石墨炉原子吸收光谱法直接测定痕量Cr及其价态

DIRECT DETERMINATION OF TRACE Cr(Ⅲ)AND Cr(Ⅵ) BY GRAPHITE FURNACE ATOMIC ABSORPTION SPECTROMETRY

利用Cr(Ⅲ)与三氟乙酰丙酮(TFA)形成易挥发的络合物Cr(TFA)_3,沸点128℃,在四甲基氢氧化铵和乙酸钠存在下,在400℃左右Cr(Ⅲ)可从石墨炉中定量除去,而cr(Ⅵ)在<1200℃条件下定量存留在石墨管中,建立了一种用石墨炉原子吸收光谱法直接测定Cr(Ⅲ)和Cr(Ⅵ)的方法。该法用于地表水、血清及尿样中铬的不同价态或总量测定。经方法考验,变异系数分别为7.2％,5.0％,4.3％;回收率为96％～108％,94％～106％,98％～108％,方法的线性范围0～40μg·(L_-)~1,检出限为102ng。

A direct, sensitive and rapid method for the determination of chromium and valency states of chromium in serum, urine and surface water by grapihte furnace atomio absorption spectrophotometry is presented. The addition of a mixture of trifluoroacetylacetone, 25％ tetramethyl-ammonium hydroxide and 0.5mol·L^(-1) sodium lacetate (1:10:10) to a sample, Cr(Ⅲ) can quantitatively be removed from a graphite tube at 400℃ while Cr(Ⅵ) quantitatively remaine in the furnace up to a temperature of 1200℃. Possible interferences from cations and anions are tried and it is shown that if their quantities below certain limit, the analyses of chromium will not be affected. The calibration graphs are linear in the range of 0 to 40ng for chromium. The detection limit is 1.02×10^(11)g and relative standard deviation of 10 determinations for samples at ng magnitude is less than 7.2％, whereas the recoveries for Cr(Ⅲ+Ⅵ) and Cr(Ⅵ) are 96％～108％ and 98％～108％ respectively.