微波萃取高效液相色谱-冷原子荧光光谱法测定沉积物中甲基汞和无机汞

建立了微波萃取高效液相色谱-冷原子荧光光谱法(MAE-HPLC-CVAFS)测定沉积物中甲基汞(MeHg+)和无机汞(Hg2+)的方法。以0.1%(V/V)2-巯基乙醇为萃取剂,用于沉积物样品中汞形态的萃取,在80℃下萃取8 min,萃取液直接注入HPLC-CVAFS系统分析。在优化条件下,MeHg+和Hg2+的检出限分别为0.58和0.48 ng/g;加标回收率分别为96.2%和95.8%;RSD(n=6)分别为5.7%和4.1%。对标准参考物质(IAEA-405和ERM-CC580)的分析结果与推荐值一致。本方法简单、快速、准确、检出限低,抗干扰能力强,具有很好的实用性和推广价值。     

Determination of methyl- and ethylmercury in natural waters at sub-nanogram per liter using SCF-adsorbent preconcentration procedure

An analytical procedure for determining methyl- and ethylmercury (MeHg/EtHg) in natural waters is described. MeHg/EtHg was preconcentrated from water on a sulfhydryl cotton fiber (SCF) adsorbent and eluted with a small volume of a mixture of 1 M hydrochloric acid and 2 M sodium chloride. The eluate was extracted with benzene. The measurements of MeHg/EtHg in benzene extract were determined by gas chromatography with electron capture detector. The detection limit for MeHg/EtHg was about 0.04 ng L-1 using a 20 L water sample. The precision was about 20%. The application of the proposed method to one snow and four freshwater samples varying in humus content is described. The MeHg concentrations found in different freshwater samples were ranged from 0.09 to 0.22 ng L-1 and the recoveries of spiked MeHg were ranged from 42 to 68% which were strongly correlated to the content of humic substances. The MeHg concentration found in snow was 0.28 ng L-1 and the recovery was 79%. The analytical results of MeHg concentration in freshwater samples are discussed in relation to the pH used in the preconcentration, the humus content, the fraction of methylmercury in organic bound mercury and mercury in fish.     

Determination of total and methyl mercury in human permanent healthy teeth by electrothermal atomic absorption spectrometry after extraction in organic phase

A simple and sensitive method has been developed for determination of inorganic and methyl mercury in biological samples by ETAAS. For determination of methyl mercury; it was transferred to toluene phase by acid leaching extraction method. For total mercury after digestion of samples; it was extracted to toluene phase by means of the chelating agent diethyldithiocarbamate. Formation of complex between MeHg and diethyldithiocarbamate enhance the MeHg signal and increases the reproducibility. Furthermore, Pd-DDC was used as modifier for both mercury and methyl mercury determinations. The optimization performance was independently carried out by modifying the parameters such as temperature of mineralization, atomization and gas flow rate for methylmercury and inorganic mercury in ETAAS. The limits of detection were 0.15 and 0.12 μg g⁻¹ for methyl mercury and total mercury, respectively. The repeatability of the measurements of whole procedure were 15.8% for methyl mercury and 16.9% for total mercury determination. The accuracy of the method has been investigated by means of spiking different amounts of methylmercury and inorganic mercury to the samples. The recoveries were found within the range of 88-95% for methyl mercury and 85-92% for total mercury. For determination of total mercury, the method was validated by CVAAS. The obtained results by the present procedure were in good agreement with those of the CVAAS. The proposed method was applied for 30 human permanent healthy teeth (without filling) which significant positive correlations were found among number of amalgam filling and total mercury and MeHg.     

Certification of two human hair reference materials issued by the International Atomic Energy Agency

Two new human hair reference materials, with different levels of mercury and methylmercury, have been developed and characterized by the International Atomic Energy Agency, for use in validation of measurements for mercury exposure. The set of materials consists of IAEA-086, with a low level of methylmercury, and IAEA-085, with an elevated methylmercury level. An international intercomparison exercise was carried out, and 68 institutes from 40 countries have contributed data. Based on the evaluation of the results from the intercomparison and analyses by expert laboratories, values of 23.2 and 0.57 mg/kg total mercury are recommended for IAEA-085 and IAEA-086, respectively. Values for methylmercury are recommended at 22.9 mg/kg, MeHg as Hg, for IAEA-085, and at 0.26 mg/kg, MeHg as Hg, for IAEA-086. Recommended and information values are also given for other selected trace elements.     

