low levels significant in aluminium corrosion. Traces of copper down to 0.001 p.p.m.can be measured absorptiometrically as cupric diethyl- dithiocarbamate after a single extraction from a 500-rnl sample into 10 ml of chloroform in the presence of a citrate buffer and of disodium ethylenediamine- tetra-acetic acid. No interference results from the presence of 1 p.p.m. of common cations or of the sulphide or cyanide anions. A simple modification is described to eliminate the interference of bismuth and antimony. “The Absorptiometric Determination of Dissolved Oxygen,” by J. Banks. The use of 3: 3’-dimethylnaphthidine as a colorimetric reagent for dis- solved oxygen in boiler feed-water is described; the range of concentrations covered is 0 to 0.1 ml per litre.The Winkler reaction is first applied to convert oxygen to its equivalent amount of iodine. The literature covering 3 : 3‘-dimethylnaphthidine is briefly summarised. “Micro-determination of Acetaldehyde as its 2 :4-Dinitrophenylhydrazone,” by G. R. A. Johnson and G. Scholes. A colorimetric method for the determination of acetaldehyde is described. Formation of the 2 : 4-dinitrophenylhydrazone in aqueous solution is followed by quantitative extraction into carbon tetrachloride. It has been found that direct addition of ethanolic sodium hydroxide to the carbon tetrachloride extract produces a strong red colour, which can be measured absorptio- metrically. Perchloric acid has been used in the preparation of the 2:4- dinitrophenylhydrazine reagent ; this has the advantage that the hydrazine is much more soluble and also that carbon tetrachloride extracts less of the unchanged reagent.Quantities down to 5 pg per 20-ml sample can be estimated with satisfactory precision. Acetaldehyde can be determined in the presence of pyruvic acid.“The Simultaneous Determination of Cadmium and Magnesium with Disodium Ethylene- diaminetetra-acetate,” by E. G. Brown and T. J . Hayes. The simultaneous determination of cadmium and magnesium by titration with a solution of disodium dihydrogen ethylenediaminetetra-acetate con- taining zinc sulphate is described. Selective c,ontrol of the pH at 6.8 permits cadmium alone to be titrated, and magnesium is subsequently titrated at pH 10 in the same solution. Solochrome Black is used as indicator for both titra- tions.The molecular ratio of magnesium to cadmium must not be greater than unity for quantitative results, but a large excess of cadmium in the presence of magnesium can be satisfactorily determined. A theory is postulated for the reaction. N 0 TIC E S Vth International Spectroscopy Colloquium UNDER the chairmanship of Prof. F. X. Mayer, the Spectrochemistry and Colorimetry Group of the Society of Austrian Chemists has undertaken the organisation of the next international Colloquium, which will be held at Gmunden, in Upper Austria, from August 30th to September Srd, 1954. As in previous Colloquia, both emission and niolecular spectroscopy will be discussed and the following topics are proposed- Emission s$ectroscofy-Analysis of non-conductors and of base metals, evaluation of spectrograms and experiences with methods not involving standard samples (e.g., Harvey, Addink).Molecular spedroscoey-Studies of artificial fibres, non-dispersive infra-red spectro- scopy, Raman spectroscopy and a critical comparison of photo-electric and photographic methods of analysis. As an innovation, it is proposed to devote the last hour of the afternoon session to correlated reviews of selected topics by one or more speakers relating their p e r s o d experiences. This will be followed by informal discussions, again stressing personal experiences. Groups in each country have been asked to circulate invitations to their members and each country is asked not to submit more than five contributions, The final selection of papers and arrangement of the programme will rest with the Austrian Group.Comments on the Austrian proposals are invited, and those intending to take part in the Colloquium are requested to communicate as soon as possible with Mr. J. R. Stansfield, Hilger & Watts Ltd., 98, St. Pancras Way, Camden Road, London, N.W.l. Symposium on Analytical Chemistry, 1954 THE Midlands Society for Analytical Chemistry has made a final announcement on the Symposium on Analytical Chemistry being held at the University of Birmingham from August 25th to September lst, 1954. The programme includes original papers by 23 authors, lectures on recent advances in industrial application and special techniques by 17 lecturers, and three plenary lectures by speakers of international repute. There will also be an exhibition of apparatus, reagents and literature, and new techniques will be demonstrated. In addition to visits and social functions, including special visits for lady visitors, there will be a Library Exhibition of historical chmica.1 literature, including the Joseph Priestley collection. Registration forms and further information can be obtained from the Symposium Secretary, J. W. Robinson, BSc., Ph.D., A.R.T.C., 139, Stourport Road, Kidderminster, Worcs. PRINTED BY W. HEFFER & SONS LTD.. CAMBRIDGE, ENGLAND

ISSN:0003-2654    

DOI:10.1039/AN954790X007

出版商:RSC    

年代:1954

数据来源: RSC

ISSN:0003-2654    

DOI:10.1039/AN95479BX011

出版商:RSC    

年代:1954

数据来源: RSC

ISSN:0003-2654    

DOI:10.1039/AN95479FP015

出版商:RSC    

年代:1954

数据来源: RSC

ISSN:0003-2654    

DOI:10.1039/AN95479BP023

出版商:RSC    

年代:1954

数据来源: RSC

摘要:

FEBRUARY, 1954 THE ANALYST Vol. 79, No. 935 PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS AND OTHER ANALYTICAL CHEMISTS DEATHS WE regret to record the deaths of May Badger Craven Percy George Terry Hand Edward Oscar Heinrich. NORTH OF ENGLAND SECTION AND MICROCHEMISTRY GROUP A JOINT Meeting of the North of England Section, the Microchemistry Group and the Liverpool and North-Western Section of the Royal Institute of Chemistry was held in Southport on Saturday, September 26th, 1953. On the afternoon preceding the meeting a visit was made to Simpson’s Gold Thread Works in Preston, Visits to the Victoria Colliery, near Wigan, and to the Southport Gas Works were made on the Saturday morning. After this an informal lunch was enjoyed at Woodhead’s Caf6, Lord Street, Southport. In the afternoon about sixty members of the two Societies were welcomed by His Worship the Mayor of Southport, Alderman Tattershall, in the Council Chamber of the Town Hall.A symposium on the Training and Education of Microchemists followed, in which Dr. Cecil L. Wilson dealt with “An Academic Approach,” Mr. Gerald Ingram put the “Technical Aspects” and Mr. Rudolph Rothwell spoke on “Industrial Requirements.” A discussion followed these papers. The meeting was under the Chairmanship of Dr. A. M. Ward. SCOTTISH SECTION AN Ordinary Meeting of the Section was held at 7.15 p.m. on Tuesday, November loth, 1953, in the Central Station Hotel, Glasgow. The following papers were presented and discussed : “Rapid Determination of Glycerol in Fermentation Solutions: A New Chromatographic Procedure,” by K.Sporek, M.A., and A. F. Williams, B.Sc., F.R.I.C. (see p. 63) ; “Field Analysis in Connection with Water Treat- ment Problems,” by I. A. Heald, BSc. (see summary below). FIELD ANALYSIS IN CONNECTION WITH WATER TREATMENT PROBLEMS MR. I. A. HEALD emphasised the necessity of an immediate analysis rather than one subjected to the delay entailed by sending samples to a central laboratory for the deter- mination of some constituents of both raw and treated waters. Owing to the wide variation of solids content, from 1 to 2 p.p.m. for condensates to 10,000 p.p.m. for low- pressure boiler waters, analytical methods must be chosen accordingly. For field tests, rapidity of determination was essential, which ruled out many methods suitable for laboratory use.Examples of test kits were shown in which the use of polythene instead of glass for reagent bottles and apparatus had effected a welcome reduction in weight, Metal hydrometers for total-solid determination had reduced the probability of breakage. A prototype protected hydrometer with coloured plastic rings to indicate approxi- mate solids within 1000 p.p.m. was exhibited. The uncertainty of the blank correction and the difficult end-point when total hardness was determined with Wanklyn’s solution in the presence of high salt concentra- tions was contrasted with the greater accuracy of determinations with ethylenediamine- tetra-acetic acid. 6162 PROCEEDINGS Pol, 79 The history of the discovery of the use of ethylenediaminetetra-acetic acid in Switzerland and its development in the United States and later in Great Britain was related. The role of murexide and Solochrome Black as indicators and the effects of interfering metals were discussed.Copper to the extent of 0-2 p.p.m. completely suppressed the end-point, but could be eliminated by sodium sulphide. Iron led to a somewhat indefinite end-point, but could usually be removed by filtration. Ethylenediaminetetra-acetic acid could also be used for the volumetric estimation of sulphate hardness. The problem of caustic embrittlemerit in boilers was also discussed, and the use of sodium nitrate instead of sodium sulphate had presented a difficult problem for rapid field analysis. Many laboratory methods were too long, but some success had been achieved by a colorimetric brucine method, a tintometer disc being used as the standard.BIOLOGICAL METHODS GROUP A MEETING of the Group was held at 8 p.nt. on Thursday, November 19th, 1953, at the Royal Society of Medicine, 1, Wimpole Street, London, W.l. The Chair was taken by Dr. H. 0. J. Collier. An address entitled “The Standardisation of a Drug in Production as Illustrated by Adrenal Cortical Extract” was given by Dr. Chester I. Bliss (see summary below). THE STANDARDISATION OF A DRUG IN PRODUCTION AS ILLUSTRATED BY ADRENAL CORTEX EXTRACT DR. C . I. BLISS described tKe experience gained over several years in standardising adrenal cortex extract from the liver glycogen of the rat as an illustration of the problems arising in the biological control of quality. The assay on each day was self-contained, with two dose levels in the ratio of 3 to 5 of the reference standard and of each test preparation or unknown.As rats were assigned in equal numbers and at random to the two dose levels of any one preparation, the potency of each unknown and its standard error could be estimated by simplified equations for a self-contained assay, as illustrated numerically. As the assay procedure was repetitive, stable laboratory estimates of the error variance or standard deviation and of the slope of the dose-response curve would further shorten the calculation of potencly and increase its reliability. The range from groups of five equivalent rats was plotted against the sum of each group to test the independence of the mean and variance, and its distribution was compared with that expected for a normal variate with a stable variance.Both tests and a study of the time relation showed adequate stability above a mean of 0-56 per cent. of liver glycogen, with a uniform laboratory variance from 1947 to May, 1950, that dropped to a lower stable value in October, 1950. The slope also proved independent of the mean response, stable in time, and normally distributed, confirming the linearity of the dose - response relation. The advantages of computing potency and its standard error with stable laboratory estimates have been exemplified. The validity of the assay technique was tested from the agreement of two to four independent assays of each of 15 lots of extracts. Their potencies agreed well within the limits expected from the standard errors. Eight other assays compared two different concentrations of each of three preparations, which were assayed against each other. Their assayed relative potencies agreed with their known true values to the extent predicted by their standard errors. The suitability of the percentage of liver glycogen as the response metameter was examined by co-variance against initial body weight and liver weight. The first had no effect, but the second was statistically highly significant, indicating that liver glycogen was not proportional to liver weight. An alternative simpler response metameter, the liver glycogen per rat, performed as well or better than the percentage of liver glycogen and gave promise of more precise estimates of adrenal cortex extract.

