Microwave-enhanced cold vapor generation for speciation analysis of mercury by atomic fluorescence spectrometry

A new and simple cold vapor generation technique utilizing microwave irradiation coupled with atomic fluorescence spectrometry is developed for the speciation analysis of mercury in biological and geological samples. In the presence of formic acid, inorganic mercury (Hg2+) and total mercury (both Hg2+ and methylmercury (MeHg)) can be converted to mercury cold vapor (He) by microwave irradiation without and with H2O2, respectively. The cold vapor was subsequently released from the liquid phase and rapidly transported to an atomic fluorescence spectrometer for the mercury detection. Optimum conditions for vapor generation as well as interferences from concomitant ions were carefully investigated. The conventionally required evaporation of the remnants of acid or oxidants was avoided because no significant interferences from these substances were observed, and thus analyte loss and potential contamination were minimized. A limit of detection of 0.005 ng mL(-1) for total mercury or inorganic mercury was obtained. A precision of less than 3% (RSD) at 2 mu g L-1 of mercury species was typical. The accuracy of the method was validated by determination of mercury in geological and biological certified reference materials. The speciation analysis of Hg2+ and MeHg was achieved by controlling the conditions of microwave-enhanced cold vapor generation and validated via determination of Certified Reference Materials DORM-2, DORM-3 and a real river water sample. (C) 2012 Elsevier B.V. All rights reserved.