ISSN:0003-2654    

DOI:10.1039/AN97499FX033

出版商:RSC    

年代:1974

数据来源: RSC

ISSN:0003-2654    

DOI:10.1039/AN97499BX035

出版商:RSC    

年代:1974

数据来源: RSC

摘要:

iV THE ANALYST [September, 1974THE ANALYSTEDITORIAL ADVISORY BOARDChairman: H. J. Cluley (Wembley)*L. S. Bark (Solford)R. Belcher (Birmingham)1. J. Bellamy, C.B.E. (Waltham Abbey)L. S. Birks (U.S.A.)E. Bishop (Exeter)OR. M. Dagnall (Hunfingdon)E. A. M. F. Dahmen (The Netherlands)*J. B. Dawson (Leeds)A. C. Docherty (Billingham)D. Dyrssen (Sweden)*W. T. Elwell (Birmingham)*D. C. Garratt (London)1. Hoste (Belgium)D. N. Hume (U.S.A.)H. M. N. H. Irving (Leeds)M. T. Kelley (U.S.A.)*J. A. Hunter (Edinburgh)W. Kemula (Poland)*G. F. Kirkbright (London)G. W. C. Milner (Harwell)G. H. Morrison (U.S.A.)*J. M. Ottaway (Glasgow)*G. E. Penketh (Billingham)S. A. Price (Tadworth)D. 1. Rees (London)E. B. Sandell (U.S.A.)*R. Sawyer (London)A.A. Smiles, O.B.E. (Harwell)H. E. Stagg (Manchester)E. Stahl (Germany)A. Walsh (Australia)T. S. West (London)P. Zuman (U.S.A.)*A. Townshend (Birmingham)* Members of the Board serving on the Executive Committee.NOTICE TO SUBSCRIBERSSubscriptions for The Analyst, Anolytlcal Abstracts and Proceedings should beThe Chemical Society, Publications Sales OiVce,Blackhorse Road, Letchworth, Herts.Rates for 1974(other than Mambara of the Society)sent to:(a) The Analyst, Analytical Abstracts, and Proceedings, with indexes . . . . f37.00(b) The Analyst, Analytical Abstracts printed on one side of the paper (withoutindex), and Proceedings . . . . . . . . . . . . . . f38.00(c) The Analyst, Analytical Abstracts printed on one side of the paper (withindex), and Proceedings .. . . . . . . . . . . . . f45.00The Analyst and Analytical Abstracts without Proceedings-(e) The Analyst, and Analytical Abstractt printed on one side of the paper (without(d) The Analyst and Analytical Abstracrs, with indexes . . . . . . . . f34.00index) . . . . . . . . . . . . . . . . . . f35.00( f ) The Analyst, and Analytical Abstracts printed on one side of the paper (withindex) . . . . . . . . . . . . . . . . . . f 42.00(Subscriptions are NOT accepted for The Analyst and/or for Proceedings alonevi SUMMARIES OF PAPERS I N THIS ISSUE [September, 1974Summaries of Papers in this IssueThe Rapid Determination of the Total Dry Extract of WinesA method is described whereby the total dry extract of wines, includingsweetened and fortified wines, can be determined from knowledge of theirrelative densities and alcoholic strengths.The method is designed to be used inconjunction with the rapid refractometric method used in this laboratory forthe determination of the alcoholic strength of wine and requires no furthermeasurements, other than that of temperature, to be made.P. J. WAGSTAFFEDepartment of Trade and Industry, Laboratory of the Government Chemist, Corn-wall House, Stamford Street, London, SE1 9NQ.Analyst, 1974, 99, 537-543.Determination of Cyanide Ion in Cyano-complexesA method is described for the determination of the CN- ion in a variety ofcyano-complexes. The method is based upon mixing and grinding the samplewith flowers of sulphur and potassium chloride in the ratio of 1 : 2 : 2; theaddition of potassium carbonate is also essential with cyano-acid complexes.After mixing, a micro-amount is fused in a test-tube a t about 300 "C for2 minutes and the tube is then broken in a few millilitres of water.In thisway the CN- ion is converted quantitatively into CNS-, which is determinedcolorimetrically. The average recovery is 98.54 per cent.S. K. TOBIA, Y. A. GAWARGIOUS and M. F. EL-SHAHATChemistry Department, Ain Shams University, and Micro-analytical ChemistryLaboratory, National Research Centre, Dokki, Cairo, Egypt.Analyst, 1974, 99, 544-546.The Determination of Small Amounts of Water inGases Using Karl Fischer ReagentTwo methods are described for the determination of water in gases.In the first method, the gas being examined is led into a Karl Fischertitration cell, and water is titrated directly.In the second method, waterfrom a gas stream is absorbed on a short column of a gas-chromatographicstationary phase. On heating the column, water is liberated and is carriedover to the Karl Fischer cell in a stream of dry nitrogen and then titrated.The validity of the direct titration method has been checked by examininggas streams that had been passed over ice a t various temperatures.E. E. ARCHERBritish Petroleum Limited, Group Research and Development Department,Epsom Division, Epsom, Surrey.and J. HILTONBP Chemicals International Limited, Grangemouth, Stirlingshire, Scotland.Analyst, 1974, 99, 547-550September, 19741 SUMMARIES OF PAPERS I N THIS ISSUEThe Use of Tiron in the Microchemical Analysisof MineralsThe complexes formed by tiron with aluminium, iron and titanium canbe used to determine these elements colorimetrically on a single aliquot ofthe solution of a mineral.The tiron also renders these solutions verysuitable for analysis in a flame, the sodium from the tiron acting as a flamebuffer and the complexing properties inhibiting chemical interferences. Asingle aliquot of solution can therefore be used to determine several elementsand the procedure can form the basis df a scheme for the microchemicalanalysis of minerals. Little is known of the use of tiron for the deter-mination of aluminium and this paper describes tests made on the usefulnessof this method.W. J.FRENCH and S. J. ADAMSGeology Department, Queen Mary College, University of London, Mile End Road,London, E.l.Analyst, 1974, 99, 551-554.Oxidation Procedures in the Assay of Some Drugs Containing aDiphenylmethylene Ether or Diphenylmethyleneamino GroupMethods for the oxidation of diphenylmethylene ethers and diphenyl-methyleneamines have been compared ; oxidation with aqueous acidic di-chromate is advocated for the former and with alkaline permanganate forthe latter in the assay of drugs containing these groups. The possible mech-anisms involved are proposed.B. CADDY, F. FISH and J. TRANTERDivision of Pharmacognosy and Forensic Science, School of Pharmaceutical Sciences,University of Strathclyde, Glasgow, G1 1XW.Analyst, 1974, 99, 555-564.Determination of the Tyramine Content of South African Cheesesby Gas - Liquid ChromatographyThe tyramine content of foodstuffs and beverages is of pharmacologicaland therapeutic importance.A simplified method for its extraction fromvarious cheeses and the application of gas-chromatographic analysis arepresented.E. R. KAPLAN, N. SAPEIKADepartment of Pharmacology, Medical School, Observatory, Cape Province,South Africa.and I. M. MOODIEFishing Industry Research Institute, University of Cape Town, Rondebosch, CapeProvince, South Africa.Analyst, 1974, 99, 565-569.The Determination of Residues of Volatile Fumigants in GrainReport by the Panel on Fumigant Residues in Grain.COMMITTEE FOR ANALYTICAL METHODS FOR RESIDUES OFPESTICIDES AND VETERINARY PRODUCTS IN FOODSTUFFS (DR.N.A. SMART, SECRETARY)Ministry of Agriculture, Fisheries and Food, Plant Pathology Laboratory, HatchingGreen, Harpenden, Hertfordshire.Analyst, 1974, 99, 570-576.Vixii SUMMARIES OF PAPERS I N THIS ISSUEModified Methylene Blue Method for the Micro - determinationof Hydrogen Sulphide[September, 1974A method is described whereby hydrogen sulphide can be determinedsimply and rapidly in the 0.04 to 0.4 pmol range.N. A. MATHESONRowett Research Institute, Bucksburn, Aberdeen, AB2 9SB.Analyst, 1974, 99, 577-579.The Determination of Nitrogen- 15 in Plant Material With anEmission SpectrometerInstrumental and procedural modifications for the use of the Statron,Model NOI-5, emission spectrometer in the determination of nitrogen- 15 arereported.An interpolative method is recommended for estimating thebackground of the nitrogen-14 - nitrogen-15 peak. This method gives alinear relationship between apparent percentage of nitrogen- 15 and the actualpercentage of nitrogen-15 over the lower, most commonly used range. Assaysrepeated at intervals over 2 months had standard errors of 0-75 per cent.The preparation of nitrogen gas samples for the emission spectrometerhas been treated as a separate operation from the determination of total plantnitrogen. After a standard Kjeldahl digestion of the plant material, theammonium ion is precipitated with a Nessler reagent. The supernatant isrejected and the precipitate treated with dilute hydrochloric acid to give anammonium chloride solution, from which an aliquot is taken for a Dumascombustion in a discharge tube.Two operators can prepare and measure upto fifty samples per day. The method has been used to analyse a range of planttissues from an apple nutrition experiment, during which replicate digestionsand analyses gave values for nitrogen- 15 enrichment that differed by anaverage of only 2.5 per cent.C. P. LLOYD-JONES, G. A. HUDD and D. G. HILL-COTTINGHAMUniversity of Bristol, Department of Agriculture and Horticulture, Research Station,Long Ashton, Bristol, BS18 9AF.Analyst, 1974, 99, 580-587.Atomic-absorption Determination of Some Common Trace Elementsin Aluminium Oxide and Other Aluminium Compounds Using aCo-precipitation Separation TechniqueAtomic-absorption spectroscopy has been used to determine micro-gram amounts of calcium, iron, manganese, silicon, titanium, vanadiumand zinc in aluminium oxide and other aluminium-rich materials after co-precipitation of these elements on zirconium hydroxide from an alkaline solu-tion of the sample.The proposed method serves both to separate the trace elements fromaluminium and also to concentrate the elements, thus improving bothaccuracy and sensitivity. The method is shown to be as accurate andprecise as colorimetric procedures, very much quicker and less tedious.The trace constituents are determined in the range 5 to 400 pg in thefinal 25 ml of sample solution on a 2-g sample of aluminium oxide, and in therange 10 to 2000 pg on a 0.5-g sample of other materials (25-ml final volume).Interference effects are reduced to a minimum by separation of theelements from aluminium and the provision of closely matched standardsolutions.P.N. W. YOUNGNew Zealand Aluminium Smelters Limited, Invercargill, New Zealand.Analyst, 1974, 99, 588-594September, 19741 SUMMARIES OF PAPERS I N THIS ISSUEAtomic-absorption Studies on the Determination of Antimony,Arsenic, Bismuth, Germanium, Lead, Selenium, Tellurium and Tinby Utilising the Generation of Covalent HydridesA method for the determination of arsenic, bismuth, germanium, lead,antimony, selenium, tin and tellurium by means of hydride generation isdescribed. The hydrides are generated by adding the acidified sample todilute (1 percent.m/V) sodium borohydride solution. The liberated hydridesare passed directly into a 17 cm long silica tube mounted in an air - acetyleneflame. The advantages of the proposed system are its simplicity, highsensitivity, high speed of analysis and the fact that background correctionfacilities are not required.The generation of plumbane for analytical purposes does not appearto have been reported previously.K. C. THOMPSON and D. R. THOMERSONShandon Southern Instruments Ltd., Frimley Road, Camberley, Surrey, GU16 5ET.Analyst, 1974, 99, 595-601.Electrolytic Extraction Combined With Flame Atomic Absorptionfor the Determination of Metal Ions in Aqueous SolutionMetals were deposited from aqueous solutions onto an iridium wire eitherby electrolysis at pH 2 or by auto-deposition at pH 9.The amount depositedwas determined by atomisation with an air - hydrogen flame into a long-tube(10 cm) atomic-absorption spectrophotometer. The sensitivities obtained byelectrolysis were comparable with those obtained by conventional sampleaspiration for magnesium, lead and zinc and an order of magnitude greater forcadmium, copper and mercury. The presence of other ions in the samplesolution generally reduced the sensitivity of the method.J. B. DAWSON, D. J. ELLIS and T. F. HARTLEYDepartment of Medical Physics, General Infirmary, Leeds, LS 1 3EX.Mrs. M. E. A. EVANS and K. W. METCALFJohnson Matthey & Co. Ltd., Group Research Laboratory, Wembley, Middlesex.Analyst, 1974, 99, 602-607.A Potentiometric Titration Method for the Rapid Determinationof Salt in Meat ProductsA method is described for the rapid determination of salt in meat pro-ducts by titration of the macerated sample with silver nitrate. The acidicand oxidising conditions specified permit the use of an ion-selectiveelectrode with a silver sulphide membrane in the potentiometric detectionof the end-point. The method is slightly more precise and very much morerapid than existing routine and reference methods.M. KAPEL and J., C. FRYProcter Department of Food and Leather Science, Leeds University, Leeds, LS2 9 JT.An~lyst, 1974, 99, 608-611.The Use of Filter-papers in the Determination of Nitrogen in FoodsD. PEARSONNational College of Food Technology, University of Reading, St. George’s Avenue,Weybridge, Surrey.Analyst, 1974, 99, 612.xii

