Determination of folates in human plasma using hydrophilic interaction chromatography-tandem mass spectrometry

Folic acid is an essential nutrient, and folate deficiency is associated with a variety of disorders including neural tube defects (during pregnancy) and heart disease. A fast, sensitive, and robust HPLC-tandem mass spectrometry (LC-MS-MS) method was developed for the quantification of free folic acid, tetrahydrofolate, 5'-methyltetrahydrofolate, and 5'-formyltetrahydrofolate in human plasma. Sample preparation required only acetonitrile precipitation of proteins followed by filtration instead of solid-phase extraction or solvent-solvent extraction as in other methods. The rapid and streamlined sample handling procedure minimized degradation of the highly unstable folate species. Hydrophilic interaction chromatography was used for additional sample cleanup on-line, and baseline separation and detection of all four folate species was achieved in less than 30 min. The folate species were detected using negative ion electrospray-tandem mass spectrometry with multiple reaction monitoring of the diagnostic fragment ions of each deprotonated molecule. The predominately organic (hydrophobic) solvent system combined with the microbore flow rate (50 microL/min) used for the chromatography resulted in enhanced electrospray signal response compared to reversed-phase HPLC using a wider bore column. The recovery of all folate species (from spiked plasma) was >97% over a concentration range from 300 pg/L to 12 mg/L with intraday precision (RSD, n = 5) of 3.7-6.5%. Stability studies were carried out for spiked samples in order to define storage and handling conditions. The folic acid limit of quantification (LOQ) in human plasma was 80 pmol/L +/- 10%, and the limit of detection (LOD) was 37.5 pmol/L. The LOQ and LOD for tetrahydrofolate, 5'-methyltetrahydrofolate, and 5'-formyltetrahydrofolate were 1250, 400, and 360 pmol/L of plasma and 425, 165, and 140 pmol/L of plasma, respectively.     

Simultaneous quantification of etoposide and etoposide phosphate in human plasma by capillary electrophoresis using laser-induced native fluorescence detection

A method using capillary electrophoresis with UV laser-induced native fluorescence detection was developed as a sensitive and selective assay for the simultaneous determination of etoposide and etoposide phosphate in human plasma. Laser-induced native fluorescence detection with a frequency-doubled argon ion laser at an excitation wavelength of 257 nm was used for the simultaneous assay of etoposide and etoposide phosphate in plasma to improve the sensitivity compared to that obtained with UV absorption. The detection system consists of an imaging spectrograph and an intensified CCD camera which views an illuminated 1.5-mm section of the capillary. This setup is able to record the whole emission spectra of the analytes to achieve additional wavelength-resolved electropherograms. In the concentration range of 200 microg/L-50 mg/L in plasma for etoposide and 100 microg/L-20 mg/L for etoposide phosphate, coefficients of correlation were better than 0.998. Within-day variation determined with three different concentrations showed accuracies ranging from 91.0 to 109.3% for etoposide and from 91.2 to 109.9% for etoposide phosphate (n = 6) with a precision of about 8%. Day-to-day variation presented accuracies ranging from 91.8 to 107.9% for etoposide and from 94.4 to 109.3% for etoposide phosphate with a relative standard deviation less than 6% (n = 5). To our knowledge, this is the first method for the simultaneous quantification of etoposide and etoposide phosphate in plasma samples.     

Ammonium exchange in aqueous solution using Chinese natural clinoptilolite and modified zeolite

In this study, the Chinese natural clinoptilolite (sample 1) was fused with sodium hydroxide prior to hydrothermal reaction, and it was transformed to modified zeolite Na-Y (sample 2). The uptake of ammonium ion from aqueous solutions in the concentration range 50-250 mg NH(4)(+)/l on to the two samples was compared and the equilibrium isotherms have been got. The influence of other cations present in water upon the ammonia uptake was also determined. The cations studied were potassium, calcium and magnesium. In all cases the anionic counterion present was chloride. The results showed that sample 2 exhibited much higher uptake capacity compared with sample 1. At the initial concentration of 250 mg NH(4)(+)/l, the ammonium ion uptake value of sample 2 was 19.29 mg NH(4)(+)g(-1) adsorbent, while sample 1 was only 10.49 mg NH(4)(+)g(-1) adsorbent. For the natural clinoptilolite, the effect of the metal ions suggested an order of preference K(+)>Ca(2+)>Mg(2+). These contrasted with the modified zeolite, where the order appeared to be Mg(2+)>Ca(2+)>K(+).     