Methylmercury determination in biota by solid-phase microextraction matrix effect evaluation

Aqueous-phase alkylation followed by, headspace solid-phase microextraction (SPME) for mercury speciation in biota, was developed a decade ago. Despite this, matrix effects in this technique have not yet been addressed. In this paper, the importance of these effects has been assessed and overcome by standard addition calibration. Furthermore, improvements were made in the extraction of methylmercury (MeHg) from biological matrixes by optimizing the matrix digestion procedure (temperature and digestion time) and the SPME parameters (aliquot volume of digested samples, extraction temperature and fibre coating), which aimed to minimize the matrix effects. Accordingly, samples were alkaline digested (KOH, 25%, w/v, 60 degrees C, 180 min) and an aliquot was propylated using an aqueous NaBPr(4) solution, headspace SPME sampling and, finally, by using GC-pyrolysis (Py)-atomic fluorescence spectrometry (AFS) determination. The procedure developed was validated using dogfish muscle reference material NRCC DORM-2.     

Simultaneous determination of methylmercury and ethylmercury in rice by capillary gas chromatography coupled on-line with atomic fluorescence spectrometry

A comprehensive method for simultaneous determination of methylmercury (MeHg) and ethylmercury (EtHg) in rice by capillary gas chromatography (GC) coupled on-line with atomic fluorescence spectrometry was developed. The experimental conditions, including the pyrolyzer temperature and flow rates of the make-up gas and sheath gas, were optimized in detail. The absolute detection limits (3sigma) were 0.005 ng as Hg for both MeHg and EtHg. The relative standard deviation values (n=5) for 10 ng Hg/mL of MeHg and EtHg were 2.5 and 1.3%, respectively. The method was evaluated by analyzing 2 certified reference materials (DORM-2 and GBW08508), and the determined values of MeHg and total mercury concentrations were in good agreement with the certified values. In addition, the recoveries of MeHg and EtHg spiked into a rice sample collected from Jiangsu province in China were 86 and 77%, respectively. The proposed method was applied to analysis of MeHg and EtHg in 25 rice samples cultivated in 15 provinces of China. In all samples, MeHg was detectable and no EtHg was found. The MeHg contents in rice samples ranged from 1.9 to 10.5 ng/g, accounting for 7-44% of the total mercury measured.     

Determination of trace amounts of methylmercury in sediment and biological tissue by using water vapor distillation in combination with RP C18 preconcentration and HPLC-HPF/HHPN-ICP-MS

A novel technique has been developed for the determination of trace amounts of methylmercury in sediment and biological tissues. The well known water vapor distillation technique for the isolation of methylmercury from different matrices was coupled with an RP C18 preconcentration using dithiocarbamate complexation. A newly developed HPLC-method allowed the separation of five different mercury species at different mercury masses with HPF/HHPN (High-Performance-Flow/Hydraulic-High-Pressure-Nebulizing) and detection by ICP-MS. The method takes advantage of the ability to measure individual isotopes. Recoveries of the water vapor distillation procedure samples for different mercury compounds from sediment were tested. For methylmercury, the detection limit for a 0.5 g sample was calculated to be 0.025 μg/kg. The new technique was assured using different reference materials. Received: 23 October 1996 / Revised: 14 February 1997 / Accepted: 16 February 1997     

Determination of trace amounts of methylmercury in sediment and biological tissue by using water vapor distillation in combination with RP C18 preconcentration and HPLC-HPF/HHPN-ICP-MS

A novel technique has been developed for the determination of trace amounts of methylmercury in sediment and biological tissues. The well known water vapor distillation technique for the isolation of methylmercury from different matrices was coupled with an RP C18 preconcentration using dithiocarbamate complexation. A newly developed HPLC-method allowed the separation of five different mercury species at different mercury masses with HPF/HHPN (High-Performance-Flow/Hydraulic-High-Pressure-Nebulizing) and detection by ICP-MS. The method takes advantage of the ability to measure individual isotopes. Recoveries of the water vapor distillation procedure samples for different mercury compounds from sediment were tested. For methylmercury, the detection limit for a 0.5 g sample was calculated to be 0.025 μg/kg. The new technique was assured using different reference materials.     

