X SUMMARIES O F PAPERS I N THIS ISSUE October, 1979Calcium Ion- selective Electrode Measurements in thePresence of Complexing LigandsCalcium ion-selective electrodes based on calcium bis[di (4-octylphenyl) -phosphate] sensor and dioctyl phenylphosphonate solvent mediator havebeen used for monitoring free calcium-ion levels (from below lo-' to above10-3 M) in the presence of citrate, malate, malonate, oxalate, EDTA, NTA,sulphate, orthophosphate, tripolyphosphate and pyrophosphate anion ligandsystems under conditions of constant ionic strength maintained by sodiumchloride. Log /3 data fall in the range of those previously measured for thevarious equilibria by alternative methods, thus demonstrating that calciumion-selective electrodes of the type used here can be employed for free calcium-ion measurements to below the detection limits characteristic of calibrationswith serial dilution standards and without disturbing the equilibria of com-plexat ion.Equilibria existing in the tripolyphosphate and pyrophosphate systemswere discerned by application of the MINIQUAD program for computing forma-tion constants and species distribution. Predictions concerning the existenceof [CaP30,J3- and [Ca(P,O,,),]*- in tripolyphosphate and of [CaP,0,I2- and[Ca( P,O,) J6-.in pyrophosphate systems are briefly discussed.These calcium ion-selective electrodes are not affected by added phosphateexcept insofar as free calcium-ion levels are lowered by complexation.Keywovds : Calcium ion-selective electvodes ; formation constants ; coiaplexationequilibriaA.CRAGGS, G. J. MOODY and J. D. R. THOMASChemistry Department, University of Wales Institute of Science and Technology,Cardiff, CF1 3NU.Analyst, 1979, 104, 961-972.Interferences of a Barium Ion- selective Electrode Used for thePotentiometric Titration of SulphateCertain cations and anions interfere with the potentiometric titration ofsulphate with barium chloride as titrant and a barium ion-selective indicatorelectrode. Thus, cations, for example potassium, which can be sensed by thebarium ion-selective electrode, give distorted titration curves, while pH valuesbelow 1.5 lead to electrode breakdown. Cations, such as calcium, whichinteract with sulphate give low sulphate recovery, while anions that inter-act with the barium titrant lead to apparently high sulphate.Treatment of samples with cation-exchange resins in the sodium form canremove cation interferences, but acidification to pH 2 with hydrochloric acidprevents interference from anions, such as phosphate, carbonate - hydrogencarbonate and organic anions.Keywords : Baviuwz ion-selective electvode ; sulphate titvation ; intevferencesDILYS L.JONES, G. J. MOODY and J. D. R. THOMASChemistry Department, University of Wales Institute of Science and Technology,Cardiff, CF1 3NU.and MAGDOLNA HANGOSInstitute for General and Analytical Chemistry, Technical University, 1502 BudapestXI, Hungary.Analyst, 1979, 104, 973-976October, 1979 THE ANALYST xib Collaborative studiesb Original papers onnew techniques,applications,0 authentic data ofcomposition studiesleading to methodsdevelopmentb Referee reportsPublished six times annually.Official publication of theAssociation of Official AnalyticalChemists-the internationallyknown organization devotedto developing and publishingreliable thoroughly testedmethods of analysis for:b foodsh drugsb cosmeticsb colorsb beveragesb flavorsb vitaminsb preservativesb fats and oilsh feedsb fertilizersb pesticidesb disinfectantsb hazardous substancesASSOCIATION OFOFFICIALANALKICALCHEMISTSJOURNALAssociation of Official Analytical ChemistsBox 540, Benjamin Franklin StationWashington, D. C.20044U.S.A.Please enter -subscription(s) to JOURNAL OF THE AOAC for197-. (Subscriptions are on calendar basis for 6 issues: Janyry, March,May, July, September, November.Back issues are sent to subscribers.)Price: $45.00 (domestic): $50.00 (foreign). $12.00 single copy.Name(please print)AddressZip Code - CityState or Country0 Payment enclosed 0 Send invoiceSignature DateIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIxii SUMMARIES OF PAPERS I N THIS ISSUE October, 1979Detection of L-Cysteine, Methionine, Thiourea, Allylthiourea anda-Naphthylthiourea in Sub-milligram Amounts Using AcidifiedPotassium Chromate SolutionShort PaperKeywords : Thio compound detection ; acidified potassium chromate CO~OZLVreagentM. NASIM BEG, FASIH A.SIDDIQUI, M. MOHTASHIM BEG,R. SHYAM and M. ARSHADDepartment of Chemistry, Aligarh Muslim University, Aligarh-202001, India.Anaylst, 1979, 104, 977-979.Implementation of a Sensitive Method for