Clean conditions for the determination of ultra-low levels of mercury in ice and snow samples

Laboratory facilities and methods are presented for the determination of ultra-low levels of mercury (Hg) in ice and snow samples originating from polar ice caps or temperate regions. Special emphasis will be given to the presentation of the clean laboratory and the cleaning procedures. The laboratory is pressurized with air filtered through high efficiency particle filters. This first filtration is not enough to get rid of contamination by Hg in air. Experiments are conducted in a clean bench, especially built for Hg analysis, equipped with both particle filter and activated charcoal filter. It allows to obtain very low levels of atmospheric Hg contamination. Ultrapure water is produced for cleaning all the plastic containers that will be used for ice and snow samples and also for the dilution of the standards. Hg content in laboratory water is about ¶0.08 ± 0.02 pg/g. A Teflon system has been developed for the determination of Hg in ice and snow samples based on Hg(II) reduction to Hg(0) with a SnCl₂/HNO₃ solution followed by the measurement of gaseous Hg(0) with a Hg analyzer GARDIS 1A+ based on the Cold Vapor Atomic Absorption Spectroscopy method. Blank determination is discussed.     

Ion chromatographic determination of common ions at ultratrace levels in Antarctic snow and ice

The simultaneous determination of major impurities present in Antarctic snow and ice at ng g^? (ppb) concentrations by ion chromatography is described. Calibration data are presented for ammonium, sodium, potassium, chloride, nitrate and sulphate ions. Special attention is paid to the different ways of removing field contamination from ice and snow cores and suitable equipment is described. The results provide evidence against the validity of published sets of concentration data for nitrogen-containing compounds (NO^?₃ and NH⁺₄ in Antarctic snow, and demonstrate a crucial contamination problem in the determination of ammonium ions.     

Non-chromatographic screening method for the determination of mercury species. Application to the monitoring of mercury levels in Antarctic samples

A simple non-chromatographic method for the determination of mercury (Hg²⁺), methylmercury (MeHg⁺), dimethylmercury (Me₂Hg), and phenylmercury (PhHg⁺) employing atomic fluorescence spectrometry (AFS) as detection technique was developed. Mercury species showed a particular behavior in the presence of several reagents. In a first stage SnCl₂ was employed for Hg²⁺ determination; in a second step, [Hg²⁺ + PhHg⁺] concentration was determined using SnCl₂ and UV radiation. MeHg⁺ decomposition was prevented adding 2-mercaptoethanol. In a third stage, [Hg²⁺ + PhHg⁺ + MeHg⁺] concentration was determined using K₂S₂O₈. Finally, the four species were determined employing NaBH₄. Reagents concentration and flow rates were optimized. The extraction technique of mercury species involved the use of 2-mercaptoethanol as ion-pair reagent. The limits of detection for Hg²⁺, PhHg⁺, MeHg⁺, and Me₂Hg were 1, 40, 68, and 99 ng L⁻¹ with a relative standard deviation of 1.5, 3.1, 4.7 and 5.8%, respectively. Calibration curve was linear with a correlation factor equal to 0.9995. The method was successfully applied to the determination of the mercury species in two Antarctic materials: IRMM 813 (Adamussium colbecki) and MURST-ISS-A2 (Antarctic Krill).     

Microwave dissolution for the determination of mercury in biological samples

Microwave dissolution in closed teflon vessels is described for the determination of ng g^?1 contents of mercury in biological materials, prior to two-stage gold amalgamation and cold-vapour atomic absorption spectrometry. Six samples can be decomposed simultaneously within 20 min, with a preset heating programme. The detection limit is 0.84 ng g^?1 for a 100-mg sample. Results for six certified reference materials agreed with the certified values.     

