Concentrations of hazardous heavy metals in environmental samples collected in Xiamen, China, as determined by vapor generation non-dispersive atomic fluorescence spectrometry.

Non-dispersive atomic fluorescence spectrometry (NDAFS) coupled with vapor generation (VG) sample introduction was applied to the determination of the concentrations of hazardous heavy metals, such as arsenic, cadmium, lead and mercury, in seawater, soils and total airborne particulate matter (PM) collected around the Xiamen area in China. Almost 100% sample introduction efficiency was achieved by using thiourea and ascorbic acid for the pre-reduction of As(V) to As(III), K3Fe(CN)6 and tartaric acid for pre-oxidation of Pb(II) to Pb(IV), and masking the interferences arising from the co-existing transition metals to As, Cd, Hg and Pb during their vapor generation process. Moreover, a novel sample pretreatment device was developed to avoid the loss of mercury, lead, cadmium and arsenic during sample pretreatment. With such methods, the detection limit (DL) of arsenic, cadmium, lead and mercury was down to 0.08, 0.03, 0.05, 0.01 ng mL(-1) (3sigma), respectively. The relative standard deviations (RSD, n = 11) for arsenic, cadmium, lead and mercury at 10 ng mL(-1) were 0.9%, 1.6%, 1.3% and 2.0%, respectively. The concentrations of hazardous heavy metals in the environmental samples collected in Xiamen, China are in the range from 0.02 +/- 0.001 ng mL(-1) in seawater to 15.3 +/- 0.2 microg g(-1) in soils. Besides flame/GF-AAS and ICP-AES/MS, VG-NDAFS should be another choice for the determination of hazardous heavy metals in environmental samples.     

Determination of cadmium by flow injection-chemical vapor generation-atomic absorption spectrometry

A method was developed for the generation of a "cold vapor" of cadmium by means of flow injection-chemical vapor generation from aqueous samples, the determination being conducted with an atomic absorption spectrometer (Pyrex glass T-cell). Several gas-liquid separator designs, atomizer designs, and the effect of several reagents previously reported as sensitivity enhancers (including cobalt, nickel, thiourea and didodecyl-dimethylammonium bromide) were investigated. The limit of detection, calculated as the concentration giving a signal equal to three times the standard deviation of the blank, was 16 ng L(-1), and the relative standard deviation was 1.4% for a concentration of 2 microg L(-1) and 3.8% for 0.1 microg L(-1). The addition of nickel and thiourea to the samples provided improved tolerance to the interference of coexisting ions. Two NIST certified reference materials, Montana Soil and Apple Leaves (respectively containing 41.7+/-0.25 mg kg(-1) Cd and 0.013+/-0.002 mg kg(-1) Cd) were accurately analyzed. The interference of lead was overcome by coprecipitation with barium sulfate, and the experimental values obtained were 41+/-1 mg kg(-1) Cd and 0.013+/-0.002 mg kg(-1) Cd, respectively.     

Mercury speciation in sea food by flow injection cold vapor atomic absorption spectrometry using selective solid phase extraction

An on-line inorganic and organomercury species separation, preconcentration and determination system consisting of cold vapor atomic absorption spectrometry (CV-AAS or CV-ETAAS) coupled to a flow injection (FI) method was studied. The inorganic mercury species was retained on a column (i.d., 3 mm; length 3 cm) packed to a height of 0.7 cm with a chelating resin aminopropyl-controlled pore glass (550 A) functionalized with [1,5-bis (2 pyridyl)-3-sulphophenyl methylene thiocarbonohydrazyde] placed in the injection valve of a simple flow manifold. Methylmercury is not directly determined. Previous oxidation of the organomercurial species permitted the determination of total mercury. The separation of mercury species was obtained by the selective retention of inorganic mercury on the chelating resin. The difference between total and inorganic mercury determined the organomercury content in the sample. The inorganic mercury was removed on-line from the microcolumn with 6% (m/v) thiourea. The mercury cold vapor generation was performed on-line with 0.2% (m/v) sodium tethrahydroborate and 0.05% (m/v) sodium hydroxide as reducing solution. The determination was performed using CV-AAS and CV-ETAAS, both approaches have been used and compared for the speciation of mercury in sea food. A detection limit of 10 and 6 ng l(-1) was achieved for CV-AAS and CV-ETAAS, respectively. The precision for 10 replicate determinations at the 1 microg l(-1) Hg level was 3.5% relative standard deviation (R.S.D.), calculated from the peak heights obtained. Both approaches were validated with the use of two certified reference materials and by spiking experiments. By analyzing the two biological certified materials, it was evident that the difference between the total mercury and inorganic mercury corresponds to methylmercury. The concentrations obtained by both techniques were in agreement with the certified values or with differences of the certified values for total Hg(2+) and CH(3)Hg(+), according to the t-test for a 95% confidence level. It is amazing how this very simple method is able to provide very important information on mercury speciation.     

