...VIIl THE ANALYST -%fay, 1978Influence of Ascorbic Acid on the Matrix Interferences ObservedDuring the Carbon Furnace Atomic-absorption SpectrophotometricDetermination of Lead in Some Drinking WatersNine samples of drinking water taken from a range of locations in Englandand Scotland have been analysed for lead by using carbon furnace atomic-absorption spectrophotometry. Spiking experiments have been carried outin order to determine the severity of the matrix interference. The suppressionof the lead signals ranged from 22 to 84%. No relationship was found toexist between the hardness of a water sample and its suppression effect.Further spiking experiments carried out in the presence of lo/, m/V ofascorbic acid showed that the suppression effect of eight of the water sampleswas reduced to a level of less than 5'x.The remaining water sample gavea suppression of 18%. This water was not the hardest examined, nor did itgive the highest suppression in the previous experiment.The natural lead contents of the nine waters were determined both bycarbon furnace atomic-absorption spectrophotometry in the presence ofascorbic acid and by a method that involves solvent extraction - ffarne atomicabsorption. Statistical analysis, using a t-test, indicated that there was nosignificant difference (at the 95% confidence level) in the results obtained byusing the two techniques.Keywords : Lead determination ; drinking water; cavbo.12 fuvnace atomic-absorfition spectrophotometry ; matrix interferences ; ascorbic acidJ.G. T. REGAN and:J. WARRENDepartment of Industry, Laboratory of the Government Chemist, Cornwall House,Stamford Street, London, SE1 ONQ.Analyst, 1978, 103, 447-451.Qualification of Estimates for Total Trace Elements in FoodstuffsUsing Measurement by Atomic -absorption SpectrophotometryThe qualification of results for small concentrations of elements in focdstuffsimplies a knowledge of the accuracy of a method when applied to focdstuffsand an assessment of the variation in results that exists in the applicationof that method.An attempt is made to describe the problems inherent in obtaining suchqualifications, and to suggest a standard procedure for accomplishing theseaims. From data obtained for a particdar method, a statistical appreciationwill give confidence limits and detecticln limits that can be applied to subse-quent results obtained, depending upon the nature of the exercise involved.Keywords : Accuracy and variation c f resulfs ; limit of detection ; statisticalappreciation ; foodstuffs analysis ; atomic-absorption spectvophotoynetryW. H.EVANSDepartment of Industry, Laboratory of the Government Chemist, Cornwall House,Stamford Street, London, SEl 9NQ.Analyst, 1978, 103, 452-468.Analysis of Metals Using a Glow-discharge Source with aFluorescent Atomic Vapoui- as Spectral-line IsolatorA compact and rugged spectral-line isolator based on atomic fluorescencefrom atoms generated by a low-pressure gas discharge has been constructed.The device is bolted to a standard glow-discharge source.A pulsed electricalcurrent generates the atoms and the fluorescence is measured by ineans of agated integrator. Several types of metals have been analysed, e.g., steel,cast iron, aluminium and gold. Good precisions and accuracies have beenobtained.H. G. C. HUMAN, N. P. FERREIRA, R. A. KRUGER and L. R. P. BUTLERNational Physical Research Laboratory, CSTR. P.O. Box 395, Pretoria 0001,Republic of South Africa.Analyst, 1978, 103, 469-47-2.Keywords : MetaE analysis ; atomic-JEuorescence spectroynetvk f a y , 1978 SUMMARIES OF PAPERS IN THIS ISSUERadiochemical Neutron - activation Analysis of Sulphide Ores UsingZinc Diethyldithiocarbamate as Extraction ReagentA procedure for the analysis of lead sulphide and mixed sulphide ores forsilver, arsenic, gold, cadmium, copper, manganese, antimony and zinc wasdeveloped with emphasis on the determination of the low gold to silverand arsenic to antimony ratios.Radiochemical neutron-activation analysiswas necessary and a solvent-extraction technique has been developed. Inthe first separation step arsenic(II1) chloride was extracted from the oresolution with benzene. The results are compared with the values obtainedafter separation of arsenic by distillation.Gold(III), silver(I), copper(II), cadmium(I1) and several other traceelements were extracted with zinc diethyldithiocarbamate in chloroform,whereas antimony(V) remained in the aqueous phase. The activities ofthe samples were counted on a germanium(1ithium) well-type detector andcompared with those of known volumes of standard solutions.Chemicalyields were determined by re-activation.The combination of conventional arsenic separation and this newlydeveloped diethyldithiocarbamate extraction technique proved to be a veryefficient and reliable method for the analysis of sulphide ores.Keywords : Sulphide ore analysis ; neutron-activation analysis ; radiochemicalseparation ; zinc