A sequential solid phase microextraction system coupled with inductively coupled plasma mass spectrometry for speciation of inorganic arsenic

A sequential solid phase microextraction (SPME) system consisting of two monolithic capillary columns was developed for simultaneous separation and preconcentration of inorganic arsenic, followed by inductively coupled plasma mass spectrometry (ICP-MS) detection. The N-(beta-aminoethyl)-gamma-aminopropyltriethoxysilane (AEAPTES) incorporated organic-inorganic hybrid monolithic column was prepared in situ by sol-gel technology in a fused capillary and employed as the extraction medium for SPME in this system, because the amino active sites on the synthesized monolith possess a high adsorption selectivity for As(V). With the on-line design of dual columns and an oxidation coil, As(V) is quantitatively extracted by the first column, and As(III) in the effluent can be quantitatively extracted by the second column after oxidization to As(V) by a make-up KMnO4 solution. The retained As(V) or As(III) is then sequentially eluted by diluted HNO3 and introduced to ICP-MS for determination. In this work, the parameters effecting the retention and elution of As(V) and As(III) were optimized in detail. On-line SPME of 1 mL sample solution gave a signal enhancement factor of 60 for both As(V) and As(III) using the system. The precision (RSD) for six replicate measurements of 1 mu g L-1 As(V) and As(III) were 3.8% and 3.2%, respectively. The limits of detection (LODs, defined as three times the signal-to-noise ratio) for As(V) and As(III) were 0.005 mu g L-1. The developed method was successfully applied to the speciation analysis of inorganic arsenic in drinking and environmental waters with satisfactory recoveries.