Kinetic-coulometric determination of mercury in biological samples

A simple approximate calculation method is given which permits determina-tion of the maximal scan rates of potential allowable for distortion-free recording of current-voltage curves with X-Y recorders. For the calculations only the response time of the recorder, the wave shape and the scan rate of potential need be known. Stationary mercury electrodes and rapid polarography with a dropping mercury electrode at controlled drop times were examined. Electroanalytical implications are discussed, with particular emphasis on the rapid a.c. polarographic method with short controlled drop times and on stationary-electrode fundamental and second harmonic a.c. voltammetry. Theoretically and experimentally it has been shown that an X-Y recorder with 0.5–1.0-s response time can be used for scan rates up to about (50/nt') mV s^-1 with a.c. techniques and about (100/nt') mV s^-1 with d.c. polarography (t'= response time of recorder, n = number of electrons).     

Pyrolysis/CVAAS for the determination of mercury in solid environmental samples

Summary A CVAAS method is reported for the determination of mercury in solid environmental materials by pyrolysis and a two-stage amalgamation on gold. Interferences by pyrolysis products are eliminated by a purification section containing a catalytic converter and two specific adsorbers for organic substances. The detection limit of the method is 5 ppb for a 20-mg sample. The reproducibility highly depends on the homogeneity of the materials.

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Pyrolyse/Kaltdampf-Atomabsorption zur Hg-Bestimmung in festen Umweltproben

Zusammenfassung Ein Kaltdampf-Atomabsorptions-Verfahren zur Quecksilberbestimmung in festen Umweltproben durch Pyrolyse und Zwei-Schritt-Amalgamierung auf Gold wurde angegeben. Störungen durch Pyrolyseprodukte lassen sich durch eine Reinigungsvorrichtung beseitigen, die einen katalytischen Konverter und zwei spezifische Absorber für organische Substanzen enthält. Die Nachweisgrenze für eine 20-mg-Probe liegt bei 5 ppb. Die Reproduzierbarkeit der Ergebnisse ist weitgehend von der Homogenität des Materials abhängig.

     

New voltammetric procedure for the simultaneous determination of copper and mercury in environmental samples

Summary A new voltammetric procedure for the simultaneous determination of Cu and Hg down to the ng/l-range in environmental samples is described. Differential pulse anodic stripping voltammetry (DPASV) at a gold electrode is applied. There are two versions. For Hg-levels typically below 100 ng/l in presence of substantially higher Cu-concentrations (300 ng/l or more), e.g. in sea water, Hg has to be determined by the subtractive mode of DPASV at a twin gold electrode and programmed polarisation has to be applied during the cathodic deposition stage, while the usually higher Cu-levels can be determined by common DPASV at a normal gold electrode. For Hglevels above 100 ng/l the determination of Hg and Cu can be performed in the same run by common DPASV at a normal gold electrode. The application of the gold electrode always requires medium exchange to 0.1 M HClO₄ plus 2.5×10^–3 M HCl subsequent to the cathodic accumulation stage before stripping. The method has been successfully applied to natural waters and wine. The necessary sample pretreatment remains simple and consists just in UV-irradiation to release the trace metal amount bound to dissolved organic matter, which is performed with samples from natural waters after prior 0.45 -filtration to separate from suspended particulate material.

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Neues voltammetrisches Verfahren zur simultanen Bestimmung von Kupfer und Quecksilber in Umweltmaterial

Zusammenfassung Als Bestimmungsverfahren werden zwei Versionen der differentiellen Pulsinversvoltammetrie (DPASV) an der Goldelektrode eingesetzt. Bei Quecksilbergehalten typisch unter 100 ng/l und gleichzeitiger Anwesenheit höherer Kupferkonzentrationen (300 ng/l), wie z.B. im Meerwasser, muß Hg mit der subtraktiven DPASV an einer Zwillingselektrode aus Gold bestimmt werden und während des kathodischen Anreicherungsschrittes erfolgt programmierte Polarisation der Goldelektrode. Hingegen können die gewöhnlich höheren Cu-Gehalte mit der üblichen konventionellen DPASV an einer normalen Goldelektrode bestimmt werden. Bei Hg-Gehalten oberhalb 100 ng/l kann die Bestimmung von Hg und Cu in einem voltammetrischen Arbeitsgang mit der konventionellen üblichen DPASV an einer normalen Goldelektrode erfolgen. Die Verwendung der Goldelektrode verlangt immer Wechsel des Mediums zu 0,1 M HClO₄ plus 2,5 ×10^–3 M HCl nach der kathodischen Anreicherung vor der stripping-Phase. Die Methode hat erfolgreiche Anwendung bei der Untersuchung natürlicher Gewässer und von Wein gefunden. Die erforderliche Probenvorbereitung bleibt einfach und besteht in einer UVBestrahlung, um den durch gelöste organische Materie gebundenen Spurenmetallanteil zu mobilisieren. Bei Proben aus natürlichen Gewässern erfolgt vorher eine 0,45 -Filtration zur Abtrennung von Schwebstoffen.