Chip-based quantitative capillary electrophoresis/mass spectrometry determination of drugs in human plasma

A chip-based capillary electrophoresis/mass spectrometry (CE/MS) system is described for the on-chip separation and coupled electrospray detection of selected small drug molecule compounds. These studies include the quantitative determination of carnitine and acetylcarnitine in analytical standard solutions as well as imipramine and desipramine in fortified human plasma samples. A clinical human plasma sample was also analyzed following the normal administration of desipramine to a volunteer, and the parent drug was determined using the described chipbased CE/MS technique. In each instance, stable isotope-incorporated internal standards were used. The chip-based CE system was microfabricated from glass and coupled to a micro ion spray device constructed in-house. The atmospheric pressure ionization system employed in this work was a PE Sciex API III tandem triple quadrupole system operated in the selected ion monitoring (SIM) mode. The results from the work reported here demonstrate the feasibility for carrying out rapid (30 s) chipbased quantitative CE/MS determinations of samples containing small-molecule compounds. Using SIM CE/ MS techniques, the described API III quadrupole system provided acceptable ion current electropherograms from subpicomole levels of the targeted compounds loaded onto the chip. The corresponding electropherograms for the standard solution of carnitines at the 1-500 microg/mL level were obtained via SIM CE/MS techniques (R2 > 0.99). In addition, analyses of fortified samples of imipramine desipramine were measured relative to their corresponding d3 internal standards to obtain calibration curves ranging from 5 to 500 microg/mL in human plasma (R2 > 0.99). The intra-assay precision ranged from 4.1 to 7.3% RSD. The intra-assay accuracy ranged from 94.0 to 104%. These results demonstrate the feasibility for on-chip CE separation and electrospray mass spectrometric determination in applications for bioanalytical measurements for these important compounds in synthetic mixtures and human plasma extracts.     

A high-efficiency cross-flow micronebulizer for inductively coupled plasma mass spectrometry

A pneumatically driven, high-efficiency cross-flow micronebulizer (HECFMN) is introduced for inductively coupled plasma (ICP) spectrometries. The HECFMN uses a smaller nozzle orifice for nebulizer gas (75 microm in diameter) and a replaceable and adjustable fused-silica capillary for sample uptake. The HECFMN is optimally operated over a wide range of sample uptake rate (5-120 microL/min) at a rf power of 1100 W and nebulizer gas flow rates of 0.8-1.0 L/min when a 50 microm i.d. by 150 microm o.d. capillary is used. The aerosol quality is qualitatively examined in a simple manner, and the transport efficiencies are determined by direct filter collection. Compared with conventional cross-flow nebulizers (CFNs), the HECFMN produces much smaller and more uniform droplets and thus provides much higher analyte transport efficiencies (generally 24-95%) at the sample uptake rates of 5-100 microL/min. Several analytical performance indexes are acquired using an Ar ICPMS system. The sensitivities and detection limits measured with the HECFMN at 50 microL/min sample uptake rate are comparable to or improved over those obtained with a conventional CFN consuming 1 mL/min sample, and the precisions with the HECFMN (typically 1.1-1.7% RSDs) are slightly better than those with the CFN (1.6-2.3% RSDs). The ratios of refractory oxide ion-to-singly charged ion (CeO+/Ce+) are typically in the range from 0.7 to 3.3% for the sample uptake rates of 5-100 microL/min. The free aspiration rate of the HECFMN is 8.9 microL/min for distilled deionized water at the nebulizer gas flow rate of 1.0 L/min without any effect of pressure. The features of the HECFMN suggest good potential for HECFMN use in interfacing ICPMS with capillary electrophoresis and microcolumn high-performance liquid chromatography.     

On-line coupling of capillary electrophoresis to hydride generation atomic fluorescence spectrometry for arsenic speciation analysis

