Vapor Atomic Absorption Spectrometry Research Articles

Mercury Determination in Fish Using Cold Vapour-Atomic Absorption Spectrometry (CV-AAS) with Sodium Borohydride (NaBH4) as the Reductor

Marine fish can potentially accumulate heavy metal pollutants, such as mercury, from anthropogenic activities that can harm people who consume it. Marine fishes like Bandeng fish (Chanos chanos), Banjar fish (Rastrelliger kanagurta), Bawal Hitam fish (Parastromateus niger), Selar Kuning fish (Atule mate), Tenggiri fish (Scomberomorini), and Tuna fish (Thunnini) are consumed a lot by people in Bandung City. All these fish were analyzed using the CV-AAS method with the United States – Environment Protection Agency (USEPA, 2006), and the reducing agent was replaced by stannous (II) chloride with sodium borohydride. Variations in the sample preparation process include drying the sample using an oven and freeze dryer. SEM-EDX in the frozen-dried samples shows that the fibbers’ morphology is intact, while the fibbers are damaged in the hot-dried samples. During characterization using FTIR, there is a slight shift in wave number. The mercury concentrations obtained from every sample were below 0.5 mg/kg based on the Indonesian National Standard (SNI) 2009 standard for total mercury in fish. Therefore, it can be concluded that the samples are safe to be consumed. Validation methods showed that 0.3% sodium borohydride as the reductor can be used to analyze mercury and replace stannous (II)chloride. However, further studies are needed to determine the optimal concentration of sodium borohydride (NaBH4) in the marine fish samples as a reduction agent.

Simple mercury determination using an enclosed quartz cell with cold vapour-atomic absorption spectrometry.

A simple method for determining total inorganic mercury (Hg) in solution using an enclosed quartz cell applying cold vapour-atomic absorption spectrometry (CV-AAS) can reduce sample volume, reductant, and cost compared with those of official methods. The Hg determination under the optimised conditions achieves precision similar to that of conventional CV-AAS.

Selected elements and fatty acid composition in human milk as indicators of seafood dietary habits

The maternal diet and living environment can affect levels of chemical elements and fatty acid (FA) composition and their stable isotopes (δ13CFA) in human milk. Information obtained from questionnaires is frequently imprecise, thus limiting proper associations between external and internal exposures as well as health effects. In this study, we focused on seafood as a source of potentially toxic and essential elements and nutritional FAs. Concentrations of selected elements in human milk (As, Cd, Cu, Mn, Pb, Se and Zn) were determined using inductively coupled plasma mass spectrometry (ICP-MS) and Hg using cold vapour atomic-absorption spectrometry (CV-AAS). The identification and quantification of FAs in maternal milk were performed by an in-situ trans-esterification method (FAMEs), and the characterization of FAMEs was performed by gas chromatography with a flame ionisation detector (GC-FID). δ13CFA was determined by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). Seventy-four lactating Slovenian women from the coastal area of Koper (KP), with more frequent consumption of seafood, and the inland area of Pomurje (MS), with less frequent seafood consumption, were included in this study. Along with basic statistical analyses, data mining approaches (classification and clustering) were applied to investigate whether FA composition and δ13CFA could improve the information regarding dietary sources of potentially toxic elements. As and Hg levels in milk were found to be statistically higher in populations from KP than in those from MS, and 71% of individual FAs and 30% of individual δ13CFA values in milk differed statistically between the studied areas. In 19 cases, the levels of FAs in milk were higher in KP than in MS; these FAs include C20:5ω3 and C22:6ω3/C24:1ω9, which are typically contained in fish. In 16 cases, the mean percentage of FAs was higher in MS than in KP; these FAs include the PUFAs C18:2ω6, C18:3ω3, and C20:4ω6 which are important for human and infant growth. The difference in δ13C levels of C10:0, C12:0, C14:0, C16:1, C16:0, C18:1ω9c, C22:6ω3, and δ13C 18:0–16:0 in the study groups was statistically significant. In all seven cases where δ13C of FA significantly differed between KP and MS, δ13C was higher in KP, indicating a higher proportion of a marine-based diet. The data mining approaches confirmed that the percentage of selected FAs (iC17:0, C4:0, C18:2ω6t, aC17:0, CLA, and C22:4ω6) and δ13CFA of C18:1ω9c in human milk could be used to distinguish between high and low frequency of fresh seafood consumption.

