April, 19731 THE ANALYST ixLECTURES AND COURSES APPOINTMENTS VACANTTHE UNIVERSITY OFMANCHESTER INSTITUTE OFSCIENCE AND TECHNOLOGYAdvances in Chemistry SeriesSPECTROSCOPICIDENTIFICATIONOF ORGANIC COMPOUNDSwill be held in the Institute from2nd to 6th July, 1973.This course is intended for chemists of graduate level, in industry orteaching, who have had little or no experience in interpreting infraredor nuclear magnetic resonance spectra.Further particulars, with form of application, can be obtained fromthe Registrar, UMIST, P.O. Box No. 88, Manchester M60 1QDPlease mentionTHE ANALYSTwhen replying to advertisementsstBOOKSMONOGRAPHSREPRINTSorders for all publications ofthe Society (except journals)odd be sent direct or througha bookseller to-THE SOCIETY FORANALYTICAL CHEMISTRYBook Department9/10 Savile Row,London, WIX IAFTHE EAST AFRICANPESTICIDESCONTROLORGANISATIONrequireAN ANALYSTt o establish a small laboratory a t Arusha for theverification of pesticide contents of selectedtechnical and formulated pesticides, and, as amember of E.A.P.C.O.t o assist in (a) promotingthe safe and effective use of pesticides and (b)enforcing conditions for the sale and proper useof efficient and appropriate pesticide-productsin East Africa.Candidates must have a good Honours degree inChemistry plus at least 4 years post-graduateexperience in Pesticide Chemistry. Knowledgeof method analysis of major pesticides i s essential.Salary is in a range of approximately f2890 -4050 a t present rate ofexchange.Appointmentis for 2 years in the f i r s t instance. A substantialgratuity is payable on completion of service.The post described is partly financed by Britain’sprogramme of aid t o the developing countriesadministered by the Overseas DevelopmentAdministration of the Foreign and Common-wealth Office.Apply to:CROWN AGENTSM. Division, 4, Millbank, London, SWI P 3JDfor application form and further particularsstating name, age, brief details of qualifi-cations and experience and quotingreference number M 3 E/720450/AA DBINDINGHave your back numbers of The Analystbound in the standard binding case.Send the parts and the appropriateindex(es) together with a remittancefor f2.40 t o :W.HEFFER & SONS LTD.,CAMBRIDGE, ENGLANx SUMMARIES OF PAPERS I N THIS ISSlilSThe Identification and Semi-quantitative Assay of Some Fat-soluble[April, 1973Vitamins and Antioxidants in Pharmaceutical Products andAnimal Feeds by Thin-layer ChromatographyA thin-layer chromatographic method for the identification and semi-quantitative assay of vitamin A (alcohol), its acetate and palmitate, vitamin D,a-tocopherol, a-tocopheryl acetate, BHA (butylated hydroxyanisole ; 2-t-butyl-4-methoxyphenol), BHT (butylated hydroxytoluene ; 2,6-di-t-butyl-4-methyl-phenol) and ethoxyquin in vitamin preparations is described. The samplesolutions are applied to thin layers of silica gel ancl the vitamins and anti-oxidants are separated by using n-hexane - ethyl methyl ketone - di-n-butylether (34 + 7 + 6) as the developing solvent.llccomposition of vitaminsA and D when applied to the adsorbent layer is inhibited by the presenceof triethylamine in the spotting solvent. The compounds are identifiedby means of their Rp values, their appearance in ultraviolet radiation ofwavelengths 254 and 360 nm and their response to iron(II1) chloride - bipyridyland iron(II1) chloride - potassium hexacyanoferrate(II1) spray reagents ;they are assayed by visual comparison with standards. The method hasbeen applied to gelatin-protected vitamin beads, animal feed additives, multi-vitamin tablets, oily vitamin concentrates and halibut-liver oil samples.A simple colour test for distinguishing vitamin I), from vitamin 11, afterremoval of vitamin A and its esters is also described.G.W. JOHNSON and C. VICKERSAnalytical Research, Quality Control, Thc Boots Company I,td., T’cnnyfoot Strcct,Nottingham.Analyst, 1973, 98, 257-267.Gas - Liquid Chromatographic Determination of Vitamin Din Cod-liver OilA gas - liquid chromatographic method for the determination of vitaminD (cholecalciferol) in cod-liver oil is described. It involves saponificationof the oil, extraction of the unsaponifiable matter, removal of interferencessuch as cholesterol and retinol (vitamin A) by precipitation, and columnchromatography on Sephadex LH-20 and Florisil ; the final determination ofcholecalciferol is carried out by gas - liquid chromatography. A determinationcan be completed in less than 2 days.J. G.BELL and A. A. CHRISTIEDepartment of Trade ancl Industry, Laboratory