On-line Solid Phase Separation/Preconcentration Coupled With Hydride Generation-atomic Fluorescence Spectrometry For Arsenic Speciation

Arsenic is a ubiquitous element existing widely in air, soils, rocks, natural waters and organisms. Meanwhile, arsenic is also one of the toxic elements hazardous to human health, and the toxicity is related greatly to the existing forms of arsenic, i.e., inorganic arsenic species are more toxic than organic ones. Therefore, the speciation analysis of arsenic in biological and environmental samples is crucial not only for the evaluation of the risks of arsenic to the environment and human health, but also for the studies of the arsenic cycling and transformation as well as the molecular toxicology and epidemiology.The purpose of this work is to develop a new method for the determination and speciation of arsenic by on-line separation and preconcentration coupled with hydride generation-atomic fluorescence spectrometry.In Chapter1, a brief review is given to the recent advances of arsenic speciation and solid phase extraction separation/preconcentration techniques. The principle for the hydride generation-atomic fluorescence spectrometry is also introduced.In Chapter2, an on-line solid phase extraction separation/preconcentration procedure for the speciation of inorganic arsenic is developed based on sequential injection technique, and hydride generation atomic fluorescence spectrometry is adopted for the quantantive determination. Multiwalled carbon nanotubes (MWNTs) modified with cationic polyelectrolyte branched polyethyleneimine (BPEI) was prepared and used as the solid-phase extraction adsorbent. The obtained material was characterized by charage analysis (Zeta potential), TGA and FT-IR. At pH5.8, an adsorption efficiency of80%can be retained for As(V) using the BPEI-MWNTs packed micro-column, while the absorption efficiency for As(III) at the same condition is less than5%. The adsorbed As(V) could be readily eluted by using NH4HCO3(0.6%, m/v). With a sample volume of2.0mL, an enhancement factor of16.3for As(V) separation/preconcentation was obtained. A detection limit of0.014μg L-1was achieved within a linear range of0.05-1.50μg L-1along with a precision of3.6%R.S.D. at0.5μg L-1As(V). The determination of As(III) was realized by pre-oxidation of the sample and deduction from the total amount of arsenic. This procedure was validated by analyzing a certified reference material of human hair, achieving satisfactory agreements between the certified and the obtained values. A spiking recovery was also performed by using a snow water sample.