A novel reagent for separation, trace determination of mercury by spectrophotometry, cold vapor atomic absorption spectroscopy (AAS), and membrane separation

Several decomposition procedures and their influence on the determination of mercury by electrothermal (ET) and cold vapour (CV) atomic absorption spectrometry (AAS) have been studied. Soil samples were decomposed by microwave digestion in closed and open vessels as well as by digestion under reflux according to German standard. The use of different acids (HNO3, HCl or aqua regia) was evaluated and compared in respect to their influence on the determination of mercury by ET AAS and CV AAS. The digestion solutions were analyzed by ET AAS with a palladium modifier and by CV AAS using SnCl2 or NaBH4, as reducing agents. The detection limits obtained with different procedures were also evaluated. For the soil containing 6.25 μg/g of Hg the ET AAS measurements were possible. In the case of lower concentration of mercury the CV AAS determination following the microwave digestion procedure with HCl or aqua regia is recommended. The accuracy of the proposed procedure was confirmed by the determination of total mercury in SRM 2711 Montana Soil.

Total Mercury Determination in Biological and Environmental Standard Samples by Gold Amalgamation Followed by Cold Vapor Atomic Absorption Spectrometry

A system for on-line treatment of liquid samples in a microwave oven digestor was evaluated for use with cold vapour (CV) and hydride generation (HG) atomic absorption spectrometry (AAS). Various oxidation mixtures were tested and those based on bromination (bromate–bromide–acid) and peroxodisulfate (persulfate–acid–complexing agent) were found to be compatible with and most appropriate for CVAAS and HGAAS. The composition of reagents and the analytical conditions were optimized for the determination of mercury, arsenic, bismuth, lead and tin in urine and environmental waters. The limits of detection were 0.01 and 0.2 µg l–1 for mercury, with and without amalgamation, respectively, 0.5 µg l–1 for arsenic, 0.07 µg l–1 for bismuth and 0.1 µg l–1 for tin and the sample throughput was between 13 and 30 h–1.

An analytical system for automated on-line pre-treatment of liquid samples in a microwave oven for flow injection cold vapour and hydride generation atomic absorption spectrometry has been designed and evaluated. The system is based on a focused microwave oven and a new manifold with two coils. A reaction coil and a ballast-load coil are placed and oriented within the digestor in a manner providing a reliable long-term operation and increased reaction time. Samples are mixed with an appropriate oxidation reagent and loaded on an autosampler; all further operations of sample uptake, digestion, measurement, calibration and data processing are performed automatically with a sample throughput rate of 20–40 h–1. For the determination of mercury at ng l–1 levels using amalgamation the sample throughput decreased to 7–20 h–1. Introducing hot sample digests into the mercury/hydride system resulted in an increased sensitivity, particularly for peak height absorbance.

Microwave digestion reduction-aeration and pyrolysis combined with cold vapour atomic absorption and cold vapour atomic fluorescence are compared for the determination of total mercury in several biological and environmental matrices. The biological samples were digested in a mixture of HNO3/H2O2, the environmental samples in a mixture of HNO3/HClO4. After reduction with SnCl2, the mercury was collected by two-stage gold amalgamation. After microwave digestion reduction-aeration, detection limits of 1.4 ng g−1 and 0.6 ng g−1 were obtained for cold vapour atomic absorption spectrometry (CVAAS) and cold vapour atomic fluorescence spectrometry (CVAFS), respectively, for 250 mg of environmental samples. For biological samples (500 mg) the detection limits were 0.7 ng g−1 (CVAAS) and 0.4 ng g−1 (CVAFS). After pyrolysis, detection limits of 3.5 ng g−1 and 1.6 ng g−1 for CVAAS and CVAFS, respectively, were obtained for a 10 mg sample. Pyrolysis can only be applied when the organic content of the sample is not too high. Accurate results were obtained for 8 certified reference materials of both environmental and biological origin. In addition, a real sludge sample was analysed.