     

A novel method for the determination of synthetic colors in ice cream samples

A simple method has been developed for the extraction, separation, and determination of synthetic colors in ice cream samples. The process involves the breakdown of emulsion by neutral detergents (Triton X-100 and Tween 20) followed by extraction with petroleum ether for removal of fat. The aqueous colored solution obtained is treated with 5% acetic acid, and the uptake of color is carried out by a wool-dyeing technique. The color is eluted from the wool with 5% ammonia solution, the solution is evaporated to dryness, and the residue is dissolved in 60% ethanol for paper chromatography using trisodium citrate-ammonia-water (2 + 5 + 95, w/v/v) as the mobile phase. The colored spots from the paper chromatogram are cut and eluted with 60% ethanol, and the absorbance is measured at the respective lambda maximum corresponding to the Rf value of the appropriate standard. The recoveries of 6 colors, including sunset yellow FCF (SSYFCF), tartrazine, carmoisine, ponceau 4R, brilliant blue FCF (BBFCF), and fast green FCF from spiked samples with either detergent were found to be >90%. However, recoveries of erythrosine were 21 and 65% with Triton X-100 and Tween 20, respectively. Indigo carmine could not be recovered at all because of its fugitive property in 5% ammonia solution, which is used to strip the color from the wool. The sensitivity of the method with the use of Tween 20 is 1 ppm (1 microg/g) for the colors in spiked ice cream samples. With this method, we analyzed samples of 20 branded colored ice cream. The results showed the presence of tartrazine (8.4-43.3 ppm), SSYFCF (23.5-117.6 ppm), carmoisine (traces-53.2 ppm), erythrosine (3.5 ppm), and BBFCF (4.1 ppm) in the ice cream samples. Apart from 2 samples of tuttifruity, all of the ice cream samples showed the presence of permitted synthetic colors below the permissible level of 100 ppm established by the Prevention of Food Adulteration Act of India.     

Analytical determination of mercury in medicinal and waste water samples

Tris(2-ethylhexyl)phosphate (TEHP) is proposed as an extractant for mercury salicylate. Optimum extraction conditons are developed and the method is used for determinations of mercury in medicinal and waste water samples.     

Voltammetric determination of mercury levels in tuna fish

Summary A reliable and rapid procedure for the determination of Hg in fish by differential pulse anodic-stripping voltammetry (DPASV) at the gold electrode has been developed for use in food control and marine ecotoxicology. Potentialities and performance are demonstrated by the investigation of tuna fish. Samples of 0.5–2.5 g are subjected to pressurized digestion with HNO₃/HClO₄ (71). The resulting analyte solution is irradiated in closed flasks with ultraviolet light in presence of H₂O₂ to decompose dissolved organic substances. This is followed by DPASV with two standard additions. The relative standard deviation for the lower g/g range is below 5%. Comparative determination by gas chromatography confirmed that in fish-muscle mercury exists almost completely in the form of toxic organomercurials, i. e. methyl- and dimethylmercury.

