Application of flow injection–green chemical vapor generation–atomic fluorescence spectrometry to ultrasensitive mercury speciation analysis of water and biological samples

Abstract

A simple, non-chromatographic and green method based on flow injection UV photochemical or ultrasonic vapor generation atomic fluorescence spectrometry (AFS) was developed for the determination and speciation analysis of mercury. Mercury cold vapor (Hg0) was generated by using only formic acid and UV or ultrasonic irradiation, and was subsequently detected by AFS. Both mercury (Hg2+) and methyl mercury (MeHg) can be converted to Hg0 for the determination of total mercury with UV irradiation, while only Hg2+ can be reduced to Hg0 with ultrasonic irradiation, thus determining only Hg2+. Then, the concentration of MeHg can be calculated by subtracting the Hg2+ concentration from the total mercury concentration. The optimal conditions for the best cold vapor generation efficiencies are discussed in detail, together with interference from transition metals. This new speciation analysis not only provides high sensitivity for the determination of mercury species but further eliminates the use of toxic reducing reagents and avoids potential destruction of analyte species that occur in chromatographic separation. Moreover, a simpler and less toxic Hg2+ standard series can be used for the calibration of both Hg2+ and MeHg. The limit of detection is 0.005 or 0.01μgL−1 for total mercury with the UV or inorganic mercury with the ultrasonic irradiation, respectively. This method was successfully applied to ultrasensitive mercury speciation analysis of water and biological samples.