A simple in-house pyrolysis chamber made of quartz material is described for the determination of total mercury content in a wide variety of organic-rich solid materials (plant, fish tissues and polymer based) by oxidative pyrolysis and cold vapour atomic absorption spectrometry (CVAAS). Oxidative pyrolysis was carried out by means of a Bunsen burner in the presence of an oxygen stream. Mercury liberated from the sample was collected in 0.1% KMnO4 trapping solution. Determination of mercury was achieved by CVAAS. Under optimal conditions, the limit of detection (LOD), calculated as the concentration of mercury yielding a signal equivalent to three times of the standard deviation of the blank value (3σ), obtained for CVAAS in conjunction with the oxidative pyrolysis method was found to be 0.08 ng g−1. Flow injection inductively coupled plasma mass spectrometry (FI-ICPMS) was used to validate the developed method. The results obtained for several reference materials, such as mussel tissue (CE-278), tuna fish (CE-463), tuna fish (464), polyethylene (EC-681), plankton (CRM-414), lichen (CRM-482) and human hair (CRM-397), by the developed method agreed well with the certified values. These studies clearly demonstrate the capabilities of the pyrolysis set-up that can potentially be used for the rapid determination of total mercury in a wide variety of organic-rich matrices.

The determination of mercury in the presence of matrix substances (such as inorganic cations and anions, and organic compounds) was studied by cold vapor atomic absorption spectrometry with „completely continuous micro flow“, using tin(II) chloride in sodium hydroxide solution as reducing reagent. The effects of the diverse substances in the proposed method were found to be much smaller than those in the conventional methods using tin(II) in acid medium or borohydride in alkaline medium as the reducing reagents.

The determination of total Hg in various environmental matrices was investigated using energy-dispersive x-ray fluorescence (EDXRF) spectrometry on both powdered and digested samples and cold vapor atomic absorption spectrometry (CV-AAS) on digested samples. Several microwave decomposition procedures were evaluated. The use of different acid mixtures, microwave power settings and decomposition times were compared, in addition to the analysis of wet and freeze dried samples. A set of standard reference samples were used to evaluate the procedures. An H 2 SO 4 -HNO 3 -H 2 O 2 mixture was found to be optimal for the complete mineralization and digestion of biological samples for Hg by CV-AAS, whereas for EDXRF both HNO 3 -H 2 O 2 and H 2 SO 4 -HNO 3 -H 2 O 2 mixtures gave good results. The detection limit of EDXRF could be significantly decreased (from 0.2 μg g -1 to 0.058 μg g -1 ) by performing the analysis on digested samples. Good agreement was obtained between the EDXRF and CV-AAS analysis. The results were also in good agreement with certified values. The methods were applied to environmental samples (coal, vegetation, fish and sediment) and human hair in a coal mining area and in locations where coal is used for cooking in Vietnam.

Determination of mercury by cold vapour atomic absorption spectrometry with derivative signal processing

Recently, a new color additive, D&C Black No. 2, a high-purity furnace black in the general category of carbon blacks, was listed as a color subject to batch certification by the U.S. Food and Drug Administration. A simple procedure was developed to determine mercury (Hg) in D&C Black No. 2, which is limited by specification to not more than 1 ppm Hg. The method uses partial acid digestion followed by cold vapor atomic absorption and was developed by modifying a method used for other color additives. The carbon black samples are treated with a mixture of nitric and hydrochloric acids and heated by microwave in sealed Teflon vessels. The resulting solutions, which are stable to Hg loss for at least 1 week, are diluted and analyzed for Hg using cold vapor atomic absorption spectrometry. Validation was performed by spiking carbon black samples with inorganic Hg (HgNO3) at levels from 0.1 to 1.5 microg/g, and by analyzing 2 standard reference materials. At the specification level of 1 ppm Hg (1 microg Hg/g), the 95% confidence interval was +/-0.01 ppm Hg (0.01 microg Hg/g). The method developed in this study gave good results for very difficult-to-analyze materials, such as coal standard reference materials and carbon black. By eliminating volatility and adsorption factors through the formation of HgCl4(-2) complexes, one can avoid using extremely hazardous acids such as HF and HClO4.

