在线流动注射螯合树脂预富集石英缝管增敏火焰原子吸收法测定水中痕量镉和铜

ON-LINE FI-PRECONCENTRATION-FAAS DETERMINATION OF CADMIUM AND COPPER IN WATER

应用高效的在线流动注射螯合树脂预富集石英缝管增敏火焰原子吸收系统直接测定水中痕量镉和铜 ,试验用内装 2 0 0 mg Amberlite XAD- 4键合的 5-磺酸 - 8-羟基喹啉螯合树脂的锥形柱 ,在 p H6条件下 ,样品流速为 6.0 ml·min-1,90 s装样 ,用 0 .5mol· L-1HCl洗脱 ,分析速度为30样·h-1分别获得 38和 40倍的富集 ,经石英缝管增敏 ,总灵敏度分别提高 1 36和 1 2 0倍 ,检出限为 0 .1和 0 .2μg· L-1。对镉和铜含量分别为 2 .0 ,5.0μg· L-1的水样连续测定 1 1次的相对标准偏差分别为 2 .8%和 3.4% ,可直接测定水体中 μg· L-1级的镉和铜。

The flowinjection system for the determination of cadmium and copper in water by on line preconcentration with chelating resin and FAAS determination with slotted quartz tube is described in this paper. The water sample is mixed with a buffer solution of pH 8.0, and then pumped through a conical column packed with 200mg of poly (8 HQ SO 3H) chelate resin, on which the cadmium(Ⅱ) and copper(Ⅱ) in the sample are adsorbed. The flow rate of the sample solution is 6.0ml·min -1 , and the sampling time is 90s. The Cd(Ⅱ) and Cu(Ⅱ) are then eluted from the resin with 0.5mol·L -1 HCl, and the eluted solution is introduced directly into the nebulizer of the atomic absorption spectrometer with a slotted quartz tube. By this FI system, the sensitivity of the determination are raised by a factor of 136 (for Cd) and 120 (for Cu) as compared with the conventional FAAS method. The detection limits (3 σ ) are found to be 0.1μg·L -1 and 0.2μg·L -1 for Cd(Ⅱ) and Cu(Ⅱ) respectively, and the RSD′s are found to be 2.8%, at the level of 2.0μg·L -1 of Cd(Ⅱ), and 3.6% at the level of 5μg·L -1 of Cu(Ⅱ). The proposed method has been successfully applied to the determination of Cd(Ⅱ) and Cu(Ⅱ) in drinking water at a sampling frequency of 30 samples per hour.