Preferential accumulation of inorganic elements in Amanita muscaria from North-eastern Poland

ABSTRACTConcentrations of Al, Ba, Cd, Ca, Co, Cu, Fe, K, Mg, Mn, Hg, Rb, Ag, Na, Sr and Zn were analysed in fruiting bodies of A. muscaria. This mushroom is considered conditionally edible, since parboiling can detoxify its fruiting bodies from the hallucinogens and render it edible. The specific purpose of the research is the little-known phenomenon of the variability of mineral composition of mushrooms for generations harvested in the same forest areas – both in terms of their nutritional value and anthropogenic influences. Fungal materials were digested in nitric acid and analysed by a validated methods using inductively coupled plasma optical emission spectrometer (ICP-OES) and cold – vapor atomic absorption spectroscopy (CV-AAS). A. muscaria collected in the same area over the period of four years showed fluctuations in the concentrations of the essential elements Co, Cu, Fe, K, Mn, Na and Zn (p < 0.05; U Mann-Whitney test), while only Ca and Mg (p > 0.05) levels were similar. In addition, concentrations of Ag, Al, Ba, Cd, Rb and Sr in fruiting bodies fluctuated, while remained at a similar level for Hg. It is important to note that statistically significant variations in levels of several inorganic elements accumulated in A. muscaria would imply a more careful consideration would be required when assessing the nutritional value of mushroom species.

Coupling of non-selective adsorption with selective elution for novel in-line separation and detection of cadmium by vapour generation atomic absorption spectrometry

Non-selective adsorption of Cd2+ ions on a cation exchange fiber and subsequent selective elution with a KI solution has been strategically utilized to develop a highly selective in-line separation of Cd2+ ions from other metal ions for its rapid and reliable quantification by cold vapour-atomic absorption spectrometry. After retention of Cd2+ with a high efficiency on cation exchange fiber, selective elution of the retained Cd2+ was subsequently accomplished with 0.3M KI. Vapour generation of Cd for in-line CV-AAS determination was then achieved by merging the eluate with HCl and NaBH4. Interferences from most base metals with the vapour generation of Cd were eliminated by this approach, with the exception of Pb2+ions which was removed by co-precipitation with BaSO4 prior to the in-line separation. Substantial improvement in sensitivity of the in-line CV-AAS determination of Cd was achieved by increasing the sample loading time. A detection limit of 0.6ngL−1 (3σ) was obtained with sample loading time of 120s, corresponding to a consumption of 24mL of sample solution. Application of the method to the determination of Cd in certified sediment and fish samples gave a good agreement with the certified values. Further validation by recovery study in real fish sample digests and water gave average Cd recoveries of 98.7±1.0% for fish and 92±3% for water with RSD of 1.5% for fish and 4% for water, respectively.

Ultra-trace arsenic and mercury speciation and determination in blood samples by ionic liquid-based dispersive liquid–liquid microextraction combined with flow injection-hydride generation/cold vapor atomic absorption spectroscopy

AbstractA simple, fast, and sensitive method for speciation and determination of As (III, V) and Hg (II, R) in human blood samples based on ionic liquid-dispersive liquid-liquid microextraction (IL-DLLME) and flow injection hydride generation/cold vapor atomic absorption spectrometry (FI-HG/CV-AAS) has been developed. Tetraethylthiuram disulfide, mixed ionic liquids (hydrophobic and hydrophilic ILs) and acetone were used in the DLLME step as the chelating agent, extraction and dispersive solvents, respectively. Using a microwave assisted-UV system, organic mercury (R-Hg) was converted to Hg(II) and total mercury amount was measured in blood samples by the presented method. Total arsenic content was determined by reducing As(V) to As(III) with potassium iodide and ascorbic acid in a hydrochloric acid solution. Finally, As(V) and R-Hg were determined by mathematically subtracting the As(III) and Hg(II) content from the total arsenic and mercury, respectively. Under optimum conditions, linear range and detection limit (3σ) of 0.1-5.0 μg L

XRF scanners as a quick screening tool for detecting toxic pollutant elements in sediments from Marín harbour in the Ría de Pontevedra (NW Spain)

