分散液-液微萃取—石墨炉原子吸收光谱法测定茶叶中的痕量铅

Dispersive liquid-liquid microextraction for separation/preconcentration and determination of lead by graphite furnace atomic absorption spectrometry in tea samples

研究了分散液-液微萃取（DLLME）分离富集茶叶中的铅,并用石墨炉原子吸收光谱法（GFAAS）测定的新方法,以8-羟基喹啉（8-HQ）为配位剂、四氯化碳为萃取剂、丙酮为分散剂,详细考察了pH值、8-HQ用量、萃取剂体积、萃取时间等因素的影响。在最佳条件下,铅离子在0.2~10.0μg/L浓度范围内线性关系良好,检出限为0.045μg/L,对1.0μg/L和5.0μg/L铅标准溶液进行11次平行测定,相对标准偏差（RSD）为3.72%和3.25%。将建立的方法应用于市场销售的7种茶叶样品（16个）中铅的检测,12.5%的茶叶样品铅含量大于国标5.0mg/kg。该方法具有简便、快速、准确等优点,可作为茶叶中铅的检测方法。

A new procedure for the determination of lead in tea samples by dispersive liquid–liquid micro extraction separation and graphite furnace atomic absorption spectrometry（GFAAS）is presented.In the proposed approach,8-hydroxyquinoline（8-HQ）,carbon tetrachloride and acetone were selected as chelating agent,extraction solvent and disperser solvent,respectively.Some effective parameters on extraction and complex formation,such as extraction and disperser solvent type and their volume,pH,concentration of the chelating agent and extraction time have been studied.After extraction,the detection limit for lead was0.045μg/L.A good relative standard deviation（RSD）were 3.72%and 3.25%for eleven repeated determinations at a concentration of 1.0and 5.0μg/L.The method was applied in the analysis of seven tea samples,and Pb content in 12.5% of 16 samples was over 5.0mg/kg.This method is simple,rapid and accurate for determination of lead in tea samples.