塞曼石墨炉原子吸收法直接测定海水中的铬

DIRECT DETERMINATION OF CHROMIUM IN SEAWATER BY ZEEMAN GRAPHITE FURNACE ATOMIC ABSORPTION SPECTROMETRY

海水基体对Cr有增感作用。本文研究了抗坏血酸、柠檬酸三铵、酒石酸、乙酸铵等有机基体改进剂对消除基体干扰效果。前二者均有效地消除基体干扰,但1％抗坏血酸+1％柠檬酸三铵混合试剂的效果更好,它不仅可以消除基体干扰,还可降低背景及噪声,Cr的吸收峰也较平滑。本法准确,相对偏差在0.7—4.4％范围内。回收率在92—109％范围内。若海水Cr含量低于定量下限时,可采用多次进样法。

Ascorbic acid, Triaminecitrate and Tartaric acid were examined for eliminating the enhancing effect of seawater matrix on Cr signal. Both ascorbic acid (A) and Triaminecitrate (B) can eliminate the matrix effect. But a mixture of 1 % A and 1 % B is even more efficient. Besides, this mixed matrix modifier can attenuate the background signal and the noise. With P.E. Z-3030 AA spectrometer, the characteristic mass, m0 for Cr in seawater and doubled distilled water are 3.5pg and 3.4pg respectively and the detection limit (3σ) 0.11μgL-1 and 0.10μgL-1 respectively indicating that the matrix interferences are eliminated. Similar results were obtained with Hitachi 180-80 AA spectrometer. The accuracy of the method was assessed by analysing three National Sea-water Standards. The results are satisfactory. 20 seawater samples from different sources were analysed by different analysts with different models of Zeeman AA spectrometers. The recoveries are in the range of 92-109%. The method is reliable, simple and rapid.