Solution cathode glow discharge induced vapor generation of mercury and its application to mercury speciation by high performance liquid chromatography-atomic fluorescence spectrometry

A novel solution cathode glow discharge (SCGD) induced vapor generation was developed as interface to on-line couple high-performance liquid chromatography (HPLC) with atomic fluorescence spectrometry (AFS) for the speciation of inorganic mercury (Hg(2+)), methyl-mercury (MeHg) and ethyl-mercury (EtHg). The decomposition of organic mercury species and the reduction of Hg(2+) could be completed in one step with this proposed SCGD induced vapor generation system. The vapor generation is extremely rapid and therefore is easy to couple with flow injection (FI) and HPLC. Compared with the conventional HPLC-CV-AFS hyphenated systems, the proposed HPLC-SCGD-AFS system is very simple in operation and eliminates auxiliary redox reagents. Parameters influencing mercury determination were optimized, such as concentration of formic acid, discharge current and argon flow rate. The method detection limits for HPLC-SCGD-AFS system were 0.67 μg L(-1) for Hg(2+), 0.55 μg L(-1) for MeHg and 1.19 μg L(-1) for EtHg, respectively. The developed method was validated by determination of certified reference material (GBW 10029, tuna fish) and was further applied for the determination of mercury in biological samples.     

Synthesis of a novel host molecule of cross-linking-polymeric-beta-cyclodextrin-o-vanillin furfuralhydrazone and spectrofluorimetric analysis of its identifying cadmium

A novel host inclusion complex of cross-linking-polymeric-beta-cyclodextrin-o-vanillin furfuralhydrazone (beta-CDP-OVFH) was synthesized and characterized with IR and 1H NMR spectra to confirm its structure. The coordination reaction of the host reagent with Cd(2+) was studied and the optimum reacting conditions were observed carefully. A highly selective and sensitive spectrofluorimetric determination of trace amount of cadmium was proposed based on the reaction of Cd(2+) with beta-CDP-OVFH in ammonia water-ammonium acetate buffer medium of pH = 11.0. The molar ratio of beta-CDP-OVFH to Cd(2+) was 1:1. The maximum excitation and emission wavelengths were 393 and 494 nm, respectively. The linear range of this method was from 3.0 to 500 microg l(-1) with a detection limit of 0.80 microg l(-1). The effect of interferences in the determination of cadmium was investigated and the results showed that the host reagent had quite high capacity of identifying Cd(2+). The proposed method was successfully applied to the determination of trace amount of Cd(2+) in mussel and tea samples.     

UV light-emitting-diode photochemical mercury vapor generation for atomic fluorescence spectrometry

A new, miniaturized and low power consumption photochemical vapor generation (PVG) technique utilizing an ultraviolet light-emitting diode (UV-LED) lamp is described, and further validated via the determination of trace mercury. In the presence of formic acid, the mercury cold vapor is favourably generated from Hg(2+) solutions by UV-LED irradiation, and then rapidly transported to an atomic fluorescence spectrometer for detection. Optimum conditions for PVG and interferences from concomitant elements were investigated in detail. Under optimum conditions, a limit of detection (LOD) of 0.01 μg L(-1) was obtained, and the precision was better than 3.2% (n = 11, RSD) at 1 μg L(-1) Hg(2+). No obvious interferences from any common ions were evident. The methodology was successfully applied to the determination of mercury in National Research Council Canada DORM-3 fish muscle tissue and several water samples.     

