Vapor Generation Atomic Absorption Spectrometry Research Articles

Estimation of Measurement Uncertainty for the Analysis of Arsenic in Water by Hydride Vapor Generation–Atomic Absorption Spectrometry

Estimation of Measurement Uncertainty for the Analysis of Arsenic in Water by Hydride Vapor Generation–Atomic Absorption Spectrometry

Towards the abatement of nitrate interference on selenium determination by photochemical vapor generation

A flow injection photochemical vapor generation atomic absorption spectrometry (FI-PVG-AAS) system was developed for selenium determination. The variables of influence of the photochemical generation process were evaluated and optimized. Sample already reduced to the Se(IV) state and mixed with the photochemical reagent (1.5% w/w HCOOH) was irradiated for 3 s. Selenium derivatives were transferred to an externally heated atomization cell by an argon-hydrogen mixture and selenium determined at 196.0 nm. Nitrogen was used as the carrier of the flow injection system. Nitrate is one of the most relevant interferents for the photochemical generation process; it is a very frequent concomitant as nitric acid is added for sample digestion or preservation. Hence, its removal before the vapor generation stage was studied. It was found that up to 3.0% w/w HNO3, it can be eliminated in the reduction stage of Se(VI) to Se(IV) with hydrochloric acid. For higher concentrations (up to 21% w/w HNO3), prior to the reduction step, the addition of 40% w/w H2CO and evaporation almost to dryness was successful for the abatement of the interference. The performance of the method was studied and its applicability evaluated with a Trace Element in Water Certified Reference Material (24.3 μg L−1 – Se, 2.8% w/w HNO3) and a spiked rice-flour microwave-assisted digest (103.1 μg L−1 – Se, 18.5% w/w HNO3).

Use of an aminated Amberlite XAD-4 column coupled to flow injection cold vapour generation atomic absorption spectrometry for mercury speciation in water and fish tissue samples

An aminated Amberlite XAD-resin as a solid phase extractant was tested for speciation of inorganic mercury, Hg(II) and methylmercury, MeHg(I) in water and fish tissue samples. It was found that Hg(II) and MeHg(I) ions could be simultaneously retained by a column filled with AAXAD-4 resin at pH 4 and the sequential quantitative elutions of Hg(II) and MeHg(I) were achieved using 10 mL of 0.1%(m/v) thiourea in 3%(v/v) HCl and 10 mL of 6 mol L−1 HCl, respectively. Hg(II) in the eluent was directly determined and MeHg(I) in the second eluent is quantified using FI-CVG-AAS after its oxidative digestion with KMnO4. The limits of detection for Hg(II) and MeHg(I) ions were found to be 0.148 and 0.157 µg L−1, respectively. The method was validated by analysing a certified reference material. The relative errors for Hg(II), MeHg(I) and T-Hg were in range of −1.8% and −3.2%.

Optimization of instrument conditions for the analysis for mercury, arsenic, antimony and selenium by atomic absorption spectroscopy

The chemical vapor generation atomic absorption spectrometry technique is extremely popular for trace analysis specifically hydride generation continuous flow systems for arsenic, antimony, selenium and cold vapor for mercury. Optimizing the instrument parameters as well as the hydride generating reactions will improve the sensitivity and reliability of the results obtained. The advantage of optimizing these conditions increases the production of hydrides or vapor species formed thereby improving recoveries. In addition this helps to reduce chemical interferences from other species that may compete with the analyte of interest for hydride formation. Parameters optimized include:•Reagent flow rate•Sample flow rate•Argon flow rate•Acetylene/Air ratio•Concentration of reagents•Read delay timeFor the analytical procedure the flow rate of the reagents and sample was affected by the tension on the peristaltic pump and the size of the tubing. The optimized flow rate for all reagents was between 0.9–1.0?mL/min and between 6–7?mL/min for the sample when both conditions were applied. The optimized type and concentrations of the reducing agent for Arsenic, Antimony and Selenium were NaBH4 (0.6% w/v), NaBH4 (0.7% w/v) and NaBH4 (0.1% w/v) in NaOH (0.5% w/v) respectively and SnCl2 (25% w/v) in HCl (20% v/v) for Mercury. The concentration and type of acid that produced the optimum signals for Arsenic, Antimony and Selenium were 5, 10 and 10?mol/dm-3 respectively. The flow rates for the carrier gas (Argon) for Arsenic, Antimony, Selenium and Mercury were optimized at 0.2, 0.2, 2.0 and 2.0?mL/min respectively. The optimized flow rate for fuel gas (Acetylene) for all the metals except Mercury was 2.5?mL/min. The optimized Instrument Read Delay Time for Mercury was 70?s and 20?s for Arsenic, Antimony and Selenium.