A method has been proposed for the differential determination of inorganic and organic mercury in environmental and biological materials, based on their successive extraction followed by a cold vapor atomic absorption spectrometric (CVAAS) determination. Mercury was first extracted by shaking a sample with 1M hydrochloric acid containing 3% sodium chloride in the presence of copper(I) chloride. In order to separate organic mercury from inorganic mercury, the extract was shaken with chloroform to extract only organic mercury. The chloroform phase was transferred into a 50ml volumetric flask and 0.4ml of 0.2% dithizone-chloroform solution was added. The contents of the flask was evaporated to dryness, followed by addition of 2ml of 1:1 nitric acid-perchloric acid solution and 5ml of concentrated sulfuric acid and heating at ca. 230°C for 30min. The hydrochloric acid phase containing inorganic mercury was transferred into a 50ml volumetric flask, followed by addition of 1ml of 60% perchloric acid and 5ml of concentrated sulfuric acid and heating at ca. 230°C for 30min. After cooling, the digested sample solution was diluted with water to 50ml. The mercury in each solution was determined by CVAAS. When 0.5g amounts of artificial standard soil samples spiked with a given amount of organic mercury and inorganic mercury {20ng (as Hg) of mercury(II) chloride and methylmercury chloride} were treated by the above-mentioned procedures, the recoveries were 102% and 97.0% with the relative standard deviations of 1.0% and 2.8%, respectively. This method was successfully applied to a differential determination of mercury in sediment, soil and fish meat samples.

A simple and fast metal extraction method that combines closed vessels and microwave heating for the simultaneous extraction of ten selected heavy metals (As, Cd, Co, Cr, Hg, Mn, Ni, Pb, Zn) from marine sediments is proposed. Digestion conditions, i.e. power and times microwave irradiation. reagent extractant, sample amount, were optimized to recover the potentially available metallic fraction not bound in silicates. A nitric acid and two step microwave program was established. The resulting solutions were analyzed by flame (FAAS), hydride generation (HGAAS) and cold vapour (CV-AAS) atomic absorption spectrometry. Quantifications were made using direct calibration with aqueous standards. The recoveries of the spiked samples investigated ranged from 89 to 113 %. The results obtained from analyzing the BCR certified reference sediment CRM 277 Estuarine Sediment were in good agreement with the certified values (93–105%), except for low values for chromium (79%). The relative standard deviations for the determination of metals were less than 4%. Finally, the technique designed herein was applied to sediment samples from La Coruña estuary, NW Spain.

Mercury as a Heavy metal is important factor must be determined and controlled in environmental air and biological. Mercury (Hg) accumulate in living tissues of human body. By NIOSH method, the briefing work place air of petrochemical worker was measured by cold vapor atomic absorption spectrometry(CV-AAS). For preparation and preconcentration samples before analysis a new method of dispersive liquid-liquid micro-extraction with ammonium salt of 1-pyrrolidinedithiocarbamate(APTC)combined with cold vapor atomic absorption spectroscopy, was developed.The influences of various analytical parameters including pH, APDC concentration and ionic liquid volume were investigated.Quantitative recoveries were obtained at pH 7.The enrichment factor was calculated as 5.The detection of limit(LOD)and detection of quantification(LOQ)of mercury were 0.06 and 0.2 μg L-1 respectively. In order accuracy determination the method,certified reference materials, NIST SRM 3133 Lot 061204 was analyzed and the recovery value 98% obtained. So, method of DLLME-APTC had good potential for preparation and preconcentration mercury samples before analysis.

Determination of total mercury in environmental and biological samples by flow injection cold vapour atomic absorption spectrometry

A new method for the determination of trace mercury is proposed by using cold-vapor atomic absorption analysis after the reduction of mercury with a mixture of sodium tetrahydroborate (NaBH4) and tin(II) chloride in acidic solution. Iodide up to 20mg/20ml did not interfere with the mercury determination, and 85% recovery of mercury was attained even in the presence of 100mg of iodide. The present method was successfully applied to the determination of mercury in complicated iodide-containing environmental samples such as wastewater discharged from universities, research institutes and so on. Furthermore, the mechanism of the interference of iodide in the determination of trace mercury was investigated electrochemically by pseudo-polarographic and potentiometric measurement.