Sensitive determination of chromium by inductively coupled plasma mass spectrometry using chelate-enhanced nebulized film dielectric barrier discharge vapor generation

Abstract

In this work, a novel and sensitive procedure for Cr determination by inductively coupled plasma mass spectrometry (ICP-MS) with a chelate-enhanced nebulized film dielectric barrier discharge (NFDBD) vapor generation sampling system was developed. Using sodium diethyldithiocarbamate (DDTC) as a chelating reagent, the sensitivity of Cr(VI) was specifically increased 10.5-fold by the DDTC-enhanced NFDBD sampling system compared with pneumatic nebulization. The enhancement mechanism and the experimental parameters for Cr(VI) determination such as the DDTC concentration, the solution pH, the input discharge voltage and the argon (DBD plasma gas) flow rate were evaluated in detail. The interferences from the sample matrix at 10–100 mg L⁻¹ level were found negligible for trace Cr(VI) determination in the NFDBD sampling system. Under optimized conditions, the relative standard deviation for Cr(VI) was 1.4% at the concentration of 5 μg L⁻¹ and the detection limit for Cr(VI) was 0.023 μg L⁻¹. After oxidation of the Cr species to Cr(VI), the total Cr in environmental and biological samples could be sensitively determined by this DDTC-enhanced NFDBD-ICP-MS system. The determined values of the total Cr (29.8 ± 0.3 ng g⁻¹ and 402.8 ± 18.8 ng g⁻¹) in the standard reference materials of the simulated natural water sample (GBW08608) and biological tissue sample (GBW10210) agreed well with the certified values (30 ± 2 ng g⁻¹ and 0.4 ± 0.08 μg g⁻¹), respectively. It is also worth noting that this is the first report to use DBD induced vapor generation of Cr. Compared with other sampling techniques such as chemical vapor generation and electrothermal vaporization, this proposed technique has a competitive detection limit for trace Cr determination. Furthermore, it eliminates the additional reducing agent for vapor generation, and could operate with low cost and low power (≤65 W).