Determination Of Mercury In Sediments Research Articles

Determining Mercury in Sediment Samples by Extraction Using a Novel-Chelating Reagent Dithiothreitol (DTT) Followed by Cold Vapor Atomic Fluorescence Spectrometry (CV-AFS)

A new analytical protocol has been developed for the determination of mercury in surface sediments using dithiothreitol (DTT) as a new chelating reagent for the extraction. This protocol requires a small sample mass (250 mg), 4.0 mL of a 0.1 M (pH = 9.0) aqueous DTT solution, and sonication for 30 min, followed by cold vapor atomic fluorescence spectrometry (CV-AFS). The limits of detection and quantification determined were 6 and 18 ng g−1, respectively. The method was validated using three standard reference materials, SRM NIST 1646a, PACS-2, and MESS-3, with recoveries in the range of 102-124%. The new analytical protocol was successfully applied in riverine surface sediments, revealing concentrations in the range of 220-340 ng g−1. The results obtained by CV-AFS were compared to those obtained by DMA-80 (direct mercury analyzer). The linear regression equation obtained was [CV-AFS] = (0.91 ± 0.07)[DMA-80] + (0.04 ± 0.02), revealing no systematic difference between the analytical methods. Hence, the proposed method does not require the complete digestion of the sediment, and was found to be comprehensive, simple, accurate and suitable to be employed for determination of mercury in sediment samples.

Determination of Mercury in Sediments by Slurry Sampling Electrothermal Atomic Absorption Spectrometry

The concentration of mercury in suspensions of sediments is determined by electrothermal atomic absorption spectrometry (ET-AAS) using a novel chemical modifier (ChM) based on activated carbon treated by iron(II) formate. The efficiency of chemical modifiers based on activated carbon, also modified by Ag(I), Au(III), Pd(II), Co(II), and Ni(II) compounds is studied. The optimum conditions are found for the temperature and time program of the atomizer; they prevent mercury losses at the stage of drying sample suspensions and also exclude spectral interferences at the stage of atomization and measurement of the analytical signals. The minimum characteristic mass of mercury (52 pg) is reached using an iron-containing chemical modifier based on activated carbon. The conditions of ET-AAS analysis using this ChM are tested on certified reference materials of sediments and a sample selected near the sea port of Temryuk (Sea of Azov). The limit of detection found by the 3s-test was 0.05 mg/kg and the relative standard deviation was 5% at the concentration of mercury in the sample 149 mg/kg.

Organic and total mercury determination in sediments by cold vapor atomic absorption spectrometry: methodology validation and uncertainty measurements

The purpose of the present study was to validate a method for organic Hg determination in sediment. The procedure for organic Hg was adapted from literature, where the organomercurial compounds were extracted with dichloromethane in acid medium and subsequent destruction of organic compounds by bromine chloride. Total Hg was performed according to 3051A USEPA methodology. Mercury quantification for both methodologies was then performed by CVAAS. Methodology validation was verified by analyzing certified reference materials for total Hg and methylmercury. The uncertainties for both methodologies were calculated. The quantification limit of 3.3 µg kg -1 was found for organic Hg by CVAAS.

Mercury determination in sediments by CVAAS after on line preconcentration by solid phase extraction with a sol-gel sorbent containing CYANEX 471X®

The development of a preconcentration method for the measurement of trace levels of mercury in digested sediments is described. Solid phase extraction (SPE) was used for the preconcentration of mercury coupled on-line by means of a flow injection (FI) system followed by cold vapour atomic absorption spectrometry (CVAAS) detection. The SPE was carried out through a column packed with a sorbent material containing triisobutylphosphine sulfide (CYANEX 471X®) as mercury extractant and prepared by the sol-gel process. The effects of FI variables (argon, eluent, and reductant flow rates, loading and elution times) as well as the eluent concentration on the analytical performance of the method were evaluated. The proposed method was validated under the optimum conditions. The calibration graph was linear from 0.05 µg L−1 to 3.0 µg L−1 of Hg. The detection limit (DL), based on three times the standard deviation of the blank measurement criterion, was 24 ng L−1. The repeatability was 1.5% and 1.8% RSD (n = 10) at concentrations of 0.5 and 1 µg L−1 of Hg, respectively. Method enrichment factors of 16 with a productivity of 30 samples h−1 or 32 with a productivity of 17 samples h−1 were achieved under selected conditions. Certified reference materials, inductively coupled plasma mass spectroscopy (ICP-MS) and cold vapour atomic fluorescence spectrometry (CVAFS), were used to evaluate the accuracy of the proposed method.

