Photo-induced chemical vapour generation with formic acid: novel interface for high performance liquid chromatography-atomic fluorescence spectrometry hyphenated system and application in speciation of mercury

Abstract

Based on a novel photo-induced chemical vapour generation (CVG) with formic acid instead of the conventional K 2 S 2 O 8 /KBH 4 system, an on-line coupled HPLC and atomic fluorescence spectrometry procedure was developed for the speciation of inorganic mercury, methylmercury (MeHg), ethylmercury (EtHg) and phenylmecury (PhHg). Under UV irradiation, the decomposition of organic mercury species and the reduction of Hg 2+ could be completed in one step with this proposed photo-induced CVG system. The novel CVG system used formic acid only, which simplified the flow system and avoided the possibility of contamination originating from additional chemicals. A number of operating parameters including organic acid species, concentration of formic acid, pH, flow rate of formic acid and flow rate of carrier gas were optimized, and comparable method sensitivities with the conventional K 2 S 2 O 8 /KBH 4 system were obtained. The limits of detection at the optimized conditions were 0.81, 0.20 and 0.87 mg L À1 forMeHg, EtHg and PhHg, respectively. The developed method was validated by determination of certified reference material DORM-2 and was further applied in determination of seafood samples. The new CVG system is simple, environmentally benign, and inexpensive for the speciation analysis of mercury. It is expected to have similar applications in other analytical atomic spectrometric techniques as well as speciation of other organic metal compounds.

Simple interface of high-performance liquid chromatography–atomic fluorescence spectrometry hyphenated system for speciation of mercury based on photo-induced chemical vapour generation with formic acid in mobile phase as reaction reagent

“…Lower sensitivity was observed for Hg(II) than other organomercurial species in this UV-CVG system. Similar phenomena were observed in UV-CVG system with formic acid [24] and mercaptoethanol [26]. The reason is not known and further investigation is required to elucidate these phenomena.…”

“…Other conditions were given in Table 1. calculated from the flow rate and the inner volume of the PTFE reaction coil. The shorter reaction time than post-column mix [24] perhaps ascribed to a higher energy mercury UV lamp used.…”

“…Also, direct vapour generation of mercury species on nano-TiO 2 under UV irradiation in the presence of a formic acid and sodium formate mixture was developed as interface of HPLC-AFS for speciation of mercury [23]. Based on photo-induced CVG with formic acid instead of the conventional K 2 S 2 O 8 /KBH 4 system, we recently developed an on-line coupled HPLC-AFS procedure for the speciation of inorganic mercury, methylmercury (MeHg), ethylmercury (EtHg) and phenylmecury (PhHg) [24]. This procedure was based on a post-column mix and reaction with formic acid.…”

Recent advances in speciation analysis of mercury, arsenic and selenium

“…Under UV irradiation, the chromatographic eluent was firstly mixed with formic acid. Then, under UV irradiation, organomercurials (MeHg, EtHg and PhHg) can be transformed to elemental Hg vapor and then detected by AFS [87,88] or ICP-MS [89]. Nano-TiO 2 photocatalysis can catalyze the reductive decomposition of organomercurials to elemental Hg [87,89].…”

Mercury speciation by a high performance liquid chromatography—atomic fluorescence spectrometry hyphenated system with photo-induced chemical vapour generation reagent in the mobile phase

“…Moreover, UVinduced photocatalytic reactions can not only reduce metal cation to its zero or low-valent species, but also degrade organometallic species to inorganic species [7]. Therefore, photo-induced chemical vapour generation was coupled with HPLC and AFS for the speciation analysis of mercury [8,9]. Under UV irradiation, chromatographic eluent was mixed with formic acid in the presence [8] or absence [9] of TiO 2 photo-catalysis.…”