New method for mercury determination in microwave digested soil samples based on cold vapor capacitively coupled plasma microtorch optical emission spectrometry: Comparison with atomic fluorescence spectrometry

A new sensitive method for total mercury determination in digested soils using a miniaturized analytical system based on cold vapor capacitively coupled plasma microtorch optical emission spectrometry was developed and compared with cold vapor atomic fluorescence spectrometry as the standardized method. The soil samples were subjected to microwave digestion in aqua regia, than Hg cold vapor were chemically generated with SnCl2 and introduced via a 150 ml min− 1 Ar flow rate in the plasma microtorch operated at 10 W power level. The optical emission signal at 253.652 nm was measured with a commercially available microspectrometer. The method detection limit was 4.8 μg kg− 1 Hg, similar to that obtained in the standardized reference method. The precision of Hg determination over the concentration range of 0.27-55 mg kg− 1 was 0.8-7.7%. Analysis of six CRMs revealed a recovery of 97 ± 7% similar to 97 ± 9% found in the method based on cold vapor atomic fluorescence spectrometry. The Bland and Altman test carried out on 31 test soil samples showed no significant statistical difference between the results obtained by the proposed method and that taken as reference. The investigated analytical system can be prototyped as an alternative for the commercially existing atomic fluorescence spectrometry instrumentation. The benefits of the system are related to small size instrumentation and low analysis cost due to the low power and low Ar consumption for plasma generation.