Determining Mercury inSurface Waters and Sediments by Cold-vapour Atomic-absorptionSpectrophotometryShort PaperKeywords Mercury deternzination ; atomic-absorption spectvophotometry ;cold-vapour method comparisons ; environmental samplesR. L. LUTZEState Pollution Control Commission, Central Square Building, 323 Castlereagh Strcet,Sydney 2001, N.S.W., Australia.Analyst, 1979, 104, 979-982.Spectrophotometric Determination of Trace Amounts of Boronin Solutions Containing Large Amounts of NitrateShort PaperKeywords : Boron determination ; nitrate interfevence ; hydvazine hydvate ;cavminic acid ; spectrophotoinetryH.J. ROSENFELD and A. R. SELMER-OLSENAgricultural University of Norway, Chemical Rescarcli Laboratory, N-1432 Ais-XLH,Norway.Analyst, 1979, 104, 983-986.Spectrophotometric Determination of Nitrite Using4,5- DihydroxycoumarinShort PaperKeywords : Nitrite determination ; spectvophotometvy ; 4,5-dilzydro~~3,cou.tnavinMOTOSHI NAKAMURA and AKIRA MURATAFaculty of Engineering, Shizuoka University, 3-5- 1, Johoku, Hamamatsu-shi,Shizuoka-ken, 432, Japan.Analyst, 1979, 104, 985-988October, 1979 THE A...NALYST XlllACS PublicationsModern Classicsin AnalyticalChemistry Vol. 2Compiled by Alvin L. BeilbyA selection from the best featurearticles that appeared in issues ofAnalytical Chemistry from 1 970 to1975.Ideal assupplementaryreadingfor theadvanced student of analyticalchemistry. Includes spectroscopy,electroc hemistry, chromatography,automation and instrumentation,measurement techniques, analyticalmethods, and art conservation.Paperbound 314pp I l ” x 8 ~ ”0 841 2 0332 6 f 6.50ReagentChemicals:5th EditionACS Specifications for 320 reagentchemicals; includes 50 pages ofdefinitions, tests, and reagentsolutions. Features flame and flame-less atomic absorption methods;new polarographic and chromato-graphic procedures; and newcolorimetric test for arsenic.Clothbound 685pp 93”x 6$’10 841 2 021 0 9 f 30.00both available from:The Chemical Society,D ist ri but io n Cent re,Blackhorse Road,Letc h wo rt h,Herts. SG6 1 HNEnglandI To: May & Baker Ltd (Wall-planner Offer) I Essex House, Station Road, Upminster, Essex RM14 2JTPlease sendI enclose€NameIIII Address II !wall-planners (1980/81) at f l eachpostal order/cheque payable to May& Baker Ltd II(please print clearly) LA16001L i r i ~ i m r ~ ~ r ~ r m r - civ THE ANALYST October, 1979CLASSIFIED ADVERTISEMENTSThe Rate for Classified Advertisements i s,9.j 0 per single column centimetre.Box Numbers are charged an extra 60p.Deadline for classified copy i s 20th of themonth preceding month of issue.All space orders, copy instructions andenquiries should be addressed toThe A dvertisement Department,The Chemical Society, Burlington House,Piccadilly, London WIV o B N .Telq5hone 01-734 9864 Telex 268001PATENTSBRITISH PATENT No.1 346 389.An Anti-Adhesive Composition.Owner desires commercial exploitationon reasonable terms by license or sale.Inquiries Fitzpatricks, Chartered Patent Agents, 14-18 CadoganStreet, Glasgow, G2 SQW and Warwick House, Warwick Court,London, WClR 5DJ.BUREAU OF ANALYSEDSAMPLES LTDNewham Hall, Newby,Middlesbroug h,Cleveland, TS8 9EA(Telephone : Middlesbrough 31 721 6)announce a new series ofLOW ALLOY CAST STEELSforSPECTROSCOPIC ANALYSISSS NOS. 611 /I -61 5/1Chief Analyst - HalifaxWe are a Group whose operations are world-wide.One of the reasons we have achieved a leadingposition in the confectionery market is that webelieve in the importance of the scientific effortinvolved in developing our products and in main-taining their quality. This vacancy reflects theemphasis placed on the work.We now seek a Chief Analyst to take charge, in thefirst instance, of the Analytical Section of thelaboratories at our Halifax factories where weproduce Quality Street, Toffo, Chewing Gum andother products.The work involves the analytical con-trol of a wide range of confectionery ingredients andproducts as well as analytical research and develop-ment. An interest in modern industrial techniques isessential.The post will be of particular interest to men orwomen who now wish to widen their experience as astep towards achieving further responsibilities.You should have a degree in food science, chemistryor physics, with a background of analytical orproducts research work and be between 25 and 35years of age.We provide a wide range of benefits- life assurance,profit sharing and removal expenses, and a widerange of social, sporting and educational facilities.Please apply quoting ref. LA.673 to:Miss D.M.N. Dick, Staff Office,Rowntree Mackintosh Ltd.,York YO1 IXY.Rswntree Mackintosh