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Voltammetrische Bestimmung von Quecksilber in Thunfischen

Zusammenfassung Für die Lebensmittelkontrolle und marine Ökotoxikologie wurde eine neue spurenanalytische Alternative zur raschen und zuverlässigen Bestimmung des Quecksilbergehaltes in Fisch unter Einsatz der differentiellen Pulsinversvoltammetrie (DPIV) und Verwendung einer Goldscheibenelektrode entwickelt.Möglichkeiten und Leistungsfähigkeit der Methode werden durch die Untersuchung von Thunfisch demonstriert. Proben von 0,5 bis 2,5 g Frischgewicht werden zunächst einem Druckaufschluß mit HNO₃/HClO₄ (71) unterworfen. Die resultierende Analytlösung wird zum Abbau gelöster organischer Substanzen im geschlossenen Gefäß einer UV-Bestrahlung (70° C, 150 W Quecksilberlampe, 4 h) unter oxydierenden Bedingungen (H₂O₂) unterzogen. Anschließend erfolgt die voltammetrische Bestimmung mit DPIV unter Vornahme von zwei Eichzusätzen. Die relative Standardabweichung liegt im unteren mg/kg-Bereich unter 5%. Die Richtigkeit wurde durch Vergleichsbestimmung mit der Gaschromatographie getestet. Die Übereinstimmung der ermittelten Quecksilbergehalte bestätigt, daß im Muskelfleisch von Fisch das Quecksilber nahezu vollständig in toxischen organischen

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Taken in part from the Ph. D. Thesis of R. Ahmed. Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980.     

Pretreatment of water samples using UV irradiation-peroxodisulfate for the determination of total mercury

Potassium peroxodisulfate (14 g l⁻¹, 25 ml) has been observed to readily oxidize water under UV irradiation (30 W mercury arc tube), even at room temperature. The reaction is complete in 20 min, producing oxygen in stoichiometric amounts. The reaction was applied to pretreatment for the determination of total mercury by cold vapor atomic absorption spectrometry (AAS).The response of mercury(II) chloride by the UV irradiation method was higher than that by the standard permanganate method (95 °C, 2 h). The conversion efficiency of mercury by the UV irradiation method, the standard method and by non-treatment was found to be 100, 93.6 and 85.0%, respectively. The study is also applied to methylmercury, ethylmercury and phenylmercury chlorides.     

ICP-MS 法直接测定冰芯样品中超痕量镉

采用 ICP- MS法对冰芯样品中超痕量 Cd的直接测定进行了研究。确定了直接测定浓度为 pg/m L 级的 Cd的最佳仪器参数、载气流速、进样速度等与灵敏度之间的关系以及浓度和扫描参数对分析精度的影响。本方法对浓度 5～2 0 0 pg/m L Cd的分析 ,RSD<1 0 % ,回收率在 88%～ 1 0 5%之间 ,检测限为0 .1 5pg/m L     

Bead-injection determination of total mercury in river water samples.

A bead-injection system is proposed for total mercury determination in river-water samples. The procedure is based on the introduction of a defined quantity of a resin suspension in the flow system. The selected beads are packed inside of a flow cell and the formed resin mini-column constitutes the optical path. The sample volume is then selected, and its passage by the mini-column allows retention of the mercury ions on the surfaces of the beads. The introduction of a spectrophotometric reagent in the flow system leads to the formation of a colored Hg-dithizone complex on the surface of the bead, which is spectrophotometricaly monitored. The spent beads are directed to waste, allowing the system to become ready to process another sample. The proposed system handles about 20 measurements per hour, consuming 1000 microl of the sample, 1 mg of Chelex 100 resin and 1.25 microg of Dithizone per determination. When 1000 microl of the sample is injected, a linear analytical curve is obtained (A = 0.0052[Hg] + 0.1028, from 0 up to 30 microg l(-1), R2 = 0.995); the detection limit is estimated to be 0.9 microg l(-1). The results are precise, r.s.d. < 9%; spiked sample recoveries within 91.2 and 109% are found.     