A novel hyphenated technique, on-line coupling of capillary electrophoresis (CE) to atomic fluorescence spectrometry (AFS), was developed for speciation analysis of four environmentally significant and toxic forms of arsenic: arsenite, arsenate, monomethylarsenic acid, and dimethylarsenic acid. Baseline separation of the four arsenic species was achieved by capillary electrophoresis in a 50 cm x 100 microm i.d. fused-silica capillary at 20 kV and using a 20 mmol L(-1) phosphate buffer (pH 6.5). A hydride generation (HG) technique was employed to convert the arsenic species from the CE effluent into their respective hydrides. The CE-AFS interface was constructed on the basis of a cross design for introducing a sheath flow around the CE capillary and a Pt electrode, which provided an electrical connection for stable electrophoretic separations and allowed on-line volatile hydride formation. A laboratory-made gas-liquid separator was used to isolate the generated volatile species from the reaction mixture solution, and an argon flow was used to transport the volatile hydrides into the atomizer of AFS for on-line detection. The precision (RSD, n = 7) ranged from 2.1 to 3.1% for migration time, from 2.8 to 4.2% for peak area response, and from 2.0 to 4.1% for peak height response for the arsenic species at the 1 mg L(-1) (as As) level. The detection limits were in the range of 9-18 microg L(-1) (as As). The recoveries of the four arsenic species in locally collected water samples and urine sample ranged from 91 to 115%. The developed technique was successfully applied to the speciation of the water-methanol extractable arsenic in a sediment sample.     

超声波提取-离子色谱法同时测定卷烟纸中的钾、钠、钙、镁

用0.02mol/L的盐酸溶液超声提取卷烟纸样品中的钾、钠、钙、镁4种离子,并采用离子色谱法进行同时测定。Ionpac CG12A(4mm×250mm)阳离子交换柱为固定相,15mmol/L的甲烷基磺酸为流动相,电导检测器进行测定。结果表明:方法的检出限为0.02～0.69mg/kg,加标回收率为90.14%～106.1%,相对标准偏差均小于5%,结果令人满意。     

Precise determination of element/calcium ratios in calcareous samples using sector field inductively coupled plasma mass spectrometry

A new method was developed for rapid and precise simultaneous determination of Mg/Ca, Sr/Ca, Mn/Ca, Cd/Ca, Ba/Ca and U/Ca ratios in foraminiferal shells using sector field inductively coupled plasma mass spectrometry (ICPMS). Element/calcium ratios were determined directly from intensity ratios using external, matrix-matched standard to correct for instrumental mass discrimination. Because of large differences in the abundance of chemical constituents of the foraminiferal shell, major elemental ratios were determined in analog mode (using (24)Mg, (43)Ca, (44)Ca, (55)Mn, and (88)Sr) whereas trace elemental ratios were determined in pulse-counting mode (using (111)Cd, (138)Ba, (238)U, and the low-abundance (46)Ca isotope). Matrix-induced variations in mass discrimination over a calcium concentration range of 2.0-24.5 mM were observed only for Mg/Ca and Cd/Ca ratios. However, these effects are negligible if the samples and standard calcium concentration are within a factor of 2-3. Multiratio method reproducibility was better than previously reported for other ICPMS methods yielding precision (1σ) of Sr/Ca = 0.45%; Mg/Ca = 0.45%, Mn/Ca = 0.8%, Cd/Ca = 1.7%, Ba/Ca = 0.7%, and U/Ca = 1.4% for foraminifera samples as small as 25 μg. Using this approach for a single-ratio analysis, Sr/Ca ratios were determined with precision of 0.06% (1σ) on carbonate samples as small as a single foraminifera shell (<10 μg). The new method is more sensitive, more precise, and simpler to use than previously available ICPMS techniques. It provides an efficient tool for simultaneous determination of several elemental ratios of paleoceanographic interest in a single foraminiferal sample, thereby reducing overall sample size requirement and analysis time.     

Hydride generation interface for speciation analysis coupling capillary electrophoresis to inductively coupled plasma mass spectrometry

A novel hydride generation (HG) interface for coupling capillary electrophoresis (CE) with inductively coupled plasma mass spectrometry (ICPMS) is presented in this work. The CE-HG-ICPMS interface was applied to the separation and quantitation of common arsenic species. Lack of a commercially available HG interface for CE-ICPMS led to a three concentric tube design allowing alleviation of back pressure commonly observed in CE-HG-ICPMS. Due to the high sensitivity and element-specific detection of ICPMS, quantitative analysis of As(III), As(V), monomethylarsonic acid, and dimethylarsinic acid was achieved. Optimization of CE separation conditions resulted in the use of 20 mmol L(-1) sodium borate with 2% osmotic flow modifier (pH 9.0) and -20 kV applied potential for baseline resolution of each arsenic species in the shortest time. Hydride generation conditions were optimized through multiple electrophoretic separation analyses with 5% HCl and 3% NaBH(4) (in 0.2% NaOH) determined to be the optimum conditions. After completion of system optimization, detection limits obtained for the arsenic species were less than 40 ng L(-1) with electromigration time precision less than 1% within a total analysis time of 9.0 min. Finally, the interface was used for speciation analysis of arsenic in river and tap water samples.     