Mercury health risk assessment among a young adult Lebanese population.

Mercury (Hg) exposure represents a significant public health concern at a global level. This study aims at assessing Hg exposure and risk among Lebanese young adults based on Hg biomonitoring and seafood intake. A group of 166 young adults were administered a questionnaire to assess Hg exposure and were asked to provide a hair sample. Risk assessment was performed: (1) using the US Environmental Protection Agency Hazard Quotient (HQ) model based on fish intake and previously studied local fish Hg concentrations, and (2) by determining the total hair Hg concentration (THHg) using continuous flow-chemical vapor generation atomic absorption spectrometry. Differences in THHg across demographic and exposure subgroups were tested using t test or ANOVA. Correlations between THHg concentrations, fish consumption, and HQ were determined by computing Pearson's r. Higher THHg correlated with higher consumption of Mediterranean rabbitfish/spinefoots (r=0.27; p=0.001) and geographical location (p<0.001) in the bivariate analysis, and remained significant in the adjusted multivariable linear regression model (geographical location: ß=0.255, 95%CI 0.121-0.388; rabbitfish/spinefoots consumption: ß=0.016, 95%CI 0.004-0.027). No significant correlations were found between HQ and THHg. In conclusion, this is the first study examining hair Hg levels and fish consumption in a young adult Lebanese population. Our findings constitute valuable baseline data for a local fish advisory and Hg monitoring.

Microwave-induced combustion of high purity nuclear flexible graphite for the determination of potentially embrittling elements using atomic spectrometric techniques

Microwave-induced combustion was evaluated for the digestion of high purity nuclear flexible graphite for further determination of potentially embrittling elements (Ag, As, Bi, Cd, Ga, Hg, In, Pb, Sb, Sn and Zn) using atomic spectrometric techniques. Flexible graphite is obtained by exfoliation process of conventional graphite using oxidant agents and subsequent fast heating at high temperatures. Thus, high chemical inertness for specific purposes is attained which causes inertness also to conventional digestion methods. Microwave-assisted digestion method using maximum temperature and pressure of 275°C and 180bar (UltraWave™ system) respectively, and dry ashing were also evaluated for flexible graphite digestion. However, insoluble residues in final digests and analyte losses were observed for those methods, respectively. For microwave-induced combustion method, the use of cellulose pellet (300mg) as combustion aid allowed the efficient oxidation of 100mg of flexible graphite. In order to assure the quantitative recovery of all analytes after microwave-induced combustion two absorbing solutions should be used: 4molL−1 HNO3 for Ag, As, Cd, Ga, Hg, In, Pb, and Zn and inversed aqua regia for Bi, Sb and Sn. As flexible graphite (or similar matrix) is not available as certified reference material, accuracy was evaluated using coal (NIST 1632c and BCR 40). For all elements, except for In (not informed in certified reference materials), significant differences were not observed by comparing the results obtained by microwave-induced combustion and certified values (t test, 95% confidence level). Limits of detection using inductively coupled plasma optical emission spectrometry and chemical vapor generation atomic absorption spectrometry (only for Hg) were lower than 12mgkg−1 and in compliance with the recommendation of General Electric for nonmetallic materials (the limit for each element is 200mgkg−1 and the sum of all embrittling elements should be lower than 500mgkg−1). Microwave-induced combustion method was suitable for quality control of high purity nuclear flexible graphite.

Suitable extraction of soils and sediments for mercury species and determination combined with the cold vapor generation atomic absorption spectrometry technique

This work reports a fast and efficient procedure for mercury species extraction using Universol® as extractor reagent in soil and sediment samples combined with the cold vapor generation atomic absorption spectrometry (CV AAS) technique. Hg total was determined after oxidation CH3Hg+ to Hg2+ with KMnO4 and reduction Hg2+ to Hg0 with NaBH4. To ensure specificity and sensitivity in the Hg2+ determination, L-cysteine was added before the reduction with SnCl2 to form complex with organic mercury species. Recovery values of between 98 and 102% were obtained for Hgtotal, and 96–100% for Hg2+. The relative standard deviations were lower than 2.7%. The detection limits were 0.07 and 0.08mgkg−1 for Hgtotal and Hg2+, respectively. The use of Universol® reagent combined with the CV AAS technique proved to be a simple and efficient procedure for the determination of Hgtotal and Hg2+ in soil and sediment samples without interconversion of species allowing chemical speciation studies.