ISSN:0003-2654    

DOI:10.1039/AN9547900061

出版商:RSC    

年代:1954

数据来源: RSC

摘要:

Feb., 19MJ SPOREK AND WILLIAMS Chromatographic Determination of Glycerol in Fermentation Solutions BY K. SPOREK AND A. F. WILLIAMS (Presented at the meeting of the Scottish Section 03% Tuesday, November loth, 1953) A new chromatographic procedure is described for the rapid determina- tion of glycerol in its mixtures with sugars and the constituents of molasses. It has been applied to the analysis of fermentation solutions derived from molasses. Alumina is used as adsorbent in conjunction with a solvent consisting of acetone containing 5 per cent. v/v of water and 0.05 per cent. v/v of glacial acetic acid. Sodium sulphite and sodium acetate are added to the sample solution to assist in the retention of sugars by the adsorbent. Glycerol is then determined in the column eluate, after removal of the solvent, by direct titration of the formic acid produced by oxidation with sodium metaperiodate.AT the beginning of this work1 there appeared to be no rapid or completely reliable procedure for the determination of glycerol in solutions derived from the sulphite fermentation of molasses? The main difficulty in devising a suitable method was the extreme complexity of such solutions. Owing to the presence of complex hydroxy compounds, such as fermentable and unfermentable sugars, which may undergo reactions similar to glycerol, procedures such as those based on acetylation or oxidation with sodium metaperiodate could not be readily applied. Indirect methods have previously been used for the analysis; they are usually based on some form of entrainment distillation of the glycerol with an organic solvent such as kerosene or cyclohexane? but in this laboratory these methods have not proved satisfactory and the procedure involved is usually lengthy and tedious.Experiments were begun to develop a chromatographic procedure for the separation of glycerol from sucrose and its inversion products, glucose and fructose, which are the major constituents of the molasses. A simple method has now been devised for this separation and it has been applied to fermentation solutions derived from the ‘‘ sulphite” process. It has also been used in this laboratory for solutions from the alkaline fermentation process of Eoff, Linder and B e ~ e r . ~ A chromatographic procedure has previously been described by Neish6 for separating milligram amounts of glycerol from small amounts of fermentation solutions. He used a column of Celite and organic solvents for extraction, the eluted glycerol being finally determined by a colorimetric procedure.The method was not considered to be suitable for rapid routine determinations in this laboratory, particularly as it was desired to use much larger amounts of sample. Qualitative chromatographic procedures involving partition chromatography on paper strips have been widely used in the separation of sugars and polyhydric alcohols.6 Experiments in this laboratory showed that glycerol could be readily separated from sucrose, glucose, fructose and mannitol with acetone, isopropanol and ut-butanol solvents. The simple glycols (ethylene, propylene and butylene) gave higher RF values than glycerol.‘The results for the three different solvents are shown in Table I. These results indicated that in any simple quantitative chromatographic procedure developed for glycerol and based on the use of an adsorbent such as cellulose, it was unlikely that a separation from the glycols would be effected, and, as such compounds often occurred with glycerol, it was important that allowance should be made for their presence. It was known that, of the direct procedures available for the determination of glycerol, the one that appeared to be most selective involved oxidation with sodium metaperiodate and titration of the formic acid produced.’ The glycols do not produce formic acid in this oxida- tion. It was clear that, provided the periodate procedure was used after chromatography, the possible presence of glycols could be ignored.Throughout the work described, therefore, the periodate oxidation procedure was used for the glycerol determination. This had the further advantage that there was no interference by common organic solvents, such as alcohols or ketones, which might be used in a chromatographic method.64 SPOREK AND WILLIAMS : CHKOMATOGHAYHIC DETERMINATION [Vol. 79 It was considered that, for‘rapid routine work, it was a pre-requisite of a chromatographic method that the solvent used should be easily removed from the eluate without danger of loss of glycerol. For this reason, initial experiments were restricted to low-boiling solvents such as acetone and isopropanol.With the technique described in the method (p. 65) but with columns of cellulose powder and aqueous sample solutions containing only glycerol, it was impossible to extract more than 80 to 90 per cent. of the glycerol in a reasonable volume (250ml) of pure acetone solvent. This figure was increased to 95 per cent. by using acetone to which 6 per cent. of water had been added. When the same conditions were used for artificial mixtures of sucrose, glucose, fructose and mannitol, there was a high degree of extraction of these substances, which increased with the amount of water present in the solvent. With isopropanol instead of acetone as solvent, this extraction was still greater. Extraction of the constituents of molasses also took place under the same conditions.TABLE I h!r; VALUES IN VARIOUS SOLVENTS ON PAPER STRIPS Solvent Compound Sucrose .. Glucose .. Fructose . . Mannitol . . Glycerol . . 2 : 3-Butanediol 1 : 2-Propanediol Ethanediol . . ,. .. .. .. 0.2 .. .. .. .. 0.18 .. .. .. .. 0.20 .. .. .. .. 0.18 .. .. .. .. 0.47 .. .. .. .. 0.77 .. .. .. .. 0.70 .. .. .* .. 0.59 r Acetone (b.p. 57’ C) isoPropano1 (b.p. 82” C) 0.01 0.02 0.02 0.54 0.82 0.77 0.69 - n-Butanol (b.p. 118’ C) 0.04 0.07 0.10 0.07 0.33 0.72 0.62 0.60 These experiments were repeated with the use, as adsorbent, of alumina supported on a short column of cellulose (see Method, p. 65), and it was found that extraction of the substances other than glycerol was considerably reduced, so further work was carried out with alumina as adsorbent. Samples (1 g) of Cuban blackstrap molasses (used for the production of glycerol by the “sulphite” fermentation process) were dissolved in 5 ml of water and extractions were made in the manner described.These molasses contained about 50 per cent. of fermentable sugars together with unfermentable sugars and hydroxylated substances of relatively high molecular weight , such as polysaccharides. Extractions were made both with and without added glycerol. It was found necessary to add a small amount of acetic acid to both the sample solution and to the solvent (see Method) in order to prevent strong retention of the glycerol by the constituents of the molasses; by using 250 ml of acetone containing 5 per cent. of water and 0.05 per cent. of glacial acetic acid, over 95 per cent.of the glycerol could then be extracted. Whereas the constituents of the synthetic sugar mixture were extracted in appreciable amount, the corresponding extraction from the molasses was only slight (see experiments 4 and 12, Table 11). The exact cause of this difference in behaviour is not readily explained, but it may partly be connected with the ratio between the amount of sucrose and its inversion products in the molasses, for sucrose is more strongly held on alumina than is glucose or fructose (see experiments 6, 7, 8 and 9, Table 11). As the fermentation solutions, for which the method was primarily required, would contain sodium sulphite, it was considered desirable to examine the effect of this salt on the extraction of glycerol and on other possible constituents of fermented liquors.As there was no obvious way of preparing such solutions free from glycerol, but identical in all other respects, the experiments were made on the original molasses, which in some respects presented a more complex sample owing to the higher concentration of fermentable sugars present in addition to all the unfermentable material. Addition of 043g of sodium sulphite to the sample solutions (1 g of molasses in 5 ml of water, with and without added glycerol) increased the extraction of glycerol to 97 per cent., and the retention of constituents of the molasses was increased. Because of this beneficial effect of sodium sulphite, a further series of experi- ments was made with artificial sugar mixtures to which sodium sulphite was added, and the same increased retention was observed.It was found that, if 1 g of sodium acetate was also added, extraction of sugars was negligible (see experiment 5, Table 11).65 Feb., 19541 OF GLYCEROL IN FERMENTATION SOLUTIONS The method for the determination of glycerol in sugar solutions and in its mixtures with substances of the type present in molasses and also in fermentation solutions is described in detail below. It involves addition of 0.8 g of anhydrous sodium sulphite and 1 g of sodium acetate trihydrate to an aqueous solution of the sample of volume about 5 ml (provided the total volume of sample solution is about 5ml the actual amount of water present is not critical so long as it exceeds about 2 ml) and then 0.1 ml of glacial acetic acid. The glycerol present is next extracted from the alumina adsorbent (supported on cellulose) in a volume of 250 ml of acetone containing 5 per cent.v/v of water and 0.05 per cent. v/v of glacial acetic acid. After removal of acetone the glycerol is determined by a periodate procedure.’ Under the conditions described, about 3 per cent. of the glycerol present in the original sample is retained on the column. For this reason the procedure is standardised by the use of a known amount of glycerol together with 1 g of molasses as sample. About eight determinations can be completed in a working day, and it is believed that the method may be applicable to many complex mixtures containing glycerol. METHOD FOR THE DETERMINATION OF GLYCEROL IN COMPLEX SUGAR MIXTURES AND FERMENTATION SOLUTIONS Preparation of solvent-Prepare a mixture of 950 ml of pure dry acetone, 50 ml of water and 0-5 ml of glacial acetic acid.CHROMATOGRAPHIC COLUMX*-- The tube used for the adsorbents was 1.8 to 2.0 cm in diameter and about 25 cm long, with a funnel at the top to facilitate introduction of the sample. It terminated in a short length of glass tubing, 6 mm in diameter. A number of indentations were made in the glass where the narrow tube joined the main column and the whole column was then made water- repellent by treating with a silicone fluid. Weigh 2.5 g of Whatman coarse-grade cellulose into a- 250-ml beaker and suspend it in 100 ml of acetone. After swirling the beaker, pour the mixture into the chromatographic tube, the outlet of which has been closed with a small rubber stopper.When the cellulose has partially settled, remove the stopper and allow the acetone to flow out of the tube; return any entrained cellulose to the column by pouring the acetone back through the funnel. When the cellulose has settled to form a smooth column, add a further amount of acetone and sprinkle 5 g of chromatographic alumina (Peter Spence, type H) into the tube. When the last of the visible acetone has drained from the column, pass 100 ml of solvent (see above) through the column, and, when the solvent layer has reached the surface of the alumina, replace the rubber stopper in the outlet of the tube, The column is then ready for use. PREPARATION OF SAMPLE SOLUTION- Weigh or measure a convenient amount of sample into a 150-ml beaker.With fermenta- tion solutions, a volume of 5 ml is usually taken. In the experiments on molasses, samples of which were relatively dry, about 1 g was taken and 4 to 5 ml of water were added. In all determinations the final volume was approximately 5 ml of aqueous solution, of which not less than about 60 per cent. was water; the exact amount of water in the sample solution was not critical. Then add sufficient anhydrous sodium sulphite to the contents o’f the beaker to bring the total amount present to 0.8 g. Add 1 g of sodium acetate, CH3COONa.3H,O, and 0.1 ml of glacial acetic acid, and allow the mixture to stand for about 5 minutes with intermittent stirring. With samples derived from the alkaline fermentation process of Eoff, Linder and Beyer, which usually contain sodium carbonate, the amount of acetic acid to be used must be increased to 0.2 to 0.3 ml. CHROMATOGRAPHIC EXTRACTION OF GLYCEROL- Add 15 g of alumina to the sample solution and stir the whole with a stout glass rod to produce a homogeneous friable mass.Transfer the mixture as completely as possible to the top of the prepared column. Add about 50ml of solvent to the 150-ml beaker and, after stirring, transfer the solvent to the column and gently beat the “wad” with a stout glass plunger to form a smooth continuation to the main column. Remove the rubber66 SPOREK AND WILLIAMS : CHROM.ATOGRAPHIC DETERMINATION Vol. 79 stopper from the base of the column and allow the solvent to fall to the level of the top of the alumina; collect the eluate in a 750-ml conical flask.Pour more solvent first into the beaker and then into the column until a total of 250 ml has been used and collected in the conical flask. Evaporate the acetone from the flask on a st2eam-bath in a well-ventilated fume cupboard until the residual aqueous volume is about 20 ml. DETERMINATION OF GLYCEROL- Dilute the residual aqueous solution to a volume of 250 to 300 ml with water and boil the solution for 1 minute to expel carbon dioxide. Then cool it thoroughly in running water and determine the glycerol by titrating the formic acid produced by oxidation with sodium metaperiodate, using a procedure similar to that described by Erskine, Strouts, Walley and Lazarus.7 It was found that 7 minutes was sulficient time of oxidation for the reaction with sodium metaperiodate and 5 minutes for the reaction of the excess of periodate with ethylene glycol (short times of reaction have also been recommended by Hartman9).Titrate the formic acid with 0.1 N sodium hydroxide standardised by carrying out the entire chromato- graphic procedure on 1 g molasses to which a known amount, about 0.5 g, of glycerol has been added. Determine the blank on the same weight of molasses. In this way any hold-up of glycerol by the adsorbent (about 3 per cent. occurs) is allowed for. The factor found for the standard alkali solution was usually of the order of 0.0095 g of glycerol per ml of 0.1 N sodium hydroxide, and the blank was about 0.3 to 0.5ml. THE EXTRACTION OF SUGARS AND CONSTITUENTS OF MOLASSES FROM CELLULOSE AND ALUMINA UNDERCONDITIONS USED FOR GLYCEROL AND THE EFFECT OF SODIUM SULPHITE AND SODIUM ACETATE The best solvent mixture for extracting glycerol was found to be acetone containing 5 per cent.v/v of water and 0.05 per cent. v/v of glacial acetic acid, the acetic acid preventing strong adsorption of glycerol by the constituents of molasses. With this solvent , incor- poration of sodium sulphite or sodium acetate in the "wad" led to decreased extraction of sucrose, glucose and other sugars, and the other constituents of molasses. With only cellulose as adsorbent and with sodium sulphite and sodium acetate together in the sample solution, experiment 2 (Table 11) shows the decrease in extraction (material dried at 110" C) from a mixture of sucrose, glucose and mannitol, compared with experiment 1, in which these salts were absent. "hen alumina was used as adsorbent under the conditions of extraction described in the method (above), the corresponding figures for artificial mixtures in experi- ments 5 and 4 were much lower.Experiment 5 shows that the extraction is reduced to less than 2 mg when sodium sulphite and acetate are present (cf. experiment 2), and alumina is shown to have a distinct advantage over cellulose. With alumina adsorbent and a sample of molasses, the results found in the presence and absence of sodium salts are shown by experiments 14 and 12, and the corresponding titrations after periodate oxidation are shown by experiments 15 and 13. These experiments show that the effect of adding salts to the sample of molasses extracted (see experiments 14 and 12) is less marked than when an artificial mixture is used (see experiments 5 and 4).It is possible that this difference can be partly explained by the higher concentration of sucrose in the molasses compared with that of invert sugar, for with sucrose alone there is much greater retention in the absence of salts than when corresponding amounts of glucose and frxtose are taken alone (experiments 6, 8 and 9). The results shown in Table I1 demonstrate the value of alumina as an adsorbent for sugars and the constituents of molasses when sodium sulphite and acetate are present in the sample solution. In all experiments under the conditions laid down in the method (p. 65), extraction of glycerol was about 97 per cent. No advantage was gained by increasing the amount of water in the acetone solvent, for although the amount of glycerol extracted was increased, extraction of other constituents was also greater.With the artificial mixture of sucrose, glucose, fructose and mannitol, a decrease in the amount of sodium sulphite from 0.8 to 0.5 g caused a slight increase in the extraction of the sugars, whereas an increase in sodium sulphite made no appreciable difference. The part played by sodium sulphite and sodium acetate in promoting retention of sugars is not clear, but it is possible that the sodium sulphite forms a complex with the sugars, whereas the sodium acetate acts as a buffer salt.Feb., 19541 OF GLYCEROL IN FERMENTATION SOLUTIONS 67 Expt. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 TABLE I1 EXTRACTION OF SUGARS AND MOLASSES FROM CELLULOSE AND ALUMINA AND THE EFFECT OF SODIUM SULPHITE AND ACETATE Sample Adsorbent 0-3 g each of sucrose, 1 g of molasses 0.3 g each of sucrose, glucose and mannitol Y Y glucose and mannitol $9 0.5 g of sucrose 0.5 g of mannitol 0.5 g of glucose 0.3 g of fructose 0.3 g of sucrose, 0.1 g each of glucose, man- nitol and fructose 77 1 g of molasses 93 77 Cellulose Y9 97 Alumina Y Y Y Y 77 Y7 37 77 3 7 9 Y? 77 77 79 THE QUANTITATIVE EXTRACTION Sodium sulphite, g Nil 0.8 Nil Nil 0-8 Nil Y Y 7Y 79 0.8 0.8 Nil 0.8 0.8 9, Sodium acetate, g Nil 1.0 Nil Nil 1.0 Nil 7) YY ?7 1.0 1.0 Nil 1.0 1.0 >3 Weight Final titration extracted after periodate (dried at oxidation, 110" C), 0.1 N NaOH, mg ml 488 - 48, 32, 80 - 215 - 192 - - 0.35 20 - - 1.10 10 - - 0-35 AND DETERMINATION OF GLYCEROL IN AQUEOUS SOLUTION AND ITS MIXTURES WITH MOLASSES By the procedure described in the method (p. 65), a series of determinations was carried out on pure glycerol solutions and on 1-g samples of Cuban blackstrap molasses to which glycerol had been added to cover a range of concentrations.The results are shown in Table 111. The accuracy of the method is reflected in the value and constancy of the factor found for each series of experiments, and it will be seen that, provided the procedure is standardised, a high degree of accuracy can be attained. The factor for the standard sodium hydroxide solution is slightly lower (nearer to the theoretical value) for glycerol in the presence of molasses than for its aqueous solutions.. TABLE I11 CHROMATOGRAPHIC SEPARATION AND DETERMINATION OF GLYCEROL IN AQUEOUS SOLUTION AND IN MIXTURES WITH MOLASSES Titration, Factor,* Glycerol taken, 0-1 N NaOH, grams of glycerol per g ml ml of 0.1 N NaOH Blank 0.1 - 0.4167 42.6 0.0098 0-3333 34.9 0-0096 0.2499 25.9 0-0097 0.2080 21.5 0.0097 0.0833 8.5 0.0099 0.4149t 43.45 0.0096 Blank 0.4 - 0.0833 9.1 0.0096 0.2499 27.0 0.0094 0-3333 35.8 0.0094 0.38 18 40-6 0.0095 ' 0.4167; 44.8 0.0094 I 0.7500 80.4 0.0094 Aqueous solution . . .. .. Sugars present . . .. .. Aqueous solution with 1 g of molasses * Factor for direct periodate determination on glycerol solution = 0.0092. -+ Sample containing 0.3 g of sucrose, 0.1 g each of glucose, mannitol and fructose. 2 0.5 g of molasses taken.68 SPOREK AND WILLIAMS : CHROMATOGRAPHIC DETERMINATION [Vol.79 APPLICATION OF THE CHROMATOGRAPHIC PROCEDURE TO THE DETERMINATION Solutions derived by sulphite fermentation of Cuban blackstrap molasses contained approximately 4 per cent. of glycerol, and a volume of 5 ml gave a reasonable titration with the 0.1 N sodium hydroxide solution at the final periodate stage of the analysis. The original solution contained approximately 0.3g of sodium sulphite (free or fixed as the bisulphite compound of acetaldehyde produced in the process) in 5ml of solution, so that a further OF GLYCEROL IN SULPHITE FERMENTATION LIQUORS TABLE IV DETERMINATION OF GLYCEROL IN FERMENTATION SOLUTIONS (SULPHITE PROCESS) : COMPARISON BETWEEN CHROMATOGR.APHIC PROCEDURE AND EXISTING KEROSENE METHOD Chromatographic method Kerosene method A A t , I \ Amount Sample taken, ml 1 5 2 5 3 5 4 5 6 5 6 5 7 5 8 5 9 5 * Factor taken = 0.0095g of Titration, 0.1 N NaOH, ml 22.7 20.1 20.9 22.9 23.0 22.3 22.1 22.0 11.1 Glycerol found,* 4.3 3.9 4.0 4.4 4 4 4.3 4.2 4.2 2.1 % w/v Glycerol found, % w/v 4.0 3.5 3-8 4.0 4.0 3-8 4.0 3.8 2.1 Corrected value for glycerol, 4.3 3.7 4.0 4.3 4.3 4.1 4.3 4.1 2.2 % w/v glycerol per ml of 0.1 N sodium hydroxide (see Method).0-5 g was added together with 1 g of sodium acetate and 0.1 ml of acetic acid. The solution was then ready for chromatography on alumina. The method was tested on a range of nine fermentation solutions, which were also analysed by a longer procedure that was the only alternative available. (i) Extraction of a weighed amount of sample, mixed with sodium sulphate, by means of hot acetone.(ii) Removal of acetone and separation of the glycerol by distillation with kerosene. (iii) Extraction of glycerol from kerosene by washing with water, followed by titration of glycerol by an oxidation procediire making use of potassium dichromate. This kerosene method was known to give results that were low to the extent of 7 per cent. when applied to fermentation solutions. Results by this procedure and s y the chromato- graphic method are shown in Table IV. It consisted of three stages, namely- TAB:LE V DETERMINATION OF SODIUM HYDROXIDE FACTORS BY ADDITION OF GLYCEROL Type of sample Fermentation liquor .. 7) n n n 79 Fermentation concentrate . . n TO FERMENTATION SOLUTIONS AND CONCENTRATES Glycerol found in Volume or Factor sample weight Glycerol Titration, found for (factor used taken added, 0.1 AT NaOH, NaOH = 0.0094),* g ml g 5ml Nil 23.5 - 4.4 (w/v) 5 ml 0.3818 63.4 0.0096 - 5 ml Nil 27.1 5.1 (w/v) 0.38 18 68.1 0.0093 - 5 ml Nil 27.2 - 5.1 (w/v) 5 ml 0.3054 60.2 0.0093 - 2.494 g Nil 40.9 15.4 * See Method, p.65, for standardisation of sodium hydroxide. 2.500 g 0.3818 81.4 0.0094 - Probable error, % -2 +1 f l Nil69 Feb., 19541 OF GLYCEROL IN FERMENTATION SOLUTIONS The results by the chromatographic procedure were completed during a working day, whereas determinations made by the kerosene procedure entailed one week of work. Table V shows the factors for the 0-1 N sodium hydroxide in grams of glycerol per ml obtained by chromatographic determinations made before and after the addition of a known weight of glycerol to samples of fermentation solution.The factors derived from determinations made before and after addition of glycerol to samples of fermentation solutions are seen to be in reasonable agreement with those obtained from molasses (Table 111). CONCLUSIONS The chromatographic method described is both simple and rapid. It provides a means for the determination of glycerol with a reasonable degree of accuracy in complex mixtures of sucrose, invert sugar, unfermentable sugars, polysaccharides and so on. The precise composition of fermentation solutions is not known, but it is considered that the chromato- graphic procedure, used in conjunction with the selective periodate technique involving oxidation of the extracted glycerol to formic acid, gives an accurate measure of the amount of glycerol present in such samples. The mechanism by which the addition of sodium sulphite and sodium acetate prevents the movement of glucose, fructose and mannitol is not easily understood, and it is possible that the complexing action of the added salts may be extended to other substances.The method is in use in this laboratory for the analysis of fermentation solutions derived from the sulphite process,2 and has been applied to the alkaline fermentation process of Eoff, Linder and Beyer.4 REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. Williams, A. F., Nature, 1953, 171, 656. Neuberg, C., and Reinfurth, E., Biochem. Z., 1918, 92, 234. Palfray, L., Sabetay, S., and Libmann, G., Comfit.Rend., 1946, 223, 247. Eoff, J. R., Linder, W. V., and Beyer, G. F., Ind. Eng. Chem., 1919, 11, 842. Neish, A. C., Canad. J . Res., B, 1960, 28, 536. Hough, L., Nature, 1950, 165, 400. Erskine, J. W. B., Strouts, C. R. N., Walley, G., and Lazarus, W., Artalyst, 1963, 78, 630. Ryan, W., and Williams, A. F., Ibid., 1952, 77, 293. Hartman, L., J. Apfil. Chem., 1953, 3, 308. RESEARCH DEPARTMENT IMPERIAL CHEMICAL INDUSTRIES LIMITED STEVENSTON, AYRSHIRE XOBEL DIVISION August 24t12, 1953 DISCUSSION DR. I. C. WILLOX asked whether Mr. Williams had any experience of the direct estimation of glycerol after separation on a paper strip. MR. WILLIAMS replied that work on these lines had been considered and that a paper-strip procedure It might be possible might be developed, but it was doubtful whether a high accuracy would be obtained. to cut off the portion of the paper containing the glycerol and to apply a colorimetric method. MR. R. KERR wanted to know if there was any development of the chromatographic method for the determination of the individual sugars present in fermentation solutions. MR. WILLIAMS said, in reply, that he had not done any work involving the use of the chromatographic technique for the separation of individual sugars present in fermentation solutions, but in view of the amount of work that had been carried out by other workers on the separation of sugars generally, it seemed reasonable to suppose that similar techniques might be applied to fermentation solutions. MR. A. CAREY asked whether the time allowed for. the oxidation of glycerol by sodium periodate was critical. MR. WILLIAMS replied that the paper by Erskine, Strouts, Walley and Lazarus in The Analyst described the procedure, but its use in the chromatographic method had shown that the time allowed for the reaction could vary over a wide range without any adverse effect. MR. J. A. EGGLESTON asked about the availability of sodium periodate of a suitable degree of purity. MR. WILLIAMS replied that the authors made their own periodate by an electrolytic procedure and the purity of the reagent was such that a blank of less than 0.1 ml of 0.1 N sodium hydroxide was obtained a t the titration stage in a determination of glycerol. He understood that supplies were now available from certain manufacturers.

