微珠析相微萃取-石墨炉原子吸收法测定岩石样品中痕量铬

采用二苯碳酰二肼为络合剂,正戊醇为萃取剂,乙醇为助溶剂,建立了微珠析相微萃取-石墨炉原子吸收法测定地质样品中痕量Cr的分析方法。实验详细探讨了微珠析相微萃取的析相条件、石墨炉原子吸收工作参数及共存离子的干扰,优化了体系萃取条件。实验结果表明:微珠析相微萃取既起到了分离富集的作用,在石墨炉升温程序中又起到了基体改进剂的作用;当萃取剂用量为0.2~1.5 mL时,使之与水完全互溶所需助溶剂体积约为水相体积的0.2~0.5倍;方法线性范围为0~10μg.L-1,检出限为0.057μg.L-1,相对标准偏差(RSD)为3.3%(c=2.5μg.L-1,n=11);当萃取剂用量为1.5 mL、水相体积15 mL时,与直接溶液进样相比其灵敏度可提高10倍。所建立的方法用于地质标准参考物质AGV-2和G-2中Cr的测定,测定值与参考值具有较好的一致性。

Determination of Trace Chromium in Rock Samples by Graphite Furnace-AAS after Microsphere Phase Separation Extraction

A new method for the determination of trace chromium in geological samples by graphite furnace atomic absorption spectrometry (GFAAS) with microsphere phase separation extraction was developed. With the existence of cosolvent of ethanol and solvent of 1-amylalcohol, the diphenylcarbazide reacted with Cr to form a complex in a homogenous phase. Then the complex was separated out with microsphere from the homogenous phase after a little water was added in the system. The operating conditions for phase separation and the heating program of graphite furnace were experimented and optimized. The interference of co-existent ions was studied. The results indicated that the microsphere phase separation extraction can be used to separate and extract the analyte, and also the microsphere can be used as the matrix modifier in the heating program of graphite furnace. As the cosolvent, the dosage of ethanol was about 0.2-0.5 times of the volume of water with the existence of 0.2-1.5 mL 1-amylalcohol. Under the optimum conditions, the linear range of the method was 0-10 microg x L(-1) and the detection limit was 0.057 microg x L(-1) with the relative standard deviation (RSD) of 3.3% (n=11). The concentration factor was 10 with 15 mL of water and 1.5 mL of 1-amylalcohol. The method has been applied to determine the concentration of Cr in geological samples and the analytical results are in agreement with the certified values.