Jiang Guibin

Determination of methylmercury in biological samples and sediments by capillary gas chromatography coupled with atomic absorption spectrometry after hydride derivatization and solid phase microextraction

A method for the extraction and determination of methylmercury in biological samples and sediments by solid phase microextraction (SPME) combined with capillary gas chromatography–atomic absorption spectrometry (GC–AAS) has been proposed. The methylmercury chloride was converted to its hydride form by potassium tetrahydroborate (KBH4) in a closed headspace vial prior to extraction. A laboratory-assembled SPME device including a capillary fused-silica fiber and a modified microsyringe was used throughout the experiment. The extraction is an equilibrium process that depends on the methylmercury hydride partitioning between the liquid phase and the fiber. When the equilibrium was reached, the fiber was directly transferred to a GC column by means of the microsyringe, where the analyte was thermally desorbed inside a heated injector and subsequently the column effluent was atomized by a heated stainless steel tube and detected by an on-line coupled AAS. Several factors affecting the SPME procedure such as fiber pretreatment with hydrofluoric acid, pH buffering, addition of salt and sampling time have been investigated and optimized. The reproducibility of the SPME procedure was 91% and the detection limit based on the signal equal to 3 times the baseline noise, was 26 ng. The method was applied to determination of methylmercury in biological samples and sediments.

Organic mercury speciation in fish by capillary gas chromatography interfaced with atomic absorption spectrometry

SummaryA rapid method for the speciation of mercury in fish has been described. Organomercurials in benzene extract were separated by glass capillary gas chromatography and detected by atomic absorption spectrometry. Spiked alkylmercury in fish yielded 95% recovery with one single extraction with benzene. The absolute detection limit was about 1.0×10−10 g mercury. The method can be applied to the determination of 0.04 ppm of mercury in a 0.5 g sample.

Determination of alkylselenides by gas chromatography–electrothermal atomic absorption spectrometry

A method for the determination of alkylselenides by gas chromatography (GC)–electrothermal atomic absorption spectrometry is proposed. Dimethylselenide, diethylselenide and dimethyldiselenide were separated by GC, followed by introduction of the separated compounds into a graphite furnace sequentially; the compounds were then adsorbed onto the palladium coated graphite furnace wall. Sufficient time was allowed for operation of the furnace programme during the time interval between each elution peak. The sensitivities expressed as characteristic mass giving 0.0044 absorbance are 0.018, 0.012 and 0.030 ng of selenium in dimethylselenide, diethylselenide and dimethyldiselenide, respectively. The proposed method was applied to the determination of organic vapour-phase selenium evolved from soil.

Headspace solid‐phase microextraction of butyltin species in sediments and their gas chromatographic determination

A rapid and solvent-free procedure for the simultaneous determination of mono-, di-, and tributyltin in sediments by headspace solid-phase microextraction (SPME) is described. The butyltin chlorides present in sediments were converted into their hydride forms by potassium tetrahydroborate prior to extraction. A quartz fiber coated with 100 mum film of polydimethylsiloxane (PDMS) is introduced into the headspace over the matrix to extract butyltin hydrides. After extraction, the fiber is directly inserted into the injector of the gas chromatograph (GC) for desorption, separation, and quantification. A laboratory modified flame photometric detector using quartz surface-induced tin emission (QSIL-FPD) was used throughout the experiment. The detection limits obtained with SPME-GC-QSIL-FPD for mono-, di-, and tributyltin are 8.8, 0.16, and 0.05 ng/g as Sn, respectively. The proposed method has been validated by analyzing standard reference material CRM-462, and successfully used for the determination of butyltin compounds in sediment collected from coastal areas of Hong Kong.

Determination of organomercurials in air by gas chromatography-atomic absorption spectrometry

A method for the determination of nanogram amounts of dimethyl- and diethylmercury and methyl- and ethylmercury chloride in air has been developed by using gas chromatography interfaced with atomic absorption spectrometry. The mercury species were separated using dual columns connected in parallel. After separation the compounds were cracked in a furnace and the resulting free mercury was passed through the optical cell of an atomic absorption instrument tuned to the mercury resonance line at 253.7 nm. Parameters including the type of column packings, the temperature of the pyrolyser and the optimum gas flow-rate were studied. The detection limits are 0.2 ng of mercury for dimethylmercury and diethylmercury and 0.5 ng of mercury for methylmercury chloride and ethylmercury chloride. Analytical results for air sampled from different sources are presented.

Vitellogenic responses of male Chinese loach (Misgurnus anguillicaudatus) exposed to the individual or binary mixtures of 17β-estradiol and nonylphenol

Male Chinese loaches were exposed to 17β-estradiol (E2) and nonylphenol (NP) both singly and in combination for 42 days using semi-static waterborne exposure system. Plasma vitellogenin (Vtg) was chosen as determining endpoint. The results demonstrated that 0.5 μg/L E2 could induce the enhancement of Vtg contents in male Chinese loaches after exposure for 21 days, which showed a time-related increasing manner; NP was also estrogenic to male Chines loach, and the vitellogenic responses showed in a time-and dose-related manner, which was less potent than that of E2. The binary mixtures of E2 and NP can significantly elicit the production of Vtg in male Chinese loaches, which was more potent than that of individual compounds, and Vtg induced in the binary mixture groups was higher than the summation of Vtg induced in the corresponding single-compound groups at the same concentration.