Headspace Solid-Phase Microextraction Coupled to Miniaturized Microplasma Optical Emission Spectrometry for Detection of Mercury and Lead.

Despite increased interest in microplasma atomic spectrometry over the past several years, its applications to field analysis of real samples still remain limited due to its low sensitivity. In this work, headspace solid-phase microextraction (HS-SPME) using PDMS/DVB fiber was used as a sample introduction method to improve the sensitivity of a miniature (6.0 cm length × 5.0 cm width × 2.8 cm height) low power (<10 W) microplasma point discharge optical emission spectrometer (PD-OES) for the determination of Hg and Pb after their derivatization with sodium tetraethylborate (NaBEt4). Owing to its advantages of combining sampling, separation, and preconcentration of analytes from sample matrices into a single step, HS-SPME not only simplifies sample pretreatment and the experimental setup but also eliminates interferences from matrices and water vapor while significantly improving analytical performance. In comparison to photochemical vapor generation PD-OES, limits of detection for Hg and Pb were enhanced by at least 100-fold, providing great potential for field analysis of these and other trace elements in real samples. Under optimal conditions, the limits of detection for Hg and Pb were 0.001 and 0.003 μg L-1, respectively, with relative standard deviations (RSDs) better than 2.1% and 4.5% at a concentration of 1 μg L-1. The accuracy of the HS-SPME-PD-OES system was validated by analysis of three Certified Reference Materials, including DORM-4 (Hg, 412 ± 36 μg kg-1; Pb, 404 ± 62 μg kg-1), TORT-3 (Hg, 292 ± 22 μg kg-1; Pb, 225 ± 18 μg kg-1) and SRM1568b (Hg, 5.53 ± 0.58 μg kg-1), providing analytical results in excellent agreement with certified values at the 95% confidence level. This method was also successfully used for the analysis of several real rice and water samples with satisfactory results (90-130% recoveries of added spikes).