Hollow fiber solid phase microextraction coupled to square wave anodic stripping voltammetry for selective preconcentration and determination of trace levels of mercury in liquid fuel samples

A sensitive, selective and reproducible method for quantification of mercury in gasoline and diesel samples has been developed. The procedure is based on the retention of Hg(II) in hollow fiber-supported sol-gel combined with Ambersep GT74 cation exchange resin. The retained Hg(II) was determined by square wave anodic stripping voltammetry (SQWASV) at gold nanoparticle-modified screen printed carbon electrodes (AuNPs-SPCEs). The optimization of different experimental parameters affecting the hollow fiber solid phase microextraction (HF-SPME) coupled to SQWASV (HF-SPME-SQWASV) procedure was performed using multivariate strategy. Under optimized conditions, a preconcentration factor of 854 was achieved. The repeatability (n = 20) and reproducibility (n = 10) expressed in terms of relative standard deviation (%RSD) were <3 and 5.3 %, respectively. The limits of detection and quantification in the original sample, were 1.0 and 3.0 ng L^-1, respectively. The accuracy of the developed HF-SPME-SQWASV method was tested by the analysis of spiked samples and the recovery percentages ranged from 96 to 100 %. The proposed method was applied for quantification of Hg(II) in commercial gasoline and diesel samples. The concentrations of Hg determined using the developed method was compared with those obtained using ICP-MS after microwave-assisted digestion. According to the Student t test, the results obtained were in close agreement (not significantly different at 95 % confidence level).