X-ray fluorescence scanners, such as the Itrax™ Core Scanner (Itrax) (Cox Analytical Systems, Mölndal, Sweden), provide high-resolution geochemical data within several hours. However, the semi-quantitative nature of these analysers has hampered their use to study pollution. This study explores Itrax’s capabilities to detect trace metals, such as Hg and Cd, in the Ría de Pontevedra harbour (NW Spain). A set of Itrax detection levels were proposed for each metal after comparison with quantitative measurements obtained from Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) and Vapour Atomic Absorption Spectrometry (CVAAS) analyses. These quantitative data obtained after a sequential extraction were used to evaluate pollutant bioavailability and to determine metal pollution levels exhibiting Hg pollution. The reliability of inc/coh and Br/Cl ratios to assess the total organic matter variability was also evaluated. The results indicated that the Itrax is an efficient and fast option to monitor contamination, thereby avoiding laborious discrete analyses and reducing analytical cost and time.

On-line UV photoreduction in a flow-injection/stopped-flow manifold for determination of mercury by cold vapour-atomic absorption spectrometry

Photo-chemical vapour generation has been applied in a flow-injection system under stopped-flow conditions for determination of Hg by atomic absorption spectrometry. The system allows mercury vapour generation without the need for conventional reduction reactions based on sodium/potassium tetrahydroborate (III) or tin chloride in acid medium. The photo-induced reaction is accomplished by applying ultraviolet irradiation (UV) to the sample solution containing Hg(II) in the presence of an organic acid (i.e., acetic, citric, oxalic, ethylendiaminetetraacetic) as precursor of reducing species. A remarkable improvement in sensitivity is observed with acetic acid when stopped-flow is employed as compared to continuous operation, meaning that kinetics play an important role in the photo-induced reaction. A detection limit of 0.3 μg L−1 can be obtained, which represents a 6-fold improvement in respect to that obtained without stopped-flow. The repeatability expressed as relative standard deviation was about 2.7% (n = 15) for a 50 μg L−1 Hg standard. The effect of potential interferences on the photo-generation of Hg vapour was investigated. In the UV-photo-induced CVG, both inorganic Hg and organomercury species can be reduced to elemental mercury with the same efficiency. The method was applied to determination of Hg in several enriched natural water samples and recoveries of MeHg+, Thiomersal, EtHg+ and PhHg+ were in the range 97% to 102%.

Determination of methylmercury and estimation of total mercury in seafood using high performance liquid chromatography (HPLC) and inductively coupled plasma-mass spectrometry (ICP-MS): Method development and validation

A method was developed for determination of methylmercury and estimation of total mercury in seafood. Mercury (Hg) compounds were extracted from 0.5 g edible seafood or 0.2 g lyophilized reference material by adding 50 ml aqueous 1% w/v l-cysteine·HCl·H 2O and heating 120 min at 60 °C in glass vials. Hg compounds in 50 μl of filtered extract were separated by reversed-phase high performance liquid chromatography using a C-18 column and aqueous 0.1% w/v l-cysteine·HCl·H 2O + 0.1% w/v l-cysteine mobile phase at room temperature and were detected by inductively coupled plasma-mass spectrometry at mass-to-charge ratio 202. Total Hg was calculated as the mathematical sum of methyl and inorganic Hg determined in extracts. For seafoods containing 0.055–2.78 mg kg −1 methylmercury and 0.014–0.137 mg kg −1 inorganic Hg, precision of analyses was ≤5% relative standard deviation (R.S.D.) for methylmercury and ≤9% R.S.D. for inorganic Hg. Recovery of added analyte was 94% for methylmercury and 98% for inorganic Hg. Methyl and total Hg results for reference materials agreed with certified values. Limits of quantitation were 0.007 mg kg −1 methylmercury and 0.005 mg kg −1 inorganic Hg in edible seafood and 0.017 mg kg −1 methylmercury and 0.012 mg kg −1 inorganic Hg in lyophilized reference materials. Evaluation of analyte stability demonstrated that l-cysteine both stabilized and de-alkylated methylmercury, depending on holding time and cysteine concentration. Polypropylene adversely affected methylmercury stability. Total Hg results determined by this method were equivalent to results determined independently by cold vapour-atomic absorption spectrometry. Methylmercury was the predominant form of Hg in finfish. Ratios of methylmercury/total Hg determined by this method were 93–98% for finfish and 38–48% for mollusks.