Automated microwave digestion of certifiable color additives for determination of mercury by cold vapor atomic absorption spectrometry

A procedure using an automated microwave flow digestion technique was developed and validated for the digestion of samples of certifiable color additives before mercury determination by cold vapor atomic absorption spectrometry. Recovery studies were performed by spiking most of the color additives subject to batch certification by the U.S. Food and Drug Administration with inorganic mercury (HgNO3) and with organic mercury (CH3HgCl). Successful recoveries of 72-113% Hg added at the 1 microg/g level were obtained. A method detection limit of 0.2 microg Hg/g was estimated from a Hg-spiked FD&C Yellow No. 6 sample. At the specification level of 1 ppm Hg (1 microg Hg/g), the 95% confidence interval was +/- 0.2 ppm (0.2 microg Hg/g).     

Preconcentration and determination of trace elements with 2,6-diacetylpyridine functionalized Amberlite XAD-4 by flow injection and atomic spectroscopy

An on-line flow injection method for the direct determination of trace elements in environmental samples is described. A mini-column packed with 2,6-diacetylpyridine functionalized Amberlite XAD-4 was used to preconcentrate and separate 8 trace metals (Cd, Co, Cu, Mn, Ni, Pb, U and Zn) from water and extracts from solid samples. The metals were eluted with 0.1 M HNO(3) directly to the detection system (either inductively coupled plasma-mass spectrometry (ICP-MS) or flame atomic absorption spectrometry (FAAS)). As well as demonstrating that the resin could be used to preconcentrate ultra-trace analytes from natural waters, it was also shown to work well at a pH of 5.5. Therefore, after treatment of sample digests with sodium fluoride, samples that contain extremely large concentrations of iron may be analysed for trace analytes without the excess iron overloading the capacity of the resin. To this end, the analytes Cd, Co, Cu and Ni were preconcentrated from acid extracts of certified soil/sediment samples and then eluted with nitric acid to be determined on-line. Limits of detection (3sigma) of Cd = 0.33 microg l(-1), Co = 0.094 microg l(-1), Cu = 0.34 microg l(-1), Mn = 0.32 microg l(-1), Ni = 0.30 microg l(-1), Pb = 0.43 microg l(-1), U = 0.067 microg l(-1) and Zn = 0.20 microg l(-1) for the FI-ICP-MS system and Cd = 22 microg l(-1), Co = 60 microg l(-1), Cu = 10 microg l(-1) and Ni = 4.8 microg l(-1) for the FI-FAAS system were obtained. Analysis of certified reference materials showed good agreement with the certified values using the two methods.     

A low consumption air-segmented sequential injection vapor generation system for the determination of mercury by atomic absorption spectrometry

A sequential injection system for the determination of mercury by vapor generation atomic absorption spectrometry (VGAAS) using tetrahydoborate reductant was developed, characterized by prevention of sample and reagent mixing in the holding coil using small air segments and initiation of the vapor generation in a flow-through gas-liquid separator. Extremely small volumes of reductant of 15-30 mul (0.2-1.0% NaBH(4)) and sample acidity as low as 0.05 mol l(-1) HCl were sufficient for achieving performance similar to flow injection (FI) VGAAS systems. A sample throughput of 90 h(-1) was achieved with 400 mul samples with a precision of 2.0% RSD at 10 mug l(-1)Hg, and a detection limit of 0.1 mug l(-1) (3sigma). Reagent consumption was reduced by a factor of 25 in comparison to the FI-VGAAS system. Good agreement with the certified value was obtained for the determination of mercury in seawater in a standard reference sample.     

