A low cost and sensitive procedure for lead screening in human whole blood with sequential injection-hydride generation-atomic fluorescence spectrometry

Abstract

An automated sequential injection hydride generation (HG) atomic fluorescence spectrometric (AFS) method was developed, with the aim of screening blood lead levels for Chinese citizens, especially for children. Lead hydride was generated from acid solution, with potassium ferricyanide as an oxidizing agent, by reaction with alkaline tetrahydroborate solution. The hydride was separated from the reaction medium in a gas–liquid separator (GLS₁) and swept directly into the atomizer. A thorough scrutiny was made of the various factors, including the modification of the AFS instrument and related parameters, the various wet digestion protocols, the variables of the flow system and the reaction conditions. Under the optimized conditions the blank signal was satisfactorily minimized, giving rise to a limit of detection of 0.014 μg l⁻¹, defined as 3 times the blank standard deviation divided by the slope of calibration graph, and a RSD value of 0.7% (at the 2.0 μg l⁻¹ level, n = 11), along with a sampling frequency of 120 h⁻¹. The sensitivity of the procedure was found to be significantly superior to those obtained by HG-atomic emission spectrometry (AES), direct sampling electrothermal atomic absorption spectrometry (ETAAS), tungsten filament atomizer ETAAS,and quartz tube atomizer HG-AAS; it was even lower than those by in-atomizer-trapping HG-ETAAS and comparable to ICPMS-based methods. The accuracy and practical applicability of the procedure were validated by analysing certified reference materials of frozen cattle blood GBW 09139 and GBW 09140, and further demonstrated by spiking recoveries of lead in human whole blood samples.