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.

Determination of copper in airborne particulate matter using slurry sampling and chemical vapor generation atomic absorption spectrometry

The present paper describes the development of a method for the determination of copper in airborne particulate matter using slurry sampling and chemical vapor generation atomic absorption spectrometry (CVG AAS). Chemometric tools were employed to characterize the influence of several factors on the generation of volatile copper species. First, a two-level full factorial design was performed that included the following chemical variables: hydrochloric acid concentration, tetrahydroborate concentration, sulfanilamide concentration and tetrahydroborate volume, using absorbance as the response. Under the established experimental conditions, the hydrochloric acid concentration had the greatest influence on the generation of volatile copper species. Subsequently, a Box–Behnken design was performed to determine the optimum conditions for these parameters. A second chemometric study employing a two-level full factorial design was performed to evaluate the following physical factors: tetrahydroborate flow rate, flame composition, alcohol volume and sample volume. The results of this study demonstrated that the tetrahydroborate flow rate was critical for the process. The chemometric experiments determined the following experimental conditions for the method: hydrochloric acid concentration, 0.208M; tetrahydroborate concentration, 4.59%; sulfanilamide concentration, 0.79%; tetrahydroborate volume, 2.50mL; tetrahydroborate flow rate, 6.50mLmin−1; alcohol volume, 200µL; and sample volume, 7.0mL. Thus, this method, using a slurry volume of 500µL and a final dilution of 7mL, allowed for the determination of copper with limits of detection and quantification of 0.30 and 0.99µgL−1, respectively. Precisions, expressed as RSD%, of 4.6 and 2.8% were obtained using copper solutions at concentrations of 5.0 and 50.0µgL−1, respectively. The accuracy was evaluated by the analysis of a certified reference material of urban particulate matter. The copper concentration obtained was 570±63mgkg−1, and the certified value was 610±70mgkg−1. This method was applied for the determination of copper in airborne particulate matter samples collected in two Brazilian regions of Bahia State, Brazil. The copper contents found varied from 14.46 to 164.31ngm−3.

In-atomizer atom trapping on gold nanoparticles for sensitive determination of mercury by flow injection cold vapor generation atomic absorption spectrometry

An in-atomizer atom trapping method based on coating gold nanoparticles onto the inner wall of a quartz tube atomizer was firstly developed and combined with flow injection cold vapor generation for the accurate determination of mercury at low μg L−1 levels by atomic absorption spectrometry. Mercury vapor generated by reducing Hg2+ with hydrochloric acid–tetrahydroborate was efficiently trapped on the surface of gold nanoparticles that were coated on the interior wall of the quartz tube atomizer prior to the determination. In situ desorption and determination of mercury was achieved by increasing the voltage (thus the temperature) to 30 V. The influence of instrumental parameters and experimental conditions on the generation, trapping and desorption of mercury vapor, as well as interference from concomitant elemental ions was investigated. A detection limit of 0.01 μg L−1 was obtained based on a 5.0 mL sampling volume. The precision was better than 4.0% at 0.5 μg L−1. Three spiked water samples and two Certified Reference Materials (dogfish muscle, DORM-4 and human hair powder GBW07601a) were analyzed to validate the accuracy of the proposed method.

Determination of mercury in naphtha and petroleum condensate by photochemical vapor generation atomic absorption spectrometry

