Silica Gel Chemically Modified with Ionic Liquid as Novel Sorbent for Solid-Phase Extraction and Preconcentration of Lead from Beer and Tea Drink Samples Followed by Flame Atomic Absorption Spectrometric Determination

Abstract

Lead is a harmful metal element that has aroused considerable concern; therefore, it is of great importance to develop sensitive and reliable analytical techniques for the precise monitoring of lead in various foodstuffs. In the present study, an enrichment and separation procedure for lead via its solid-phase extraction as dithizone chelate on an ionic liquid 1,3-di(n-butyl) imidazolium hexafluorophosphate [DnBIM][PF₆]-chemically modified silica gel has been established prior to its flame atomic absorption spectrometric determination. The parameters that affect the extraction recovery of lead was investigated, including sample pH, dithizone concentration, eluent type and volume, and flow rate of sample and eluent. The analytical performance of the method was evaluated. Under the optimized conditions (sample pH, 8.0; dithizone concentration, 0.0005 % (w/v); eluent, 2 mL of 1.0 mol/L HNO₃; sample flow rate, 3 mL/min; eluent flow rate, 0.5 mL/min), the limit of detection was 0.36 μg/L (3σ, n = 7), and the relative standard deviation was 3.5 % (c = 5.0 μg/L, n = 7). The proposed method was successfully applied to the determination of trace lead in beer and tea drink, and the recoveries for the spiked samples were in the range of 97.3–102.5 %.