Validation of an isotope dilution, ICP-MS method based on internal mass bias correction for the determination of trace concentrations of Hg in sediment cores

The development and validation of a method for the determination of mercury in sediments using a sector field inductively coupled plasma mass spectrometer (SF-ICP-MS) for detection is described. The utilization of isotope dilution (ID) calibration is shown to solve analytical problems related to matrix composition. Mass bias is corrected using an internal mass bias correction technique, validated against the traditional standard bracketing method. The overall analytical protocol is validated against NRCC PACS-2 marine sediment CRM. The estimated limit of detection is 12 ng/g. The proposed procedure was applied to the analysis of a real sediment core sampled to a depth of 160 m in Lake Como, where Hg concentrations ranged from 66 to 750 ng/g.

Comparison of three strategies to evaluate uncertainty from in-house validation data. A case study: mercury determination in sediments

In the present paper, three approaches are compared for the evaluation of the combined uncertainty in the determination of mercury in aquatic sediments by an aqua regia extraction procedure. For this, the data obtained in validation studies from five certified reference materials (CRMs), covering a range of concentrations from 0.8 to 130 mg kg(-1) of mercury and analysed by three atomic spectroscopic techniques (cold vapour generation atomic fluorescence spectrometry, CV-AFS, cold vapour generation atomic absorption spectroscopy, and inductively coupled plasma mass spectroscopy), were considered. The combined uncertainty was firstly assessed by considering separately the data obtained for each CRM analysed (approach A). Moreover, this assessment was also performed with two other calculation approaches (B and C) based on the pooled data obtained from the validation step. The comparison of the results obtained for the different techniques showed a clear bias effect when using CV-AFS with nitric acid as a diluent. In relation to the strategies tested for the combined uncertainty assessment, approach C proved to be the easiest and friendliest method for uncertainty assessment.

Optimisation of microwave assisted digestion of sediments and determination of Sn and Hg

The determination of Sn by flow injection–hydride generation–quartz furnace atomic absorption spectrometric (FI–HG–QFAAS) was optimised following different experimental designs. The best conditions were: 0.2% HCl (v/v), 0.5% NaBH 4 (w/v) and the furnace temperature 875 °C. Under those conditions, the limit of detection was 0.17 ng dm −3 and a precision of 5.3% was obtained. One of the aims of this work was to optimise the closed vessel microwave assisted digestion (MAD) of sediments for the determination of Sn and Hg in the same extract using the analytical conditions previously optimised for Sn in the FI–QFAAS. The optimisation of the MAD of sediments was accomplished following a D-optimal design, including the composition of the HCl–HNO 3 mixture, the pressure and irradiation time. However, we could not determine tin in the extracts due to the formation of foams, the optimisation of the digestion conditions were taken from the FI–cold vapour (CV)–QFAAS measurements of mercury. The optimum conditions were: 2.1 bar of pressure during 10 min of irradiation and two local optima composition of the acid mixtures: 80% HCl–20% HNO 3 and 60% H 2O–20% HCl–20% HNO 3. The determination of mercury in sediments was validated with the CRM-580. In order to determine Sn in sediments the solutions from the same D-optimal design were analysed using an ICP-MS and the digestion conditions were optimised for Sn and for other 8 metals. In this case the same optimal conditions were obtained (2.1 bar and 10 min) but different acid mixture composition 20% HCl–80% HNO 3. The determination of Sn and the other metals in sediments was validated using two other CRMs (PACS-2 and SGR-1).

