STUDY OF THE DETERMINATION OF TRACE AMOUNTS OF CHROMIUM BY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY WITH A POLY(TETRAFLUOROETHYLENE) SLURRY AS A CHEMICAL MODIFIER

Using poly(tetrafluoroethylene) (PTFE) slurry as a chemical modifier, the process of vaporization and atomization of Cr in a graphite furnac e for electrothermal atomic absorption spectrometry was investigated. It was shown that PTFE could react with Cr to form chromium fluoride a nd suppressed the formation of refractory metal carbides. The addition of PTFE clearly enhanced the analytical sensitivity of Cr and signifi cantly reduced the interferences of a 10(3)-10(4)-fold excess of matri x elements. The detection limit (DL) and characteristic mass (m(ch)) o f the conventional method are 9.6 and 24.5 pg (Cr), respectively, wher eas with PTFE the best DL and m(ch) values of the proposed method are 2.73 and 10.0 pg (Cr), respectively. The calibration graph is linear i n the range 5-80 ng ml(-1) (Cr) with RSDs of 1.1-6.6%. The method was applied to the determination of trace amounts of Cr in surface water a nd copper chloride samples. The Cr recoveries from the samples were 96 .4-103.7%.