ISSN:0003-2654    

DOI:10.1039/AN97499FP093

出版商:RSC    

年代:1974

数据来源: RSC

摘要:

xii SUMMARIES OF PAPERS I N THIS ISSUEModified Methylene Blue Method for the Micro - determinationof Hydrogen Sulphide[September, 1974A method is described whereby hydrogen sulphide can be determinedsimply and rapidly in the 0.04 to 0.4 pmol range.N. A. MATHESONRowett Research Institute, Bucksburn, Aberdeen, AB2 9SB.Analyst, 1974, 99, 577-579.The Determination of Nitrogen- 15 in Plant Material With anEmission SpectrometerInstrumental and procedural modifications for the use of the Statron,Model NOI-5, emission spectrometer in the determination of nitrogen- 15 arereported. An interpolative method is recommended for estimating thebackground of the nitrogen-14 - nitrogen-15 peak. This method gives alinear relationship between apparent percentage of nitrogen- 15 and the actualpercentage of nitrogen-15 over the lower, most commonly used range.Assaysrepeated at intervals over 2 months had standard errors of 0-75 per cent.The preparation of nitrogen gas samples for the emission spectrometerhas been treated as a separate operation from the determination of total plantnitrogen. After a standard Kjeldahl digestion of the plant material, theammonium ion is precipitated with a Nessler reagent. The supernatant isrejected and the precipitate treated with dilute hydrochloric acid to give anammonium chloride solution, from which an aliquot is taken for a Dumascombustion in a discharge tube. Two operators can prepare and measure upto fifty samples per day. The method has been used to analyse a range of planttissues from an apple nutrition experiment, during which replicate digestionsand analyses gave values for nitrogen- 15 enrichment that differed by anaverage of only 2.5 per cent.C.P. LLOYD-JONES, G. A. HUDD and D. G. HILL-COTTINGHAMUniversity of Bristol, Department of Agriculture and Horticulture, Research Station,Long Ashton, Bristol, BS18 9AF.Analyst, 1974, 99, 580-587.Atomic-absorption Determination of Some Common Trace Elementsin Aluminium Oxide and Other Aluminium Compounds Using aCo-precipitation Separation TechniqueAtomic-absorption spectroscopy has been used to determine micro-gram amounts of calcium, iron, manganese, silicon, titanium, vanadiumand zinc in aluminium oxide and other aluminium-rich materials after co-precipitation of these elements on zirconium hydroxide from an alkaline solu-tion of the sample.The proposed method serves both to separate the trace elements fromaluminium and also to concentrate the elements, thus improving bothaccuracy and sensitivity.The method is shown to be as accurate andprecise as colorimetric procedures, very much quicker and less tedious.The trace constituents are determined in the range 5 to 400 pg in thefinal 25 ml of sample solution on a 2-g sample of aluminium oxide, and in therange 10 to 2000 pg on a 0.5-g sample of other materials (25-ml final volume).Interference effects are reduced to a minimum by separation of theelements from aluminium and the provision of closely matched standardsolutions.P. N.W. YOUNGNew Zealand Aluminium Smelters Limited, Invercargill, New Zealand.Analyst, 1974, 99, 588-594September, 19741 SUMMARIES OF PAPERS I N THIS ISSUEAtomic-absorption Studies on the Determination of Antimony,Arsenic, Bismuth, Germanium, Lead, Selenium, Tellurium and Tinby Utilising the Generation of Covalent HydridesA method for the determination of arsenic, bismuth, germanium, lead,antimony, selenium, tin and tellurium by means of hydride generation isdescribed. The hydrides are generated by adding the acidified sample todilute (1 percent. m/V) sodium borohydride solution. The liberated hydridesare passed directly into a 17 cm long silica tube mounted in an air - acetyleneflame. The advantages of the proposed system are its simplicity, highsensitivity, high speed of analysis and the fact that background correctionfacilities are not required.The generation of plumbane for analytical purposes does not appearto have been reported previously.K.C. THOMPSON and D. R. THOMERSONShandon Southern Instruments Ltd., Frimley Road, Camberley, Surrey, GU16 5ET.Analyst, 1974, 99, 595-601.Electrolytic Extraction Combined With Flame Atomic Absorptionfor the Determination of Metal Ions in Aqueous SolutionMetals were deposited from aqueous solutions onto an iridium wire eitherby electrolysis at pH 2 or by auto-deposition at pH 9. The amount depositedwas determined by atomisation with an air - hydrogen flame into a long-tube(10 cm) atomic-absorption spectrophotometer. The sensitivities obtained byelectrolysis were comparable with those obtained by conventional sampleaspiration for magnesium, lead and zinc and an order of magnitude greater forcadmium, copper and mercury. The presence of other ions in the samplesolution generally reduced the sensitivity of the method.J.B. DAWSON, D. J. ELLIS and T. F. HARTLEYDepartment of Medical Physics, General Infirmary, Leeds, LS 1 3EX.Mrs. M. E. A. EVANS and K. W. METCALFJohnson Matthey & Co. Ltd., Group Research Laboratory, Wembley, Middlesex.Analyst, 1974, 99, 602-607.A Potentiometric Titration Method for the Rapid Determinationof Salt in Meat ProductsA method is described for the rapid determination of salt in meat pro-ducts by titration of the macerated sample with silver nitrate. The acidicand oxidising conditions specified permit the use of an ion-selectiveelectrode with a silver sulphide membrane in the potentiometric detectionof the end-point. The method is slightly more precise and very much morerapid than existing routine and reference methods.M. KAPEL and J., C. FRYProcter Department of Food and Leather Science, Leeds University, Leeds, LS2 9 JT.An~lyst, 1974, 99, 608-611.The Use of Filter-papers in the Determination of Nitrogen in FoodsD. PEARSONNational College of Food Technology, University of Reading, St. George’s Avenue,Weybridge, Surrey.Analyst, 1974, 99, 612.xii

ISSN:0003-2654    

DOI:10.1039/AN97499BP105

出版商:RSC    

年代:1974

数据来源: RSC

摘要:

SEPTEMBER, 1974 Vol. 99, NO. 1182. THE ANALYST The Rapid Determination of the Total Dry Extract of Wines BY P. J. WAGSTAFFE (De9avlment of Trade and Industry, Laboratory of the Government Chemist, Cornwall House, Stamford Street, London, SE1 9NQ) A method is described whereby the total dry extract of wines, including sweetened and fortified wines, can be determined from knowledge of their relative densities and alcoholic strengths. The method is designed to be used in conjunction with the rapid refractometric method used in this laboratory for the determination of the alcoholic strength of wine and requires no further measurements, other than that of temperature, to be made. THE total dry extract of wine is usually determined by a process involving the removal of volatile material and, after suitable readjustment of volume, measurement of the relative density of the resulting solution.The relative density thus found is expressed in terms of the equivalent concentration of sucrose by reference to tables. Generally, this operation is effected on the residual solution resulting from distillation of the wine when determining its alcoholic strength. The total dry extract found by this procedure differs only slightly from that found by the more accurate method of evaporating a known volume of wine and weighing the residue. In fact, the densimetric procedure is the official method of the European Economic; Community (EEC).l To distil all wines in order to determine their total dry extract could be inconvenient,' particularly as the alcoholic strength of most of them can be determined by a rapid refracto- metric method2 with an accuracy sufficient for many purposes.Several workers394 have attempted to devise methods in which distillation is avoided, most of them involving measure- ment of refractive index or relative density, or both. Unfortunately, none of these methods satisfy our requirements as regards accuracy, compactness of tables and, most important, the range of composition of wines with which they can cope. The present work describes the development and use of tables that overcome these difficulties. EXPERIMENTAL A large number of aqueous ethanoIic sucrose solutions of accurately known composition were prepared covering, in uniform increments, the range 0 to 350 g 1-1 of sucrose and 0 to 25 per cent.VjV of ethanol. Their relative densities, D, were measured by pycnometry and their refractive indices, R, by means of immersion refractometers calibrated in the arbitrary Zeiss scale, all measurements being made at 20 "C. The results of these determinations were plotted in various ways as shown in Figs. 1, 2 and 3. Each of these relationships was expressed mathematically by means of a computerised regression analysis, which fitted third-order equations to the experimental data, each equation expressing sucrose concentration as a function of the ethanol concentration and ( R + D), R or D. The situation was complicated to some extent €or the relationships involving refractive index. In order to cover the whole range of compositions it is necessary to use two refracto- meter prisms, each covering a different range of refractive indices.Unfortunately, a graph of refractometric scale readings versus true refractive indices exhibits a discontinuity where the two scales overlap, which is revealed as the breaks in the lines representing 150 and 200 g 1-1 in Figs. 1 and 2. It was therefore necessary to derive two equations for each of the relation- ships involving refractive index, one relating to the range covered by the No. 1 prism ai;d the other to that covered by the No. 2 prism. The suitability of these equations for determining the total dry extract was assessed by substituting into each the appropriate results obtained by analysis of a series of table wines. By comparing the values of dry extract thus found with those obtained by the densimetric method it was demonstrated that the equation relating dry extract to alcoholic strength and 537 0 SAC; Crown Copyright Reserved.538 40 WAGSTAFFE : THE RAPID DETERMINATION 0 - - No.1 I I I I [Analyst, VOl.99 Sucrose concentratiodg 1-1 240 2 200 - m > 160 120 80 No. 2 Ethanol, per cent. V/V Fig. 1. Variation of the sum R + D with concentration of ethanol at various sucrose concentrations relative density gave by far the best results, the errors obtained having the lowest mean-value and a distribution whose standard deviation was less than one third of those resulting from the use of the relationships involving refractive index. In view of this finding and because of the previously mentioned complications associated with immersion refractometers, it was decided to derive tables that relate dry extract to alcoholic strength and relative density.20 0 Sucrose 1 concentration/g 1-1 Q, > 1 120- VJ e, rr .- N cy 8 0 - No. 1 Y 40 - NO. 1 I I I I I 1 5 10 15 20 25 0 Ethanol, per cent. V/V Fig. 2. Variation of the refractive index (Zeiss scale) with concentration of ethanol a t various sucrose concentrations The equation relating sucrose concentration to the concentration of ethanol and relative density of aqueous ethanolic sucrose solutions is given as it provides in itself a means of determining dry extract (see below).September, 19741 OF THE TOTAL DRY EXTRACT OF WINES 539 Sucrose (g 1-l) = (399.443A x + (259.3490 x lo-?) - (642*503Ae x + (1211.760A3 x + (1.297n3 i< - (18.005AD x + (148.071A2D2 x lo-') -!- (488*320A30 x lo-') - (378*544A3O3 x lo-'') .. (1) where and A = ethanol concentration, per cent. V/V I ) == 1000 (relative density, 20 OC/ZO "C) - 1000. DERIVATION OF TABLES FOR THE DETERMINATION OF TOTAL DRY EXTRACT FROM KNOWLEDGE OF THE RELATIVE DENSITY AND ALCOHOLIC STRENGTH OF WINE- The principal difficulty in producing tables of the type required lies in reaching a com- promise between accuracy and compactness. This compromise was finally achieved as follows: Fig. 3 demonstrates the decrease in relative density that occurs as the concentration of ethanol in an aqueous ethanolic sucrose solution is increased. It can be shown that the lines representing solutions of equal sucrose concentration become increasingly parallel to each other as the sucrose concentration increases.Now, in any given aqueous ethanolic sucrose solution the relative density of the corresponding ethanol-free solution can be considered to be the relative density of the mixture increased by an amount dependent on the concentration of ethanol. If all the constant sucrose lines were entirely evenly spaced, as measured in a direction parallel to the D axis, the influence of the ethanol on the relative density would be independent of the actual sucrose concentration ; therefore, provided the relative density and the concentration of ethanol in the mixture were known it would be possible to deduce the relative density of the corresponding ethanol-free solution. This would be, in effect, a more precise form of the Tabarie e q ~ a t i o n , ~ but allowing for contraction in volume when sucrose solutions and ethanol solutions are mixed together. 