Exploiting the bead injection concept for sequential determination of copper and mercury ions in river-water samples

A procedure involving bead-injection concept and sequential determination of copper and mercury ions in river-water samples is proposed. The method is based on the solid-phase extraction of both metal ions on the same beads surface (Chelex 100 resin) and in their subsequent reaction with the colorimetric reagents (APDC and Dithizone for copper and mercury ions, respectively). For this task, a resin mini-column is established in the optical path by the selection, introduction and trapping of a defined volume of the Chelex-100 resin beads suspension in the flow system. The passage of the sample solution through the resin mini-column promotes the sorption of Cu(II) ions and, making the APDC colorimetric reagent flows through the beads, the formation of the coloured complex on the solid phase surface occurs. The absorbance of the formed APDC-Cu complex is then monitored at 436 nm and the spent beads are discarded. Packing another resin mini-column in the flow cell and repeating the concentration step it is possible to carried out the mercury determination by using Dithizone as reagent. The absorbance of the Dithizone-Hg complex is monitored at 500 nm. After each measurement, the spent beads are wasted and a new portion of fresh one is trapped in the system, letting it ready for the next measurement. The bead injection system is versatile and can be used to concentrate different sample volumes, which permits the determination of a wide range of copper and mercury ions concentrations. When the sample-selected volumes are 100 and 1000 μl the analytical ranges were 5.0 up to 500.0 μg l⁻¹ and 2.5 up to 30.0 μg l⁻¹ for Cu(II) and Hg(II) ions, respectively. Under these conditions, the detection limit was estimated as 0.63 and 0.25 μg l⁻¹ for copper and mercury ions determination. The system consumes 2 mg of Chelex 100 resin beads, 0.20 mg of APDC or 1.25 mg of Dithizone per determination and the traditional organic solvent extraction methodology, normally used in connection with APDC and Dithizone reagents, is not used here which permits to classify the present method as green.     

Non-dispersive atomic-fluorescence spectrometry for the determination of mercury and its application to fish samples.

A simple non-dispersive atomic-fluorescence spectrometer is described for the assay of mercury in solution at the μg l^?1 level; it has also been applied to fish samples at the mg kg^?1 level. After destruction of the fish sample, the mercury is reduced by tin(II) chloride and released from solution by a stream of argon which crosses the beam of a mercury lamp. The fluorescence signal is detected directly by a solar-blind phototube without the need for monochromators or filters. One analysis requires less than 40 min. The results correlate well with those from atomic-absorption spectrometry and neutron-activation analysis.     

Atomic fluorescence spectrometry combined with reduction aeration for the determination of mercury in biological samples

A sensitive atomic fluorescence system for the determination of mercury was optimized. The system consists of a continuous-flow mercury vapour generator coupled to a fluorescence spectrometer specific for mercury. A new gas-liquid separator was developed. A detection limit of 0.9 ng Hg 1^?1 was obtained. The system was combined with a microwave oven for dissolving samples in closed Teflon PFA vessels. Accurate results were obtained for certified reference materials, and biological samples such as urine and hair were analysed.     

Simultaneous neutron-activation determination of selenium and mercury in biological samples by volatilization

A method is described for the determination of selenium together with mercury in biological samples by neutron-activation analysis based on quantitative volatilization of both elements. The technique originally developed for mercury, based on pyrolysis with filtration of undesirable impurities and selective trapping from the gas phase, is now extended to selenium. The radionuclides (197)Hg and (75)Se, from one sample, are trapped separately and counted in a well-type NaI(Tl) detector and gamma-spectrometer for maximum sensitivity. The method has been tested by comparative analyses and analyses of standard biological materials, and gives good results. It is simple and is especially effective in studies of the interaction of mercury and selenium in biological systems; a positive correlation for these elements was found for human tissues. On décrit une méthode pour le dosage du sélénium conjointement au mercure dans les échantillons biologiques par analyse par activation de neutrons basée sur la volatilisation quantitative des deux éléments. La techniqu initialement développée pour le mercure, basée sur la pyrolyse avec filtration des impuretés indésirables et captage sélectif de la phase gazeuse, est maintenant étendue au sélénium. Les radionuclides (197)Hg et (75)Se, d'un échantillon, sont captés séparément dans un détecteur NaI(Tl) du type puits et un spectromètre gamma pour la sensibilité maximale. La méthode a été essayée par des analyses comparatives et des analyses de produits biologiques étalons, et donne de bons résultats. Elle est simple et particulièrement efficace dans les études de l'interaction du mercure et du sélénium dans des systèmes biologiques; on a trouvé une corrélation positive pour ces éléments pour des tissus humains.