Determination of trace cadmium in environmental water samples using ion-interaction reversed-phase liquid chromatography with fluorescence detection

An ion-interaction reversed-phase liquid chromatographic method has been developed for the determination of cadmium at low microg/l concentrations in environmental water samples. Cadmium and other matrix metals were separated through on-column complexation with 8-hydroxyquinoline sulphonate, using an octadecylsilica column and a mobile phase containing 15% acetonitrile, 10-13 mM tetrabutylammonium hydroxide, 5 mM 8-hydroxyquinoline 5-sulphonic acid and 10 mM acetic acid-acetate buffer (pH 4.8-5.4). Under the above conditions Cd(II) could be easily resolved from excess concentrations of matrix metals and could be detected at concentrations as low as 2 microg/l using fluorescence detection at 500 nm (based upon a 100-microl injection). The method showed a slightly curved detector response over the range of interest [up to 1 mg/l Cd(II)] and was successfully applied to the determination of trace Cd(II) in water samples containing large excesses of Mg(II) and Zn(II) and other matrix metals.     

Determination of mercury(II) ion by electrochemical cold vapor generation atomic absorption spectrometry.

A technique for determination of mercury is described; it is based on electrolytic reduction of Hg(II) ion on a graphite cathode, the trapping of mercury vapor and its volatilization into a quartz tube aligned in the optical path of an atomic absorption spectrometer. The electrochemical cell consisted of a graphite cathode and an anode operating with constant direct current for the production of mercury atoms. A pre-activated graphite rod was used as the cathode material. The optimum conditions for electrochemical generation of mercury cold vapor (the electrolysis time and current, the flow rate, the type of electrode and electrolyte) were investigated. The characteristic electrochemical data with chemical cold vapor using NaBH4-acid were compared. The presence of cadmium(II), arsenic(III), antimony(III), selenium(IV), bismuth(III), silver(I), lead(II), lithium(I), sodium(I) and potassium(I) showed interference effects which were eliminated by suitable separation techniques. The calibration curve is linear over the range of 5-90 ng ml(-1) mercury(II). The detection limit is 2 ng ml(-1) of Hg(II) and the RSD is 2.5% (n = 10) for 40 ng ml(-1). The accuracy and recovery of the method were investigated by analyzing spiked tap water and river water.     

Spectrophotometric studies on the simultaneous determination of cadmium and mercury with 4-(2-pyridylazo)-resorcinol

A new method for direct spectrophotometric determination of cadmium with 4-(2-pyridylazo)-resorcinol is reported. Absorption maximum, molar absorptivity and Sandell's sensitivity of the 1:1 (M:L) complex are 510 nm, 2.5 x 10(5) l mol(-1) cm(-1) and 3.55 ng cm(-2), respectively. A linear calibration graph is obtained up to 4.49 microg ml(-1). The zero-crossing measurement technique is found suitable for the direct measurement of the first-derivative value at the specified wavelengths. Cadmium(II) (0.42-9.2 microg ml(-1)) and mercury(II) (0.35-7.4 microg ml(-1)) in different ratios have been determined simultaneously. A critical evaluation of the proposed method is performed by statistical analysis of the experimental data. The developed method was applied to the simultaneous spectrophotometric determination of Cd and Hg in some synthetic mixtures and was found to give satisfactory results.     

Direct determination of mercury in cosmetic samples by isotope dilution inductively coupled plasma mass spectrometry after dissolution with formic acid

A new method was proposed for the accurate determination of mercury in cosmetic samples based on isotopic dilution (ID)-photochemical vapor generation (PVG)-inductively coupled plasma mass spectrometry (ICP MS) measurement. Cosmetic samples were directly dissolved in formic acid solution and subsequently subjected to PVG for the reduction of mercury into vapor species following by ICP MS detection. Therefore, the risks of analyte contamination and loss were avoided. Highly enriched ²⁰¹Hg isotopic spike is added to cosmetics and the isotope ratios of ²⁰¹Hg/²⁰²Hg were measured for the quantitation of mercury. With ID calibration, the influences originating from sample matrixes for the determination of mercury in cosmetic samples have been efficiently eliminated. The effects of several experimental parameters, such as the concentration of the formic acid, and the flow rates of carrier gas and sample were investigated. The method provided good reproducibility and the detection limits were found to be 0.6 pg mL⁻¹. Finally, the developed method was successfully applied for the determination of mercury in six cosmetic samples and a spike test was performed to verify the accuracy of the method.     