diethyldithiocarbamate ; gavnma-ray spectrometryE. PERNICKA, P. A. SCHUBIGER and 0. MULLERMax-Planck-Institut fur Kernphysik, Postfach 103980, D-6900 Heidelberg, WestGermany.Analyst, 1978, 103, 475-481.ixPyrolysis - Mass Spectrometry of Textile FibresA procedure for pyrolysis - mass spectrometry is described and the spectra(mass pyrograms) of various textile fibres are presented.The method iscompared with infrared spectroscopy for the forensic characterisation ofsynthetic fibres. Samples of less than 5 pg can be analysed.Keywords ; Textile fibre cliavacterisation ; pyrolysis - ma.ss spectrometry ;infrared spectroscopyJ. C. HUGHES, B. B. WHEALS and M. J. WHITEHOUSEMetropolitan Police Forensic Science Laboratory, 109 Lambeth Road, London,SE1 7LP.Analyst, 1978, 103, 482-491.Determination of Probenecid in Serum by High-performanceLiquid ChromatographyThe determination of probenecid in serum samples by using high-performanceliquid chromatography is described. The method gives satisfactory resultsover the normal therapeutic range, namely up to 150 pgml-l of probenecidin serum, and is not affected by metabolites of the drug.The method doesnot require derivatisation of the drug, as in gas - liquid chromatographicprocedures, and is less subject t o interferences than spectrophotometricprocedures. It has been used in analysis of several hundred serum samplesand has given a satisfactory performance in respect of precision and accuracy.Keywords : Probenecid determination ; serum ; high-performance liquidclz YO mat ograph yR. K. HARLE and T. COWENInternational Development Laboratories, E. R. Squibb and Sons Limited, Moreton,Merseyside, L46 1QW.Analyst, 1978, 103, 492-49X THE ANALYST May, 1978NewE U R 0 -STAN D A R Dnow availableE. s 377 - 1Furnace Dust (LD Converter)Certified for the following elements :Fe, Si, Ca, Mg, At, Ti, Mn, P, S, Na,K, F, V, Cr, Ni, C, Zn, Pb, Cu and AsFull details obtainable from :Bureau of Analysed SamplesLtd.Newham Hall, Newby,Middlesbrough, Cleveland TS8 8EATelephone: Middlesbrough 31 721 6ANALYSTProfessionaIly quaIified analyst is required for our up-to-date anal y-tical laboratory which is situated in pleasant rural surroundings.This is a challenging new post which results in part from our recentpurchase of a scanning electron microscope with X-ray analysisfacilities.Postgraduate experience of energy dispersive X-ray analysisis necessary, together with some experience in, or a willingness i:olearn chemical, thermal (TGA, DSC) or spectroscopic (UV, IR, NMII,AA) techniques of analysis.Alternatively we might consider a graduate with considerable ex-perience of some of these latter techniques, and willing to learn X-rayanalysis.Applicants should possess drive, versatility, the ability to develop newanalytical methods with a minimum of supervision, and the abilityto work on a number of different topics simultaneously.A salary commensurate with experience will be offered, together withparticipation in the FSSU superannuation scheme.Please write in confidence to: Director of Research (quoting ref.BKT)The Malaysian Rubber Producers’ Research Association, Tun AbdulRazak Laboratory, Brickendonbury, Hertford SG13 8NL.CLASSIFIED ADVERTISEMENTSThe Rate for Classified Advertisements is g2.30 per singlecolumn centimetre (minimum L4.60).Box Numbers are charged a n extra sop.Deadline for classified copy is 20th of the mc’zlh precedingmonth of issue.All space orders, copy instructions and enyzriries should beaddressed to The Advertisement Department,The Chemical Society, Burlington House, Piccadilly,London WIV oBNTelephone 01-734 9864 Telex 268001THE QUEEN’S UNIVERSITYOF BELFASTMSc COURSE inANALYTICAL CHEMISTRYApplications are invited for admission to thisestablished 12 month full-time MSc coursewhich provides a comprehensive training inthe theory and practice of modern chemicaland instrumental methods of analysis.Appli-cants should normally possess an honoursdegree (or equivalent) in chemistry or cognatesubjects. Part-time courses are available.The Science Research Council has recognisedthe course for tenure of its Advanced CourseStudentships.A description booklet and application formscan be obtained from Professor D. ThorburnBurns, Dept. of Chemistry, Queen’s Universityof Belfast, Belfast,BT7 lNN,Northern Ireland.PLASMA ANALYSISScientific Conference Services Limited willbe holding a three day workshop forusers and potential users of InductivelyCoupled Plasmas as an analytical spectro-scopic source at Imperial College from3rd to 5th July 1978.Topics will include a brief theoreticalintroduction on plasma emission spectro-scopy, instrumentation, the application ofthe technique to various analytical fieldsand practical demonstrations. These willbe presented by internationally recognisedexperts in the ICP field.For further information contact :Dr. M. D. SilvesterScientific Conference Services Limited14 Trading Estate RoadGreat Western Trading EstateLondon NWlO 7L