ISSN:0003-2654    

DOI:10.1039/AN9547900063

出版商:RSC    

年代:1954

数据来源: RSC

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70 AHLERS AND MCTAGGART: THE DETERMINATION OF p o l . 79 The Determination of Hydroxyl, Ketone and Ester Groups in Autoxidised Fatty Esters and Related Compounds by Infra-red Spectroscopy BY N. H. E. AHLERS AND N. G, McTAGGART Infra-red spectroscopic methods have been devised for the quantitative determination of hydroxyl, ketone anti ester groups in autoxidised or co- polymerised fatty esters and related compounds. The technique consists in relating the intensity measurements in solution at the wavelengths of the characteristic absorption bands to those of suitable reference compounds. Provision is made for the elimination of errors arising from scattered radiation, finite slit width, association phenomena. and so on. The methods are simple and rapid in operation. They require only small amounts of sample, about 20 mg, which can be recovered unchanged after the examination.The accuracy of each determination is similar to that of the corresponding conventional chemical method. STUDIES of the oxidation of fatty esters require accurate analytical methods for the deter- mination of the variety of oxygen-containing groups introduced during oxidation. These groups include hydroxyl and carbonyl, and this paper is concerned with their determination. Of the several methods in use for the determination of the hydroxyl group, the most widely used is the acetic anhydride - pyridine method,l by which only primary and secondary alcoholic hydroxyl groups are measured. Another method in common use, that of Zerevitinov,2 requires correction for carboxylic hydroxyl groups, since it determines those as well as the alcoholic hydroxyl groups.Most of the methods proposed for the determination of ketone groups in fatty esters and related compounds depend on the reaction with either phenylhydra~ine~ or hydroxyl- amine.41~ These methods are not reliable in the presence of organic peroxides, which are known to be present in autoxidised fatty ester systems. A more recent methode is based on the oxidation of aluminium isopropoxide to acetone, which is then determined as its dinitrophenylhydrazone. The normal chemical methods of determining esters are based on direct saponification. There are, however, a number of compounds for which chemical saponification methods are not completely satisfactory. Alcohol-insoluble polymers of low ester content, e g ., certain styrene - fatty ester copolymers, are difficult 1.0 saponify. Moreover, for some autoxidised fatty ester systems there is evidence that saponification leads to chemical changes other than simple hydrolysis of the esters present, For compounds unsuitable for saponification this paper describes methods, dependent on infra-red spectroscopy, that can be carried out rapidly and require but small amounts of sample, about 20 mg, which can, if required, be recovered unchanged at the end of the examination. These methods are applicable to a wide range of materials and appear to be as accurate as the more lengthy chemical methods, which require from 0.25 to 1.Og of sample. THEORETICAL CONSIDERATIONS The theoretical aspects of infra-red absorption spectroscopy and the techniques involved in its use for both qualitative and quantitative determinations on organic molecules have already been reviewed.' Vapours and dilute solutions of compounds containing an alcoholic hydroxyl group all show an absorption band in the infra-red region near 3600 cm-', which is attributed to the OH-stretching vibration.Hence the infra-red spectrum of a hydroxy fatty ester, methyl ricinoleate, in dilute carbon tetrachloride solution, shows a sharp absorption band at 3625 cm-'. With an increase in the concentration of the solution, the intensity of this band decreases and a new broad band appears at 3460 cm-l. This new band is ascribed to the presence of associated hydroxyl groups.Feb., 19541 HYDROXYL, KETONE AND ESTER GROUPS 71 It is not practicable to use the associated hydroxyl band to assess the hydroxyl content of a sample with any precision because the degree of association, and hence the intensity of absorption, varies markedly with the concentration and the nature of the sample.If, however, very dilute solutions of the sample are used, the degree of association is negligible and measurements of the intensity of the unassociated or “free” hydroxyl absorption band serve to provide the specific extinction coefficient8 (defined on p. 73) of the hydroxyl group and hence permit the determination of the hydroxyl content of the sample. The general procedure is to use a pure substance of known hydroxyl content, e.g., methyl ricinoleate, to determine the reference specific extinction coefficient. This can then be used to determine the hydroxyl content of other similar samples by comparison of the relative intensities of the unassociated hydroxyl absorption bands.All compounds containing a carbonyl group show a characteristic absorption band in the 1700 cm-l region of the infra-red spectrum, which arises from the CO-stretching vibration - Unassociated hydroxyl absorption - I I I I I I - Associated h yd rox yl abror ption , j 0-4 Concentration, g per 100 ml Fig. 1. Beer - Lambert relationship for methyl ricinoleate in carbon Theoretical hydroxyl content of methyl ricinoleate = tetrachloride solution. 5-46 per cent.; k = 0.068; path length = 1 cm of the system. The exact location of the band depends on whether the group is present in the molecule as ester, ketone, aldehyde or other configuration, and it is also affected by the nature of adjacent grouping^,^ particularly if the group is conjugated with a double bond.Previous work on the analysis of autoxidised fatty ester systems by infra-red spectroscopy has shown the necessity for using reference standards with a molecular structure similar to that of the samples under investigation. The infra-red spectra of methyl stearate and methyl ketostearate show bands characteristic of the ester group at 1742cm-1 and the spectrum of the keto compound shows a band arising from the ketone valence vibration at 1718 cm-1. These compounds form suitable standards for ester and ketone determinations. At first sight it would appear that the ketone content of an unknown sample could be determined directly by comparing the intensity of the ketone absorption band with that of methyl ketostearate; but this method is complicated by the presence of the ester group, which shows considerable general absorption near the ketone absorption wavelength.Unless a correction is made for this general absorption, the results will be inaccurate, particularly if the ketone content is low. The reverse effect is negligible and the ester content can be calculated from a direct comparison of the absorption intensity at the ester wavelength with that of methyl stearate. The procedure found to be satisfactory involves measurement of the absorption intensity72 AHLERS AND MCTAGGART: THE DETERMINATION OF [Vol. 79 at the specific ketone wavelength, determination of the ester content, and correction of the ketone absorption from the determined ester content. EXPERIMENTAL In the determination of hydroxyl the measurements must be confined to the range of concentrations within which no appreciable association of the hydroxyl group occurs.This is readily effected by diluting the solution until. no absorption characteristic of the associated hydroxyl is observed. It is also necessary to check the validity of the Beer - Lambert law for solutions of the material to be examined. Data establishing this relationship for methyl ricinoleate a t 3623 cm-l in a 1-cm cell in carbon tetrachloride solution are shown in Fig. 1. Similar linear relationships are observed for methyl ketostearate at 1718 cm-l and for methyl stearate at 1742 cm-l.METHODS The results in this paper were obtained with a Perkin Elmer Model 12C infra-red spectro- meterlo equipped with a rock-salt optical system. The sample under investigation was weighed and dissolved in purified carbon tetra- chloride1* contained in a calibrated flask. The concentration of the solution was then adjusted so that the measured optical density in a 1-cm cell lay within the range of 0.4 to 0.8. In making absorption measurements the practice was to record the reference spectrum of the cell filled with carbon tetrachloride. The cell was then carefully washed out and filled with the solution and the spectrum was recorded again, The intensity of the characteristic absorption band was determined by difference between the two sets of spectra.Scattered radiation was eliminated by the use of a glass shutter in the 1700 cm-l region. The effect of slit widthll on intensity measurements in the infra-red spectrum is important, especially in dealing with sharp absorption bands, The true intensity of an absorption band can only be found by extrapolating a series of measurements to zero slit width. In Fig. 2 the effect of