A validated cold vapour-AAS method for determining mercury in human red blood cells

A cold vapour-atomic absorption spectrometry (CV-AAS) method for determining mercury in dental students and clinical teaching staff red blood cells at a dental school using amalgam as a restorative material has been validated. A number of blood samples ( n = 122) from dental students in years I to V, clinical teachers in restorative dentistry and controls were collected and analysed. Accuracy, linearity, precision (repeatability and reproducibility) and robustness of the method have been determined, and detection and quantification limits have been calculated. Linearity of response was verified for concentrations ranging from 5 to 40 μg L −1 of mercury. Correlation coefficient of the calibration straight lines was always ≥0.99. Intra-day precision of the method gave coefficient of variation (CV) of 5.51%. Inter-day precision of the method calculated after analysis of five different concentrations of mercury standard solutions by the same analyst in different days and by two different analysts in different days gave coefficient of variation 4.89 and 5.44%, respectively. The accuracy of the method was calculated a CRM NIST 966 (toxic metals in bovine blood) total amount of mercury was found a concentration of 28.83 ± 2.2 μg L −1. Recovery was 89.27%. Robustness of the method evaluated by changing different experimental conditions under which analyses performed, fractional factorial design was done for assessing robustness of the method. Root mean square error was found out as 1.56. Limits of detection and quantification were 1.84 and 4.03 μg of Hg per litre of sample, respectively. Results show the suitability of the method for direct measurement of mercury in red blood cells and the importance of the working conditions for people dealing with amalgam at a dental school.

Effect of Exhaustion Hood Flow Rate in Flow Injection Cold Vapor and Hydride Generation Atomic Absorption Spectrometry

The effect of exhaustion hood flow rate in the laboratory was investigated. It has been observed that this parameter significantly affects the analytical signal. This effect was more evident in cold vapor (CV) atomic absorption spectrometry (AAS) signal when unheated quartz T‐tube atomizer (QTA) was used as atom cell. At maximum exhaustion hood flow rate, the peak height and peak area values for Cd decreased to 36% and 35%, respectively, of those obtained under no exhaustion. When CV cell with both ends covered with quartz plates was used, exhaustion hood flow rate did not affect the analytical signal significantly. The exhaustion hood flow rate effect was less pronounced in case of heated QTA as compared to unheated QTA. In addition to exhaustion hood flow rate, the air movements around the atom cell also influenced the analytical signal and precision of the measurement.

Avaliação da concentração de mercúrio em sedimentos e material particulado no rio Acre, estado do Acre, Brasil

A avaliação dos teores de mercúrio em sistemas aquáticos sem influência direta de fontes antropogênicas conhecidas não tem sido conduzida com freqüência na região Amazônica. Visando contribuir para esclarecer a ocorrência de valores elevados de Hg em peixes consumidos pela população de Rio Branco - AC, o Instituto Evandro Chagas - IEC, realizou um estudo para quantificar os teores de Hg em sedimentos de fundo e material particulado no rio Acre e alguns afluentes, além da caracterização físico-química das águas entre as cidades de Brasiléia e Assis Brasil. As amostras de sedimentos foram peneiradas na fração &lt; 250 mesh e o material particulado obtido por floculação com Al2SO4 . Uma massa de 250 mg dos materiais foram submetidos a digestão ácida e as determinações de Hg realizadas por Espectrofotometria de Absorção Atômica, com geração de vapor frio. Os parâmetros físico-químicos pH, condutividade elétrica, temperatura e sólidos totais dissolvidos, foram feitos no campo, por métodos potenciométricos. Os teores de Hg nos sedimentos de fundo variaram entre 0,018 e 0,184 mig g-1, com média de 0,054 ± 0,034 mig g-1, enquanto que no material particulado a variação foi de 0,067 a 0,220 mig g-1e média de 0,098 ± 0,037 mig g-1. As águas possuem características levemente ácidas indicadas pelos valores de pH que variaram entre 5,80 - 6,95. A condutividade elétrica variou de 151,60 - 1.151,00 miS cm-1. Os teores de Hg nos materiais analisados encontram-se dentro da faixa dos valores observados para os rios amazônicos "não poluídos". Entretanto, estudos complementares deverão ser implementados para elucidar a origem e os processos de biodisponibilidade do mercúrio.