0 5 10 15 20 25 Ethanol, per cent.V/V Fig. 3. Variation of relative density with con- centration of ethanol a t various sucrose concentrations As, in fact, the lines representing equal sucrose concentrations are not completely parallel, a mathematical analysis was undertaken to determine the line whose slope best represented the slopes of all the constant sucrose lines represented in Fig. 3. The equation representing the line thus derived is DA = -1*149012A + 0.02059A2 - 0*00042A3 . . . . . . . , (2) Equation (2) was used to calculate the correction terms DA corresponding to unit increments of ethanol concentration over the range 0 to 25 per cent, V/V.Thus, in any given aqueous540 WAGSTAFFE : THE RAPID DETERMINATION [Analyst, VOl. 99 ethanolic sucrose solution the relative density of the corresponding ethanol-free solution can be determined by adding to the relative density of the mixture an amount DA, determined from equation (2), dependent on the concentration of ethanol. In order to avoid the necessity of converting relative densities thus determined into their corresponding sucrose concentrations it was decided to express all relative densities directly in terms of grams of sucrose per litre of solution. This was achieved by use of Savage's table,5 which relates the relative density, 20 "C/20 O C , to grams of sucrose per litre of solution at 20 "C. Fortunately, this relationship between relative density and sucrose concentration is virtually linear over the range of interest, hence the sucrose concentrations obtained by conversion of the relative densities can be assumed to be additive.TABLE I CORRECTION TERMS (g 1-1 OF SUCROSE) CORRESPONDING TO CONCENTRATION OF ETHANOL, Ethanol, per cent. v/v 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0 20.0 21.0 22.0 23.0 24.0 25.0 7 0.0 3.8 7.4 11.0 14.6 18.0 21.3 24.6 27.9 31.1 34.2 37.3 40.3 43.4 46.4 494 52.4 55.4 58.4 61.4 64.5 67-5 70-6 73.7 76.9 80.1 The ethanol correction 0.1 0.4 4.2 7.8 11.4 14.9 18-3 21.6 24.9 28.2 31.4 34-5 37.6 40.6 43.7 46.7 49.7 52.7 55.7 58.7 61.7 64.8 67.8 70.9 74.0 77.2 0.2 0.8 4.5 8.1 11.7 15.3 18.7 22.0 25.3 28.5 31.7 34.8 37.9 40.9 44-0 47.0 50-0 53.0 56-0 59.0 62.0 65.1 68.1 71.2 74.3 77.5 PER CENT.v,/v, AT 20 "c Intermediate ethanol concentrations, per cent. V / V - 0.3 1-1 4.9 8.5 12.1 15.6 19.0 22.3 25.6 28.9 32.0 35.1 38.2 41-2 44.3 47.3 50.3 53.3 56.3 59.3 62-3 65.4 68.4 71.5 74.7 77.9 0.4 1.5 5.2 8.8 12.4 16.0 19.3 22.6 25.9 29.2 32-3 35.4 38.5 11.5 44.6 47.6 50.6 53-6 56.6 59.6 62.6 65.7 68.7 71.8 75.0 78.2 0-5 1.9 5.6 9.2 12-8 16.3 19.7 22.9 26.3 29.5 32.7 35.7 38.8 41.9 44.9 37.9 50.9 53.9 56-9 59.9 62.9 66.0 69.1 72.2 75-3 78.5 0.6 2.3 6.0 9.6 13.2 16.6 20.0 23.3 26.6 29.8 33.0 36.1 39-1 42.2 45.2 48.2 51.2 54.2 57.2 60.2 63.3 66.3 69.4 72.5 75.6 78.8 0.7 2-7 6.3 9.9 13.5 17.0 20.3 23.6 26.9 30.1 33.3 36.4 39-4 42.5 45.5 48.5 51-5 54.5 57.5 60.5 63.6 66.6 69.7 72.8 75-9 79.1 terms derived from equation 0.8 3.0 6.7 10.3 13-9 17.3 20.6 23.9 27.2 30-5 33.6 36.7 39.7 42.8 45.8 48.8 51-8 54.8 57-8 69.8 63.9 66.9 70.0 73.1 76.3 79.5 0.9 3-4 7.0 10.6 14.2 17.7 21.0 24-3 27-6 30.8 33.9 37.0 40.0 43.1 46.1 49.1 52.1 55.1 58.1 61.1 64.2 67.2 70.2 73.4 76.6 79.8 (2) for unit increments of ethanol concentration were converted into the corresponhing sucrose concentration, intermediate values corresponding to tenths of a per cent.VjV being obtained by linear interpolation and the results expressed as in Table I. Table I1 is a rearranged version of Savage's table and gives the apparent sucrose concentrations corresponding to the relative density of the mixture (in the tables used in practice, entries of D are given to 0.1 unit). Hence the sucrose con- centration of an aqueous ethanolic sucrose solution can be determined by adding, algebraically, the value found in Table I corresponding to the ethanol concentration to the value found in Table TI corresponding to the relative density of the mixture.TABLE I1 VALUES FOR SUCROSE CORRESPONDING TO Dzo oc/30 oc D Sucroselg 1-1 D Sucroselg 1-1 D Sucrose/g 1-1 D Sucrose/g 1-1 D Sucrose/g 1-1 970 -77.7 1005 12.9 1040 103.7 1075 195-1 1110 287.2 975 -64.7 1010 25.8 1045 116.7 1080 208.3 1115 300.5 980 -51.7 1015 38.7 1050 129.8 1085 221.3 1120 313.7 985 -38.7 1020 51.7 1055 142.8 1070 234.5 1125 326.9 990 -25.8 1025 64.7 1060 115.9 1095 247.5 1130 340.2 995 -12.9 1030 77.8 1065 169.0 1100 260.9 1000 0.0 1035 90.7 1070 182.0 1105 274.0 In the table used in practice, entries of D are given to 0.1 unit.September, 19741 OF THE TOTAL DRY EXTRACT OF WINES 541 The usefulness of these tables was examined critically.Table I11 illustrates the errors result- ing from applying the tables to the data obtained from measurement of aqueous ethanolic sucrose solutions of known composition. TABLE I11 ERRORS (gl-1 OF SUCROSE) PRODUCED BY APPLICATION OF TABLES I AND I1 TO AQUEOUS ETHANOLIC SUCROSE SOLUTIONS OF KNOWN COMPOSITION Ethanol concentration, per cent. V / V Sucrose/ I A \ g 1-1 0 2.0 5.0 10.0 15.0 20.0 25.0 20 50 100 150 200 250 300 350 +0*1 +0*1 + 0.1 +0.1 + 0.2 0.0 + 0.2 0.0 - 0.5 - 0.5 - 0.3 - 0.1 -0.1 +0*1 + 0.2 + 0.2 - 0.2 + 0.1 - 0.1 - 0.1 0.0 + 0.2 + 0.3 + 0-5 - 0.5 - 0.3 - 0.2 - 0-2 - 0.3 0.0 - 0.2 0.0 0.0 + 0.2 +0.1 + 0.2 - 0.2 - 0.2 - 0.6 - 0.9 + 0.8 + 0.5 + 0.4 0-0 - 0.5 - 1.4 - 1.8 - 2.5 +2.1 + 1.9 + 1.2 + 0.5 - 0.6 - 2.0 - 3.3 - 4.6 Error = determined value - true value.As can be seen from Table 111, the error increases with increase in both the ethanol and sucrose concentrations. The standard deviation of the error over the whole range of compo- sitions is 1.05. If the region exceeding 250 g 1-1 of sucrose and 15 per cent. VlV of ethanol is excluded the standard deviation is 0.55, giving approximate 95 per cent. confidence limits Tables I and I1 were further examined by applying them to a wide variety of wine samples. These samples included some table wines but emphasis was placed on sweetened and fortified wines. The alcoholic strength of each wine was determined by distillation and by the refractometric method, ie., by measurement of refractive index and relative density at 20 "C.The total dry extract was determined from Tables I and I1 employing the alcoholic strengths determined by both methods. In addition, the suitability of equation (1) for determining total dry extract was examined by substituting into it the appropriate values, again employing alcoholic strengths determined by distillation and by the refractometric method. The results were compared with the dry extract values obtained by the official EEC method and are summarised in Table IV together with results obtained in a similar way on a series of table wines. of * l a 1 g 1-1. TABLE I V SUMMARY OF ERRORS (g I-') I N DETERMINATIONS OF TOTAL DRY EXTRACT BY VARIOUS PROCEDURES Samples Procedure A 7 7 From table From equation r - - - .~ ___h---------q A Ethanol by Ethanol by Ethanol by Ethanol by refractometer distillation refractometer distillation I \ Sweet, sweetened and fortijied wines (68 samples)-- Mean error . . .. . . . . - 1.1 - 0.5 - 0.8 - 0.3 95 per cent. confidence limits . . & 2-6 1.4 * 2.0 * 1.2 Mean error . . . . . . . . - 0-7 - 0.6 - 0.6 - 0.2 95 per cent. confidence limits . . * 1.9 1.4 1.7 0.8 Error = determined value -- true value. Table wines (36 samples)- The results shown in Table IV are much as would be expected. An increase in error of the value for total dry extract results from the use of the tables instead of the more precise equation and, to a greater extent, from the use of the refractometric method to determine the ethanol content.Nevertheless, a 95 per cent. confidence limit of *2.6 g l-l, as found for the sweetened and fortified wines when using the tables in conjunction with the refractometric method, should prove to be adequate for most purposes.542 WAGSTAFFE : THE RAPID IIETERMIN~ITIC'F [A?znlyst, 1701. 99 INFLUENCE OF TEMPERATURE ON THE DETERMINATION OF TOTAL DRY EXTRACT- The rapid refractometric method for determining the ethanol content is, effectively, temperature independent; the only condition that needs to be satisfied is that measurement of both the refractive index and relative density are made at the same temperature. Unfortu- nately, the method described here for determining dry extract does not exhibit this temperature independence.The need to attemperate all samples to 20 "C in order to determine the extract could be inconvenient and would greatly restrict the usefulness of the refractometric method. For this reason, temperature correction tables were devised, which enable allowance to be made for the influence of temperature on the determination of dry extract. The relative densities D,oc/zuoc of a series of aqueous ethanolic sucrose solutions were measured at 15, 20 and 25 "C, no allowance being made for the thermal expansion of the borosilicate pycnometer used. The differences between the relative densities at 15 and 20 "C and between thosc at 20 and 25 "C were plotted against ethanol concentration at several different sucrose concentrations. The differences in relative density at suitable increments in ethanol concentration were read off from the graphs, expressed in terms of sucrose coii- centration (grams per litre) employing Savage's table, and the results set out in tabular form.The intermediate points between 15 and 20 "C and between 20 and 25 "C were found by interpolation, assuming linearity over 5 "C intervals. Table V shows part of the temperature correction table, the full version of which extends from 0 to 350 g 1-1 in 50 g 1-1 increments. The appropriate correction term is found from the known ethanol concentration and approximate extract value as determined from Tables I and 11. It is evident from Table V that the actual magnitude of the correction term is not strongly dependent on the dry extract level, thereby justifying the use of the approximate value of dry extract in order to determine the correction.TABLE V TEMPERATURE CORRECTION TERMS (g 1-l) TO RE ADDED TO OR SUBTRACTED FROM THE APPARENT EXTRACT FOUND FROM MEASUREMENT O F D AT TEMPERATURES OTHER THAN 20 "c Ethanol, Temperature/"C Apparent per extract/ cent. g 1-1 v/v 50 0 5 10 12.5 15 17.5 20 22.5 25 100 0 5 10 12.5 15 17.5 20 22.5 25 Subtract -- 7 15 2.4 2.5 2.9 3.2 3.5 4.0 4.4 4.9 5.5 2.7 2.8 3.2 3-5 3.9 4.3 4.8 5.3 5.8 16 1.9 2.0 2-3 2.6 2.8 3.2 3.5 3.9 4.4 2.2 2-2 2.6 2.8 3.1 3.4 3.8 4.2 4.6 17 1.4 1-5 1.7 1.9 2.1 2-4 2.6 2.9 3.3 1.6 1.7 1.9 2.1 2.3 2.6 2.9 3.2 3.5 18 1.0 1.0 1.2 1.3 1-4 1.6 1.8 2.0 2.2 1.1 1.1 1-3 1.4 1.6 1.7 1.9 2.1 2.3 19 0-5 0.5 0.6 0.6 0.7 0.8 0.9 1.0 1.1 0.5 0.6 0.6 0.7 0.8 0.9 1.0 1.1 1.2 Add A , - 21 0-6 0.6 0.7 0.8 0.8 0.9 1.0 1.1 1.2 0.7 0.7 0-8 0.8 0.9 1.0 1.0 1.2 1.3 22 1.2 1.3 1.4 1.6 1.7 1-8 2.0 2.2 2-4 1.4 1.4 1-5 1.7 1.8 2.0 2.1 2.4 2.6 23 1.9 1.9 2.1 2.3 2.5 2.8 3.1 3.3 3.7 2.0 2.1 2.3 2.5 2.7 2.9 3.2 3.5 3.8 24 2-5 2.6 2.8 3-1 3.4 3.7 4.1 4.4 4.9 2.7 2.8 3.0 3.4 3.6 3.9 4.2 4.7 5.1 25 3-1 3.2 3.5 3.9 4-2 4.6 5-1 5.5 6.1 3.4 3.5 3.8 4.2 4.5 4.9 5.3 5.9 6.4 The tables used in practice extend from 0 to 350 g 1-1 of sucrose in 50 g 1-1 increments.Little additional error results from measuring the relative density at ambient temperature and applying the temperature corrections. Although Table V was derived for use with a borosilicate pycnometer it does not matter if soda-glass instruments are used instead. These remarks apply equally to results obtained with glass hydrometers, which can be used if preferred.September, 19741 OF THE TOTAL DRY EXTRACT OF WINES 543 This paper has been published with the permission of the Government Chemist. The assistance of Mr. 0. F. Newman and Mr. I. Telford with the statistical analysis and computer programming is gratefully acknowledged. REFERENCES 1. 2. 3. 4. 5. “Recueil des M6thodes Internationales d’Analyse des Vins,” Office International de la Vigne et du Vin, Paris, 1958, Part A3, p. 5. Cooke, J. R., Analyst, 1974, 99, 306. Petro-Turza, M., and Kovacs-Klement, M., Mitt. Rebe Wein, 1971, 4, 289. Ribdreau-Gayon, J., and Peynaud, E., “Analyse et Controle des Vins,” Second Edition, Beranger, Savage, R. I., Int. Sug. .J., 1972, 74, 167. Paris, 1968, p. 62. Received A9ril l s t , 1974 Accepted April 17fh, 1974

