Trace arsenic analysis in edible seaweeds by miniature in situ dielectric barrier discharge microplasma optical emission spectrometry based on gas phase enrichment

Abstract

In this work, a novel method using low-cost miniaturized hydride generation optical emission spectrometry equipment coupled with an in situ dielectric barrier discharge trap (HG-in situ DBD trap-OES) was established for the determination of As in edible seaweed samples. An improved peak volume algorithm, where the start time point and end time point of the spectrum at each concentration are determined according to the unified judgment criteria, was first proposed to extend the linear range from 1–100 μg L⁻¹ to 1–200 μg L⁻¹, and increase the sensitivity by about 30%. In addition, a modification was done on the DBD implementation, providing an enhancement of sensitivity by a factor of about 4 for As. All in all the detection limit (LOD) was improved from 0.5 μg L⁻¹ to 0.2 μg L⁻¹. By applying the method to seaweed samples, a method detection limit (MD) of 0.25 mg kg⁻¹ was achieved, with less than 3% relative standard deviations (RSDs). The calibration linearity reached R² > 0.990 in the 1.25–250 mg kg⁻¹ range. Results obtained by the proposed method showed good agreement with that of certified reference materials (CRMs), and spiked recoveries were 103% to 114%, indicating favorable accuracy. The proposed method is attractive in terms of instrumentation size (0.6 m × 0.5 m × 0.3 m), power consumption (<60 W), manufacturing cost, and gas consumption (300 measurements for 4 L compressed Ar/H₂ gas), and therefore more advantageous than conventional atomic spectrometric methods.