SIMPLEX OPTIMIZATION OF CONDITIONS FOR THE DETERMINATION OF ANTIMONY IN ENVIRONMENTAL-SAMPLES BY USING ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

Analysis of the total antimony in plant material was unsuccessful usin g the electrothermal atomic absorption spectrometry (ETAAS) conditions recommended by the instrument manufacturer. For this reason, an optim isation procedure utilising the Plackett-Burman method, simplex optimi sation and visualisation of the generated response surface via princip al components analysis, was carried out. The Plackett-Burman method wa s used to eliminate four of the initial variables chosen. Four variabl es (atomisation temperature, atomisation time, ash temperature and mod ifier concentration) were subsequently optimised using the composite m odified simplex method and the results were visualised as a contour di agram, after reduction to two principal components. The optimised cond itions were used for the analysis of both an acid digested pine needle standard reference material (NIST 1575) and a pond weed sample, colle cted from a contaminated site at Yellowknife Bay, Yellowknife, NWT, Ca nada. The total concentration of antimony present in the pine needles was statistically indistinguishable from the non-certified value, as w as the value for the pond weed sample, compared with a value determine d by neutron activation analysis (NAA). The results for the analysis o f the pond weed sample by ETAAS agreed with those obtained from a subs equent analysis by inductively coupled plasma-mass spectrometry. (C) 1 997 Elsevier Science B.V.