Analysis of acrylamide in water using a coevaporation preparative step and isotope dilution liquid chromatography tandem mass spectrometry

Acrylamide is a probable human carcinogen, and the drinking water quality guideline for this compound is 0.5 mg/L. However, analysis of this compound in water is difficult because of its very high water solubility, which limits the efficiency of sample preconcentration prior to analysis. We developed a robust and sensitive analytical method for the determination of trace quantities of acrylamide in samples of water using a novel preparative technique and isotope dilution liquid chromatography tandem mass spectrometry with atmospheric pressure chemical ionization as the ion source (LC-APCI-MS/MS). The preparative method involves coevaporation of acrylamide with water at pH 10 using a rotary evaporator, followed by acidification to pH 3.0 and concentration of the sample prior to analysis by LC-APCI-MS/MS. To compensate for the loss of the analyte during sample preparation and signal suppression due to interference from the sample matrix, isotope dilution with acrylamide-d3 was used for quantitation. Using this method, analyte recoveries ranged from 74 to 103% for acrylamide spiked into water at a concentration of 0.4 ng/mL. The limit of detection and limit of quantification (LOQ) for acrylamide in water were 0.02 and 0.06 ng/mL, respectively. This method was successfully applied to determine trace levels of acrylamide in samples of river water and in runoff from an agricultural field to which municipal biosolids (i.e., sludge) had been applied. Concentrations of acrylamide in these samples ranged from 相似文献   

离子色谱法对糕点中丙酸钙的测定

本文采用抑制型电导检测器建立了离子色谱法测定糕点中丙酸钙含量的方法。糕点经蒸馏、提取、过滤后,用Dionex Ion Pac ASl9(4×250mm)分离柱分离,以RFC-30淋洗液自动发生器产生的5 mmol KOH为淋洗液,流速1.0ml/min,经抑制电导检测器检测。该方法在0.10～20.0mg/L范围内线性关系良好,检出限达0.02 mg/L。该方法稳定,重现性好,保留时间相对标准偏差RSD(n=7)为0.18%,峰面积RSD(n=7)为1.15%。将该方法用于糕点实际样品的测定,回收率为91.77%,结果良好。     

Simultaneous uptake of ammonium and phosphate ions by compounds prepared from paper sludge ash

Al-containing CaO-SiO(2)-H(2)O phases were prepared by hydrothermal treatment of mixtures of paper sludge ash (PSA) with various silica and calcia sources and their properties were determined with particular reference to the simultaneous uptake of ammonium and phosphate ions, which are implicated in the eutrophication of lakes and ponds. After examination of various silica and calcia sources, Ca(OH)(2) and SiO(2) sol were selected as the most appropriate starting materials. Dry milling was found to be superior to wet milling in avoiding contamination from the milling media during mixing. Nine samples with three different Ca/Si ratios and Al(2)O(3) contents were prepared with various mass ratios of Ca(OH)(2), PSA and SiO(2). The chemical compositions of the hydrothermal products of these mixtures moved towards the tieline of CaSiO(3)-PSA, with respect to the starting compositions. The major phase formed in all samples was poorly crystalline C-S-H(I), with hydroxysodalite also formed in the Al-containing mixtures. All the products showed a capacity for the simultaneous uptake of ammonium and phosphate ions. The saturated sorption capacities calculated from the Langmuir equation ranged from 0.9 to 2.4mmol/g for the ammonium ion and from 3.3 to 5.2mmol/g for the phosphate ion. Since the sorption capacities for both ions increased with increasing Ca contents of the product, substitution of Ca(2+) for NH(4)(+) and the formation of calcium phosphate phases such as apatite and brushite by precipitation are thought to be the main sorption mechanisms.     

Development of a solid-phase microextraction GC-NPD procedure for the determination of free volatile amines in wastewater and sewage-polluted waters.

