螯合棉纤维预富集流动注射在线测定痕量铅

将自制的性能优越、成本低廉的新型吡咯烷二硫代甲酸铵螯合棉纤维(CG-APDC)作为固相富集材料,经稀硝酸洗脱液的流动注射预富集,用石墨炉原子吸收光谱测定了痕量铅.流动注射预富集分六步完成.用稀硝酸作洗脱液,完全洗脱需0.15 mL,大大超过石墨管进样体积.实验将洗脱的前40μL定量弃去,采用定体积取样法,将浓度最高的40μL洗脱液加入GYAAS中,提高了测定的准确度.另外在石墨炉灰化阶段高记忆效应的消除中,将惯用的停气方式改为小流量(30 mL·min-1,富集1 min)气体原子化,使拖尾现象得到了明显的改善,且空白值低而稳定.考察了实验参数,如酸度,洗脱液浓度,洗脱速度及采样速率等)对分析性能的影响.采用螯合棉纤维作分离富集材料,选择性好,方法灵敏度高,可以在线分离干扰,采样速度50次·h-1.富集倍数15倍,检测下限0.2μg·L-1,相对标准偏差1.4%(n=10),回收率95%～105%,样品测定结果令人满意.

Determination of Lead with GFAAS Using Online Flow Injection

A cheap, rapid and sensitive method for the determination of trace amount of lead in water samples by graphite furnace absorption spectrometry coupled with online flow injection preconcentration with ammonium pyrrolidine dithiocarboxylate chelating cellulose (CC-APDC) was developed. There were six steps in the preconcentration of flow injection: first, 0.15 mL nitric acid was used for a complete elution, which exceeded the volume of the graphite tube, so the 40 mL solution was removed before eluting. Secondly, 40 mL maximum concentration elution solution was added to GFAAS by fixed volume sampling to improve the accuracy. In addition, traditional stopping gas measurement was substituted with small flow gas atomization (30 mL x min(-1), preconcention for 1 min) during the removal of high memory effect for ashing stage in graphite furnace, which develops tail-out phenomenon and makes blank value low and steady. Various parameters affecting the adsorption and elution, such as pH of the solution, eluent concentration, sample flow rate etc, were optimized. If miniflow in atomization step was used, the memory effect in the determination of lead by GFAAS could be removed. The CC-APDC was used for preparation and preconcentration. A good precision (RSD = 1.4%, n = 10), high enrichment factor (15) and sample throughput (50 h) with detection limit 0.12 microg x L(-1) were obtained. This method has been successfully applied to the water sample for lead determination with a recovery of 95%-105%.