Evaluation of a new electrolytic cold vapor generation system for mercury determination by AFS

In this study we firstly report a new electrolytic cold vapor generation system for mercury determination on Pt/Ti cathode in the presence of organic acid catholyte. Comparing with the traditional inorganic acid, formic acid increased the signal intensity of Hg vapor from electrolytic generation on Pt cathode and reduced the impact of cathode erosion on the stability of signal intensity. Moreover, formic acid has better interference tolerance. The introduction location for carrier gas is probably the most important factor that influences the signal intensity of Hg from electrolytic vapor generation. The effects of the electrolytic conditions and interference ions on the ECVG have been studied. Under the optimized conditions, the detection limit (3σ) of Hg (II) in aqueous solutions is 1.4 ng L⁻¹; a relative standard deviation of 2.3% for 1 μg L⁻¹ Hg was obtained. The accuracy of this method was verified by the determination of mercury in the certified reference materials. This system has been applied satisfactorily to the determination of Hg in Traditional Chinese Medicines samples.     

An evaluation of analytical techniques for determination of lead, cadmium, chromium, and mercury in food-packaging materials

Closed microwave digestion and a high-pressure asher have been evaluated for wet-oxidation and extraction of lead, cadmium, chromium, and mercury from a range of typical packaging materials used for food products. For the high-pressure asher a combination of nitric and sulfuric acids was efficient for destruction of a range of packaging materials; for polystyrene, however, nitric acid alone was more efficient. For microwave digestion, a reagent containing nitric acid, sulfuric acid, and hydrogen peroxide was used for all materials except polystyrene. Use of the high-pressure asher resulted in the highest recoveries of spiked lead (median 92%), cadmium (median 92%), chromium (median 97%), and mercury (median 83%). All samples were spiked before digestion with 40 microg L(-1) Cd, Cr, and Pb and 8 microg L(-1) Hg in solution. The use of indium as internal standard improved the accuracy of results from both ICP-MS and ICP-AES. Average recovery of the four elements from spiked packaging materials was 92 +/- 14% by ICP-MS and 87 +/- 15% (except for mercury) by ICP-AES. For mercury analysis by CVAAS, use of tin(II) chloride as reducing agent resulted in considerably better accuracy than use of sodium borohydride reagent.     

Spectrophotometric determination of trace amounts of cadmium and zinc in waste water with 4-(2-pyridylazo)-resorcinol and mixed ionic and non-ionic surfactants

A spectrophotometric method for determination of trace amounts of cadmium and zinc in waste water with PAR and mixed ionic and non-ionic surfactants is described. The interferences of foreign ions can be eliminated by masking with a mixture of triethanolamine, potassium fluoride, ethylenediamine and sodium hexametaphosphate. By virtue of the difference between the absorbances before and after addition of a little sodium diethyldithiocarbamate, cadmium and zinc can be determined directly in aqueous solution without separation. Beer's law is obeyed for 0-20 microg of Cd or 0-12 microg of Zn in 25 ml of solution. The apparent molar absorptivities at 505 nm are 8.65 x 10(4) l.mole(-1).cm(-1) for Cd and 8.21 x 10(4) l.mole(-1).cm(-1) for Zn. Results obtained by applying the proposed method to waste-water samples agree well with those obtained by atomic-absorption spectrophotometry.     

Determination of cadmium by flow injection-chemical vapor generation-atomic absorption spectrometry

A method was developed for the generation of a “cold vapor” of cadmium by means of flow injection-chemical vapor generation from aqueous samples, the determination being conducted with an atomic absorption spectrometer (Pyrex glass T-cell). Several gas-liquid separator designs, atomizer designs, and the effect of several reagents previously reported as sensitivity enhancers (including cobalt, nickel, thiourea and didodecyl-dimethylammonium bromide) were investigated. The limit of detection, calculated as the concentration giving a signal equal to three times the standard deviation of the blank, was 16 ng L^–1, and the relative standard deviation was 1.4% for a concentration of 2 μg L^–1 and 3.8% for 0.1 μg L^–1. The addition of nickel and thiourea to the samples provided improved tolerance to the interference of coexisting ions. Two NIST certified reference materials, Montana Soil and Apple Leaves (respectively containing ¶41.7 ± 0.25 mg kg^–1 Cd and 0.013 ± 0.002 mg kg^–1 Cd) were accurately analyzed. The interference of lead was overcome by coprecipitation with barium sulfate, and the experimental values obtained were 41 ± 1 mg kg^–1 Cd and 0.013 ± 0.002 mg kg^–1 Cd, respectively.     