ISSN:0003-2654    

DOI:10.1039/AN9749900537

出版商:RSC    

年代:1974

数据来源: RSC

摘要:

544 Analyst, September, 1974, Vol. 99, $9. 544-546 Determination of Cyanide Ion in Cyano-complexes BY S. K. TOBIA, Y. A. GAWARGIOUS AND M. F. EL-SHAHAT (Chemistry Department, A in Shams University, and Micro-analytical Chemistry Laboratory, National Research Centre, Dokki, Cairo, Egypt) A method is described for the determination of the CN- ion in a variety of cyano-complexes. The method is based upon mixing and grinding the sample with flowers of sulphur and potassium chloride in the ratio of 1 : 2 : 2; the addition of potassium carbonate is also essential with cyano-acid complexes. After mixing, a micro-amount is fused in a test-tube a t about 300 "C for 2 minutes and the tube is then broken in a few millilitres of water. In this way the CN- ion is converted quantitatively into CNS-, which is determine? colorimetrically.The average recovery is 98-54 per cent. THE determination of the cyanide ion in cyano-complexes and, in particular, in relatively stable compounds, constitutes one of the important problems in analytical chemistry because of a lack of methods for the analysis of such complexes. This is the reason why cyanide in cyano- complexes is usually determined with the help of micro-scale elemental analysis. However, such methods, in addition to requiring the use of sophisticated apparatus, usually yield low results for carbon and nitrogen contents, probably owing to the formation of very stable carbides and nitrides, respectively, with the central metal ion of the complex. Other possible methods are based upon decompositionl9 of the complex, with the liberation of hydrogen cyanide gas.The latter can either be determined as such, using a gas-chromatographic method3** (although this technique has been attempted only with pure hydrogen cyanide) or, after conversion into the cyanide of an alkali metal, by a variety of techniques, e.g., titri- metry, K s * polarography7 9 or colorimetry. lo In the present work a method has been developed for the determination of cyanide ion in different cyano-complexes. The method is based upon gradual heating, to 300 "C, of the sample after admixture with potassium chloride and flowers of sulphur. After breaking the ignition tube in a small volume of water and the colorimetric determination of the thiocyanate formed, the cyanide content is calculated.EXPERIMENTAL REAGENTS- All reagents used were of analytical-reagent grade unless otherwise specified. Potassium thiocyanate solzttion, 2227 9.p.m. of CNS- (=lo00 p.6.m. of CN-)-Dissolve about 3.73 g of dried potassium thiocyanate in double-distilled water, dilute the solution to 1 litre and standardise it against standard silver nitrate solution. The concentration of the solution is such that 1 ml contains 1 mg of CN-. Solutions containing the required microgram amounts were prepared by suitable dilution. Iron(1lI) chloride, 10 per cent. solution-Dissolve 10 g of the hydrated salt, FeCl,.GH,O, in 100 ml of nitric acid (1 + 1). Potassium chloride. Potassium carbonate. Flowers of sulphur. PROCEDURE- Mix the sample under test thoroughly in an agate mortar with flowers of sulphur and potassium chloride in the ratio 1 : 2 : 2.The complex cyanides analysed were potassium hexac y ano f errat e (I I), potassium hexac yano f errat e (I I I), sodium t e t rac y anonickelat e (I I) , potassium pentacyanonitrosylchromate( 111) and zinc cyanide. Weigh accurately on a micro- balance a few milligrams (about 12-6 to 34-3 mg) of the sample mixture, i.e., about 2.5 to 7.5 Ing of cyanide complex, and transfer them into a micro-scale test-tube. Heat the tube gradually in a micro-flame until the temperature reaches about 300 "C and continue heating it at this temperature for about 2 minutes. Break the tube in a small beaker containing about @ SAC and the authors.TOBIA, GAWARGIOUS AND EL-SHRHAT 545 10 ml of double-distilled water, bring the solution to the boil, cool and filter it, collect the filtrate in a measuring flask and dilute it to 25 ml.Transfer 5 ml of the filtrate into a 100-ml calibrated flask, dilute it with double-distilled water, add 5 ml of the iron(II1) chloride solution and dilute the mixture to the mark. Mix well and measure the absorbance of the solution against a blank by use of a Hilger Biochemical Colorimeter, a l-cm cell and a greenish blue filter (470 nm). Calculate the cyanide content of the sample with the aid of a c,alibration graph. The same procedure was applied to the determination of the cyanide ion in hexacyano- ferric(I1) acid, hexacyanoferric(II1) acid and potassium hexacyanocobaltate(III), with which complexes potassium carbonate (one sixth of the amount of potassium chloride) should be well admixed with the flowers of sulphur and potassium chloride.RESULTS AND DISCUSSION The cyanide-ion content of solutions of simple cyanides can be determined colorimetrically after their conversion into thiocyanate with sodium tetrathionatell or yellow ammonium sulphide.12 However, simple cyanides are usually determined by a Konig-type reaction.13914 No attempt to determine cyanide ion in complexed cyanides has so far been reported. Deter- mination of these complexes with S,062- or S2- ions was found to be unsatisfactory. The drawbacks of these methods are a low recovery (about 70 per cent.) and also that they cannot be used for insoluble compounds. The low results obtained were attributed to incomplete conversion of cyanide into thiocyanate; it was therefore necessary to modify the method so that almost complete conversion into thiocyanate occurs.When micro-scale amounts (about 5 to 10 mg) of the cyano-complexes were heated in small test-tubes with various amounts of flowers of sulphur, this stage being followed by colorimetric measurement of the thiocyanate produced, consistent, but low, cyanide recoveries of about 66 per cent. were obtained. This result indicates that in all instances the percentage conversion into thiocyanate is only two thirds of that of the original, irrespective of the amount of sulphur added. The loss was found to be caused by an evolution of gas, which was identi- fied as being a mixture of hydrogen cyanide and dicyanogen. These gases were detected, in turn, by applying the copper - benzidine15 and 8-hydroxyquinoline16 tests.The evolution of both gases can be attributed to the high temperature used. In attempting to overcome this difficulty, it was thought that the gas loss would be prevented if the reaction were allowed to take place at a lower temperature. This temperature reduction has been achieved by the addition of a salt to act as a flux. The use of potassium chloride in an amount twice the expected amount of cyanide ion gave rise to satisfactory cyanide recoveries. In the presence of this salt, the melting-point dropped from 242 to 165 "C when potassium hexacyanoferrate(II1) was under test. Under these conditions no hydrogen cyanide or dicyanogen gas could be detected on heating. Quantitative recoveries (Table I) were obtained with a potassium chloride to cyanide ion ratio of 2 : 1 for the following cyano-complexes : potassium hexacyanoferrate(II1) and hexacyano- ferrate(I1) ; potassium pentacyanonitrosylchromate(II1) ; and sodium tetracyanonickelate(I1).In addition, results were obtained for simple zinc cyanide. Amounts of potassium chloride greater than that indicated by the specified ratio also proved efficient. The maximum absolute error is h4.9 per cent. and the over-all average cyanide recovery is ,t98.58 per cent. TABLE I POTASSIUM CHLORIDE (RATIO 1 : 2 : 2) DETERMINATION OF CYANIDE IN CYANO-COMPLEXES BY USING FLOWERS OF SULPHUR AND Amount of cyanidelmg (- p1 Recovery, Complex * Expected Found per cent. 1.378 1.362 98.7 1 1.490 1.467 98.7 1 1.802 1.780 98.58 I< 3[Cr (CX) ,NO] Na JNi (CN) 4] 1.336 1.296 97.14 * The results given are an average of five experiments for each complex.K*[Fe(CN) 61 K,[Fe(CN),I Zn (W?. 1.801 1.799 99.94546 TOBIA, GAWARGIOUS AND EL-SHAHAT However, the addition of potassium chloride did not prove successful with hesacyano- ferric(I1) and hexacyanoferric(II1) acids, nor with potassium hexacyanocobaltate(III), which may still be attributed to the loss of some CN- ion as hydrogen cyanide gas, tlie results obtained being low by about 25 per cent. The addition of a substance that would prevent the loss of hydrogen cyanide, such as the carbonate of an alkali metal, was next tried. For a potassium carbonate to potassium chloride ratio of 1 : 5, satisfactory results (Table 11) were obtained.This procedure was iound to be necessary for complex cyanides that lose hydrogen cyanide on heating, such as the cyano-acids or their ammonium salts, and when dicyanogen is evolved, especially if the central atom of the complex has oxidising properties, e.g., iron(II1) or cobalt(II1). In these instances, very gentle and gradual heating is required until a temperature of about 300 “C is reached; the temperature should then be kept constant so as to prevent the possible formation of dicyanogen gas. This modification afforded a maximum absolute error of h3.2 per cent. and a total average recovery of h98.46 per cent. TABLE I1 DETERMINATION OF CYANIDE I N CYANO-COMPLEXES BY USING FLOWEKS OF SULPHUR, POTASSIUM CHLORIDE -4ND POTASSIUM CARBONATE (RATIO 3 : 6 : 6 : 1) Cyanide content/mg F-----~-, Recovery, Complex’ Expected Found per cent. K,[Co(CN) sj 1.356 1.338 98-95 H,[Fe(CN) a1 1-369 1.350 98.61 H,[Fe(CN) 1.751 1.713 97.82 * The results given are an average of four experiments for each complex. Mixing micro-scale amounts of the cyano-complex, sulphur and potassium chloride (in addition to potassium carbonate in certain instances) in a test-tube, followed by fusion a t 300 “C, gave rise to unreliable results owing to inhomogeneity.In order to obtain a homogeneous mixture it was found that preliminary grinding was necessary. The grinding of such micro-amounts in an agate mortar introduced a serious source of error because of unavoidable sample losses. Therefore, the mixing and grinding of macro-amounts was adopted in order to obtain a representative mixture.A micro-amount of this mixture was then weighed for analysis. Following this grinding technique satisfactory results were obtained in all instances. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. REFERENCES M-illiams, H. E., “Cyanogen Compounds, Their Chemistry, Detection and Estimation,” Second Kruse, J . M., and Mellon, N. G., Sewage l n d . Wclstes Engng, 1951, 23, 1402; Chem. Absly., 1052, 46, Woolmington, K. G., J . Appl. Chem.., Lond., 1961, 11, 114. Schneider, C. R., and Freund, H., Avialyf. Chem., 1962, 34, 69. Laszlo, L., Magy. KLnz. FoZy., 1968, 74, 61; Chem. Abstr., 1968, 68, 84042e. Nomura, T., Takeuchi, K., and Komatsu, S., Nippon Kagaku Zasski, 1968, 89, 291; Cliem. Abstr., Jura, W. H., Analyt. Chem., 1954, 26, 1121. Hetman, J., J . A$#. Chem., Lond., 1960, 10, 16. Johnson, M. 0.. J . Amer. Chem. SOC., 1916, 38, 1230. Guilbault, G. G., and McQueen, R. J., Analytica Chim. Acta, 1968, 40, 251. Kolthoff, I. M., 2. analyt. Chew., 1924, 63, 188. Rozina, A. M., Dankova, N. M., Amitina, N. I., and Rutshtein, E. M., h’ohs Khim., 1957, 5, 45; Chem. Abstr., 1957, 51, 13359e. Konig, W., J . prakt. Chem., 1904, 69, 105. -, 2. angew. Chem., 1905, 115. Moir, J., Chem. News, Lond., 1910, 102, 17. Feigl, F., and Hainberger, L., Analyst, 1955, 80, 807. Edition, Edward Arnold (Publishers) Ltd., London, 1948, p. 168. 36858. 1968, 68, 119227t. Received July 301h, 1973 Accepted Februwy 21st, 1974

ISSN:0003-2654    

DOI:10.1039/AN9749900544

出版商:RSC    

年代:1974

数据来源: RSC

摘要:

AnaLjst, September, 1974, Vol. 99, $9. 547-550 547 The Determination of Small Amounts of Water in Gases Using Karl Fischer Reagent BY E. E. ARCHER (British Petrolt-uni Limited, Group Rcsearch and Developnzent Department, Epsom Division, Epsom, Surrey) AND J. HIL~ON (BP Cheniicabs International Limited, Grangemouth, Stirlingshire, Scotland) Two methods are described for the determination of water in gases. In the first method, the gas being examined is led into a Karl Fischer titration cell, and water is titrated directly. In the second method, water from a gas stream is absorbed on a short column of a gas-chromatographic stationary phase. On heating the column, water is liberated and is carried over to the Karl Fischer cell in a stream of dry nitrogen and then titrated. The validity of the direct titration method has been checked by examining gas streams that had been passed over ice at various temperatures.THE direct determination of water in gases by absorption in a Karl Fischer cell followed by titration has been described in the literature.1-4 This method has been tried at the parts per million range in various laboratories with which we have been acquainted, but the validity of the results obtained was not generally accepted. Although in two of the papers referred to1y2 success at the parts per million level was claimed, we would not accept their validity as they are based on end-point detection techniques in which current differences are observed, and in our opinion such techniques are not sufficiently sensitive to determine water at the microgram level.I t is not generally recognised that in mainly methanolic titration mixtures reaction near the end-point is very slow, and consequently a true end-point cannot be achieved with any degree of certainty. In our work, a more sensitive end-point detection system based on voltage measureme~its~-~ and a titration medium in which reaction is rapid are used. The limit of detection of the direct method is of the order of 2 p.p.m. by mass. With the aim of increasing sensitivity, a methods in which water from a gas was absorbed on a gas- chromatographic column and subsequently eluted and determined with a gas-chromatographic detector was examined. At low levels of water inconsistent results were obtained and the errors appeared to be due to the absorption and desorption of water on the rather complex pipe-work involved.However, when water was absorbed from very large volumes of gas, and on desorption determined by Karl Fischer titration, consistent results were obtained. Sample gas at flow-rates up to 5 1 min -1 was passed through a short column of PEG 200 on Celite, which was cooled in a solid carbon dioxide - acetone bath. Water from the gas was absorbed on the column, which was then heated in boiling water. Water was liberated from the column and carried by a stream of dry nitrogen into the Karl Fischer cell, where it was tit rated. EXPERIMENTAL APPARATUS- Cell and titration assembly-Most of the details of this assembly are as previously de- scribed,' except that the syringe burette driven by an Agla micrometer movement has been replaced by a Metrohm 5-ml piston-type burette and the cell outlet marked D in the previous paper is taken over in the form of an inverted U.The apparatus has now been constructed to form one integral unit and will shortly be produced by Analysis Automation Ltd., Oxford. The stainless-steel column is in the form of a U-tube, Q inch 0.d. x 16 s.w.g. A Rulon-faced three-port valve is used as a two- way tap. The connection from the column to the titration cell is made of &inch stainless steel, terminating in &-inch stainless steel. The actual connection to the cell is made via a R7 polythene stopper, drilled so as to take the &-inch tubing in a tight fit. The column is packed with 30 per cent. PEG 200 on 60 to 80-mesh Celite, the packing extending to within about 4 inch of each end and being held in position with siliconised glass- @ SAC and the authors.Absorptioiz coZumn-This column is shown in Fig. 1.548 ARCHER AND HILTON: THE DETERMINATION OF SMALL AMOUNTS [Analyst, VOl. 99 wool. Before use, “condition” the column in order to remove trace amounts of water from the Celite support by passing dry nitrogen through it at 150 “C for 1 hour at the flow-rate of 60 ml min -l. Fig. 1. Absorption column Dry nitrogen suP$ly-The dry nitrogen supply is obtained by passing tank nitrogen first through a B24 gas scrubber jar containing 5A molecular sieve and then through a second jar containing an approximately 1 + 1 V/V mixture of 4-mm single-turn glass helices and phos- phorus(v) oxide.The outlet of the second jar is terminated by B-inch 0.d. glass tubing so that connection can be made directly via a Drallim connector to the column inlet. Lead-in tube for direct sampling method-This tube is similar to the connection from the column to the cell used in the collection method; an + to &inch Drallim connector is fitted so that connection can be made directly to plant pipe-work. REAGENTS- Cell base liquid-Previous work7 showed that there was a slight end-point drift when a base liquid that contained N-ethylpiperidine was used. A base liquid in which reaction is rapid, but which is free from end-point drift, is prepared as follows. Mix 300 ml of dry methanol and 110 ml of anhydrous pyridine in a 750-ml conical flask and slowly pass sulphur dioxide into this solution, mixing carefully, until the increase in mass is 32 g.Cool the solution in a freezing mixture and, when c,ool, add sufficient AnalaR-grade iodine to give a permanent brown colour. Add 63 g of iodine and swirl the mixture until it has dissolved, then make the volume up to 500 ml with dry methanol (solution A). Mixing carefully, slowly add 20 g of sulphur dioxide to 180 ml of anhydrous pyridine (solution B). To prepare the base liquid, add 55 ml of dry methanol and 75 ml of solution B to 55 ml of solution A in a round-bottomed flask. Boil the mixture under reflux for 10 minutes, then cool it. Just before use, add sufficient water to the base liquid in the titration cell to bring the cell contents to the null-point. Karl Fischer reagent-This reagent is prepared exactly as solution A referred to above.METHODS Add 20 ml of base liquid to the titration cell. DIRECT SAMPLING METHOD- Connect the lead-in tube to the plant stream, and purge with a rapid flow of gas so as to remove water from the connections. Pass gas at the rate of about 500 ml min-l into the titration cell, measuring the flow with a gas meter connected to the cell outlet. Continuously titrate the solution so as to maintain the cell contents at the null-point. After 10 minutes, note the burette and meter readings and, after a further 30 minutes, again note these readings. COLLECTION METHOD- First “condition” the PEG - Celite column in order to remove any traces of water. Immerse the column in a beaker of boiling water and pass dry nitrogen through the column at the rate of 500 ml min-1 for 15 minutes.Move the port over to the vent position and couple it to the stream to be examined by means of Drallim connectors. Vent a suitableSeptember, 19743 OF WATER IN GASES USING KARL FISCHER REAGENT 549 amount of gas so as to sweep the connecting pipes and port assembly; no fixed recommenda- tion can be made for this amount as it will depend on the length of the connecting pipes. Immerse the column in a beaker containing a solid carbon dioxide - acetone mixture and connect a 0 to 5 1 min-l rotameter to the outlet via the B7 polythene stopper. By using a beaker surrounded by cotton-wool as a bath, and adding some large pieces of solid carbon dioxide, the bath can be maintained at -70 "C for over 1 hour without attention.Change the port over so that the gas passes through the column and adjust the flow-rate to about 5 1 min-l. Allow the gas to flow for up to 1 hour, depending on the anticipated water content of the sample, then return the port to the vent position and turn off the sample gas stream. Wipe off any water that has condensed around the top of the polythene stopper (frost condenses for most of the length of the stainless-steel tube connection). Remove the tube leading to the rotameter and close the end with a B7 tube pushed on to the polythene stopper. Disconnect the apparatus from the plant and remove it to the laboratory, leaving the U-tube in the solid carbon dioxide - acetone bath. Connect the apparatus to the dry nitrogen supply and, with the port still in the vent position, pass dry nitrogen through the connections at the flow-rate of 500 ml min-l for 10 minutes.Charge the Karl Fischer cell and titrate its contents to the null-point. Insert the delivery tube from the column into the titration cell via the polythene stopper and move the port so that dry nitrogen is passed through the cell. Water picked up on the connections will be carried into the cell. Titrate back to the null-point, and continue to titrate until a steady state has been reached. When the system is in a steady state, remove the solid carbon dioxide - acetone bath and surround the column with a beaker containing boiling water. Titrate the water evolved, recording the titration at 1-minute intervals. The pattern of titration to be expected is illus- trated in the results given below.From the titration obtained and the amount of gas passed, calculate the water content of the gas. RESULTS CHECK OF EFFICIENCY OF ABSORPTION OF WATER INTO KARL FISCHER REAGENT- Using two sets of apparatus, the outlet of the first cell was connected to the inlet of the second cell. A stream of moist nitrogen was passed at the flow-rate of 500 ml min-1 through the system and both cells were titrated to the null-points. Constant small additions of reagent were necessary in order to maintain the first cell at the null-point, but after the first adjustment no additions to the second cell were necessary. SPECIMEN TITRATION PATTERN- The titration pattern obtained on an actual sample of ethylene is given in Table I. Ethylene was passed at the rate of 5 1 min -l for 30 minutes.The starting point was about 3 minutes after the delivery tube had been inserted in the cell; water picked up from the delivery tube had been titrated out and an almost steady state had been reached. TABLE I TITRATION RESULTS OBTAINED ON A SAMPLE OF ETHYLENE Titre/ml of Karl Fischer Time/minutes reagent Time/minutes 0 0-000 6 1 0.00 1 7 2 0.002 8 3 0.002 9 4 0.002 10 5 0.002* * Boiling water added. Titre/ml of Karl E'ischer reagent 0.026 0.040 0.042 0.042 0.042 The dry nitrogen supply, which was examined in the same way, was found to be com- pletely free from water.550 ARCHER AND HILTON EXAMINATION OF GAS STREAMS IN EQUILIBRIUM WITH ICE- Two copper U-tubes were constructed from Q-inch 0.d. tubing and packed with copper turnings.About 5 ml of water were added to each tube and they were connected in series with each other. A connector from one of the tubes led into a Karl Fischer cell and a stream of dry nitrogen was connected to the other tube. The two tubes were immersed in a beaker containing acetone, which was cooled to various temperatures by the addition of solid carbon dioxide, while a stream of nitrogen was passed through the apparatus at the rate of 500mlmin-1, Water in the gas stream was measured as described under Direct sampling method. The theoretical water content was calculated from the following equation : Calculated water content, p.p.m. by mass = M w - x- fiw x 106 M , p-pw where &Iw is the relative molecular mass of water, M , is the relative molecular m a s of the gas, P is the total pressure of the gas stream and 9, is the saturated vapour pressure at the temperature of the U-tubes.Zimmerman and Lavines stated that the vapour pressure of supercooled water should be taken, but our results, given in Table 11, are more consistent with the vapour pressure of ice. TABLE I1 WATER CONTENT OF NITROGEN TemperaturelOC - 16 - 20 -21 - 28 - 34 - 36 - 37 - 42 - 49 - 50 - 58 Water, p.p.m. by mass Measured Calculated 700 960 490 655 460 690 250 297 150 158 115 127 120 116 70 66 27 28 26 26 8 9 A I 1 DISCUSSION The methods described are applicable to any gas that does not react with Karl Fischer reagent. Although no rigid proof of the validity of the methods has been attempted, it was demon- strated that water is completely removed fIom a gas stream by bubbling the gas through Karl Fischer reagent, which is continuously kept at the null-point.In addition, substantially correct results were obtained when dry gas was passed over ice at low temperatures. To give an indication of the sensitivities of the two methods, if 0.010 ml is the smallest titre that can be regarded as significant, it will correspond to 2 p.p.m. by mass in the direct method and 0.2 p.p.m. by mass in the collection method. It is assumed in obtaining these figures that the direct method is run for 30 minutes with a gas flow-rate of 500 ml min-1 and the collection method is run for 30 minutes with a gas flow-rate of 5 1 min-1. The collection method is particularly useful in plant areas where only apparatus that is “intrinsically safe” is permitted. They are absolute and hence no calibration is necessary. REFERENCES 1. 2. 3. 4. 5. 6. 7 . 8. 9 . Roman, W., and Hirst, A., Analyst, 1951, 76, 10. hluroi, K., Japan AnaZyst, 1961, 10, 847. Griies, H., and Heincke, W., Erdiil Kohle, 1661, 14, 714. Capitani, C., and Milani, E., Chim. I n d . , Milaizo, 1954, 36, 177. Hawkins, A. E., Analyst, 1964, 89, 432. Brown, J . F., and Volume, W. F., Ibid., 1956, 81, 308. Archer, 1;. E., Jeater, H. W., and Martin, J., Ibid., 1967, 92, 524. Carlstrom, A. .\., Spencer, C. F., and Johnson, J. F., Analyt. Chem., 1060, 32, 1056. Zimmerman, 0. T., and L,avine, I., “Psychrometric Tables and Charts,” Industrial Research Service Received November 15th, 1973 Accepted Apvil 8th, 1974 Inc., Dover, New Hampshire, 1964.