CVAAS determination of naturally occurring levels of mercury in sediments after on-line preconcentration with a sol–gel sorbent doped with CYANEX-301

A new on-line preconcentration method for total mercury determination in sediments by cold vapour atomic absorption spectrometry (CVAAS) was developed. The automated on-line preconcentration step was carried out using a micro-column packed with a sorbent prepared by the sol–gel technique. Tetraethoxysilane (TEOS) as the silica precursor and bis(2,4,4-trimethylpentyl)-dithiophosphinic acid (CYANEX 301) as the mercury extractant were used in the sol–gel sorbent preparation. Mercury was eluted quantitatively from the column using 2 mol L−1 HCl and mixed on-line with NaBH4 as the reducing agent. The effect of various instrumental parameters on the analytical performance was studied. The method detection limit (DL) traced back to the quantity of sample, based on three times the standard deviation of ten sample blank measurements, was 13.2 ng g−1. The calibration curves were linear from 0.1 μg L−1 to 2 μg L−1 of Hg. The measurement precision, evaluated as the relative standard deviation obtained after analyzing ten replicates, was 0.83% and 1.04% at the 1 and 0.5 μg L−1 level of Hg(II), respectively. The accuracy of the method was examined by the analysis of certified reference materials and confirmed by ICP-MS determinations. A sample throughput of 30 measurements per hour was possible.

Determination of mercury in estuarine sediments by flow injection-cold vapour atomic absorption spectrometry after microwave extraction

A flow injection-cold vapour atomic absorption spectrometric (CVAAS) method was developed for the determination of mercury at trace level in estuarine sediments using sodium tetrahydroborate (III) as reductant. The mercury was solubilized with nitric acid in closed vessels and microwave oven heating. Instrumental and operational conditions (volume and concentration of reagents, reaction time, etc.) were optimized. The effect of several ions on the analytical signal was also studied; no interferences were recorded excepting for copper and nickel which caused a serious depressing effect. The detection limit obtained was 0.01 μg g -1 . The validation of the method was performed analyzing a certified reference sediment, BCR CRM 277 Estuarine Sediment. Good recovery (c.a. 98%) and precision (< 3%, RSD) were achieved. The proposed method was successfully applied to the determination of mercury in sediment samples from Ares-Betanzos Estuary (Galicia, NW Spain).

Reversible intermittent flow-injection determination of mercury in sediments and vinasses by cold vapor atomic absorption spectrometry

A reversible intermittent flow-injection procedure is proposed for the automated determination of mercury in sediments and vinasses by cold vapor atomic absorption spectrometry, CVAAS. Solutions of sample and stannous chloride are carried by two air streams and sequentially injected into the generator/separator chamber in a segmented asynchronous merging zone configuration. The intermittent flow in the forward direction carries the mercury vapor through the flow cell, and in the backward direction, it aspirates the remaining solution from the vessel to waste. We investigated composition and concentration of reagents, flow rates, commutation times, reactor configuration, and conditions for mercury release. The accuracy was checked by mercury determination in a certified sediment and spiked vinasses and river waters. The system handles about 100 samples per hour (0.50–5.00 μg L−1), consuming ca. 2.5 mL of sample and 50 mg of SnCl2 per determination. Good recoveries (92–103%) were obtained with spiked samples. Results are precise (RSD <3% for 2.5 μg Hg L−1, n = 12) and in agreement with values for certified reference material at 95% confidence level. © 1999 John Wiley & Sons, Inc. Lab Robotics and Automation 11: 304–310, 1999

Direct Determimnation of Mercury in Sediments by Atomic Absorption Spectrometry

A pyrolysis chamber is described for the direct determination of mercury in sediments by atomic absorption spectrometry. The finely ground and dried sample is weighed (2.0–60.0 mg), transferred to a quartz cup, inserted in a pyrolysis chamber and heated at 1100 °C for 30 s by means of three focused infrared lamps in the presence of an air stream as the carrier gas. Interfering substances are destroyed by a precolumn containing alumina, silica and copper(II) oxide, and the released mercury is amalgamated on to a gold-coated collector. Mercury vapour is later measured by AAS after thermal desorption. Calibration is easily performed by flow injection, in which known volumes of mercury-saturated air are introduced into the same air carrier stream. The absolute detection limit was 0.26 ng Hg and the relative standard deviation of measurements (n=12) from a typical 4.0 mg sample was about 7%. By applying a t-test, there was no significant difference at the 5% probability level between the results obtained with the proposed method and those certified or recommended for NIST materials. One analysis takes only 2 min, including sample weighing.