Simultaneous determination of trace levels of ethylmercury and methylmercury in biological samples and vaccines using sodium tetra(<Emphasis Type="Italic">n</Emphasis>-propyl)borate as derivatizing agent

Because of increasing awareness of the potential neurotoxicity of even low levels of organomercury compounds, analytical techniques are required for determination of low concentrations of ethylmercury (EtHg) and methylmercury (MeHg) in biological samples. An accurate and sensitive method has been developed for simultaneous determination of methylmercury and ethylmercury in vaccines and biological samples. MeHg and EtHg were isolated by acid leaching (H₂SO₄–KBr–CuSO₄), extraction of MeHg and EtHg bromides into an organic solvent (CH₂Cl₂), then back-extraction into Milli-Q water. MeHg and EtHg bromides were derivatized with sodium tetrapropylborate (NaBPr₄), collected at room temperature on Tenax, separated by isothermal gas chromatography (GC), pyrolysed, and detected by cold-vapour atomic fluorescence spectrometry (CV AFS). The repeatability of results from the method was approximately 5–10% for EtHg and 5–15% for MeHg. Detection limits achieved were 0.01 ng g⁻¹ for EtHg and MeHg in blood, saliva, and vaccines and 5 ng g⁻¹ for EtHg and MeHg in hair. The method presented has been shown to be suitable for determination of background levels of these contaminants in biological samples and can be used in studies related to the health effects of mercury and its species in man. This work illustrates the possibility of using hair and blood as potential biomarkers of exposure to thiomersal.     

Speciation analysis of mercury by solid-phase microextraction and multicapillary gas chromatography hyphenated to inductively coupled plasma-time-of-flight-mass spectrometry

This paper reports the development of an analytical approach for speciation analysis of mercury at ultra-trace levels on the basis of solid-phase microextraction and multicapillary gas chromatography hyphenated to inductively coupled plasma-time-of-flight mass spectrometry. Headspace solid-phase microextraction with a carboxen/polydimethylsyloxane fiber is used for extraction/preconcentration of mercury species after derivatization with sodium tetraethylborate and subsequent volatilization. Isothermal separation of methylmercury (MeHg), inorganic mercury (Hg2+) and propylmercury (PrHg) used as internal standard is achieved within a chromatographic run below 45 s without the introduction of spectral skew. Method detection limits (3 x standard deviation criteria) calculated for 10 successive injections of the analytical reagent blank are 0.027 pg g(-1) (as metal) for MeHg and 0.27 pg g(-1) for Hg2+. The repeatability (R.S.D., %) is 3.3% for MeHg and 3.8% for Hg2+ for 10 successive injections of a standard mixture of 10pg. The method accuracy for MeHg and total mercury is validated through the analysis of marine and estuarine sediment reference materials. A comparison of the sediment data with those obtained by a purge-and-trap injection (PTI) method is also addressed. The analytical procedure is illustrated with some results for the ultra-trace level analysis of ice from Antarctica for which the accuracy is assessed by spike recovery experiments.     

Preconcentration speciation method for mercury compounds in water samples using solid phase extraction followed by reversed phase high performance liquid chromatography

A simple and rapid method for in situ preconcentration of inorganic and organic mercury compounds in water samples, based on solid phase extraction using dithizone immobilised on a reversed-phase C18 cartridge, has been developed. The adsorbed complexes were stable on the cartridge for at least 2 weeks. The speciation analysis of methylmercury (MeHg), phenylmercury (PhHg) and inorganic mercury (Hg (II)) were done by reversed-phase high performance liquid chromatography. The calibration graphs of MeHg, PhHg and Hg (II) were linear (r>0.999) from the detection limits (0.58, 0.66 and 0.54 ng) to 38, 25 and 26 ng of Hg, respectively. The average recoveries of MeHg, PhHg and Hg (II) from spiked samples (0.3-48.0 mug l(-1) Hg) were 98+/-3, 99+/-1 and 100+/-7%, respectively. By applying SPE procedure a 200-fold concentration of the sample was obtained.     

A new pyrrolidinedithiocarbamate screening method for the determination of methylmercury and inorganic mercury relation in hair samples by HPLC-UV-PCO-CVAAS

A new analytical screening technique for the determination of methylmercury and inorganic mercury in hair samples by HPLC-PCO-CVAAS has been developed. It is based on the extraction of mercury compounds by a buffered sodium pyrrolidinedithiocarbamate solution, separation by reversed-phase HPLC, post column oxidation by UV-irradiation, reduction with alkaline sodium borohydride, and determination by cold vapour atomic absorption detection. The standard deviation was 7% and recoveries were 90% for both compounds. The limit of detection (S/N = 3) for both compounds was calculated to be about 4 ppb.     