ISSN:0003-2654    

DOI:10.1039/AN9749900547

出版商:RSC    

年代:1974

数据来源: RSC

摘要:

Afialysf, September, 1974, Vol. 99, $9. 551-554 55 1 The Use of Tiron in the Microchemical Analysis of iMimerals BY W. J. FRENCH AND S. J. ADAMS (Geology Deparfnient, Queen Mary College, University of London, Mile End Road, London, E . l ) The complexes formed by tiron with aluminium, iron and titanium can be used to determine these elements colorirnetrically on a single aliquot of the solution of a mineral. The tiron also renders these solutions very suitable for analysis in a flame, the sodium from the tiron acting as a flame buffer and the complexing properties inhibiting chemical interferences. A single aliquot of solution can therefore be used to determine several elements and the procedure can form the basis of a scheme €or the microchemical analysis of minerals. Little is known of the use of tiron for the deter- mination of aluminium and this paper describes tests made on the usefulness of this method.HEY has pointed out that it should be possible to carry out chemical analyses of minerals by using about 1 mg of materia1.l Recently, we have attempted to analyse grains cut from thin sections of rocks to determine a range of elements, the total amount of material available being rather less than 1 mg. In setting up the required methods it was desirable to work on a single solution if possible and two such solution techniques were considered: decomposi- tion with hydrofluoric acid in sealed plastic vessels2 and fusion with lithium metaborate.3 Use of the former technique gives solutions that are suitable for flame-photometric analysis, silicon and iron being determined colorirnetrically.However, the flame routines consume solution and have low sensitivity for aluminium and titanium, while the fluoride limits the application of colorimetric procedures. The fusion technique has fewer limitations but con- siderable errors are introduced because of the large ratio of fusion compound to mineral necessary and the impurities in the borate. A compromise was found by using two solutions, one prepared by a conventional digestion with hydrofluoric acid - perchloric acid and the other by dissolution with hydrofluoric acid in a sealed vessel. This approach was made possible by the use of tiron (1,2-dihydroxybenzene- 3,5-&sulphonic acid, disodium salt) for the determination of iron, titanium and aluminium on a single aliquot of the solution of a mineral.This tiron - mineral solution was also found to make an ideal medium for the atomic-absorption spectrophotometric determination of mag- nesium and calcium, therefore all five elements could be determined on a single aliquot of the solution of the mineral. Silicon, sodium and potassium were determined on the second solution. The least well known aspect of this scheme of analysis was the use of tiron in the deter- mination of aluminium. It involves working in the ultraviolet region of the spectrum and close to an organic absorption band. These conditions are not ideal but as Hey1 and Mercy and Saunders4 have pointed out, there are numerous deficiencies in most colorimetric methods for determining aluminium in silicates, those methods requiring considerable concentrations of the element being the most reliable.The possibility of using tiron for this determination was therefore investigated in detail. DEVELOPMENT OF THE METHOD Tiron has been widely used for the determination of iron and titanium in a variety of materials. Many of the advantages and drawbacks of the method have been described.”g One source of error is that the reagent is consumed by elements with which it forms complexes that do not absorb in the visible region. Aluminium is one such element, the absorbance of the aluminium - tiron complex being greatest at 315 nm and linear with concentration for concentrations up to at least 3 p g ml-l. Iron(II1) and titanium - tiron complexes also absorb at 315nm but aluminium absorbs more strongly than the other two complexes.The ab- sorptivities are approximately: aluminium, 440; iron(III), 245; and titanium, 192. The @ SAC and the authors.552 absorbance of the iron(II1) - tiron complex is usually measured at 560 nm because at this wavelength absorption by the aluminium and titanium complexes is very low (generally regarded as being negligible). The absorbance of the titanium - tiron complex is usually measured at about 410 nm, where the absorbance due to the iron complex is at a minimum and that due to aluminium is negligible. This wavelength is also preferred when the iron is reduced, as then the absorbance due to titanium is very large compared with that of other compounds. However, there is always a small contribution from all three element - tiron complexes at each wavelength, and for high titanium to iron ratios, even the determination of iron is impaired.I t is therefore preferable to measure standards of all three elements at the three wavelengths. Different buffer mixtures have different absorptivities. At 315 nm the reagent blank shows an increase in absorbance as the acetate molarity is increased and the effect is greater if ammonium acetate is used in place of sodium acetate. When the total acetate molarity is about 0-6, however, the absorbance is insensitive to acetate concentration so that satisfactory results can be obtained if the acetate molarity is fixed at about this level and a pH of 5.65 is maintained. The metal - tiron complex absorbance increases with the concentration of tiron but the absorbance increases only very slowly with excess of reagent.The concentration of tiron is therefore selected to give a slight excess over metal ions so that blank readings are kept to a minimum. Full colour development for all three complexes occurs within a few minutes and the absorbances have been found to be unchanged after several hours. These conditions were applied to solutions containing aluminium equivalent to 200 pg of aluminium oxide and a range of elements that could possibly interfere in the determination (Table I). Measurements were made on a Pye Unicam SP500 spectrophotometer. Chromium, tungsten, vanadium, molybdenum and boron all showed an increase in absorbance over that due to the aluminium while the presence of fluorine reduced the absorbance. Only fluorine and chromium showed differences that were likely to be significant in rock analysis.Chrom- ium will increase the apparent amount of aluminium found and a correction would be required if samples containing substantial amounts of this element were to be determined. FRENCH AND ADAMS: THE USE OF TIRON [Andyst, VOl. 99 TABLE I INFLUENCE OF VARIOUS ELEMENTS ON THE ABSORBANCE GIVEN BY 200 pg OF ALUMINIUM OXIDE COMPLEXED WITH TIRON AND DILUTED TO loom1 Absorbance of 200pg of aluminium oxide complexed with tiron = 0.467 Element added as MgO CaO K,O p,o, MnO Li Ba Rb Amount added1p.g 200 200 200 100 50 200 100 200 Absorbance 0.464 0.466 0.466 0.460 0.470 0.465 0.466 0.467 Element added as Zr co Sr B Cr w v Amount added1p.g 100 100 100 100 100 100 100 Absorbance 0.467 0.467 0.466 0.472 0.701 0.515 0.606 Fluorine should, of course, be removed during dissolution of the sample.Large amounts of beryllium (e.g., 1Og1-1) slightly inflate the absorbance of the blank, but not sufficiently to invalidate the method if the element is used in measured amounts to suppress interference from small amounts of fluoride. Interference has not been detected from the usual minor elements in minerals, but it might occur if the substance was unusually rich in, for example, rare earths. REAGENTS- Standard aluminium solution-Dissolve 0.8894 g of aluminium ammonium sulphate in water that has been acidified with a few drops of sulphuric acid and dilute the solution to 1000 ml. This dilution gives a concentration equivalent to 100 pg ml-l of aluminium oxide. Standard titanium solution-Fuse 0.20 g of Specpure titanium(1V) oxide with 1.5 g of potassium pyrosulphate in a platinum crucible.Heat the crucible gently (not above dull red heat) and when dissolution is complete, cool it and dissolve the cake in sulphuric acid The conditions outlined above were tested on a series of rocks.September, 19741 I N THE MICROCHEMICAL ANALYSIS OF MINERALS 553 (1 + 1). Dilute the solution to 2000 ml to give a concentration equivalent to 100 pg ml-1 of titanium (IV) oxide. Standard iron solzition-Dissolve 0.4911 g of ammonium iron(I1) sulphate in 100 ml of water, and to this solution add 6 ml of sulphuric acid (1 + 1) and 0.5 ml of 100-volume hydro- gen peroxide solution.Boil the solution for a few minutes in order to expel the excess of hydrogen peroxide, then cool and dilute it to 1000 ml. This procedure gives a concentration equivalent to 100 pg ml-l of iron(II1) oxide. Bufer solution-Dissolve 250 g of sodium acetate hydrate in water, add 11 ml of glacial acetic acid and dilute the mixture to 1000 ml. Tiron solution-Dissolve 1-5 g of tiron (1,2-dihydroxybenzene-3,S-disulphonic acid, disodium salt) in water and dilute to 100 ml. PROCEDURE- Rock solutions v;ith a concentration of 1 g 1-1 of rock were prepared by the method of Riley.1° Volumes (2 ml) of each rock solution, the blank and the standard were transferred by use of a pipette into 100-ml calibrated flasks. Next, 5 ml of tiron solution were added accurately, followed, after mixing, by 30 ml of buffer solution; each mixture was then diluted to 100 ml.The absorbance of each solution was measured four times at 315 nm (in 5-mm cells), at 560 nm and 410 nm (in 20 or 40-mm cells) and the concentrations of aluminium, iron and titanium were calculated by the method of simultaneous equations.11 The procedure was applied to four standard rocks and the results given in Table I1 were obtained. Each result is the average of fourteen separate determinations, each of which represents four measurements of absorbance at each wavelength. The precisions of the iron and titanium determinations are satisfactory because of the small contributions to the total absorbance made by each at the wavelength of determination of the other. The lower pre- cision of the aluminium determination can be mitigated by increasing the number of measure- ments at 315 nm.However, in view of the difficulty normally encountered in determining aluminium in rocks (Mercy and Saunders4) the present method was regarded as being satis- factory and applicable to a wide range of materials. TABLE I1 COMPARISON OF RESULTS (PER CENT. m/m) OBTAINED BY USING THE PROPOSED METHOD WITH PREVIOUS RESULTS *41,O, Fe,O, Ti0 - -7 a b C a b C a b C Q.M.C.11 13.66 0.10 13.89 0.50 0.02 0.59 0.04 0.01 0.06 Q. 31. C. I3 13.18 0.09 13-14 16.28 0.04 16.23 2.55 0.02 2-59 Q. 31. C.M2 23.65 0.12 24-00 9-23 0.03 9.13 0.80 0.01 0.72 The standard rocks are obtainable from Dr. A. B. Poole, Geology Department, Queen Mary College, Mile End Road, London, E.l. The rock types are as follows: Q.M.C.11, granite; Q.M.C.13, doleritc; Q.M.C.MZ, pelitic schist; and (?.M.C.MS, calc-silicate rock.Q.M.C.M3 17.54 0.08 17.65 4.58 0.03 4-54 1.00 0.01 0.91 a, This method; b, standard deviation (14 determinations) ; c, mean o f all previous results. MICRO-ANALYTICAL PROCEDURE- Weigh out between 250 and 500pg of each mineral as accurately as possible and digest them in 10-ml crucibles (platinum or PTFE) with ten drops of hydrofluoric acid (40 per cent. m/V) and two drops of concentrated perchloric acid. Heat each crucible with an overhead infrared heater until the fluoride has been removed and the crucible is almost dry. Cool, add about 3 ml of water and warm the crucible gently for a few minutes to complete dissolution, then transfer the solution into a 25-ml calibrated flask, keeping the volume of wash water to below 10 ml.Add accurately 1 ml of 2 per cent. m/V tiron solution and mix well. Finally, add 7.5 ml of buffer solution and dilute the mixture to 25 mi. Measure the absorbance of each solution at 315, 410, and 560 nm and calculate the percentages of aluminium oxide, titanium- (IV) oxide and iron(II1) oxide. Aspirate the residual solution into an air - acetylene flame to determine magnesium oxide and a nitrous oxide - acetylene flame for calcium oxide. Standardise the colorimetric analysis with laboratory reagents or standard rock solutions prepared in an equivalent manner; use Conserve as much of the solution as possible.554 FRENCH AND ADAMS rock solutions to standardise thc atomic-absorption analysis. Place about 500 mg of each mineral into a weighed polycarbonate autoclave tube, then add five drops of hydrofluoric acid (40 per cent.m/V) and one drop of aqua regia. Digest the mixture in a pressure cooker for about 15 minutes, cool it, and add 3 per cent. m/V boric acid solution to bring the total mass of solution to 20 g. Determine the silica content by the method described by RileylO and sodium and potassium by use of flame photometry. Standardise the procedure with standard rock or mineral solutions. RESULTS The proposed scheme of analysis was applied to ten portions of an amphibole previously analysed by use of conventional techniques. In general, blanks were found t o be high but the results indicate that, with care, elements can be deter- mined with a relative standard deviation of about 2 per cent.or better. As expected, alu- minium gave the greatest spread of results, but even here the results are adequate for many purposes. The processes of weighing and sampling probably contribute considerably to the errors. The results are given in Table 111. TABLE I11 ANALYSES (PER CENT. m/m) OF A HORNBLENDE FROM COUNTY DONEGAL SIC), TiO, X1,0, Fe,O, MgO CaO Na,O K,O (average of two determinations) . . . . 43.40 2.05 12-35 15.88 12.62 9-52 1.87 1-09 (average of ten determinations) . . . . 43-10 2.09 12-51 16.00 12.50 9.68 1.90 1-06 present method.. . . . . . . . . . . 0.62 0.03 0.20 0.06 0.08 0.06 0-03 0.02 Normal macrochemical technique Present method Standard deviation of results by CONCLUSION Tiron - metal complexes, because of their sensitivity, can iorm the basis of a system of partial microchemical analysis applicable to minerals in amounts of about 1 mg.The method may be applicable to a wider range of materials but the relative errors are such that further reduction in the scale of analysis is not likely to be successful. It has not been found possible to determine manganese, phosphorus or water, but iron(1I) could be determined on a further small portion of the mineral.12 The method can be considered rapid in that between six and ten samples can be analysed in two working days. 1 . 2. 3. 4. 6 . 6. 7. 8. 9. 10. 1 1 . 12. REFERENCES Hey, 31. H., Min. Mug., 1973, No. 301, 4. French, W. J., and Adarns, S. J., Analytica Chinz. Acta, 1973, 62, 324. Medlin, J. H., Suhr, N. €I., and Bodkin, J . B., Atom. ,4bsorption Newsl., 1962, 8, 26. Mercy, E. P., and Saunders, M. J., Earth Planet. Sci. Lett., 1966, 1, 169. Yoe, J. H., and Jones, .%. L., Ind. Engng Chem., Analyt. Edn, 1944, 16, 111. Yoe, J . H., and Armstrong, A. R., Science, N.Y., 1945, 102, 207. Corey, R., and Jackson, M., Analyt. Chem., 1953, 25, 264. Nichols, P. N. R., Analyst, 1960, 85, 452. Lacourt, A., Sommereyns, G., Degeyndt, E., Ihruh, J., and Gillard, J . , Nature, Lond., 1949, 163, Riley, J. P., Annlytica Chim. Acta., 1958, 19, 413. Willard, H. H., Merritt, L. L., and Dean, J. A., “Instrumental Methods of Analysis,” Fourth French, W.J., and Adams, S. J., Analyst, 1972, 97, 828. 999. Edition, D. van Nostrand Co. Ltd., London, 1965. Received January 17th, 1974 Accepted March 25th, 1974