variation of slit width on optical density is shown for a solution Slit width. rnrn Fig. 2. Effect of variation of slit width on optical density for a solution of methyl ricinoleate in carbon tetrachloride. Concentration = 0.233 g per 100 ml; path length = I cm of methyl ricinoleate in carbon tetrachloride. For the relative measurements in this work a constant slit width suffices and consequently all determinations were made with an aperture of 0.02mm for the hydroxyl and 0.06mm for the carbonyl determinations. DETERMINATION OF HYDROXYL- calculated theoretical hydroxyl content (5.45 per cent.) of pure methyl ricinoleate.The slope of the line in Fig. 1 provides the reference specific extinction coefficient for theFeb., 19641 HYDROXYL, KETONE AND ESTER GROUPS Now, D = kcZ from the Beer - Lambert relationship, D is the optical density of the hydroxyl band, k is the specific extinction coefficient, c is the concentration in g per litre and Z is the path length in cm. where 73 The reference specific extinction coefficient then becomes 0-068. The specific extinction coefficient of the sample, k’, is then measured and the hydroxyl content of the sample is obtained from the relation- k‘ ’ 5*45 per cent.hydroxyl content = 0.068 Determinations of the hydroxyl content of many autoxidised fatty esters and related compounds by both the acetic anhydride and the infra-red methods have shown satisfactory agreement. A selection of the results is shown in Table I. TABLE I -4 COMPARISON OF THE HYDROXYL VALUES OBTAINED BY THE ACETIC ANHYDRIDE AND INFRA-RED METHODS Hydroxyl value, per cent. Acetic anhydride Infra-red Sample method method A r \ Linseed oil monoglyceride . . .. .. 7.52 7.70 Dimethylstearyl alcohol . . .. .. 5-70 5-87 10.10 Methyl dihydroxystearate .. .. 10.30 Castor oil . . .. .. .. .. 4-80. 4.74 Dehydrated castor oil . . .. .. 1-27 1 *65 Methyl hydroxystearate . . 0 . ..5.42 5-34 DETERMINATION OF ESTER- The reference specific extinction coefficient, k , at 1742cm-1 for the calculated ester- group content (-COOCH, = 19.8 per cent.) for pure methyl stearate, i.e., the slope of the graph representing the Beer - Lambert relationship, is 1-48. The specific extinction coefficient of the sample, k’, is then measured and the ester content calculated from the relation- ’’ ’ ’’.* per cent. ester content = 1-48 or saponification value = ” lg8 mg of KOH per g. 1 -48 When the method is to be used for a large number of routine analyses a direct calibration curve may be used. Either ester content or saponification value can be plotted against the observed specific extinction coefficient for the reference materials. Such a graph prepared from data for methyl stearate is shown in Fig.3. Saponification values can then be read directly from the graph. Fig. 3. Relation between saponification value and specific extinction coefficient for methyl stearate74 AHLERS AND MCTAGGART: THE DETERMINATION OF [Vol. 79 Comparison of the results for a number of samples with those obtained by the normal saponification method are given in Table I1 and show that the spectroscopic method gives, in general, results in good agreement with the chemical procedure. TABLI; I1 COMPARISON OF THE ESTER CONTENTS OBTAINED BY THE SAPONIFICATION AND INFRA-RED METHODS Ester content, Saponification value, per cent. mg of KOH per g G G Z % A Z a l I n f r a - r e d a l method method* method? method Methyl azelate . . .. .. .. . . 55.0 55.7 523 528 Methyl myristate .... .. . . 24.1 24.4 229 231 Methyl ketostearate . . .. . . . . 19.1 18.9 182 180 Methyl dihydroxystearate . . .. ~. 17-9 17-9 170 I70 Autoxidised methyl elaeostearate fraction . . 17.7 23.7 168 225 Hydrogenated autoxidised methyl elaeo- stearate fraction . . . . .. . . 18.8 18.3 178 175 Methyl ester fraction from autoxidised linseed oil . . .. .. .. .. . . 17.8 23.7 169 225 . . - I 197 195 Linseed oil .. I . Impatiens oil . . . . .. . . . . I 231 237 Styrene copolymer . , * . . . .. 2-85 3.06 27-1 29.1 * Calculated from the saponification value, measured chemically. t Calculated from the ester content, measured spectroscopically. .. . . - The tabulated results indicate satisfactory agreement between the spectroscopic and chemical procedure with all samples except the autoxidised methyl elaeostearate and linseed oil fractions, On hydrogenation of the autoxidised methyl elaeostearate sample, the chemical saponification value falls and agreement with the spectroscopic method is attained.I t appears that certain autoxidised materials contain reactive groupings that lead to high saponification values. Hydrogenation removes these groupings and the true ester content is given by saponification of the hydro- genated material. DETERMINATION OF KETONE- This analysis depends, in the first place, on the determination of the ester content of the sample relative to methyl stearate. Frorn this datum, the true intensity of the ketone absorption in fatty esters can be deduced and compared directly with that of the reference material, methyl ketostearate.The specific extinction coefficient, k,, for methyl keto- stearate at 1718 cm-1 in carbon tetrachloride solution, i.e., the slope of the graph representing the Beer - Lambert relationship, is 0.921. Let k, be the observed extinction Coefficient for methyl stearate in carbon tetrachloride solution at 1742 cm-l, k, be the observed extinction coefficient for methyl stearate in carbon tetrachloride solution at 1718 cm-l, k, be the observed extinction coefficient for methyl ketostearate in carbon tetra- chloride solution at 1718 cm-I and k, be the observed extinction coefficient for methyl ketostearate in carbon tetra- chloride solution at 1718 cm-I corrected for the absorption at this wavelength due to its ester content.For methyl stearate the ester content is 19.8 per cent. and for methyl ketostearate the ester content is 18.9 per cent. and the ketone content is 8-95 per cent. For methyl ketostearate, the contribution of the ester content to absorption at 1718 cm-l is given by- For these, the chemical method gives a higher value. 18-9 k2 x - 19.8' whence k , = k 3 - - ( k 2 x z ) . . . . ..Feb., 19541 HYDROXYL, KETONE AND ESTER GROUPS 75 Let k, be the observed extinction coefficient for the sample in carbon tetrachloride solution at 1742 cm-l; then the ester content of the sample is given by- * (2) Let k, be the observed extinction coefficient for the sample in carbon tetrachloride solution at 1718cm-l. This extinction coefficient is then corrected for the contribution at this wavelength due to the ester content given by equation (2).Then k,, the observed extinction coefficient for the sample in carbon tetrachloride solution at 1718 cm-1, corrected for the “interference” of the ester content is given bv- k, = k, -[ (2 x 1943)(k)] or The expression for the (3) and (1). .. .. . . (3) .. .. k 7 = k 6 - - ( 7 ) k2 x k5 - . ketone content of the sample can then be obtained from equations Ketone content = 5 = per cent. k4 k, - ( k z x g) With the reference data obtained- .. .. k6 x 0.085k5 per cent, 0.089 ketone content = The infra-red method for the determination of ketone content has been tested on a number of mixtures of methyl stearate and methyl ketostearate made up to give known ketone contents (see Table 111) and various fatty oil samples on which ketone determinations had been made by the hydroxylamine method4s5 (see Table IV).The results show that the spectroscopic method gives results in good agreement with the chemical procedure. TABLE I11 KETONE CONTENTS OF VARIOUS MIXTURES OF METHYL STEARATE AND METHYL KETOSTEARATE Ketone content, per cent. 0.70 0.75 0.90 1.00 2.10 2.20 2.90 2.60 3.80 3.40 5.55 5.48 Theoretical Infra-red method TABLE IV COMPARISON OF THE KETONE CONTENTS DETERMINED BY THE HYDROXYLAMINE AND INFRA-RED METHODS Ketone content, per cent. Hydroxylamine Infra-red Sample method method A r \ Oiticica oil . . .. . . . . . . . . 6-00 6-20 Hydrogenated peroxidised methyl elaeostearate : (Fraction A) . . .. .. .. .. 0.70 0.82 (Fraction B) .. .. .. .. .. 0-45 0.47 The authors wish to thank the Council and Director of the Research Association of British Paint, Colour and Varnish Manufacturers for permission to publish this paper, which is based on work carried out at the Paint Research Station.76 RILEY : THE SPECTROPHOTOMETRIC DETERMINATION REFERENCES 1. 2. 3. 4. 5. 6. 7. a. 9. 10. 11. British Standard Specification No. 684, British Standards Institution, 1960. Zerevitinov, T., 2. anal. Chem., 1913, 729. Marks, S., and Morrell, R. S., Analyst, 1931, 56. 508. Luthe, N., Fette u. Seifen, 1938, 615. Feuell, A. J., and Skellon, J. H., Analyst, 1953, 78, 135. Hilton, F., Inst. Rubber Ind. Trans., 1942, 17, 319. Coggeshall, N. D., Anal. Chem., 1950, 22, 381. Ramsay, D. A., J . Amer. Chem. SOL, 1952, 74, 72. Hampton, R. H., and Newell, J. E., Anal. Chem., 1949, 21, 914. Ahlers, N. H. E., J . Oil Col. Chem. Ass., 1950, 33, 421. Hampton, R. H., Anal. Chem., 1949, 21, 923. PAINT RESEARCH STATION TEDDINGTON, MIDDLESEX Pol. 79 Jfcne 5th, 1953