An analytical procedure for the determination of free volatile C1-C6 amines in aqueous matrixes has been developed and applied to their determination in waste-water, primary and secondary effluents, and sewage-polluted river samples. The developed analytical procedure involves headspace sampling using solid-phase microextraction with a poly(dimethylpolysiloxane) coating (100 microns) followed by GC-NPD determination and GC/MS confirmation using a tailor-made PoraPLOT amines capillary GC column for volatile amines. Procedural detection limits were compound dependent but ranged from 3 to 56 micrograms L-1, being close to or lower than the odor threshold concentration, and the reproducibility was ca. 15% (N = 5) in real water samples. The developed analytical procedure is solvent free, cost-effective (no cryogenic trap needed), and faster than existing methods because no derivatization step is involved in the determination. Linearity was compound dependent but ranged at least from 50 to 600 micrograms L-1.     

Removal of aqueous lead ions by hydroxyapatites: equilibria and kinetic processes

The capacity of hydroxyapatite (HAp) to remove lead from aqueous solution was investigated under different conditions, namely initial metal ion concentration and reaction time. The sorption of lead from solutions containing initial concentrations from 0 to 8000 mg/L was studied for three different HAp powders. Soluble Pb and Ca monitoring during the experiment allows characterizing the mechanism of lead uptake. Dissolution of calcium is followed by the formation of a solid solution, Pb(x)Ca(10-x)(PO4)6(OH)2, with a Ca/P ratio decreasing continuously. Langmuir-Freundlich classical adsorption isotherms modeled adsorption data. The adsorption capacities calculated from this equation vary from 330 to 450 mg Pb/g HAp for the different solids. Modeling of the sorption process allows to determine theoretical saturation times and residual lead concentrations at equilibrium.     

Sonoelectrochemical deposition of calcium phosphate coatings on carbon materials—effect of electrolyte concentration

Calcium phosphate was deposited on carbon materials using a sonoelectrochemical method in an electrolyte containing calcium and phosphate ions. The effect of electrolyte concentration on sonoelectrochemically deposited calcium phosphate coatings was investigated and the underlying deposition mechanisms were discussed. The morphology, size and composition of the crystalline deposits changed with the electrolyte concentration. A mixture of plate, sphere and needle-like deposits was obtained at Ca(2+) ion concentrations greater than 16 mM, however needle-like hydroxyapatite (HA) was obtained at lower Ca(2+) concentrations. Analysis revealed that the sonoelectrochemical deposition of calcium phosphate consists of two processes-nucleation and crystal growth. The results suggest that the homogeneous nucleation of calcium phosphates in solution, followed by their absorption onto the carbon surface may account for the mechanism of coating observed at higher ionic concentrations. At lower concentrations, heterogeneous nucleation occurs on the surface of the carbon fibres, followed by the development of islands of crystal growth. The lower ionic concentration was shown to favour the generation of hydroxyapatite on carbon-based materials.     

离子色谱法检测含蛋白质食品中三聚氰胺

目的:建立离子色谱法检测含蛋白质食品中三聚氰胺的方法。方法:样品经冰乙酸溶液提取并沉淀蛋白,Dionex OnGuardⅡ RP样品前处理小柱除去脂肪等大分子有机物,采用Dionex IonpacCS17分离柱,3mmol/L H2SO4淋洗液等度淋洗,流速:1.2mL/min,在紫外波长240nm下检测。结果:三聚氰胺在0.5-50.0mg/L的范围内,质量浓度与色谱峰面积呈良好的线性关系(R2>0.9992),方法检出限(MDL)为0.06mg/kg,不同加标量的阴性样品加标回收率在84.8%-103.2%范围内,相对标准偏差RSD<4.0%。结论:该方法简便易行、快速,无干扰,不用有毒试剂,对环境友好,检测成本低,灵敏度高,检测结果准确度高,易于推广,适合对各种含蛋白食品中三聚氰胺的检测分析。     

Analysis of neuroactive amines in fermented beverages using a portable microchip capillary electrophoresis system

A portable microfabricated capillary electrophoresis (CE) instrument is used for the determination of neurologically active biogenic amines, especially tyramine and histamine, in fermented beverages. The target molecules are labeled on their primary amino groups with fluorescamine in a 10-min reaction, and the samples analyzed directly, producing a detailed electropherogram in only 120 s on a microfabricated glass CE device containing 21.4-cm-long separation channels. Tyramine was found mainly in red wines at <1-3.4 mg/L, while the histamine content of these samples ranged from 1.8 to 19 mg/L. The highest levels of histamine (20-40 mg/L) were found in sake. The analysis of samples drawn from grape crush through malolactic fermentation in four varieties of zinfandel red wines revealed that histamine and tyramine are produced during yeast and malolactic fermentation, respectively. Following malolactic fermentation, the histamine content in these samples ranged from 3.3 to 30 mg/L, and the tyramine content ranged from 1.0 to 3.0 mg/L. This highly sensitive and rapid lab-on-a-chip analysis method establishes the feasibility of monitoring neurologically active amine content and potentially other chemically and allergenically important molecules in our food supply.     