A new pyrrolidinedithiocarbamate screening method for the determination of methylmercury and inorganic mercury relation in hair samples by HPLC-UV-PCO-CVAAS

A new analytical screening technique for the determination of methylmercury and inorganic mercury in hair samples by HPLC-PCO-CVAAS has been developed. It is based on the extraction of mercury compounds by a buffered sodium pyrrolidinedithiocarbamate solution, separation by reversed-phase HPLC, post column oxidation by UV-irradiation, reduction with alkaline sodium borohydride, and determination by cold vapour atomic absorption detection. The standard deviation was 7% and recoveries were 90% for both compounds. The limit of detection (S/N = 3) for both compounds was calculated to be about 4 ppb.     

Methylmercury determination in biological samples using electrothermal atomic absorption spectrometry after acid leaching extraction

An efficient and sensitive method for the determination of methylmercury in biological samples was developed based on acid leaching extraction of methylmercury into toluene. Methylmercury in the organic phase was determined by electrothermal atomic absorption spectrometry (ETAAS). The methylmercury signal was enhanced and the reproducibility increased by formation of certain complexes and addition of Pd-DDC modifier. The complex of methylmercury with DDC produced the optimum analytical signal in terms of sensitivity and reproducibility compared to complexes with dithizone, cysteine, 1,10-phenanthroline, and diethyldithiocarbamate. Method performance was optimized by modifying parameters such as temperature of mineralization, atomization, and gas flow rate. The limit of detection for methylmercury determination was 0.015 μg g⁻¹ and the RSD of the whole procedure was 12% for human teeth samples (n=5) and 15.8% for hair samples (n=5). The method’s accuracy was investigated by using NIES-13 and by spiking the samples with different amounts of methylmercury. The results were in good agreement with the certified values and the recoveries were 88–95%.     

Instrumental neutron activation analysis for quality assurance of a hair reference material for mercury speciation

Instrumental neutron activation analysis (INAA) has been employed in the investigation of mass balance for mercury species analysis in the analytical process. A new human hair reference material (IAEA-085) was analyzed for methylmercury using a solid/liquid extraction procedure, with samples of extracts, residues, and untreated samples being analyzed by INAA. The certified reference material NIES CRM No. 13, human hair, was analyzed in parallel. From the results obtained through the mass balance studies, it was found that the extraction procedure was quantitatively complete, and that there was no difference between the mass balance of Hg and the total Hg in the untreated materials.     

光诱导蒸气发生-高效液相色谱-电感耦合等离子体质谱联用测定汞形态

以紫外光诱导化学蒸气(UV-CVG)发生为接口,建立了高效液相色谱与电感耦合等离子体质谱联用测定无机汞、甲基汞的分析方法.对色谱条件、紫外光化学反应还原剂甲酸浓度、紫外光化学反应管长度等系统操作条件进行了优化.在优化的系统条件下,4 μg/L无机汞和甲基汞的色谱峰高的相对标准偏差(RSD,n=11)分别为0.72％和0.66％;无机汞和甲基汞的线性范围为0.1～10μg/L,100 μL进样检出限分别为0.011和0.0093 μg/L.用DORM-2角鲨鱼肉参考物质验证了方法的准确性,测试结果与推荐值吻合;对沼泽湿地水样中无机汞和甲基汞的加标回收率分别在99％～106％和94％～110％范围内.     

气相色谱仪和测汞仪联机测定人发中的甲基汞

本文在前报^[1]工作基础上,将气相色谱仪和测汞仪联机测定有机汞的方法,用于人发中甲基汞的测定。根据Birke等人报导^[2],人发和血液中只查到甲基汞,未查到乙基汞和更高级的烷基汞;同时本工作所用的人发试样,经白求恩医科大学环境医学研究室分析,除甲基汞外未查到乙基汞。因此本法测得的总有机汞能代表甲基汞。目前尚未见到类似方法的报导。     

Applicability of multisyringe chromatography coupled to cold-vapor atomic fluorescence spectrometry for mercury speciation analysis