ISSN:0003-2654    

DOI:10.1039/AN9547900070

出版商:RSC    

年代:1954

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76 Wol. 79 The Spectrophotometric Determination of Hydrazine in Dilute Solutions BY J. P. RILEY A method is described for the determination of hydrazine at concentra- tions as low as lO-6M with a coefficient of variation of about 1.0 per cent. Hydrazine solution is treated with a so'lution of picryl chloride in chloroform and, after addition of an alcoholic solution of potassium acetate, the intensity of the resultant brown colour is measured spectrophotometrically. Beer's law is obeyed for up to 40 parts of hydrazine per million. The interference of hydroxylamine and a number of inorganic anions and cations has been investigated. THE normal methods of determining hydrazine by making use of its reducing power,l although accurate, are not suitable for the analysis of extremely dilute solutions.Two procedures have been described for the colorimetric determination of hydrazine at low concentrations. Pesez and Petit2 made use of the orange azine formed when hydrazine reacts with P-dimethyl- aminobenzaldehyde in the presence of hydrochloric acid. The same method was used by Watt and Chrisp? who reported a coefficient of variation of 1 per cent. for hydrazine con- centrations ranging from 0-06 to 0-47 parts per million. Kul'berg and Cherkesov4 treated the test solution with an ethanolic solution of picryl chloride, forming bistrinitrophenyl- hydrazine, I, which, when buffered with borate, developed a red colour, whose intensity (measured after excess of reagent had been removed by filtration) was proportional to the concentration of hydrazine. In the course of work on the oxidation of hydrazine in dilute aqueous solution by either oxygen or nitrate ion, a method was required for the determination of hydrazine at con- centrations as low as 10" M .The method of Kul'berg and Cherkesov4 gave erratic results (about k20 per cent.). The error was attributed to- (i) the rapidity with which picryl chloride is hydrolysed in water, (ii) the instability of the alcoholic solution of the reagent)77 (iii) the difficulty of obtaining absolutely clear solutions after removal of excess of reagent and (iv) the effect of light on the initial reaction between hydrazine and picryl chloride. To minimise the last of these difficulties all subsequent work was carried out in artificial light only. EXPERIMENTAL Feb., 19541 OF HYDRAZINE IN DILUTE SOLUTIONS In unsuccessful attempts to improve the accuracy of the procedure, a number of water- soluble solvents for picryl chloride other than alcohol were tested.When a solution of 0 Wavelength, rnp Fig. 1. Influence of concentration of picryl chloride on absorption spectra, 2.5 ml of 0.001 per cent. hydrazine and 1 ml of picryl chloride reagent and 5 ml of 0.02 per cent. potassium acetate made up to 25 ml with absolute alcohol. Concentration of picryl chloride: curve A, 4 per cent.; R, 2 per cent.; C, 1 per cent.: D, 0.5 per cent. Reagent blank solutions with various concentrations of picryl chloride; curve A', 4 per cent., B', 2 per cent. ; C', 1 per cent.; D', 0-5 per cent. picryl chloride in chloroform was used as a reagent and an alcoholic solution of potassium acetate was subsequently added, reproducibility was improved. The effect of concentration of picryl chloride on the absorption spectrum of the reaction mixture with these reagents is shown in Fig.1 ; the absorption maximum of the red colour is at 494 mp and not, as stated by Kul'berg and Cherkesov, at 530 mp. To establish the optimum conditions for the determination of hydrazine, 2-5-ml samples of hydrazine sulphate solution (0-001 per cent. with respect to hydrazine) were treated with 1-ml portions of picryl chloride at several concentrations. After 1 minute various amounts of a 0.05 per cent. alcohoIic solution of potassium acetate were added and the mixtures were diluted to 25 ml with ethanol. After 1 hour the optical densities of the solutions were measured at 530 mp and gave the results shown in Fig.2. On consideration of Figs. 1 and 2 and on taking into account the desirability of having low reagent blanks, it was evident that the most suitable amounts of reagents were 1 ml of 2 per cent. picryl chloride and 5 ml of 0.05 per cent. potassium acetate solution; these amounts were used in all subsequent work.78 RILEY : THE SPECTROPHOTOMETRIC DETERMINATION Wol. 79 On allowing the picryl chloride solution to stand in contact with the hydrazine solution for various periods before adding the potassium acetate reagent and making up to volume, it was found that the initial reaction was complete within 15 seconds and that no change took place within at least 16 minutes. The development of the red colour after the addition of the potassium acetate solution was complete after 40 minutes and the colour remained stable for at least a further 4 hours.EFFECT OF TEMPERATURE- When the determination was carried out at 30"C, it was found that although the maximum colour intensity developed in approximately 15 minutes, the extinction coefficient was only 0.9 per cent. higher than that found at 20" C. f I L 5 10 i s 20 Amount of 0'05 per cent alcoholic potassium acetate solution Fig. 2. Effect of amount of potassium acetate solution on optical density for various concentrations of picryl chloride, 2.5 ml of 0.001 per cent. hydrazine and 1 ml of picryl chloride + x ml of 0.05 per cent. alcoholic potassium acetate solution made up to 25 ml with alcohol.Concen- tration of picryl chloride: cu.rve A, 4 per cent.; B, 2 per cent.; C, 1 per cent.; D, 0.5 per cent. INFLUENCE OF SAMPLE VOLUME- As the position of equilibrium of the initial reaction is a function of the amount of water present, the flasks in which the determination is carried out should be dry, and the same volume of test solution should always be taken. With 25-pg samples of hydrazine in various volumes of water the following results were obtained- Volume of sample, ml . . . . 1.0 1.5 2.0 2.5 3.0 4.0 5.0 Optical density at 494 m p (l-cm cell) . . , . .. . . 0.801 0*'750 0.720 0.663 0.620 0.535 0.450 EFFECT OF pH- Solutions of hydrazine sulphate (containing 0-001 per cent. as hydrazine), adjusted to cover a range of pH values by addition of hydrochloric acid or sodium hydroxide were79 Feb., 19543 OF HYDRAZINE IN DILUTE SOLUTIONS examined, and gave the results shown in Fig.3. Over the pH range 3.2 to 5-00 there was an increase in optical density of 0.7 per cent. Above a pH value of 5 there was a more rapid increase up to pH 11.5, and solutions more alkaline than this absorbed strongly owing to the pH value Fig. 3. Effect of pH on optical density measured for 2.5 ml of 0.001 per cent. hydrazine solution. reaction of picryl chloride itself with the buffer. No colour was formed below a pH of 2.3. To avoid any risk of oxidation of hydrazine from the air, the pH value of test solutions should lie between 3.3 and 5-0. METHOD All measurements of optical density were made with a Unicam SP500 spectrophotometer and 2-mm, 1-cm or 7-5-cm cells, as appropriate.REAGENTS- Hydrazine sulphate stock sozution-A solution containing 0.4062 g of hydrazine sulphate (assaying at 99.3 per cent. of hydrazine sulphate) per litre. Hydruzine sulphate dihte solution-Dilute 100 ml of the stock solution to 1 litre. This solution, which contains 10 mg of hydrazine base per litre, must be prepared fresh daily. Picryl chloride reagent-Dissolve 0.5 g of picryl chloride in 15 ml of chloroform, filter the solution into a dry 25-ml calibrated flask and dilute to volume with chloroform. Potassizcm acetate solution, 0.05 per cent.-Dissolve 0-125 g of anhydrous potassium acetate in 250 ml of absolute ethyl alcohol. PROCEDURE- Place, by means of a pipette, 26ml of the test solution (pH value 3.3 to 5) in a clry 25-ml calibrated flask, and add from a micro-burette 1 ml of 2 per cent.picryl chloride reagent. Shake the flask and set it aside for at least 40 seconds. Add 5 ml of 0.05 per cent. potassium acetate solution, mix well and dilute to 25ml with absolute alcohol. Measure the optical density of the solution at 494 mp (or at 530 mp if very low concentrations of hydrazine are being determined or if hydroxylamine is present). Determine the blank value for thereagents in the same manner, using 2.5 ml of distilled water. Calibrate the method with the dilute hydrazine sulphat e solution. RESULTS Replicate determinations were made over a considerable range of hydrazine con- centrations to test the accuracy of the method. For the determination of less than 1 part of hydrazine per million the optical density was measured in a 3-inch cell at 530 mp instead of 494mp; this reduced the reagent blank.The figures in Tables I and I1 indicate that Beer's law is obeyed for up to about 30 parts of hydrazine per million with a coefficient of variation of 1 per cent. ; above this concentration the deviation from linearity increases rapidly.Amount of hydrazine, 0.5 1 2 4 6 8 10 12 14 16 18 20 25 30t 40t sot Got sot Prg per ml RILEY : THE SPECTROPHOTOMETRIC DETERMINATION TABLE I DETERMINATION OF HY DR AZI NE Mean optical density less blank at 494 mp 0.033 0.067 0.133 0.268 0.388 0.51 8 0-650 0.784 0*924* 1.055* 1*200* 1.298* 1-642* 1*964* 2-694* 3.4 14* 4*164* 5.620* Number of determina- tions Standard deviation 4.0 1.2 0.7 1.1 0.2 0.4 0.4 0.6 0.2 0.7 0.3 0.4 0.5 0.2 0-2 0.8 0.4 0- 8 Deviation from linearity, % -+ 0.6 f 2.1 + 1.3 - 1.4 - 1.1 - 0.9 - 0.9 - 0.4 + 0-6 f 0.4 7 0.6 - 1.0 + 0.2 - 0.2 + 2.6: +44$ +5-7: +&9: * Measured in 2-mm cell and calculated to l-cm cell.t Ten millilitres of 0-05 per cent. potassium acetate added. 2 Excluded from calculation of mean slope and standard deviation from linearity. NOTE-Amount of hydrazine, p.p.m. = -Optical density 0.0656 TABLE I1 DETERMINATION OF LOWER CONCENTRATIONS OF HYDRAZINE Amount of hydrazine, Prg Per ml 0.04 0.1 0.2 0.4 0.6 0.8 1.2 1.6 Mean optical density less blank at 630 mp* 0.01 8 0.034 0.078 0.166 0.230 0-307 0.471 0.629 Number of determina- tions [Vol. 79 Standard deviation, Yo 5.5 0.0 0.0 0.6 0.3 0.2 0.3 0.3 Deviation from linearity, % f 15.0 & 0.0 + O O - 1.8 - 1.5 + 0.6 f 0.6 - 12.9 * Three-inch ceii.KoTE-Amount of hydrazine, p.p.m. =: Pptical density 0.390 INTERFERENCE OF FOREIGN ANIONS AND CATIONS- Twenty-five-millilitre portions of 0-2 per cent. and 2 per cent. solutions of a number of salts were treated with 5ml of hydrazine suilphate solution (0.01 per cent. as hydrazine) and diluted to 50ml. The diluted solutions were analysed for hydrazine, any precipitate formed being removed by centrifugation before the optical density was measured. None of the salt solutions tested in the absence of hydrazine showed greater absorption than the reagent blank. The results shown in Table I11 are expressed in terms of the percentage reduction in optical density compared with the optical density in the absence of the salt.Chloride ion causes a much greater reduction in colour than other anions (except azide) probably because of its influence on the equilibrium in the reaction of hydrazine with picryl chloride. EFFECT OF HYDROXYLAMINE- Preliminary experiments showed that hydroxylamine hydrochloride when treated with picryl chloride and potassium acetate exhibited appreciable light absorption at 494 mp,Feb., 19543 OF HYDR,AZINE IN DILUTE SOLUTIONS 81 but absorbed only slightly at 530 mp. Solutions of hydroxylamine hydrochloride containing 0~0001,0~001 and 0.005 per cent. of hydroxylamine and various concentrations of hydrazine were examined by the proposed method, all solutions being measured at 530mp. The figures shown in Table IV indicate that interference at a concentration of 04001 per cent.of hydroxylamine is negligible; with 0-001 and 0.005 per cent. hydroxylamine the optical density is reduced by 5-1 and 9.9 per cent., respectively. Hence, hydrazine can be deter- mined with reasonable accuracy in the presence of at least its own weight of hydroxylamine. TABLE I11 INFLUENCE OF FOREIGN IONS ON DETERMINATION OF 0.001 PER CENT. HYDRAZINE Reduction in optical density at 494 mp for Compound Sodium chloride Sodium azide Potassium chloride Potassium sulphate Potassium nitrate Ammonium chloride Ammonium sulphate Magncsium chloride Calcium chloride Barium chloride Zinc sulphate Cadmium chloride Lead acetate Manganese chloride 0.1 per cent. Present as solutions , % NaCl 8.8 KC1 9.8 KNO, 2.5 NaNs 22.1 K2SO4 NH4Cl 20.0 (NH4)2S04 2.0 - MgC1,. 6€&0 20.4 CaCl,.6H20 15.0 BaC1,.2H20 7.0 ZnS0,.7H20 40.0 CdCl2.6H,O 21.0 Pb(OOC.CH8),.2H,0 0.0 MnCI,. 6H20 31.0 3 1 per cent. solutions, % 27.6 24.6 0.0 19.1 60.0 25.0 72.0 52.0 - - - 21.2 - OPTICAL DENSITIES MEASURED AT 530 mp OF SOLUTIONS CONTAINING HYDROXYLAMINE AND HYDRAZINE AFTER REACTION WITH PICRYL CHLORIDE Concentration I A \ Optical densities of solutions containing various concentrations of hydrazine of 0 0.0002 0~0006 0.001 0.0015 0.002 hydroxylamine, O ! per cent. per cent. per cent. per cent. per cent. 0 '- 0.01 1 0.114 0.270 0.528 0.786 1.045 0~0001 0.014 0.1 14 0.270 0-533 0.810 1.050 0.001 0.018 0.110 0.256 0.500 0.760 1.020 0-005 0.021 0.105 0-245 0.474 0.720 0.980 REFERENCES 1. Penneman, R. A., and Audrieth, L. F., Anal. Chem., 1948, 20, 1058. 2. Pesez, M., and Petit, A., Bull. SOC. Chim. France, 1947, 122. 3. Watt, G. W., and Chrisp, J. D., Anal. Chem., 1952, 24, 2006. 4. Kul'berg, L. M., and Cherkesov, A. I., J. Anal. Chem. U.S.S.B., 1951, 6, 364. 5. Deavergnes, L., Monit. Sci., 1925, 15, 77. THE UNIVERSITY DEPARTMENT OF OCEANOGRAPHY LIVERPOOL, 3 July 6th, 1953