Mercury in the marine food chain in the Southern Ocean at Macquarie Island: an analysis of a top predator, Patagonian toothfish ( Dissostichus eleginoides ) and a mid-trophic species, the warty squid ( Moroteuthis ingens )

The characteristics and habitat of the Patagonian toothfish (Dissostichus eleginoides) are typical of fish that accumulate high concentrations of mercury. In this study, mercury determinations were made on samples of muscle tissue from Macquarie Island toothfish and the Southern Ocean deepwater warty squid (Moroteuthis ingens). The analysis of mercury in the biological tissues was made by cold vapour-atomic absorption spectrometry following acid digestion. Performance of the analytical procedure was assessed by analysis of certified reference material (DORM-2, dogfish muscle). Mercury concentrations of 16 Macquarie Island toothfish ranged from 0.12 mg kg–1 (550 g, 381 mm TL) to 0.59 mg kg–1 (6,100 g, 823 mm TL), with a mean concentration of 0.33±0.12 mg kg–1. A significant correlation was found between mercury and either toothfish weight or total length. The fish analysed were juveniles, which suggests that larger individuals would have higher mercury concentrations well exceeding food standard code limits for mercury in fish (typically 0.5 mg kg–1). Warty squid, also from around Macquarie Island, had a low mean mercury concentration of 0.086 mg kg–1 in mantle tissue; no significant correlation existed between mercury concentration and either squid mantle length or total weight. It is postulated that the squid have a mechanism, possibly involving the digestive gland, that prevents bioaccumulation of mercury in the mantle, and presumably other body tissues.

Content and bioconcentration of mercury in mushrooms from northern Poland

Mercury (Hg) was quantified using cold vapour-atomic absorption spectrometry (CV-AAS) in the fruiting bodies of nine edible and five inedible mushrooms and in underlying soil substrate samples. In total, 404 samples comprising caps and stalks and 202 samples of soil substrate (0–10 cm layer) were collected in 1996 from Trójmiejski Landscape Park, northern Poland. Mean Hg concentrations in the soil substrate for different species varied between 10 ± 3 and 780 ± 500 ng g -1 dry wt (range 2.3–1700). Among edible mushroom species, Horse Mushroom (Agaricus arvensis), Brown Birch Scaber Stalk (Leccinum scabrum), Parasol Mushroom (Macrolepiota procera), King Bolete (Boletus edulis) and Yellow-cracking Bolete (Xerocomus subtomentosus) contained elevated concentrations of Hg ranging from 1600 ± 930 to 6800 ± 4000 ng g-1 dry wt in the caps. Concentrations of Hg in the stalks were 2.6 ± 1.1 to 1.7 ±1.0 times lower than those in the caps. Some mushroom species investigated had high Hg levels when compared with specimens collected from the background reference sites elsewhere (located far away from the big cities) in northern Poland. Bioconcentration factors of Hg in the caps of Horse Mushroom, Parasol Mushroom and Brown Birch Scaber Stalk were between 150 ± 58 and 230 ± 150 ng g-1 dry wt, respectively, and for inedible Pestle-shaged Puffball (Claviata excipulformis) was 960 ± 300 ng g-1 dry wt. Linear regression coefficients between Hg in caps and in stalks and Hg soil concentrations showed a positive relationship for A. arvensis and Horse mushroom (p < 0.05) and a negative correlation for the caps of Death Caps (Amanita phalloides) and Woolly Milk Cap (Lactarius torminosus) (p < 0.05), while for other species no clear trend was found.

Release of mercury from dental amalgam and its influence on salivary antioxidant activity.

Dental amalgam fillings are known to release significant amounts of mercury (Hg) in saliva which could represent a continuous source of oxidative damage to mouth tissues. The present investigation was aimed at verifying this hypothesis by determining a possible correlation between salivary Hg levels and salivary total antioxidant activity (TAA), which is used as an index of oxidative stress. Samples of saliva from 34 healthy donors were analyzed for Hg content, by vapor atomic absorption spectrometry, and for TAA, by determining the ferric reducing ability ('FRAP' method). A significant correlation between Hg and the number of amalgam restorations or total amalgam surface was evident in both the male and female subjects. A significant negative correlation between TAA and Hg levels or number of amalgam restorations or amalgam surface was evident in females, indicating that small increases in salivary Hg were sufficient to produce a decrease in salivary TAA. On the other hand, no significant correlation was found in the males. The present study provides, for the first time, evidence of a pro-oxidant role of the amalgam Hg chronically released in saliva.