Single-run capillary electrophoretic determination of inorganic nitrogen species in rainwater

A capillary electrophoretic (CE) method for the simultaneous determination of nitrate, nitrite, and ammonium ions has been developed. Direct (NO3-, NO2-) and indirect (NH4+) UV detection at 214 nm in conjunction with electromigration sampling from both ends of the capillary was used. The optimized separations were carried out in 10 mmol/L imidazole sulfate, 2 mmol/L 18-crown-6, and 0.02 mmol/L tetradecyltrimethylammonium hydroxide electrolyte (pH 4.0). The method permits excellent separation of three nitrogen species in only 4 min. A 1 x 10(-4) mol/L KBr solution was used as an internal standard to limit possible electrokinetic injection biases. Experimental results showed that the use of an anionic internal standard for cationic analytes and vice versa gives only slightly better precision than analysis with no internal standard. Using Br- internal standard for NO3- and NO2- ions and K+ for NH4+, peak area RSD values decrease significantly. The proposed system was applied to the speciation of inorganic nitrogen ions in rainwater samples. The recovery tests established for external calibration and standard addition techniques using one or two internal standards were within the range 100 +/- 10%. The CE results agree with those obtained by spectrophotometric methods.     

Calcium and zinc ion release from polyalkenoate cements formed from zinc oxide/apatite mixtures

Calcium and zinc ion release from hydroxyapatite-zinc oxide-poly(acrylic acid) (HAZnO-PAA) composite cements into deionised water was investigated as a function of HA content, PAA concentration, PAA molecular weight and maturation time. At any given maturation time, zinc ion release was constant until the HA content was at the maximum loading (60 wt%) resulting in the cement matrix breaking up, allowing exacerbated ion release. The calcium ion release increased with increased HA content in the composite until the maximum loading where the release drops off. Up to this point, the release of both ionic species was proportional to square root time for the initial 24 hour period, indicating that the release is diffusion controlled. In agreement with related data from conventional Glass Polyalkenoate Cements (GPCs), it is the concentration of the PAA, not the molecular weight, that influences ion release from these materials. However, unlike GPCs, the release of the active ions results in a pH rise in the deionised water, more conventionally seen with Bioglass and related bioactive glasses. It is this pH rise, caused by the ion exchange of Zn(2+) and Ca(2+) for H(+) from the water, leaving an excess of OH(-), that should result in a favourable bioactive response both in vitro and in-vivo.     

Speciation of mercury by hydrostatically modified electroosmotic flow capillary electrophoresis coupled with volatile species generation atomic fluorescence spectrometry

A novel method for speciation analysis of mercury was developed by on-line hyphenating capillary electrophoresis (CE) with atomic fluorescence spectrometry (AFS). The four mercury species of inorganic mercury Hg(II), methymercury MeHg(I), ethylmercury EtHg(I), and phenylmercury PhHg(I) were separated as mercury-cysteine complexes by CE in a 50-cm x 100-microm-i.d. fused-silica capillary at 15 kV and using a mixture of 100 mmol L(-1) of boric acid and 12% v/v methanol (pH 9.1) as electrolyte. A novel technique, hydrostatically modified electroosmotic flow (HSMEOF) in which the electroosmotic flow (EOF) was modified by applying hydrostatical pressure opposite to the direction of EOF was used to improve resolution. A volatile species generation technique was used to convert the mercury species into their respective volatile species. A newly developed CE-AFS interface was employed to provide an electrical connection for stable electrophoretic separations and to allow on-line volatile species formation. The generated volatile species were on-line detected with AFS. The precisions (RSD, n = 5) were in the range of 1.9-2.5% for migration time, 1.8-6.3% for peak area response, and 2.3-6.1% for peak height response for the four mercury species. The detection limits ranged from 6.8 to 16.5 microg L(-1) (as Hg). The recoveries of the four mercury species in the water samples were in the range of 86.6-111%. The developed technique was successfully applied to speciation analysis of mercury in a certified reference material (DORM-2, dogfish muscle).