ISSN:0003-2654    

DOI:10.1039/AN9547900076

出版商:RSC    

年代:1954

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82 HASLAM AND SWIFT: EXPERIMENTS ON THE HYDROLYSIS Pol. 79 Experiments on the Hydrolysis of 610, 66 and 6 Nylon BY J. HASLAM AND MISS S. D. SWIFT Comparative tests have been carried out on the hydrolysis with 26 per cent. w/v hydrochloric acid in sealed tubes of samples of 66, 610 and 6 nylon. The extent of the hydrolysis has been determined by potentiometric titration of the hydrolysis products with standard alkali. IN the original work1 on the analysis of nylon samples it was the practice to hydrolyse the sample in the first place with 20 per cent. v/v hydrochloric acid solution (100 ml of this solution contained 20ml of hydrochloric acid, sp.gr. 1-18) for extended periods of time. This caused difficulties where samples of 610 nylon were concerned, and it was shown that it was desirable to prepare the 610 nylon samples by re-precipitation in a finely divided form before hydrolysis.Since this early work, however, it has been shown that the hydrolysis of 66 and 610 nylons and copolymers can be carried out much more effectively with 50 per cent. v/v hydrochloric acid solution (100 ml of this solution contained 50 ml of hydrochloric acid, sp.gr. 1.18). With this strength of acid it is no longer necessary to prepare a re- precipitated specimen of 610 nylon before hydrolysis. Zahn and Wolf,2 who have carried out a considerable amount of work on the chromatographic examination of nylon hydrolysis products, hydrolyse 50 mg of perlon L or nylon in a sealed tube for 24 hours at 110" C with 0.5 ml of 6 N hydrochloric acid. For samples of perlon U, the hydrolysis is carried out with 0.5 ml of 12 N hydrochloric acid.Ecochard and D ~ v e a u , ~ in their work on the examination of interpolyamides, hydrolyse a mixture of 610 and 6 polyamides by heating ]I g of the mixture with 2 ml of hydrochloric acid (260 g of hydrogen chloride per litre) in a sealed tube at -130" C for about 6 hours. Sub- sequently the hydrolysis product is dissolved in water and titrated potentiometrically. From the result of this titration the proportions of 6101 and 6 polymers in the mixture are deduced. Incidentally, the example these authors give of the result of the hydrolysis of a mixture of 0.71 g of 6 polymer and 0.29 g of 610 polymer on p. 154 of their paper is erroneous. For such a mixture the amount of alkali used between the first and second end-points of the potentiometric titration should be 8.34 ml of N sodium hydroxide, and not 9.50 ml as stated by them.This 8-34 ml is made up of (a) 6.28 ml of N sodium hydroxide corresponding to the hydrochloric acid in the e-aminocaproic acid hydrochloride derived from 0.71 g of polymer 6 and (b) 2.06ml of N sodium hydroxide corresponding with the sebacic acid derived from 0-29g of polymer 610. Nevertheless it seemed to us that the principle of the method used by Ecochard and Duveau might be very usefully extended to a study of the hydrolysis of various nylons and related polymers with hydrochloric acid solution. For example, after a known amount of 66 nylon polymer had been heated with hydrochloric acid, it would be possible on completion of the hydrolysis to carry out a potentiometric titration with alkali of the hydrolysis products. The first end-point would give the free hydrochloric acid, and the adipic acid resulting from the hydrolysis would be titrated between the :first and second end-points.This difference between the first and second end-points would, therefore, give a simple measure of the extent of the hydrolysis and it was hoped, therefore, that considerable information could be quickly obtained by means of this comparatively simple test. Such tests have been carried out on the hydrolysis of samples of nylon 66, 610 and 6, a ratio of 4 ml of 26 per cent. w/v hydrochloric acid solution (100 ml of this solution contained 26 g of hydrogen chloride) to 2 g of polymer being used and the hydrolyses being carried out for varying periods of time.No advantage was found in increasing the amount or concentration of the acid. Other workers have used rather different procedures. EXPERIMENTAL NYLON 66- A 2-g sample of nylon 66 was weighed into a glass tube, 10 inches by $-inch diameter, and 4 ml of 26 per cent. w/v hydrochloric acid. were added. The tube was then sealed and placed in an oven at 130" C. After 1 hour the tube was shaken gently to assist solution,Feb., 19541 OF 610, 66 AND 6 NYLON 83 and again shaken at half-hourly intervals until solution of the nylon was complete. This usually occurred after 2 hours. It was noticed that the solution became light brown in colour during the hydrolysis. After a definite time the tube was removed and allowed to cool.When cool it was opened and the contents were washed with distilled water into a 500-ml beaker. To dissolve all the adipic acid the beaker and contents were warmed gently and then allowed to cool to room temperature. The final volume of solution was approximately 150 ml. POTENTIOMETRIC TITRATION OF THE HYDROLYSIS PRODUCT- The initial pH of the solution was usually 1-3. A 10 per cent. solution of sodium hydroxide was run in until a pH of 2 was reached. At this point N sodium hydroxide was used and the additions were made in 0.2-ml portions. The burette readings and the corre- sponding pH values were noted and recorded until it was apparent that the first end-point had been passed. This first end-point, which represents the amount of free hydrochloric acid in the solution, occurred at about pH 3.Small additions of 0.2 ml were again made, the burette reading and pH values for each addition being noted as before until the second end-point had been passed. This second end-point occurred at or near pH 8.3. For deducing the end-points, the method of Gran4 was used, i.e., dV/dpH was plotted against V + *dV. The graphs obtained were similar to that shown in Fig. 1. N sodium hydroxide was then run in until pH 6 was reached. 1.5 1.7 ..........._- 0.5 I .o I I I 0 .o 18.5 19.0 V * + d V Typical graph of end-points, plotted by Gran's method4 Fig. 1. The amount of alkali used between the first and second end-points is equivalent to the adipic acid in the solution and hence is a measure of the amount of hydrolysis that has taken place.Table I shows how the degree of hydrolysis attained varies with the time of heating. The sample of nylon 66 used in these experiments had a moisture content of 2-4 per cent., which has not been allowed for in the percentages quoted. TABLE I DEGREE OF HYDROLYSIS OF NYLON 66 Time of heating at 130" C, hours . . .. 2 4 6 8 12 16 Degree of hydrolysis, per cent. 76.9 84.9 96.4 97.6 98.2 ' ' { ii:: 82.5 88.6 95.8 96-9 98.4 . . NYLON 610- The procedure for hydrolysing nylon 66 was first followed, i.e., 2 g of the polymer was heated in 4 ml of 26 per cent. w/v hydrochloric acid at 130" C. It was found that the polymer was slow to hydrolyse ; after heating for 6 hours only approximately 16 per cent. had hydrolysed and after 12 hours less than 70 per cent.84 HASLAM AND SWIFT: EXPERIMENTS ON THE HYDROLYSIS [vol.79 It was then decided to fit an apparatus for shaking the tubes in the oven in the hope that continuous shaking would promote hydrolysis. The apparatus, shown in Fig. 2, consisted of a horizontal rod to which the tubes were attached and which was driven by an electric motor placed outside the oven. The results attained with this method of sh.aking showed a marked improvement, after 6 hours from 16 per cent. (without shaking) to 63 per cent. (with shaking) and after 12 hours from less than 70 peer cent. (without shaking) to 92 per cent. (with shaking). Nylon 610, however, was still much slower to hydrolyse than nylon 66, the highest figure attained being 97.7 per cent. hydrolysis after 24 hours.Connected 'externally to a stirring motor Fig. 2. Continuous-shaking apparatus The potentiometric titration for the hydrolysis products of nylon 610 was similar in principle to that of nylon 66, the end-points being finally deduced by the method of Gran.4 In order to facilitate solution of the sebacic acid formed in the hydrolysis, ethyl alcohol was used to wash out the reaction tubes. The final solution for titration consisted of approxi- mately 100 ml of ethyl alcohol and 50 ml of water. The initial pH of the solution was usually 1-3. The first end-point in the solution occurred. at pH 3.8 and the second end-point at pH 8.2 approximately. The difference between the first and second end-points corresponded to the sebacic acid in the solution and hence to the degree of hydrolysis achieved.Table I1 shows the degree of hydrolysis of nylon 610 attained by varying the time of heating. Shaking was used in these experiments. The moisture content of the nylon 610 was 1-3 per cent. TABLE I1 DEGREE OF HYDROLYSIS OF NYLON 610 Time of heating at 130" C, hours . . 4 6 8 12 14 16 24 Degree of hydrolysis, per cent. 58.5 63.1 81.9 92.0 91-2 91.2 94.8 57.1 90.0 90.2 85.4 93.6 96.4 88-4 89.8 86.0 92.7 It should be noted that with the hydrolysis products from 66 and 610 nylon, the hexa- methylenediamine dihydrochloride produced plays no part in the potentiometric titration. NYLON 6 (CAPROLACTAM POLYMER)- nylon 66 and 610. Nylon 6 shows great ease of hydrolysis when submitted to the conditions outlined forFeb., 19541 OF 610, 66 AND 6 NYLON 85 A 2-g sample of polymer and 4 ml of 26 per cent.w/v hydrochloric acid were sealed in a reaction tube and heated, with shaking, for various lengths of time. The polymer dissolved after 15 minutes, and after 2 hours as much as 91.8 per cent. had hydrolysed, as compared with 66 to 73 per cent. of nylon 66 and less than 10 per cent. of nylon 610. To determine the degree of hydrolysis of nylon 6, it is necessary to determine the amount of e-aminocaproic acid hydrochloride present in the reaction product. The procedure is similar to that followed in determining the amounts of adipic and sebacic acids from nylon 66 and 610, i.e., potentiometric titration. The first end-point gives the free hydrochloric acid present and the difference between the first and second end-points gives the eaminocaproic acid hydrochloride.The initial pH of the reaction product was 0.4 to 0.5. The first end-point occurred at pH 2.6 and the second between pH 7.4 and 8.7. Table I11 shows the degree of hydrolysis of nylon 6 for various times of heating. The moisture content of the polymer was found to be 2.17 per cent. TABLE I11 DEGREE OF HYDROLYSIS OF NYLON 6 Time of heating at 130” C, hours . . . . 2 4 6 8 10 12 91.5 94.9 96.7 96.3 97.0 97.8 Of per cent* * * { 91.8 95.9 96.9 97.4 97.8 These experiments indicate that 6 nylon is readily and completely hydrolysed by 26 per cent. w/v hydrochloric acid, that the hydrolysis of 66 nylon proceeds to completion with greater difficulty and that 610 nylon is most difficult to hydrolyse and in our experience hydrolysis is not quite complete under the most rigorous conditions. In general, the hydrolysis of 610 nylon gives rather variable results. REFERENCES 1. Clasper, M., and Haslam, J., Analyst, 1949, 74, 224. 2. Zahn, H., and Wolf, H., Melliand Textilber., 1951, 32, 317. 3. Ecochard, F., and Duveau, N., “Die Makromolekulure Chemie,” Band VII, Heft 2, Verlag Karl 4. Gran, Gunnar, Acta Chem. Scand., 1950, 4, 569. Alber, Freiburg, Munchen, 1961, p. 148. IMPERIAL CHEMICAL INDUSTRIES LIMITED PLASTICS DIVISION BLACK FAN ROAD WELWYN GARDEN CITY, HERTS. August 4th, 1963

ISSN:0003-2654    

DOI:10.1039/AN9547900082

出版商:RSC    

年代:1954

数据来源: RSC