of the Govcrnnicnt Chemist,Cornwall House, Stamford Street, London, SIC1 YNQ.Analyst, 1973, 98, 268-273.The Determination of Trace Amounts of Cobalt and Other Metalsin High-purity Water by Using Ion-exchange MembranesMicrogram amounts of cobalt, chromium, copper, iron, nickel and zincare concentrated on ion-exchange resin impregnated membranes from largevolumes of reactor cooling waters. Atomic-absorption measurement on theacid-extracted membranes has permitted the determination of cobalt downto 0.01 pg 1 in water samples, with an analytical precision of rf- 12 per cent.a t the 96 per cent. confidence limit, based on twelve replicate observations.Garnma-spectrometric measurement of the nuclide cobalt-ti0 present in thereactor cooling waters has enabled membrane efficiency to be determined ;at cobalt levels of 0.01 and 0.1 p g l-l, the efficiencies arc- shown to bc 85 percent.and greater than 99 pcr cent., rcspectivclly.H. JAMESAtomic Energy Establishment, Winfrith, I>orchestcr, Dorset.Analyst, 1973, 98, 274-288xii SUMMARIES OF PAPERS IN THIS ISSUE [April, 1973Indirect Complexometric Titration of Barium and Strontiumafter Stepwise Precipitation as Sulphate fromHomogeneous SolutionAn indirect method has been developed for the stepwise titration ofbarium and strontium with EDTA, based on precipitation of the elementsas sulphate from a homogeneous solution. Barium, strontium and othermultivalent cations are complexed by titration with EDTA a t pH 10.0 byusing a mixed indicator comprising Eriochronie black T, Titan yellow andNaphthol green B.Barium is then selectively replaced from its EDTAcomplex and precipitated as the sulphate with an excess of magnesiumsulphate solution. The excess of magnesium is determined by titration withEDTA and the equivalent concentration of barium is calculated. Strontiumis determined in the same solution in the same way, with an excess of zincsulphate solution.The optimum conditions for precipitation and the interferences due tovarious anions and cations have also been studied. Copper, nickel, cobaltand iron interfere and a second method for the determination of bariumalone has been derived wherein the interfering elements are complexed withtriethanolamine, potassium cyanide and ascorbic acid.Phosphate andchromate interfere and require to be separated.B. C. SINHA and S. K. ROYCentral Glass and Ceramic Research Institute, Calcutta-32, India.Analyst, 1973, 98, 289-292.Molecular Interaction Errors in Phase-solubility AnalysisResults are presented for the assay by phase-solubility analysis of ibufenac(4-isobutylphenylacetic acid) and of saccharin in the presence of variousimpurities. The results for impurities obtained for ibufenac mixtures werealmost twice those expected, while those for saccharin mixtures were normal.From a consideration of these results, the effect of compound formation bymolecular interaction is discussed.D.THORBURN BURNS, J. B. GALLAGHER, R. J. STRETTONDepartment of Chemistry, University of Technology, Loughborough, Leicestershire,L E l l 3TU.and J. S. WRAGGAnalytical Research, Quality Control, The Boots Company Ltd., Pennyfoot Street,Nottingham.Analyst, 1973, 98, 293-296.A Critical Examination of Procedures for the Assay ofSodium FluorideReport prepared by the Fluorine Sub-committee.ANALYTICAL METHODS COMMITTEE9/10 Savile Row, London, W1X 1AF.Analyst, 1973, 98, 297-302April, 19731 THE ANALYST xiiiSELECTED ANNUALREVIEWSof theAN A LY T I CAL SC I EN C ESVolume 2 - 1972Just publishedCONTENTSThe Techniques and Theory of ThermalAnalysis Applied to Studies on lnorganicMaterials with Particular Reference t oDehydration and Single Oxide Systems- D.DollimoreDevelopments in Ion Exchange -F. VernonThermometric and Enthalpimetric Titri-metry - L. S. Bark, P. Bate and J. K.GrimePp. vi + 149 f5.00; U.S. $13.00Obtainable from-The Society for Analytical ChemistryBook Department,9/10 Savile Row, London, W I X IAFMembers of The Chemical Society may buy person;copies at the special price of f3.00; U.S. $8.00SPECIALIST ABSTRACTJOURNALSpublished bySCIENCE AND TECHNOLOGY AGENCYAtomic Absorption and FlameEmission Spectroscopy AbstractsVol. 5,1973, bimonthly €24X-Ray Fluorescence SpectrometryAbstractsVol. 4, 1973, quarterly ’ €24Thin-Layer Chromatography AbstractsVol. 3, 1973, bimonthly €24Gas Chromatograph y-MassSpectrometry AbstractsVol.4, 1973, quarterly €37Nuclear Magnetic ResonanceSpectrometry AbstractsVol. 3, 1973, bimonthly €30Laser-Raman Spectroscopy AbstractsVol. 2, 1973, quarterly €30X-Ray Diffraction AbstractsVol. 