Comparison of the cold vapor generation using NaBH4 and SnCl2 as reducing agents and atomic emission spectrometry for the determination of Hg with a microstrip microwave induced argon plasma exiting from the wafer

摘要

A 2.45 GHz low power microwave micro-strip plasma (MSP) exiting the wafer and operated with Ar at atmospheric pressure was used for the optical emission spectrometric determination of Hg with the aid of a miniaturized optical fiber spectrometer with a CCD detector and the cold vapor (CV) generation technique using NaBH4 and SnCl2 as reductants.The experimental conditions were optimized with respect to the relative intensity of the Hg 1253.6 nm line and its signal-to-background intensity ratio (SBR).So as to understand the results of the optimization experiments,the excitation temperatures as measured from Ar I lines (T_(exc)) and the electron number densities (n_e) for the Ar MSP loaded with Hg vapors were determined and found to be in the range from 5500 to 6300 K and from 1.4 to 2.0 x 10~(14) cm~(-3),respectively.Under the optimized conditions,the detection limit for Hg of the CV-MSP-OES using SnCl2 as the reducing agent was found to be much lower (0.11 ng mL~(-1)) than in the case where NaBH4 was used (9 ng mL~(-1)).The linearity range was found to be up to 1 mu g mL~(-1) while the precision was of the order of 0.7-5%.The proce-dure with SnCl2 as reductant was used for the determination of Hg at a concentration of 0.2 mu g mL~(-1) in synthetic water samples containing 1 to 4% (m/v) of NaCl with an accuracy of 3% as well as in a solution of the domestic sludge standard reference material (NIST SRM 2781) with a certified concentration for Hg of 3.64 ± 0.25 mu g g~(-1) for which 3.55 ± 0.41 mu g g~(-1) was found.