Simultaneous determination of arsenic, antimony, bismuth and mercury in geological materials by vapor generation-four-channel non-dispersive atomic fluorescence spectrometry

Chemical vapor generation (CVG) coupled with non-dispersive atomic fluorescence spectrometry (NDAFS) has been widely used for determination of vapor-forming elements, but most of such works have been focused on single element analysis, and reports dealing with more than three elements simultaneous determination by CVG-NDAFS are rare. In this work, a sensitive and robust analytical procedure for the simultaneous determination of arsenic, antimony, bismuth and mercury in geological materials using vapor generation-four-channel non-dispersive atomic fluorescence spectrometry has been developed. The conditions of instrumentation and vapor generation of arsenic, antimony, bismuth and mercury were optimized. The optimized concentrations of KBH(4) and HCl required for analytes generation were 1.3% (m/v) and 20% (v/v), respectively. The interferences of coexisting ions and mutual hydride interferences were investigated carefully. One thousand milligrams per litre of Fe(3+); 500mgl(-1) of Pb(2+), Zn(2+), Mn(2+); 50mgl(-1) Cu(2+), Ni(2+), Cr(6+), Co(2+); 10mgl(-1) Ag(+) and 5mgl(-1) Au(3+) does not interfere with the determination of As, Sb, Bi and Hg. Associating a dilution of 1:250 (m/v) in the procedure of sample pretreatment, the tolerant concentrations of As, Sb, Bi and Hg in real geological materials are 2500, 1000, 250 and 5000ppm, respectively. Under optimal conditions, the detection limits for As, Sb, Bi and Hg were determined to be 0.068, 0.047, 0.037 and 0.008ngml(-1), respectively. The precisions for seven replicate determinations at the 5ngml(-1) of As, Sb, Bi and 1ngml(-1) of Hg were 0.47, 0.60, 0.97 and 0.93% (R.S.D.), respectively. Sample digestion was carried out on 500mg sample with 3ml HNO(3) and 10ml HCl, followed by addition of thiourea solution for the quantitative reduction of As(V), Sb(V) to As(III), Sb(III). The proposed method was successfully applied to the simultaneous determination of As, Sb, Bi and Hg in a series of certified geological reference materials using simple aqueous standard calibration technique. The results obtained are in good agreement with the certified values.     

化学蒸汽发生/电感耦合等离子体质谱法测定近岸及河口海水中的超痕量砷、锑、铋、锗、锡、汞

建立了化学蒸汽发生(CVG)电感耦合等离子体质谱(ICP MS)同时测定近岸及河口海水中超痕量As、Sb、Bi、Ge、Sn和Hg元素的方法.研究了CVG过程中KBH4、盐酸和硫脲的浓度以及样品流速、载气流速、海水样品盐度等对方法分析性能的影响.结果表明,在0.70％6盐酸、0.10 g/L硫脲、11.0 g/L硼氧化钾...     

Determination of cadmium and copper with ET-AAS after electrochemical deposition on a graphite electrode

The electrodeposition of cadmium and copper on a special graphite disk electrode has been performed at controlled potential. The electrode with the deposit has been inserted into the graphite atomizer HGA-400 by an adapted automatic sampler for the final determination by ET-ASS. The sensitivity of determination has been 0.371 (microg l(-1))(-1) for cadmium and 0.025 (microg l(-1))(-1) for copper for 2 min electrodeposition and increased linearly with the time of deposition. The limit of detection (3s(bl)) has been 7.9 ng l(-1) Cd(2+) and 0.11 microg l(-1) Cu(2+) for 2 min deposition and it has been improved with increased time of electrodeposition. The technique has been applied to the determination of both metals in seawater and to speciation in the presence of EDTA complexing agent.