1-2, 1973, quarterly €30Neutron Activation Analysis AbstractsVol. 2-3, 1973, quarterly €30Electron Microscopy AbstractsVol. 1, 1973, quarterly €30Liquid Chromatography AbstractsVol. 1, 1973, quarterly €30Electron Spin Resonance SpectroscopyAbstractsVol. 1, 1973, quarterly €30Sample copies on request from:SCIENCE AND TECHNOLOGY AGENCY,3 DYERS BUILDINGS, HOLBORN,LONDON, E.C.1, ENGLAND01 -405 932xiv THE ANALYST [April, 1973(CARLO ERBAAnalytical Standards forTrace Elements AnalysisDIVISIONE CHIMICA INDUSTRIALE / VIA C.IMBONATI 24 I20159 MILAN0Modern trace analysis techniques more and more frequently nall for the use of referencestandards of metals.Spectrography, Atomic Absorption Spectrophotometry, Emission Spectrophotometry, X rayFluorescence are techniques which particularly require the use of these standards.It is however necessary to make a distinction between application of such techniques towater, or to other solutions whatever the basic solvent, oil or hydrocarbon.In fact if one uses the same technique on an aqueous solvent, one must use an aqueoussolution. If one uses a non-aqueous solvent the standards used must be soluble in thissolvent.Standards for atomic absorptionshould actually be called standard solutions for metaltrace anlysis, where the metal is in an aqueoussolution acidified by nitric acid, and may therefore beused as a standard for any analytical techniquerequiring it.Atomic absorption spectrophotometry is now beingused more and more in analysis in both research andindustrial laboratories, as this is the fastest andeasiest independent method for metal determinations.it may be applied to any soluble matrix.As for any instrumental technique, it is important tohave available standards of the metals involved,to set both the method and apparatus, and to revealany interference or positive or negative effects(caused by the matrix, solvent, etc.).In any case a control against a standard is advisablewhen plotting calibration curves.In fact in atomicabsorption spectrophotometry, the theoretical linearrelationship between absorbance and concentration,known as Beer’s law, is effective only within verynarrow limits.It will now be clear how important it is to haveavailable solutions with a known content, at least forthe most frequently determined metals.Carlo Erba STANDARDS for Atomic Absorption are thefollowing concentrated solutions of metal nitratewhich, when diluted to 1000 ml with distilled water,give a slightly acidic solution (about 0.1% HNO,) at aconcentration of metalAluminium STANDARDBarium STANDARDCadmium STANDARDCalcium STANDARDChromium STANDARDCobalt STANDARDCopper STANDARDiron STANDARDLead STANDARDion of 1000 ppm:Lithium STANDARDMagnesium STANDARDManganese STANDARDNickel STANDARDPotassium STANDARDSilver STANDARDSodium STANDARDStrontium STANDARDZinc STANDARDSpecial booklet available on requestnMetallorganic standardsThese compounds are in fact improperly calledmetallorganic, as they are generally metal salts ofcarboxylic organic acids or organic metal complexes;but this expression has been chosen because it givesa more immediate idea of the metal atom being linkedto an organic radical which eases solution in oils,even when the substance involved is not an alkyl oran aryl.They are used as oil-soluble standards in thespectrographic analysis of traces of metals in oils andfats, in petroleum derivatives and in lubricatingagents.The analysis of metals in non-aqueous media iscarried out with spectographs and atomic absorptionspectrophotometers using samples of known contentas controls. Therefore it has been necessary to studyand develop organometallic compounds and organicsalts of metals, having a known metal content.The stability is obtained by the use of solubilisingagents such as 2-l-Ethylhexanoic acid,6-Met h I y-2,4- heptan d i o ne, 2-Et h y l-h exy lam i n e, andbis-(2-Ethyl hexy1)dithiocarbamicacid-bis-(2-ethylhexyl)arnmonium salt, with Xylene.Thus, clear and stable solutions in an oil base areobtained, with concentrations up to 500 ppm of metal.It is also possible to prepare solutions containingmore than one metal, bearing in mind that mixtures ofmetals are more soluble than the individualconstituents.Carlo Erba metallorganic standards available in 5 g.vials concern the following elements:Aluminium, Barium, Bismuth, Boron, Cadmium,Calcium, Chromium, Cobalt, Copper, iron,Lanthanum, Lead, Llthlum, Magnesium, Manganese,Nickel, Phosphorus, Potassium, Siiicium, Silver,Sodium, Strontium, Tin, Vanadium, Zinc