A method has been developed for the simultaneous determination of arsenic, antimony, bismuth, selenium and tellurium by generation of their gaseous hydrides and introduction of these hydrides into an inductively coupled plasma source where the atomic line emission from the elements is detected. The effect of different plasma-torch assemblies on the detection limits attainable has been studied and suitable compromise conditions have been established for the simultaneous generation of the hydrides of the analyte elements and their determination by optical ernission spectrometry in t h e plasma source. Dctection limits of 1 ng ml-1 or below for aqueous solutions of the elements studied have been obtained under the conditions employed to allow their determination in samples of interest in geochemistry.Keywovds A rsenic, antimony, bismuth, seleniunz and tellurium detevminat i o n ; geochemical samples ; hydride generatiox. ; inductively coupled plasma etnission spectrometry

In the simultaneous determination of arsenic, antimony, bismuth, selenium and tellurium by measurement of the atomic line emission from the elements in an inductively coupled plasma source after their introduction as the gaseous hydrides, two types of possible interferences were investigated. Mutual interferences between the analytes were found to be negligible under the operating conditions used. The presence of certain metal ions in solution resulted in low recoveries of some of the analytes, especially selenium ancl tellurium. However, this could be overcome by prior separation of the analytes by co-precipitation on lanthanum hydroxide.Keywords Arsenic, a n t i m o n y , bismuth, selenium a n d tellurium determination ; geocheniical saiq!des ; hydride generation ; inductively coupled plasma einission spectrometry ; interferences

Trace amounts of arsenic, antimony and bismuth in soils and sediments are determined simultaneously by an inductively coupled plasmavolatile hydride method after rapid attack with concentrated hydrochloric acid in sealed tubes. The samples are treated with the acid a t 150 "C for 2 h in capped test-tubes. After addition of potassium iodide solution, the hydrides are formed by mixing the solution with sodium tetrahydroborate(II1) solution in a continuousflow system, and are swept into the plasma by a stream of argon for determination by atomic-emission spectrometry. Acceptable precision and accuracy are obtained, and the detection limits for all three analytes are about 0.1 p g g-l. Approximately 200 samples can be analysed by one person in a 2-d cycle.

Keywords ; Arsenic, antimony and bismuth determination ; JLerbuge ; hydride generation ; inductively coupled plasma ; atomic-emission spectrometryIn previous papers a system for the simultaneous determination of arsenic, antimony, bismuth, selenium and tellurium in aqueous solution was described, and the characteristics of this method were reported.lP2 The elements were reduced to hydrides by sodium tetrahydroborate(II1) solution in a continuous-flow system, and the hydrides injected into an inductively coupled plasma (ICP) for determination by atomic-emission spectrometry. The system was used subsequently for the determination of arsenic, antimony and bismuth in soils3 and of selenium in soils.* This paper describes the use of the system for the simultaneous determination of arsenic, antimony and bismuth in herbage after the samples had been dry ashed in the presence of magnesium nitrate. Magnesium nitrate has been used successfully as an ashing aid in the determination of arsenic5 and antimony6 in organic matter. Its role is the prevention of loss of analytes by volatilisation or incorporation into the walls of crucibles, and leaving the analyte residue in a readily soluble form. The method combines well with hydride generation,' as the ashed residue dissolves quickly in the reaction medium, dilute hydrochloric acid (1 + l ) , and the reduction of the analytes to hydrides is unaffected by high concentrations of the magnesium ion.2

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