ISSN:0003-2654    

DOI:10.1039/AN9749900551

出版商:RSC    

年代:1974

数据来源: RSC

摘要:

Analyst, September, 1974, Vol. 99, $9. 555-564 555 Oxidation Procedures in the Assay of Some Drugs Containing a Diphenylmethylene Ether or Diphenylmethyleneamino Group BY B. CADDY, F. FISH AND J. TRANTER" (Division of Pharntacognosy and Forensic Science, School of Pharmaceutical Sciences, University of Strathclyde, Glasgow, G1 1XW) Methods €or the oxidation of diphenylmethylene ethers and diphenyl- methylenearnines have been compared ; oxidation with aqueous acidic di- chromate is advocated for the former and with alkaline permanganate for the latter in the assay of drugs containing these groups. The possible mech- anisms involved are proposed. THE use of oxidation procedures for enhancing the ultraviolet absorbance of compounds, thereby lowering their limits of detection, has been described by several authors.1-3 In order to obtain a rational approach to this method of analysis, we have studied several oxidation procedures applied to various groups of compounds. In addition to using oxidation methods in quantitative analysis we were also interested in assessing their routine use in toxicological screening for drugs (mainly basic drugs). This report concerns the oxidation of drugs con- taining the diphenylmethylene ether (Table I) or diphenylmethyleneamino group (Table 11) with aqueous acidic dichroinate and alkaline permanganate. EXPERIMENTAL REAGENTS- Hexane. Potassitdm dichtromate. Potassium permanganate. Sodium hydroxide, pellets. Sul9huric acid, concentrated. Diethyl ether. All of the above materials were of analytical-reagent grade.APPARATUS- A Unicam SP800A, ultraviolet - visible spectrophotometer and a Varian Aerograph 1400 gas chromatograph with a flame-ionisation detector were used. The conditions used were as follows: 1, a 6 foot x g inch i.d. glass column packed with 10 per cent. Apiezon L on Chromo- sorb G (60 to 80 mesh), operated at 250 "C with a nitrogen flow-rate of 50 ml min-1, injection block and detector block being maintained at 270 "C; 2, a G foot x Q inch i.d. glass column packed with 1 per cent. OV-25 on Chromosorb G (60 to 80 mesh), operated at 160 "C with a nitrogen flow-rate of 50 ml min-l, injection block and detector block being maintained at 200 "C. OXIDATION PROCEDURES- glass-coated magnetic follower (Note 2). Place a suitable amount of the drug (Note 1) in a 250-ml conical flask containing a 1-inch Add 20 ml of oxidant (Note 3) and 5 ml of hexane NOTES- The drug was usually introduced as an aqueous solution of one of its salts (e.g., 1 ml of a 0-01 per cent, In/ V solution prepared by diluting a 0.05 per cent.m/ V stock solution). When the solubility was insufficient, a 0.01 per cent. vn/V solution of the base in a suitable organic solvent (usually chloro- form or ethanol) was prepared. In such instances 1 ml of the solution was introduced into a 250-ml conical flask and evaporated to dryness at 50 to 60 "C under reduced pressure. It is imperative that all the organic solvent is removed because even a trace amount can drastically reduce the effective- ness of the oxidant, particularly with the permanganate reagent.* Present address : Government Laboratory, Oil Street, North Point, Hong Kong. Q SAC and the anthors. 1.556 CADDY, FISH AND TRANTER: OXIDATION PROCEDURES [AYZalyd, VOl. 99 Tt was neceiwry to use glass-coxtetl magnetic followers as both P T F F and other plastic- coated followers appeared to adsorb some of the oxidation product. The alkaline permanganate reagent should be prepared immediately before use by mixing 5 nil of 4 per cent. aqueous potassium permanganatc solution with 5 ml of 8 N aqueous sodium hydroxide 3olution. The acidic dichrornate reagent was prepared by mixing 5 ml of 4 per cent. potassium dichrornate solution with 15 ml of 12 II' sulphuric acid. 2 . 3. to the flask and heat the mixture at 60 to 70 "C under reflux, with constant stirring, for approxi- mately 40 minutes.Cool the flask and, with the condenser still in position, rinse them with approximately 5 ml of water. Transfer the contents of the conical flask into a 40-ml glass- stoppered test-tube. Place an aliquot of the hexane layer in a cell of l-cm path length and determine the ultraviolet spectrum between 225 and 400 nm, using hexane in the reference cell. Measure the absorption maxima at the appropriate wavelengths (Tables I and 11) and calculate concentrations by reference to a standard graph. TABLE I OXIDATION PRODUCTS, THEIR ABSORPTION MAXIMA AND YIELDS FROM CONTAINING A DIPHENYLMETHYLENE ETHER GROUP Compound Benztropine Bromodiphenh ydramine ChIorphenoxaminc Di phen ylpyral ine Diphenh ydramine Embramine Orphenadrine Benzh ydrol Deptropine Q R' R" H ANCH3 H CH,CH,N(CH,), CH, CK,CH,N(CH,) , H O C H .H CH,CH,N(CH,) CH, CH,CH,N(CHJ H CH,CH,N(CH,), H H ACH3 go R"' H 4-Br 4-C1 H I< 4-Br 2-C€I, H COMPOUNDS Oxidation yield, per cent. * - Oxidation product A,,./nm A Benzophenone 247 90 4-Eromobenzophenone 257 96 4-C.hlorobenzophenone 254 89 Benzophenone 247 96 13enzophenone 247 9Q 4Bromobenzophenone 257 71 2-Methylbenzophenone 247 90 Benzophenone 247 97 .4 :I)iHDBCHS B :Anthraquinone I3 73 66 + 64 70 .I. 63 100 _ _ * Alean values from at least two determinatiom. A: Potassium dichromate, 1 per cent. m/V in 9 N sulphuric acid a t about 60 "C. 13 : Potassium permanganate, 1 per cent. m/ I' in 6 N sodium hydroxide solution a t about 60 "C. t Insignificant. 2 DiHDBCH : 10,l l-Dihydro-5H-dibenzo[a,d]cyclohepten-5-one.Preparation of standard calibration graphs-Calibration graphs were prepared from the results of triplicate determinations by each of the oxidation procedures described above. The drug concentrations were varied so as to give between 2.0 and 20.0 pg ml-l of the benzo- phenone in the final hexane solution (0.1 to 1.0 ml of 0.01 per cent. m/V aqueous solutions of drug salts were used). HYDROLYSIS OF DIPHENHYDRAMINE- hydramine was hydrolysed under both acidic and alkaline conditions. In order to determine the possible reaction route with ethers, the compound diphen-September, 19741 IN THE ASSAY OF SOME DRUGS TABLE I1 OXIDATION PRODUCTS, THEIR ABSORPTION MAXIMA AND YIELDS FROM COMPOUNDS CONTAINING A DIPHENYLMETHYLENEAMINO GROUP 557 Compound R' Oxidation yield, per cent.* - R" Oxidation product Amax./nm A B A ~ C ( C " 3 ) ~ 4-Chlorobenzophenotie 254 32 '32 -NwN-c"2 Buclizine n I \ Chlorc Cyclizine yclizi tie E} -N\_/NCHs 4-Chlorobenzophenone 254 4 89 Benzophenone 247 4 04 4-Chlorobenzophenone 264 9 88 n Meclozine -NwN-cH2Q --.I CH3 * Mean values from at least two determinations. A: Potassium dichromate, 1 per cent. m/V in 9 h' sulphuric acid at about 60 "C. B: Potassium permanganate, 1 per cent. m/V in 6 N sodium hydroxide solution at about 60 "C. Acid hyd.p.oZysis-A solution of about 100 mg of diphenhydramine hydrochloride in 50 ml of 9 N sulphuric acid was heated at 60 "C under reflux for about 2 hours. After cooling, the solution was extracted twice with equal volumes of hexane. The ultraviolet spectrum of the hexane phase was recorded and compared with that obtained with authentic benzhydrol and diphenhydramine (Table 111). About 10 ml of the hexane solution were evaporated to small volume (about 0.2 ml) on a water-bath and a sample was submitted to gas-chromatographic analysis (condition 1).AZkaZine hyllrolysis-A solution of about 100 mg of diphenhydramine hydrochloride in 50 ml of 6 N sodium hydroxide solution was heated at 60 "C under reflux. After cooling, the solution was adjusted to pH 4 with sulphuric acid and quickly extracted (shaking vigorously by hand for 3 minutes) with two 50-ml volumes of hexane. The organic phase was then subjected to ultraviolet spectrophotometric and gas-chromatographic examination as described above. TABLE I11 ULTRAVIOLET SPECTROPHOTOMETRIC AND GAS - LIQUID CHROMATOGRAPHIC RESULTS FOB BENZHYDROL, DIPHENHYDRAMINE AND THE HYDROLYSIS PRODUCTS OF DIPHENHYDRAMINE Gas - liquid chromatographic retention value Amax.in hexanelnm relative to Material \ benzhydrol* f A Benzh ydrol 252-5 258 265 268(S) 1.oot Diphenhydraniine 252 257.5 264(S) 268(S) 1.77 Diphenhydramine hydrolysis pyoducts- Acid hydrolysis, acidic fraction 252-5 258 265 268(S) 1.00 Alkaline hydrolysis, acidic fraction No spectrum obtained I Alkaline hydrolysis, basic fraction 252 257.5 264(S) 268(S) 1.77 S = Shoulder. * Benzhydrol had a retention time of 2.6 minutes under the conditions used. t Condition 1 (see under Experimental).568 CADDY, FISH AIiD TRANTER: OXIDATION PROCEDURES [A%a&St, VOl. 99 The aqueous phase was made alkaline with 6 N sodium hydroxide solution and re- extracted with 50 ml of hexane, the final hexane layer being examined as before. The retention data for the products of hydrolysis are given in Table 111. EFFECT OF ACID CONCENTRATION ON THE RATE OF HYDROLYSIS OF DIPHENHYDRAMINE- About 100 mg of diphenhydramine hydrochloride were dissolved in sulphuric acid of various concentrations and the solutions were maintained at 40 "C for 45 minutes. After 25 and 45 minutes, aliquots of the solutions were removed, cooled, extracted quickly with an equal volume of hexane in order to remove liberated benzhydrol and the ultraviolet spectrum o f the aqueous phase was recorded in each instance (Table IV).TABLE IV ACID CONCENTRATIONS USED FOR THE HYDROLYSIS OF DIPHENHYDRAMINE AND THE ABSORBANCE OF EACH AQUEOUS PHASE AFTER 25 AND 45 MINUTES Absorbance at 257.5 nm after Concentration I A 'L of acid/N 25 minutes 45 minutes 6.0 0.06 * 0.01 * 4.8 0.12 0.06" 3-6 0.83 0.2 1 2.4 0.95 0.56 1.2 1.22 1.06 0.3 1.34 1-31 0-ot 1.40 1 *40 * No distinct maxima.t Aqueous drug solution. <;AS CHROMATOGRAPHY OF OXIDATION PRODVCTS- In order to confirm the identity of the various oxidation products listed in Tables I and I1 gas - liquid chromatography was employed. Hexane solutions from the oxidation of each particular drug were bulked and reduced to small volume (about 0.2 ml) at GO "C under reduced pressure. Samples of these solutions (2 to 3 pl) were injected on to the chromatographic column (condition 2) and retention values recorded relative to a suitable standard.Examination was also made of solutions of authentic benzophenones prepared at a concentration of approximately 0.05 per cent. m/V in hexane, which were diluted sufficiently to give detector responses similar to those obtained with the oxidation products. RESULTS AND DISCUSSION PRECISION OF THE OXIDATION PROCEDURES- For the study of precision of the methods used, diphenhydramine and cyclizirie were selected as, apart from being important in the context of toxicology, they represented the different chemical groups being examined. These drugs were subjected to fifteen replicate determinations by the procedure that gave the highest oxidation yield in each instance, and for diphenhydramine the alternative potassium permanganate procedure was also examined.The results (Table V) indicated that the selected oxidation procedures were acceptable for the assay of dipheihydramine and cyclizine and there is no reason to believe that the other drugs which gave a high oxidation yield could not be assayed with the same levels of precision. The increase in coefficient of variation that accompanies a decrease in oxidation yield is a trend exhibited in the oxidation of other compounds, which will be the subject of a further paper. TABLE V REPRODIJCIBILITY OF YIELDS ON OXIDATION FOR REPRESENTATIVE COMPOUNDS Mean absorbance Coefficient Oxidation Drug procedure* (247 nm) deviation variation per cent. Oxidation at Anl$*. Standard of yield, Diphenhydramine A 1-30 0.034 2.6 97 Cyclizine B 1-13 0.034 3.0 84 (20 pg ml-l) B 0.97 0.033 3.4 70 (20 p g ml-1) *A: Potassium dichromate, 1 per cent.m/V solution in 9 N sulphuric acid a t about 60 "C. B: Potassium permanganate, 1 per cent. m/V solution in 6 N sodium hydroxide solution a t about 60 "C.September, 19741 I N THE ASSAY OF SOME DRUGS 559 YIELDS OETAINED ox OXIDATION OF DIPHENYLMETHYLENE ETHERS- Table I. The drugs studied, their oxidation products and their oxidation yields are given in Yields were calculated from the equation 60 x x A!!d A b x Mb Percentage oxidation = where Z is the experinlentally observed absorbance following an oxidation equivalent to 20 pg nil-l of drug (or drug salt) in the final hexane solution; f i f d is the relative molecular mass of the drug (cr drug salt); .4b is the