In this work the feasibility of mercury determination in naphtha and petroleum condensate by photochemical vapor generation was investigated. The samples were pumped through the photochemical reactor as microemulsions and the volatile compounds formed were conducted to a quartz cell for the atomic absorption measurements. All the parameters of the system (sample preparation, organic precursor, sample flow rate, carrier gas flow rate and evaluation of the signal measurement mode) were investigated. The microemulsions were prepared mixing the samples with propan-1-ol and a small amount of water. The addition of low molecular weight organic acid was investigated and it was found not necessary once the propan-1-ol itself was efficient for promoting the generation of the volatile compounds of mercury. Calibration curves obtained with organic and inorganic standards showed correlation coefficients higher than 0.99 and characteristic mass of 2.0 and 2.4 ng of mercury for organic and inorganic standards, respectively, was obtained. There was no significant difference between the sensitivity of inorganic or organic standards for the calibration. Relative standard deviations ranged from 1 to 5% for three consecutive measurements. The limit of detection of 0.6 μg L− 1, calculated for the amount of sample used in the microemulsion (1.0 mL), was obtained. A sample throughput was 2 samples per hour, considering triplicate analysis. Different naphtha and petroleum condensate samples were analyzed. No mercury was found in the naphtha samples, considering the limit of detection. In the petroleum condensate samples the concentrations ranged from 76 to 105 μg L− 1. The accuracy was evaluated by assessing the recoveries of inorganic and organic species of mercury added to the samples, being obtained values in the range of 92 to 113%. The developed method was simple and fast, allowed direct analysis of naphtha and petroleum condensate with a reduced amount of reagents, thus contributing to green chemistry.

Mercury species determination by task specific ionic liquid-based ultrasound-assisted dispersive liquid–liquid microextraction combined with cold vapour generation atomic absorption spectrometry

Task specific ionic liquid-based ultrasound-assisted dispersive liquid–liquid microextraction (TSIL USA DLLME) combined with cold vapour atomic absorption spectrometry (CV AAS) for determination of mercury species in water and biological samples was developed. The proposed procedure was free of volatile organic solvents, and there was no need to use any dispersive solvents and complexing agents, in contrast to standard DLLME. Analytical signals were obtained without the back-extraction of the mercury species from the TSIL phase into an aqueous phase prior to their determination by CV AAS. The reducing agent Sn2+ could reduce Hg2+ and CH3Hg+ for determination of total mercury. Some essential parameters of the microextraction and cold vapour generation, such as the pH of sample solution, volume of the ionic liquid, ultrasonication time, cooling time, centrifugation time, matrix interferences and salt effect have been studied. Under optimal conditions, high extraction efficiency was achieved for the extraction of 1.0ngmL−1 of Hg2+ and 5ngmL−1 CH3Hg+ in 10.0mL of water solution employing 30μL of methyltrioctylammonium thiosalicylate as the extraction solvent. The enrichment factor for the method was 310 for Hg2+ and 200 for CH3Hg+. The detection limits were 0.03ngmL−1 for Hg2+ and 0.4ngmL−1 for CH3Hg+ respectively. The accuracy of the proposed method was evaluated by analysis of the Certified Reference Materials (NRCC DOLT-2, NIST 1643e). The method was applied to analysis of the tap, river, lake and sea water samples. The recoveries for reference materials and spiked samples were in the range of 95-103%.

Application of the high-speed self-reversal background corrector to the determination of cadmium by chemical vapor generation atomic absorption spectrometry

Concentrations of cadmium (Cd) in extracting solutions (neutral salts) from contaminated soils are often too low to be determined by conventional flame atomic absorption spectrometry. For this reason, determination of Cd requires sensitive analytical methods free from interference problems generated by samples. In this context, vapor generation atomic absorption spectrometry (HGAAS) was combined with a high-speed self-reversal background corrector. This new approach was successfully applied after optimization of the analytical parameters to obtain a maximal absorbance signal of the volatile Cd species. The optimum condition was achieved with a 3% (m/v) NaBH4 in 1.5% (m/v) NaOH reducing solution and a solution containing 0.3 mol/L HNO3. The detection limit was 1 ng mL–1 under the previous conditions and the relative standard deviation was up to 5% for 10 replicate analyses of Cd at 0.2 and 1 ng mL–1, reflecting a very highly sensitive and reproducible method. Moreover, the results showed that the proposed combination was an efficient method to overcome the interference problems caused by different coexisting cations, As, Al, Ca, Cu, Fe, Mg, Mn, Ni, Pb, Se and Zn, up to 10 µg mL–1. The method was validated with analyses of two standard reference materials and was used for Cd determination in 0.01 mol/L CaCl2 extracts from contaminated kitchen garden soils. The data were compared with those obtained by two other more conventional methods, electrothermal atomic absorption spectrometry (ETAAS) and flame atomic absorption spectrometry (FAAS). The analytical results obtained by the ETAAS and HGAAS were in a good agreement, suggesting the suitability of the method for Cd determination in 0.01 mol/L CaCl2 extracting solution.

