2-(2-喹啉偶氮)-1,5-二氨基苯固相萃取光度法测定钴

CHROMOGENIC REACTION OF COBALT(Ⅱ) WITH 2-(2-QUINOLYLAZO)-1,5-DIAMINOBENZENE AND ITS SOLID-PHASE EXTRACTION AND PHOTOMETRY

合成了新试剂2 (2 喹啉偶氮) 1,5 二氨基苯(QADAB),研究了其与钴的显色反应及C18固相萃取小柱对显色络合物的固相萃取,在pH3.5磷酸盐缓冲介质中,CTMAB存在下,QADAB与钴反应生成2∶1稳定络合物,该络合物可用C18固相萃取小柱富集,小柱上富集的络合物用乙醇(内含2%乙酸)洗脱后用光度法测定,λmax=590nm,ε=8.36×104L·mol-1·cm-1。钴含量在0.01～0.80mg·L-1内符合比耳定律,方法用于环境样品中钴含量的测定,结果满意。

A new chromogenic reagent, namely 2-(2-quinolylazo)-1,5-diaminobenzene (QADAB) was synthesized and its molecular structure was identified by methods of elementary analysis, IR-spectroscopy, NMR and MS. It was found that in a phosphate buffer medium of pH 3.5 and in the presence of CTMAB, QADAB reacts with Co(Ⅱ) ion to form a stable coordination complex with the mole ratio (R∶Co) of 2 to 1. The Co-QADAB complex in 50ml of solution was concentrated on a C_(18) solid-phase extraction column by passing the solution through the column at a flow-rate of 10ml·min^(-1). The solution in the column was removed by suction. The Co-QADAB complex was then eluted with 2.5ml of ethanol, which contains 2% (by volume) of acetic acid. The eluate was transfered to a micro absorption cell of 1cm in light-path and of a volume of 0.5ml. Its absorbance was measured at its λ_(max) 590nm, with reagent blank as reference solution. Beer′s law holds in the range of 0.01～0.80mg of Co(Ⅱ) per liter of solution, with a molar absorptivity of 8.36×10~4L·mol^(-1)·cm^(-1) at 590nm. This method has been applied to the analysis of environmental samples. RSD′s found were less than 3%. Recoveries were found in the range from 96%～105%. Results obtained by this method checked quite well with those obtained by AAS method.