Multivariate optimisation of hydride generation procedures for single element determinations of As, Cd, Sb and Se in natural waters by electrothermalatomic absorption spectrometry

Continuous flow hydride generation procedures for As(III), total inorganic As, Cd, total inorganic Sb, Se(IV) and total inorganic Se from sea and hot- spring water samples were optimised by experimental designs. Ir-coated grap hite tubes were used as preconcentration and atomisation medium of the hydr ides generated. Several factors affecting the hydride generation efficiency were studied. Results obtained from Plackett-Burman designs suggest that s odium borohydride flow rate and reduction coil length, are significant fact ors for total inorganic arsenic hydride generation. For cadmium hydride gen eration the significant factors are hydrochloric acid concentration, hydroc hloric acid and sodium borohydride flow rates and reduction coil length. Fo r total inorganic antimony hydride generation the factors affecting the hyd ride generation procedure are hydrochloric acid and potassium iodide concen trations and reduction coil length; finally, pre-reduction coil length and oven temperature for the pre-reduction step are statistically significant f actors for total inorganic selenium hydride generation. In addition, the fa ctors studied for the arsenic and selenium hydride generation from As(III) and Se(IV) are not significant. From these studies, the sinificant variable s were optimised by central composite designs. Validation carried out analy sis on three reference materials: SLRS-4 (Riverie water), CASS-3 (seawater) and NIST-1643d. (C) 2001 Elsevier Science B.V. All rights reserved.