Survey of total mercury and arsenic content in infant cereals marketed in Spain and estimated dietary intake

Due to the fact that infants and children are especially sensitive to mercury and arsenic exposure, predominantly through diet, a strict control of the most widely consumed infant foods, especially infant cereals, is of paramount importance. Levels of both total mercury and arsenic in 91 different infant cereals from ten different manufacturers in Spain were determined by flow injection adapted to cold vapor and hydride generation atomic absorption spectrometry, respectively. Cereals were assessed in terms of the different types, the predominating cereal in the formulation, the added ingredients, and whether the cereal was organically or conventionally obtained. In general, the content of toxic elements (median (Q1; Q3)) found in infant cereals based on conventionally obtained raw materials (n = 74, Hg: 2.11 (0.42; 4.58), As: 21.0 (9.4; 50.9) μg Kg−1) was lower than in cereals produced by organic methods (n = 17, Hg: 5.48 (4.54; 7.64), As: 96.3 (87.5; 152.3) μg Kg−1). Mercury content in infant cereals shows the higher values in those formulations with ingredients susceptible to particulate contamination such as gluten-free or cacao-based cereals. The highest arsenic content appears in the rice-based cereals. The mercury and the inorganic arsenic dietary intakes for infants fed on the infant cereals studied were assessed, taking into account the different stages of growth. Organic infant cereals based on cocoa showed the highest risk intakes of mercury, very close to exceeding the intake reference. Just the opposite, 95% of the organically produced infant cereals and 70% of the conventional gluten-free infant cereals showed an inadmissible risk of arsenic intake. Thus, it seems prudent to call for continued efforts in standardizing routine quality control and in reducing arsenic levels in infant cereals; in addition it is essential that relevant legislation be established and regulated by EC regarding these two toxic elements.

Mercury determination and speciation analysis in surface waters

Abstract A sorbent L-cysteine grafted silica gel has been evaluated for separation and enrichment of dissolved inorganic i-Hg(II) and methylmercury CH3Hg(I) from surface waters at sub-µg L−1 concentrations. Chemical parameters for mercury species enrichment and separation have been optimized. Analytical schemes for the determination of Hg species, using selective column solid phase extraction (SPE) with continuous flow chemical vapor generation atomic absorption spectrometry (CF-CVG-AAS) or inductively coupled plasma-mass spectrometry (ICP-MS) were developed. Possibilities for on-site SPE enrichment were demonstrated as well. The limits of quantification were 1.5 and 5 ng L−1 for dissolved i-Hg(II) and CH3Hg(I) by CF-CVG-AAS and 1 and 2.5 ng L−1 by ICP-MS with relative standard deviations between 7–12% and 7–14%, respectively. The chemically modified SPE sorbent has demonstrated high regeneration ability, chemical and mechanical stability, acceptable capacity and good enrichment factors. Results for total dissolved mercury were in reasonable agreement with those from independent analyses by direct ICP-MS determinations for river waters and for estuarine water certified reference material.

Simultaneously determination of methyl and inorganic mercury in fish species by cold vapour generation atomic absorption spectrometry

A simple and rapid non-chromatographic method was developed to determine methylmercury (MeHg) and inorganic mercury (iHg) levels in muscles tissues of 10 freshwater fish species. The MeHg and iHg were determined by cold vapour atomic absorption spectrometry after alkaline wet digestion of samples. The digested samples were reduced sequentially with stannous chloride and sodium tetrahydroborate for iHg and MeHg, respectively. Parameters such as carrier gas flow rate (argon), volume of oxidizing and potassium persulphate solutions were investigated in detail. The accuracy of the technique was evaluated by using certified reference material (DORM-2) and spiking the both Hg species in muscles tissue of a fish. The limits of detection were 0.117 and 0.133 μg kg(-1) for MeHg and iHg, respectively. The concentrations of MeHg and iHg in muscles tissues of ten fish species were found in the range of (28.4-56.3) and (3.01-8.11) μg kg(-1), respectively.

Sensitivity enhancement using nanometer silica particles on the surface of a quartz cell in mercury and selenium determination by vapor generation atomic absorption spectrometry

The sensitivity of on-line vapor generation atomic absorption spectrometry of mercury and selenium was improved by using a new atom trap technology. The inner wall of a T-shaped quartz tube was coated with nanometer SiO2 so increase the residence time of the analyte atoms in the light path. The linear range of the calibration plots thus was increased to a range from 5.0 to 150 ng mL−1 for mercury, and from 4.5 to 100 ng mL−1 for selenium. The detection limits are 0.9 ng mL−1 for Hg and 1.0 ng mL−1 for Se which is a 2-fold improvement. The technique was applied to the determination of Hg and Se in herbs and hair.