Comparison of Acid Mixtures in High-Pressure Microwave Digestion Methods for the Determination of the Total Mercury in Sediments by Cold-Vapor Atomic Absorption Spectrometry

Four closed-vessel microwave digestion methods were compared for the accurate determination of mercury in sediments by flow-injection cold-vapor atomic absorption spectrometry. The results showed that several acid mixtures (HNO3/H2SO4, HNO3/HClO4, HCl/HNO3 and HCl/HNO3/HF) completely digested the soil matrix for the determination of mercury. The method using aqua regia is preferred because it is time saving, less dangerous and suitable for other trace-metal analyses. The merits of pressure-feedback microwave digestion is that it simplifies soil sample digestion, and there is no loss of mercury. The digestion methods were evaluated by determining mercury in NIST SRM 1645 River Sediment, NIES CRM No. 2 Pond Sediment and NRCC BCSS-1 Marine Sediment. Recoveries of 92-108% were achieved. Good recoveries of 94-104% were also obtained for soil and marine-sediment samples spiked with different species of mercury.

Effective monitoring of pollution by toxic trace elements in waters, sediment and biota of the Derwent River Estuary, Tasmania, through long-term retention of analytical facilities

This study considers the effectiveness of the monitoring of toxic trace elements in various media from a polluted river estuary over a period of 15 years, using the same analytical techniques, facilities and, in some cases, the same operators. It shows that reliable comparisons can be made for monitoring waters, sediment and biota from the Derwent River Estuary between 1975 data and that from 1990. Rigorous studies were undertaken before and during 1975 to ensure that reliable data was achieved at that time. Such studies are reviewed and included the evaluation of digestion techniques for a range of heavy metals, specific attention to the reliability of mercury determination in sediments between laboratories, a comparison of direct calibration and standard addition techniques for metals in seawater, recoveries of an organomercury compound from fish, and sources of error arising from sample preparation of biota for subsequent metal analysis. Comparative results for standard reference materials in both 1975 and 1990 show good agreement and are considered reliable except for lead at low concentrations. The long-term retention of the analytical facilities permits a direct comparison of data from 2 monitoring programmes over the space of 15 years.

Determination of mercury in lake sediments using a gold film mercury analyser

A gold film mercury analyser was used for the determination of mercury in lake sediments. Sediment and soil standards and sediment samples were extracted with a mixture of nitric and hydrochloric acids. Aliquots of the extracts containing between 30 and 50 ng of mercury were used for the determination with the gold film analyser. An absolute deviation of approximately 0.05 µg g–1 and an accuracy of ±0.02 µg g–1 can be considered typical for the investigated method. The results of the determination of mercury in the sediment standard by the gold film analyser were compatible with the recommended value.

A rapid method for the determination of mercury in sediments, suspended solids and soils

Abstract A rapid method for the determination of mercury in sediments, suspended solids and soils is described. Many of the complications of existing cold vapour AAS analysis have been eliminated while retaining acceptable accuracy, precision and detection limit. The productivity is greater than 100 samples per day.

Automated determination of mercury in sediments

Automated determination of mercury in sediments

A method for the determination of mercury in sediments by the automated cold vapor atomic absorption technique after digestion

A manual method for the extraction of inorganic mercury and the oxidation of organomercurials has been modified and incorporated into an automated procedure for the determination of mercury in sediments. The method includes a digestion of the wet sediment with sulfuric and nitric acids followed by oxidation of the organomercurials with potassium permanganate and potassium persulfate. Errors caused by coprecipitation and adsorption of mercury on manganese dioxide are avoided by reduction of the dioxide with a solution of hydroxyammonium sulfate and sodium chloride. The mercury content in solution is determined by a cold vapor technique with tin(II)sulfateas a reductant in an automated system. This method can detect down to 10 p.p.b. of mercury in sediment (based on 1-g samples) and can handle automatically 20 samples per h after manual digestion.