Coupling of cold vapor generation with an atmospheric pressure glow microdischarge sustained between a miniature flow helium jet and a flowing liquid cathode for the determination of mercury by optical emission spectrometry

Abstract

A direct current atmospheric pressure glow microdischarge (dc-mAPGD), generated between a miniature flow He jet nozzle anode and a small-sized flowing liquid cathode, was combined with a continuous flow cold vapor generation (CVG) system to improve the sensitivity of the determination of Hg by optical emission spectrometry (OES). In this arrangement, Hg(II) ions were converted to cold vapor in the reaction with NaBH 4 and subsequently delivered in a stream of He carrier/jet-supporting gas to the microdischarge through the nozzle anode. Additional He shielding gas was used to prevent discharge zones from the access of ambient air. A vertical distribution of emission from the Hg I 253.7 nm line between both electrodes was acquired, and the highest response for Hg was established in the nearanode region of the microdischarge. Several operating parameters that affect the CVG reaction and discharge were optimized. Under compromised conditions, the intensity of the Hg I line was improved over 4000 times compared to that obtained in a mAPGD-OES system without the CVG system. The efficiency of CVG of Hg and its transport to the microdischarge was evaluated to be 98 AE 1%. For comparison, in the mAPGD system without CVG, the efficiency of sputtering was merely lower by about 20%, i.e., 77 AE 4%. A likely explanation of the enhancement of Hg response observed for CVG-mAPGD was discussed. The detection limit (DL) of Hg assessed for CVG-mAPGD-OES was 0.14 mg L À1 (3s criterion). To assess the accuracy of the new method, Hg was quantified in a certified reference material (CRM) of human hair (NCS ZC 81002). Excellent agreement between certified and measured concentrations of Hg was obtained. In addition, recoveries of Hg added to samples of different waters were evaluated. They were in the range of 96-103% proving the good accuracy of CVG-mAPGD-OES.The repeatability of the signal over the linearity concentration range of 5-500 mg L À1 of Hg was within 2.1-4.1% (as relative standard deviation, RSD).

On the coupling of hydride generation with atmospheric pressure glow discharge in contact with the flowing liquid cathode for the determination of arsenic, antimony and selenium with optical emission spectrometry

“…He shielding gas passing through the discharge chamber was primarily used to remove H 2 O vapor and prevent the discharge from contact with ambient air, which both have recently been recognized to affect the performance of APGD [28]. When the flow rate of this gas was increased up to 2.1 L min À 1 the emission from As was practically constant.…”

“…Emission spectra of the discharge were acquired with a 0.01 nm step and an integration time of 0.1 or 0.5 s. Profiles of emission lines were recorded in $ 1.0-1.5 nm spectral windows. Further details on the optical detection arrangement are described in the paper [28].…”

“…A continuous flow HG system has already been described in details in our recent paper [28]. Volatile hydrides of As, Sb and Se along with H 2 were swept into the near-anode region of APGD through the stainless steel nozzle.…”

“…In our recent paper [28], a successful coupling of atmospheric pressure glow discharge (APGD) generated between a small-sized liquid flowing cathode (LFC) and a He jet with cold vapor generation (CVG) of Hg has been demonstrated. The proposed approach led to the improvement of the LOD of Hg by 4 orders of magnitude (as compared to a corresponding APGD system with conventional sputtering of Hg from a LFC solution).…”

Sono-induced cold vapour generation interfaced with capacitively coupled plasma microtorch optical emission spectrometry: analytical characterization and comparison with atomic fluorescence spectrometry

“…33,38,39 Our detection limit was also better than 2.8 mg L À1 achieved by Abdul-Majeed et al by cold vapour dielectric barrier discharge microplasma optical emission spectrometry (CV-DBD-OES). 40 On the other hand, the detection limit in SICV-mCCP-OES is poorer than 0.08 ng L À1 , reported by Yuan et al in cold vapour atmospheric pressure pulsed direct current microplasma optical emission spectrometry (CV-Pdc-OES) using additional puried SnCl 2 and Hg preconcentration by gold amalgamation.…”