The Application and Development of Electrochemical Hydride Generation in Atomic Spectrometry Analysis

Electrochemical hydride generation (EcHG) is an effective gas sampling method developed for atomic spectrometers. Electrode reactions are adopted in an electrochemical cell to generate hydride and mercury vapor in the cathode chamber for EcHG instead of traditional chemical reducing method. Compared with the traditional KBH₄ (NaBH₄)-acid chemical system, no other chemical reagents but the supporting electrolyte is needed for EcHG as electron transfer plays the reducing role instead of the reducing reagents. For EcHG, hydride and mercury vapor are directly led to the atomizer from the cathode chamber for determination. The analysis price and time for making up solutions are decreased in large degree meanwhile the blank value introduced from the analytic process is reduced remarkably for EcHG. Moreover, EcHG is lower pollution and more environmental friendly due to none chemical reagent used. Recently, rapid development has been made for atomic spectrometry analysis including Atomic Fluorescence Spectrometry (AFS), atomic Absorption Spectrometry (AAS), Atomic Emission Spectrometry (AES) coupled with electrochemical hydride generation. The analytical range for this technology has been extended to speciation analysis from only total amount of element analysis. The requirement for trace or even ultra trace detection has gradually been satisfied instead of merely micro-analysis. As for the analytical performance, most of the regular chemical hydride generated elements are covered, including As, Se, Pb, Cd, Sn, Sb, Ge and Hg. Generally, μg/L level can be achieved for the detecting limits of characteristic elements by EcHG coupled with AAS and Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES). While for EcHG-AFS, it can be reduced to 0.1 μg/L (ng/L level for mercury). The relative standard deviations are lower than 10%. The spiked recoveries are 90%-110% and determination results for standard matters are favorable. A series of real samples (foods, tobacco, fodder, etc) were successfully analyzed by this technique. The related study on mechanism has already started, by which theoretical support for this technique is supplied and it can also be found naturally. Nevertheless, the analytical range for this technique has been only focused on inorganic species of certain elements, and the organic species are still expected to be analyzed, which forms a hot and difficult spot in this area. Based on the previous studies, the mechanism for EcHG, the further configuration optimization of the electrolytic flow cell, and the extension of elemental speciation range will become the potential developing trends for this technique.