In this paper, a novel automatic approach for the speciation of inorganic mercury (Hg(2+)), methylmercury (MeHg(+)) and ethylmercury (EtHg(+)) using multisyringe chromatography (MSC) coupled to cold-vapor atomic fluorescence spectrometry (CV/AFS) was developed. For the first time, the separation of mercury species was accomplished on a RP C18 monolithic column using a multi-isocratic elution program. The elution protocol involved the use of 0.005% 2-mercapthoethanol in 240 mM ammonium acetate (pH 6)-acetonitrile (99:1, v/v), followed by 0.005% 2-mercapthoethanol in 240 mM ammonium acetate (pH 6)-acetonitrile (90:10, v/v). The eluted mercury species were then oxidized under post-column UV radiation and reduced using tin(II) chloride in an acidic medium. Subsequently, the generated mercury metal were separated from the reaction mixture and further atomized in the flame atomizer and detected by AFS. Under the optimized experimental conditions, the limits of detection (3σ) were found to be 0.03, 0.11 and 0.09 μg L(-1) for MeHg(+), Hg(2+) and EtHg(+), respectively. The relative standard deviation (RSD, n=6) of the peak height for 3, 6 and 3 μg L(-1) of MeHg(+), Hg(2+) and EtHg(+) (as Hg) ranged from 2.4 to 4.0%. Compared with the conventional HPLC-CV/AFS hyphenated systems, the proposed MSC-CV/AFS system permitted a higher sampling frequency and low instrumental and operational costs. The developed method was validated by the determination of a certified reference material DORM-2 (dogfish muscle), and was further applied for the determination of mercury species environmental and biological samples.     

Certification of methylmercury in cod fish tissue certified reference material by species-specific isotope dilution mass spectrometric analysis

A new cod fish tissue certified reference material, NMIJ CRM 7402-a, for methylmercury analysis was certified by the National Metrological Institute of Japan in the National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). Cod fish was collected from the sea close to Japan. The cod muscle was powdered by freeze-pulverization and was placed into 600 glass bottles (10 g each), which were sterilized with γ-ray irradiation. The certification was carried out using species-specific isotope dilution gas chromatography inductively coupled plasma mass spectrometry (SSID–GC–ICPMS), where ²⁰²Hg-enriched methylmercury (MeHg) was used as the spike compound. In order to avoid any possible analytical biases caused by nonquantitative extraction, degradation and/or formation of MeHg in sample preparations, two different extraction methods (KOH/methanol and HCl/methanol extractions) were performed, and one of these extraction methods utilized two different derivatization methods (ethylation and phenylation). A double ID method was adopted to minimize the uncertainty arising from the analyses. In order to ensure not only the reliability of the analytical results but also traceability to SI units, the standard solution of MeHg used for the reverse-ID was prepared from high-purity MeHg chloride and was carefully assayed as follows: the total mercury was determined by ID–ICPMS following aqua regia digestion, and the ratio of Hg as MeHg to the total Hg content was estimated by GC–ICPMS. The certified value given for MeHg is 0.58 ± 0.02 mg kg⁻¹ as Hg. Figure NMIJ CRM 7402-a: cod fish tissue for MeHg analysis     

Determination of methylmercury and inorganic mercury in whole blood by headspace, cryofocusing gas chromatography and atomic absorption spectrometry

A method for the determination of different mercury species in whole blood is described. Inorganic mercury (InHg) was determined in 2 ml of standard solutions or blood samples using head space (HS) injection coupled to atomic absorption spectrometry (AAS) after treatment with concentrated sulfuric and tin(II) chloride as a reductant agent in a closed HS vial. After stirring, the InHg was converted to elementary mercury and carried with a nitrogen flow through a quartz cell heated at 200 degrees C and the absorbance signal was evaluated by AAS. For the determination of methylmercury (MeHg), 2 ml of a standard solution or a blood sample were treated with 10 mg of iodoacetic acid and 0.4 ml of concentrated H2SO4. Then, the MeHg species were HS-injected into a gas chromatograph (GC), separated on a semicapillary column (AT-1000) with a flow of helium, then carried to the quartz cell heated at 1000 degrees C and detected by AAS. The high content of salts in blood samples, where sodium chloride is the major component (0.14 mol l-1), affected the gas-liquid distribution coefficient of both mercury species in the HS vial. A linear calibration graph was obtained in the ranges 1-20 and 1-125 micrograms Hg l-1 added as InHg and MeHg, respectively. The detection limits for InHg and MeHg were 0.6 and 0.2 microgram Hg l-1, respectively. The relative standard deviations for eleven independent measurements were 5% for both mercury species. Recovery values ranging from 98 to 106% for InHg and from 95 to 105% for MeHg and from 93 to 95% for ethylmercury (EtHg) were obtained. The accuracy of the proposed method was also established by the analysis of certified whole blood samples for InHg and MeHg. No difference between the sum of these two species determined by our procedure and the recommended total mercury concentrations in the certified samples was observed. Results for the determination of MeHg and InHg in 30 controls and 30 dentists are presented to illustrate the practical utility of the proposed method.