C_(18)与PTFE表面收集Cd(OH)_2沉淀的比较研究及电热原子吸收光谱法测定痕量镉

An Octadecyl Immobilized Silica Beads Packed Microcolumn Versus Polytetrafluoroethylene Knotted Reactor for Cd(OH)_2 Precipitate Collection Coupled to Electrothermal Atomic Absorption Spectrometry for Cadmium Screening

C18表面被证实可有效收集Cd(OH)2沉淀。本研究比较了阀上实验室中C18微填充柱与顺序注射系统中PTFE-KR(polytetrafluorothylene-knotted reactor)编结反应器收集Cd(OH)2沉淀的性能。以NaOH为沉淀剂,在线生成的沉淀吸附在C18表面或PTFE-KR内表面而与基体分离。沉淀经HNO3洗脱后用电热原子吸收测定。当进样量为600(L时,以C18微柱和PTFE-KR为收集媒介,测得的富集系数、吸附效率(%)、精密度(%,0.05μg/L)、进样频率和检出限(ng/L)依次分别为28/14、93/48、2.1/4.7、13/20和1.7/3。测定了3种标准样品中的痕量镉,所得结果与标准值相符。

Octadecyl immobilized surface was proved to be an effective collecting medium for cadmium hydroxide precipitate. A thorough scrutiny comparison of precipitate collection and related analytical performances were made by employing a C18 microcolumn packed in a lab-on-valve system and a polytetrafluoroethylene knotted reactor （PTFE-KR）. Cadmium was isolated as hydroxide precipitate and collected on the surface of the C18 microcolumn or the inner surface of the PTFE-KR. The precipitate was afterwards quantitatively eluted with 20 μL nitric acid （ 1% ） , and the eluate was subsequently transported into the graphite tube of the electrothermal atomic absorption spectrometry （ETAAS） instrument for atomization. With a sampling volume of 600 μL, the obtained detection limits （ng/L） , enrichment factors, retention efficiencies （ % ） , precisions （%, 0.05 μg/L, n = 7） and sampling frequencies by using a C18 mieroeolumn/PTFE-KR were 1.7/3, 28/14, 93/48, 2. 1/4. 7 and 13/20, respectively. The procedure was validated by analyzing cadmium contents in three certified references materials, river sediment （CRM 320）, sea lettuce （CRM 279） and frozen cattle blood （GBW 09140）. Agreements between the obtained results and the certified values were achieved.