enhanced absorbance value of 10 pg ml-l of the authentic benzophenone in hexane (Note 4); and M b is the relative molecular mass of the benzophenone.Note 4. In calculating the yields on oxidation it was necessary to take into account the enhance- ment of the ultraviolet absorption of the benzophenones themselves brought about by the oxidation procedure and considered t o be attributable t o evaporation of the hexane.4 The enhancement for ben- zophenone was 7.7 per cent. and the assumption was made that all benzophenones showed a similar enhancement. Oxidation with acidic dichromate-It is difficult to comment on variations in yield of 90 to 98 per cent. for those compounds which possess two aliphatic hydrogen atoms but this effect must be due, at least partly, to the variation in purity of the commercial samples tested.No attempt was made to assay their purity but some of them were known to be less than 100 per cent. pure (e.g., benztropine mesylate, 95.7 per cent.), whereas the yields on oxidation were calculated on the basis of 100 per cent. purity for each drug. With the exception of chlorphenoxamine (89 per cent.) and embramine (71 per cent.), oxidation of the studied compounds with hot acidic dichromate solution gave yields of 90 per cent. or more of the expected benzophenone (Table I). The lower yields from the former must arise from the presence of a methyl substituent instead of hydrogen on the a-carbon atom, as this is a feature present in the two drugs but absent from the remainder. Vessman, Hartvig and Stromberg2 found, by using a non-aqueous solution of chromic acid as oxidant, that yields in excess of 90 per cent.were obtained from ethers that possess a hydrogen atom on the a-carbon atom. Replacement of this a-hydrogen atom by a methyl group resulted in a lower yield. These authors pointed out that the yields parallel those obtained from the oxidation of benzhydrol and its a-methyl analogue. The same authors further agreed with the view of Sasakis and of Wallace, Biggs and Dahll that the oxidation of diphenhydramine proceeds via hydrolysis to benzhydrol. In the present work, hydrolysis with sulphuric acid was found to yield benzhydrol (con- firmed by gas - liquid chromatography and ultraviolet spectrophotometry, Table 111) in agreement with the report of Kikkawa, Sasaki, Iwasaki and Ueda.6 The rate of hydrolysis was acid dependent (Table IV), which is consistent with the report of Staude and Patat.' These authors, while pointing out that no valid information on the kinetics of hydrolysis of aliphatic ethers is available, suggested two possible reaction routes following protonation of the ether (Scheme 1).The second reaction route would appear to be particularly acceptable in the present instance as the carbonium ion W O U J ~ be stabilised by resonance. Scheme 1 1 2 slow fast R '6" ROH C R6Hz - 2ROH + H30' R' H20 R .- fast R --+I- slow ROH + R' 's 2ROH i- "3"560 CADDY, FISH AND TRANTER: OXIDATION PROCEDURES [Analyst, \'Ol. 99 The intermediates with chlorphenoxamine and embramine would possess the extra stability of a tertiary cx-carbon atom and a halogen atom, which coulcl enter into resonance, consequently resulting in their lower yields on oxidation.The oxidation of a secondary alcohol with aqueous dichromate is usually quantitativc8 Vessman et aZ.2 reported the quantitative oxidation of heiizhydrol using non-aqueous condi- tions and this finding has been confirmed in the present work with aqueoxs acidic dichromate. The oxidation rate law,9 which applies to all secondary alcohols, is complex but readily indicates that the rate is dependent on both acid and oxidant concentration. The reaction scheme proposed9 to fit the kinetic data is shown in Scheme 2. Scheme 2 R2CHOH + H C r q i- H' - R2CHOCr03H + H20 Wibergs suggested three possible mechanisms for the decomposition of the chromate ester (Scheme 3).Whichever mechanism is in operation, it immediately becomes apparent that none is suitable for chlorphenoxamine and embramine because the alcohols arising from their hydrolysis will not possess cc-hydrogen atoms. The oxidation rate for tertiary alcohols has been found to be independent of the oxidant concentration and to correspond to the rate of acid dehydration of alcohols.lOrll On this basis, the oxidation of embramine and chlorphenoxamine can be rationalised by the scheme illustrated in Fig. 1. Oxidation with alkaliite permaizganate-Oxidation with alkaline permanganate of ethers of the type under discussion led to lower yields of benzophenones than oxidation with acidic dichromate, with chlorphenoxamine and embramine giving no detectable yields.Scheme 3 1 2 3September, 19741 IN THE ASSAY OF SOME DRUGS 561 X Q That diphenhydramine was inert to alkaline hydrolysis became evident from both ultra- violet spectrophotometric and gas-chromatographic examination of the hydrolysis mixture (Table 111), which is not surprising as alkyl ethers are reported to be stable to alkaline oxida- tion.' Obviously, the oxidation proceeds via a totally different route from that of oxidation with dichromate and this conclusion is further supported by the fact that benzhydrol gives a quantitative yield of benzophenone following oxidation with permanganate, whereas the best yield from the ether is only 73 per cent. 8 I H+ Q Q CH~-C-OCH~CH~N(CH~)Z - CH,-C-OH 0 0 X Q X X 1- H20 CxCH2 [Ol 4--- Embramine X 5 H Chlorphenoxamine X = CI Fig.1. Proposed oxidation route of embramine and chlorphenoxamine While no report on the mechanism of the oxidation of alkyl ethers under alkaline condi- tions could be found, the reaction probably proceeds via hydrate abstraction from the a- carbon atom. This view is supported by the fact that the two compounds chlorphenoxamine and embramine, which do not possess an a-hydrogen atom, appear to be inert to oxidation with permanganate. In addition, the carbonium ion produced by hydride abstraction would be stabilised by resonance. Wallace et aZ.l and Caddy, Fish, Mullen and Tranter3 found that the oxidation of diphenhydramine with alkaline permanganate gave a good yield of benzophenone and the latter group of workers also reported that the oxidation of orphenadrine gave a good yield.Deptropine gives a 55 per cent. yield of anthraquinone, which is typical of l0,ll-dihydro- 5N-dibenzo[a,d]cyclohepten-5-yl compounds. Oxidation of these and related compounds will be discussed in a separate paper. YIELDS OBTAINED ON OXIDATION OF DIPHENYLMETHYLENEAMINES- Compounds of this type were found to be readily oxidised with hot alkaline permanganate to the expected benzo- phenone in good yield. The amines examined in the present work are listed in Table 11. Conversely, hot acidic dichromate gave poor yields.562 CADDY, FISH AND TRANTER: OXIDATION PROCEDURES [Analyst, Vol. 99 Oxidation with alkaline permanganate-Under the basic conditions employed, solutions of permanganate might be expected to abstract a-hydrogen atoms12 rather than substitute on the nitrogen atom.A pertinent example of tertiary amine oxidation with permanganate is that of NN-dimethylbenzylamine to benzaldehyde.8 If one of the a-hydrogen atoms is replaced by a phenyl group the resulting amine will be similar to those under discussion, the corresponding oxidation product being benzophenone. The permanganate oxidation of the present drugs would be more facile than that of NN-dimethylbenzylamine as hydrogen atoms on tertiary carbon atoms are well known for their lability. The probable reaction route, which bears a superficial resemblance to that proposed for permanganate oxidation of ethers (as indicated above), is illustrated in Scheme 4. Scheme 4 I CH-NR2 Q x -H’ d Q +C--/\NR2 0 X + C=NR2 0 X 8 6 x X =p CI or H The slightly lower relative yield of the oxidation product from cyclizine may possibly be attributed to lack of purity in the commercial product examined, whereas the still lower yield from hydroxyzine may reflect the presence of an additional centre for oxidation, namely the primary alcohol group.Oxidation of this group to a carboxylate ion might either inhibit the abstraction of a hydride ion or result in stabilisation of the initially formed carbonium ion. Oxidation with acidic &chromate-Neumann and Gould, l3 in their studies on the oxidation of arylalkylamines, favoured the first of their proposed routes (Scheme 5) involving a free- Scheme 6 1 Ar R~CH-N’ a ‘R Ar H+ 2 R2CH-N’ - ‘R Ar Ar +/ - R2C-N-R - H+ -q + / H radical mechanism. However, in view of the fact that some yields were obtained (Table VI), and because of possible delocalisation of the negative charge resulting from the removal of a proton (Fig.2), the second route seems more likely.September, 19741 I N THE ASSAY OF SOME DRUGS 563 rl o C-N+ H R~ 0 C-N+ H R2 Fig. 2. Delocalisation of the anion formed by oxida- tion of diphenylmethyleneamine with acidic dichromate solution Other workers have commented on the oxidation with acidic dichromate or alkaline per- manganate of some of the amines studied in the present work. In assays for amitriptyline14 and chlorprothixene, 15 using oxidation with buffered alkaline pennanganate, cyclizine has been described as an interfering substance. Caddy et aL3 reported good yields of benzo- phenones following the oxidation of cyclizine and chlorcyclizine with a similar reagent.Vessman et aZ.2 reported low yields of benzophenones from those compounds following their oxidation procedure with non-aqueous dichromate, while Vessman and Hartvig16 reported yields of 69.0 to 72.5 per cent. for cyclizine, chlorcyclizine, hydroxyzine and meclozine, using a similar reagent but with a reaction time exceeding 24 hours. The latter authors also reported that doubling the oxidant concentration doubled the oxidation rate for cyclizine, but in the present work (with aqueous media) changing the dichromate concentration from 1 to 4 per cent. had only a minimal effect on the yield following a reaction time of 40 minutes although yields were significantly increased by increasing the acid concentration (Table VI).TABLE VI VARIATION I N YIELDS ON OXIDATION FOR CYCLIZINE AND CHLORCYCLIZINE WITH CHANGES I N ACID AND DICHROMATE CONCENTRATION Sulphuric Dichromate acid/n concentration, per cent. 9 1 4 12 1 4 16 1 4 20 1 4 Oxidation yield, per cent. Cyclizine Chlorcyclizine 4 4 6 6 4 4 6 6 9 20 11 32 24 41 28 42 r A > CONCLUSIONS Oxidation of drugs containing the diphenylmethyleneamino group with alkaline per- manganate gave good yields of benzophenones, which were shown to obey Beer - Lambert’s law over the concentration range studied. Oxidation with acid dichromate was found to be inadequate. With the exception of the oxidation of embramine and chlorphenoxamine with alkaline permanganate both reagents appear satisfactory for the oxidation of most compounds con- taining the diphenylmethylene ether group. Satisfactory calibration graphs were obtained for all other compounds over the concentration range studied but the acidic potassium di- chromate method was the better of the two as it invariably gave higher yields of benzophenone. REFERENCES 1. 2. 3. 4. 5. 6. 7. Wallace, J. E., Biggs, J. D., and Dahl, E. V., Analyt. Chem., 1966, 38, 831. Vessman, J., Hartvig, P., and Stromberg, S., Acta Pharm. Suec., 1970, 7, 373. Caddy, B., Fish, F., Mullen, P. W., and Tranter, J., J . Forens. Sci. Soc., 1973, 13, 127. Tranter, J ., Ph.D. Thesis, University of Strathclyde, Glasgow, 1973. Sasaki, D., J. Osaka Cy Med. Cent., 1954, 3, 207. Kikkawa, M., Sasaki, D., Iwasaki, T., and Ueda, J., Ibid., 1956, 3, 69. Staude, S., and Patat, I?., in Patai, S., Editor, “The Chemistry of the Ether Linkage,” Interscience Publishers Inc., New York, 1967, pp. 21-80.564 8. 9. 10. 1 1 . 12. 13. 14. 15. 16. CADDY, FISH AND TRANTER Wiberg, K. B., “Oxidation in Organic Chemistry, Part A,” Academic Press, New York and Westheimer, I?. H., and Novick, A., J . Chem. Phys., 1943, 11, 506. Sager, W. F., J . Amev. Chem. Soc., 1956, 78, 4970. Rocek, J., Chemicke‘ Listy, 1957, 51, 1838. Schechter, H., and Rawalay, S. S., J . Amer. Chem. Soc., 1964, 86, 1706. Neumann, F. W., and Gould, C. W., Analyt. Chem., 1963, 25, 751. Wallace, J. E., and Dahl, E. V., J . Forens. Sci., 1967, 12, 484. Wallace, J . E., J . Pharnt. Sci., 1967, 56, 1437. Vessman, J., and Hartvig, P., A d a Pharm. Sztec., 1971, 8, 229. London, 1965. Received January 24th, 1974 Accepted March 22nd, 1974