The multivariate optimisation of ultrasonic bath-induced acid leaching for the determination of trace elements in seafood products by atomic absorption spectrometry

The effects of several variables on the As, Ca, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Pb, Se and Zn ultrasonic bath induced-acid leaching from lyophilised seafood samples have been studied by experimental designs. The determinations were carried out by electrothermal atomic absorption spectrometry (As, Cd, Co, Cr, Mn, Pb and Se), flame atomic absorption spectrometry (Ca, Cu, Fe, Mg and Zn) and by cold vapour-atomic absorption spectrometry (Hg). A Plackett–Burman experimental design was used to select the most significant variables that affect to the acid leaching process, while central composite designs were used to found optimum values for the variables involved in the acid leaching. The optimum conditions found for each variable and each element were tabulated. Accurate results were obtained by measuring DORM-1, DOLT-1 and TORT-1 certified reference materials, and the procedure was finally applied to mussel, clam and tuna samples.

Factorial designs for Cd, Cr, Hg, Pb and Se ultrasound-assisted acid leaching from human hair followed by atomic absorption spectrometric determination

An acid leaching procedure, for use as a sample pre-treatment, was developed for Cd, Cr, Hg, Pb and Se determination in human hair. A Plackett–Burman experimental design was used as a multivariate strategy for the evaluation of the effects of varying several variables at once. The effects on acid leaching of metals of nitric acid, hydrochloric acid and hydrogen peroxide concentrations, acid solution volume, exposure time to ultrasound, temperature of the ultrasonic bath, and hair particle size, have been investigated. From these studies, certain variables showed up as significant, and they were optimised by a 23 + star central composite design, which involved 16 experiments. Optimum values of the variables were selected for the development of acid leaching procedures to extract trace metals from human hair. Electrothermal atomic absorption spectrometry (ETAAS) was used to determine Cd, Cr, Pb and Se, while cold vapour-atomic absorption spectrometry (CVAAS) was used for Hg measurements. An acid digestion induced by microwave energy was used to obtain the total metal concentration and also for comparative purposes. IAEA-085 and NIES No. 13 certified reference materials, which offer certified values for some elements, were used in order to verify the accuracy of the methods.

Analysis of Metals in Marine Sediments by Microwave Extraction and Flame, Hydride Generation and Cold Vapour Atomic-Absorption Spectrometry

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.

Influence of Sediment Preservation on Total Mercury and Methylmercury Analyses

Estuarine and riverine sediments from fourlocations showing different sediment structures wereanalysed as fresh, thawed and lyophilised samples fortotal mercury (TotHg) and methylmercury (MeHg)concentrations, and results were compared to addresseffects of sample preservation on Hg speciation. TotHg was measured by cold vapour atomic absorptionspectrometry (CVAAS). MeHg was isolated bydistillation and ion-exchange and analysed by coldvapour atomic fluorescence spectrometry (CVAFS) afterpreconcentration on a gold trap. No loss of TotHg norMeHg due to lyophilisation was found. Concentrationsof TotHg and MeHg respectively ranged from 92 to 267ng g-1 dw and 1.1 to 2.9 ng g-1 dw in freshsamples, from 94 to 215 ng g-1 dw and 1.1 to 2.8ng g-1 dw in thawed samples, and from 100 to 256ng g-1 dw and 1.2 to 3.1 ng g-1 dw inlyophilised samples. Lyophilised samples showedbetter homogeneity and better MeHg analysisreproducibility compared with wet samples.

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

A continuously operating monitoring method for total mercury at sub-ng/ml level in environmental and biological samples by cold vapour atomic-absorption spectrometry with NaBH4 as a reductant was developed. The mercury vapour generator and absorption cell closed-end by quartz were used in this study. The detection limit (S/N = 3) and relative standard deviation of 12 determinations of 10 ng/ml Hg(II) were 0.11 ng/ml and 1.1%, respectively. The range of standard calibration curve was 0–50 ng/ml Hg, The proposed method was successfully applied to the completely continuous monitoring of total mercury in waste water, sediments and pork liver.