Solid phase extraction of cadmium on 2-mercaptobenzothiazole loaded on sulfur powder in the medium of ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate and cold vapor generation–atomic absorption spectrometric determination

A novel solid phase extractor for preconcentration of cadmium at ng L −1 levels has been developed. Cadmium ions were retained on a column packed with sulfur powder modified with 2-mercaptobenzothiazole (2-MBT) in the medium of 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim] +PF 6 −) ionic liquid. The presence of ionic liquid during modification of sulfur enhanced the retention of cadmium ions on the column. The retained cadmium ions were eluted with 2 mol L −1 solution of HCl and measured by cold vapor generation–atomic absorption spectrometry (CVG–AAS). By using reaction cell-gas liquid separator (RC-GLS), gaseous cadmium vapors were produced and reached the atomic absorption spectrometer, instantaneously. The influence of different variables on both processes of solid phase extraction and CVG–AAS determination of cadmium ions was investigated. The calibration curve was linear in the range of 10–200 ng L −1of cadmium in the initial solution with r = 0.9992 ( n = 8) under optimum conditions. The limit of detection based on three times the standard deviation of the blank (3S b, n = 10) was 4.6 ng L −1. The relative standard deviation (R.S.D.) of 25 and 150 ng L −1 of cadmium was 4.1 and 2.2% ( n = 8), respectively. The procedure was validated by the analysis of a certified reference material (DORM-3), water and fish samples.

Vapor Generation Atomic Absorption Spectrometric Determination of Cadmium in Environmental Samples with In-Line Anion Exchange Separation

A novel in-line anion exchange separation method is described for the removal of Mn(2+), Fe(3+), Ni(2+), Co(2+), Cu(2+), Zn(2+), and Pb(2+) from Cd(2+) and for its subsequent determination by vapor generation atomic absorption spectrometry. High Cd(2+) retention efficiency and maximum exclusion of other metal ions were achieved by using Cl(-), Br(-), or I(-) loaded strong base anion exchange resin and fiber in chloride medium. SO(4)(2-) and NO(3)(-) affected the retention of Cd(2+) on Cl(-) or Br(-) loaded exchangers but were beneficial for elution from I(-) loaded exchangers. Fast and efficient elution from the exchangers was achieved by using ethylenediamine solution. The removal of Zn(2+) was unnecessary as it prevents a decline in the sensitivity of cadmium response when ethylenediamine and high acid concentration were used. Under optimum conditions, the achievable detection limits (3sigma) with sample loadings of 0.48 and 9.6 mL were 40 ng L(-1) and 3 ng L(-1), respectively. Interference of residual organic matrix, in sample digests, with the separation and retention of cadmium were eliminated by use of microwave assisted digestion. The method was successfully applied to the determination of Cd in river sediment, fish liver, and water samples.

Determination of inorganic and total mercury by flow injection vapor generation atomic absorption spectrometry using a W-coil atomizer

A tungsten coil (150 W, 15 V) was used as the atomizer for the proposed Flow Injection Vapor Generation Atomic Absorption Spectrometry (FI-VGAAS) system to determine inorganic mercury and total mercury concentrations. In the proposed method inorganic mercury was measured when the W-coil is at room temperature and total mercury was measured when the W-coil temperature was set to 500 °C. The organic mercury concentration was calculated by subtracting the inorganic mercury concentration from the total mercury concentration. The calibration graphs were linear up to 100 ng ml−1. Limit of detection (LOD) values for inorganic mercury and methyl mercury were 0.60 ng ml−1 and 0.89 ng ml−1 respectively. The precision of the method in terms of RSD was between 2–3%, and the sampling frequency was 100 h−1. In order to validate the proposed method, known concentrations of methyl mercury and inorganic mercury were spiked into deionized water and tap water samples. Certified reference materials (CRM) IAEA-085 and NRC DOLT-3 were analyzed after microwave assisted extraction with 6.0 mol l−1HCl solutions. Both inorganic mercury and methyl mercury concentrations were in agreement with the certified values.