ISSN:0003-2654    

DOI:10.1039/AN9749900555

出版商:RSC    

年代:1974

数据来源: RSC

摘要:

Analyst, September, 1974, Vol. 99, pp. 565-569 565 Determination of the Tyramine Content of South African Cheeses by Gas - Liquid Chromatography BY 1:. R. KAPLAN, N. SAPEIKA (Department of Pharmacology, Medical School, Observatory, Cape Province, South Africa) (Fishing Industry Research Institute, University of Cape Town. Rondebosch, Cape Province, South Africa) AND I. M. MOODIE The tyramine content of foodstuffs and beverages is of pharmacological and therapeutic importance. A simplified method for its extraction from various cheeses and the application of gas-chromatographic analysis are presented. TYRAMINE is an indirectly acting sympathomimetic amine that releases noradrenaline from adrenergic neurones. Foods such as cheese, red wine, yeast extracts and pickled herrings may contain large amounts of tyramine.l Dietary tyramine does not normally produce any hypertensive effects because both the intestinal wall and liver contain the enzyme monoamine oxidase, which oxidises the tyramine before it can pass into the general circulation.However, if the activity of the enzyme at these sites is inhibited by a monoamine oxidase inhibitor drug, any tyramine absorbed from the gut passes freely into the circulation, thus causing the exaggerated hypertensive and other effects, which are produced by adrenergic substances and which may be mild, severe or even fatal. There is also evidence that this recognised “cheese reaction” may be partly caused by the presence of other substances such as histamine and 5-hydroxytryptamine which, like tyramine, would remain protected from destruction by inhibited monoamine oxidase.The development of the hypertensive reaction depends on the concentration of tyramine in the food. With cheese, tyramine is formed during the cheese-making process by the bacterial degradation of milk proteins to tyrosine (and other amino-acids) and subsequent decarboxylation of tyrosine to tyramine. The amount of tyramine in different cheeses varies greatly and even within a single cheese the tyramine content can vary considerably between a sample taken from the centre of the cheese and a sample taken near the rind.2 This variation may explain why the ingestion of a portion of certain cheeses may not necessarily cause a hypertensive c r i s i ~ . ~ , ~ Previous w ~ r k e r s ~ ~ ~ ~ ~ have used extraction and fluorimetric assay techniques in the determination of tyramine in cheeses.However, the methods of extraction are laborious and involve steps in which there is a real risk of introducing errors. In particular, special care must be exercised in maintaining the correct pH in order to ensure optimum extraction of tyramine as the free base. At the high pH used it is not possible to extract all the tyramine and frequent checks have to be made on the efficiency of extraction. In the present investigation, representative samples from each cheese were selected and the tyramine, as its hydrochloride salt, was extracted in acidic medium, the amount of tyramine obtained being determined by gas chromatography. As amines cannot be satisfactorily determined by direct gas-chromatographic analysis, it becomes necessary to adopt a procedure involving the forination of derivatives.Several methods for the separation and determination of biological amines by gas chromatography of their derivatives have been de~cribed.~-~ The procedure used in the proposed method is based on that of Irvine and Saxbylo for the separation of primary and secondary amines. The tyramine hydrochloride (I) is converted at room temperature into the ON-bistrifluoroacetyl (TFA) derivative (11) with a large excess of trifluoroacetic anhydride and determined by gas chromatography, using ephedrine hydrochloride as an internal standard. 0 SAC and the authors.566 ---l KAPLAN et al. : DETERMINATION OF THE TYRAMINE CONTENT [Analyst, Vol. 99 OCOCF3 $ - Excess (CF3CO120 0 CH2CHzNH2.HCI CH2 CH2 NHCOCF3 I II METHOD REAGENTS- Tyramine hydrochloride (Nutritional Biochemicals Corp., m.p.271 to 273 "C) and ephe- drine hydrochloride (May and Baker, m.p. 217 to 219 "C) were checked for purity by forming their derivatives and subjecting the latter to gas chromatography (Figs. 1 and 2). L I I I I I I I I . - 18 14 10 6 2 0 Ti me/m i nu tes t E4 n 0 E k 18 14 10 i Time/minutes Fig. 1. Chromatogram of ephedrine Fig. 2. Chromatogram of tyramine derivative on 2 per cent. OV-17 - 1 per derivative on 2 per cent. OV-17 - 1 per cent. OV-210 on acid-washed, silanised cent. OV-210 on acid-washed, silanised Chromosorb W. Column programmed Chromosorb W. Column programmed from 120 to 220 "C a t 6 "C min-' from 120 to 220 "C a t 6 "C min-1 EXTRACTION- A known amount of cheese (1.0 -& 0.4 g) was homogenised with 20 ml of 0.01 N hydrochloric acid and the mixture centrifuged for 5 minutes.The supernatant fluid was removed and sampled for derivative formation. DERIVATIVE FORMATI ON- TO a 5-ml aliquot of the aqueous extract, 400 pg of ephedrine hydrochloride were added and the solution was evaporated to dryness in vacuo. The residual solid was azeotropically dried twice by repeated additions of anhydrous methylene chloride, which were removed by evaporation in vacuo. The residue was then treated with 3 ml of a 1 + 3 trifluoroacetic anhydride - methylene chloride solution followed by ultrasonic mixing, which yielded a solution of the derivatives that was immediately available for gas-chromatographic analysis.Inj ec- tions of 2 4 of this solution were made as soon as possible after derivative preparation as prolonged storage can lead to degradation of the products. The procedure differs from that used by Senll in that the excess of trifluoroacetic an- hydride is not removed from the final product, which is thereby protected from any traces of moisture with which it might come into contact. Samples were taken from different parts of each particular brand of cheese.September, 19741 GAS - LIQUID CHROMATOGRAPHIC ANALYSIS- A Hewlett-Packard 7610 gas chromatograph fitted with flame-ionisation detectors and coupled to a Hewlett-Packard 3370A electronic integrator was used. The columns used were of glass, U-shaped (1.5 m x 4 mm i.d.) and silanised, and were packed with 2 per cent.OV-17 and 1 per cent. OV-210 on acid-washed DMCS Chromosorb W (80 to 100 mesh) and conditioned for 16 hours at 235 "C with nitrogen carrier gas flowing at the rate of 20 to 30 ml min-1. Injector and detector temperatures were 205 and 260 O C , respec- tively. The column temperature for analytical runs was programmed from 115 to 220 "C at 6 "C min -l. A stock solution of tyramine hydrochloride (25.00 mg; 144 mmol) and ephedrine hydro- chloride (29-03 mg; 144 mmol) in 50 ml of 0.01 N hydrochloric acid was prepared. A typical chromatogram of cheese extract is shown in Fig. 3. OF SOUTH AFRICAN CHEESES BY GAS - LIQUID CHROMATOGRAPHY 567 t 0 Lu n LT 1 1 1 1 1 1 1 1 1 18 14 10 6 2 0 Time/minutes Fig. 3. Typical chromatogram of acid-soluble components of cheese (mature cheddar), after derivative formation, on 2 per cent.OV-17 - 1 per cent. OV-210 on acid-washed, silanised Chromosorb W. Column programmed from 115 to 220 "C at 6 "C min-1. A, ephedrine, and B, tyramine derivatives RESULTS AND DISCUSSION The amount of tyramine present in each sample was calculated after first establishing the relative molar response (RMR) of the tyramine derivative (T) with respect to that of the internal standard (IS), ephedrine hydrochloride. Thus the value of R.MRT/Is was determined by repeated analysis of derivatives prepared from aliquots of a stock standard solution con- taining equimolar amounts of tyramine hydrochloride and ephedrine hydrochloride, using the following equation- . . * * (1) RMRTp = - ... . AIBInIs where A is the peak area and n the number of moles. present in the stock solution, then As equimolar amounts of tyramine hydrochloride and ephedrine hydrochloride are Values for this relative molar response were determined from ten separate chromato- graphic analyses and are shown together with the retention and peak area values in Table I.568 KAPLAN et d.: DETERMINATION OF THE TYRAMINE CONTENT [AndySt, VOl. 99 TABLE I PEAK AREA VALUES FOR STOCK SOLUTION No. of analysis 1 2 3 4 5 6 7 8 9 10 Area of TFA- tyramine peak 6868 3850 3480 2328 6278 2435 4706 6669 2566 2162 ( A T) Area of TFA- ephedrine peak 8538 4715 4564 2739 7854 3026 6060 8085 3145 2620 ( A 1s) 0.80 0.82 0.76 0.85 0.80 0.80 0.78 0.82 0.82 0.83 After an accurately known amount of internal standard had been added to the aliquot of cheese extract, derivatives were formed in the mixture and chromatographed, the peak areas for tyramine and internal standard (shown in Table 11) being obtained.By taking equation (1) above in expanded form and rearranging the terms, an equation for the amount of tyramine is readily obtained: where A is the peak area, g the amount and M the relative molecular mass, then By using the results shown in Table 11, the average value for RMRTilS (0.81, derived from values in Table I) and the relative molecular masses of tyramine and ephedrine hydrochloride, the amounts of tyramine in the extracts can be calculated. The tyramine contents of the original cheese samples are then determined and are shown in Table 111. TABLE I1 PEAK AREA VALUES FOR VARIOUS CHEESES Sample of cheese Roquefort Cheshire Camembert Cottage (cream) Pont 1’Eveque Cheddar (mature) Cheddar (1st grade) Area of tyramine peak 3108 62 1 36 10 124 1818 2884 TFA- (AT) Area of TFA- ephedrine peak 1553 2762 3643 11 510 15 430 3094 6029 !A IS) Sample of cheese Brie Cottage (low fat) Cheddar (wedges) Cheddar (wedges) Cheddar (wedges) Gruy&re Sweet milk Area of tyramine peak 63 1 64 2358 424 1846 122 152 TFA- (AT) Area of ephedrine peak 5865 12 640 10 230 3183 5179 5419 9261 TFA- ( A 1s) In order to ensure that the extraction was operating satisfactorily, a sample of cheese was split into four portions.Three portions were “spiked” with different levels of tyramine and then together with the “unspiked” fourth portion were extracted and the mixtures centrifuged.Internal standard was added to 5-ml aliquots of the extract and the analysis conducted as already described. The tyramine contents (Table IV) of the four samples were calculated by using the results shown in Table IV and equation (3). A comparison of the calculated value of added tyramine with the actual value of added tyramine shows good agreement and reflects an efficient extract ion procedure.September, 19741 OF SOUTH AFRICAN CHEESES BY GAS - LIQUID CHROMATOGRAPHY TABLE I11 TYRAMINE CONTENTS OF VARIOUS CHEESES 569 Sample of cheese Roquefort Cheshire Camembert Cottage (cream) Pont 1’Eveque Cheddar (mature) Cheddar (1st grade) Brie Cottage (low fat) Cheddar (wedges) Cheddar (wedges) Cheddar (wedges) Gruybre Sweet milk Amount of cheese sample/ g 1.0226 1.0177 1.0334 1.0315 1.0015 1.0188 1.0156 1.0197 1.0300 1-0026 1.0200 1~0000 1~0000 1.0080 Amount of tyramine (gT) in 5 ml of extract/ 167.8 75.5 3.3 1.0 2.7 197.4 160.7 36.2 1.7 77.4 44.7 119.7 7.6 5.5 rLg Tyramine content of cheese/ 656.4 296.7 12.8 5.0 10.8 775.0 632.9 142.0 6.6 308.8 175.3 478.8 30-4 21.8 r g g-’ From the results it can be seen that aged (mature) cheese ( e g ., Cheddar) contains relatively large concentrations of tyramine compared with those found in cheese of the “cottage” variety. Such cheese with a high tyramine content must especially be avoided by persons who take anti-depressive drugs of the monoamine oxidase inhibitor variety; certain other foods con- taining tyramine should also be avoided. TABLE IV EFFICIENCY OF EXTRACTION OF TYRAMINE FROM CHEESE Area of Area of TFA-tyramine TFA-ephedrine Tyramine Amount of cheese Tyramine peak peak found in sample/g added/pg (AT) ( A IS) extract/ p g 0.9400 - 14 688 24 026 82 1 1.0712 1580 32 342 18 567 2340 1.0980 790 19 169 15 611 1650 1.0440 395 14 954 16 611 1209 Apparent tyramine added/pg 1519 829 388 - 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. REFERENCES Stockley, I. H., Phavm. J., 1973, 210, 590. Price, K. and Smith, E., Lancet, 1971, i, 130. Sjoqvist, F., Proc. R. Soc. Med., 1965, 58, 967. Spector, S., Melmon, K., Lovenberg, W., and Sjoerdsma, A., J . Pharmac. Exp. They., 1963, 140, 229. Horwitz, D., Lovenberg, W., Engelman, K., and Sjoerdsma, A., J . Amer. Med. Ass., 1964, 188, 1108. Sen, N. P. and McGreer, P. L., Biochem., Biophys. Res. Commun., 1963, 13, 390. Beckett, A. H. and Wilkinson, G. R., J. Pharm. Pharmac., 1965, 17, 104s. Capella, P. and Horning, E. C . , Analyt. Chem., 1966, 38, 316. Cancalon, P. and Klingman, J. D., J. Chromat. Sci., 1972, 10, 253. Irvine, W. J., and Saxby, M. J.. J. Chromat., 1969, 43, 129. Sen, N. P., J. F d Sci., 1969, 34, 22. Received September loth, 1973 Amended Mavch llth, 1974 Accepted Mawh 19th, 1974

ISSN:0003-2654    

DOI:10.1039/AN9749900565

出版商:RSC    

年代:1974

数据来源: RSC