Cross double point discharge as enhanced excitation source for highly sensitive determination of arsenic, mercury and lead by optical emission spectrometry

Abstract

A new cross double point discharge (CrossPD) microplasma was designed as an excitation source to construct a miniaturized optical emission spectrometer with hydride generation (HG) for sample introduction. The CrossPD was designed with four electrodes arranged as a cross to generate a discharge with an enlarged microplasma region for improved excitation capability. The gaseous analyte generated in the HG process was transported to and intercepted by the enlarged discharge; thus most of it had to enter into the microplasma and participated in the excitation process instead of bypassing the microplasma area as in a conventional single point discharge (SinPD). Under optimized conditions, examples of arsenic, mercury and lead were successfully determined, with limits of detection (LODs) of 2.4, 0.15 and 1.9 μg L⁻¹, respectively, and relative standard deviations all less than 4% (n = 5, at concentrations of 50, 10 and 50 μg L⁻¹, respectively). Compared with a traditional SinPD for excitation, the analytical sensitivities for As, Hg and Pb were improved by 3–4 times. Its reliability and practicability were demonstrated by the analysis of Certified Reference Materials (CRMs, including water, soils, cosmetics and biological samples) and real water samples. This provides a useful scheme to enhance the analytical performance of discharge microplasma based miniaturized atomic emission spectrometers, and would be promising in the field analysis of As, Hg, Pb and other elements.