Determination of arsenic in mussels by slurry sampling and electrothermal atomic absorption spectrometry (ETAAS)

A method for the determination of arsenic in slurries of mussel tissue using palladium-magnesium nitrate as modifier was optimized. The slurry was stabilized by a 0.015% (v/v) of Triton X-100. To achieve complete mineralization the slurries were ashed at 480 °C for 10s in an air flow (50 ml/min) and at 1200 °C for 15s in an argon flow (300 ml/min) in the presence of Pd—Mg(NO₃)₂ as modifier. The optimum atomization temperature was 2200 °C. The precision and accuracy of the method were studied using the Reference Material BCR n ° 278 Mussel Tissue (Mytilus edulis). The detection limit (LOD) of the final slurry solution was 1 g/l of arsenic corresponding to an arsenic level in the mussel of 1.3 g/g, for a 0.5% (m/v) slurry. Results of calibration using aqueous standards and the standard additions method were compared. The method was applied to the determination of arsenic in mussels from the Galician coast. The levels found lie between 2 and 9.3 g/g of arsenic.     

Cloud point extraction of aluminum (III) in water samples and determination by electrothermal atomic absorption spectrometry,flame atomic absorption spectrometry and UV-visible spectrophotometry

Cloud point extraction was applied as a preconcentration step for the determination of trace level of Al(III) in water samples with electrothermal atomic absorption spectrometry (ETAAS), flame atomic absorption spectrometry (FAAS) and UV-visible spectrophotometry. The aluminum was extracted as aluminum-Eriochrome Cyanine R (ECR) complex, at pH 6 by micelles of the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114). The investigations showed that the same CPE procedure can be used for different detection techniques. The results obtained from these techniques were evaluated. Under the optimal conditions, limit of detection obtained with ETAAS, FAAS and UV-visible spectrophotometry were 0.03 ng mL^?1, 0.06 µg mL^?1 and 0.01 µg mL^?1, respectively. The accuracy of the procedure was tested by analysing certified reference material. The method was successfully applied to determination of aluminum in water samples and dialysis fluid.     

On-line bi-directional electrostacking for As speciation/preconcentration using electrothermal atomic absorption spectrometry

A method using bi-directional electrostacking (BDES) in a flow system is presented for As preconcentration and speciation analysis. Some parameters such as electrostacking time and applied voltage, support buffers and their concentrations were investigated. Boric acid plus sodium hydroxide at 0.1 mol/l concentration was selected as support buffer to improve the pre-concentration factor (PF) for As(V). An analytical range from 2.0 to 50.0 μg l⁻¹, and 0.35 μg l⁻¹ as limit of detection, when applied 750 V for 20 min, were achieved. Under these conditions, a pre-concentration factor of 4.8 was obtained. The proposed method was applied to determine As(V) in mineral water and natural water samples (river, fountain and gold mine) from Ouro Preto city. Recoveries from 93.5 to 106.4% were achieved at 10 μg l⁻¹ added As level (R.S.D.s between 3 and 7%). Potassium permanganate (10 mg l⁻¹) was used for oxidising As species in order to determine total As, being established the concentration of As(III) from the difference between total As and As(V).     

Determination of mercury species in gas condensates by on-line coupled high-performance liquid chromatography and cold-vapor atomic absorption spectrometry

A method for the speciation of mercury in gas condensates is reported. Mercury(II) chloride (HgCl₂), methylmercury chloride (MeHgCl), phenylmercury acetate (PhHgAc) and diphenylmercury (Ph₂Hg) are separated by reversed-phase high-performance liquid chromatography (HPLC) using gradient elution. Prior to the determination, the organic ligands and the matrix were destroyed by oxidation with K₂Cr₂O₇. Mercury is detected with cold-vapor atomic absorption spectrometry (CVAA), where the mercury compounds are reduced to metallic mercury by a treatment with NaBH₄. In a continuous-flow system the concentrations of the reagents used are optimized using a modified simplex algorithm. Detection limits for mercury are at the 10 ng ml^?1 level. Analysis of multi-compound mixtures indicates that chemical reactions between HgCl₂ and Ph₂Hg and between MeHgCl and Ph₂Hg take place. The method developed was applied to the speciation of mercury in gas condensates and did not require use of any solvent extraction or chemical derivatization steps. In the gas condensates, mercury(II) compounds were found to be present at the 100 ng ml^?1 level.     

Speciation of iron in breast milk and infant formulas whey by size exclusion chromatography-high performance liquid chromatography and electrothermal atomic absorption spectrometry

Speciation of iron in milk was carried out by high performance liquid chromatography (HPLC) and electrothermal atomic absorption spectrometry (ETAAS). Milk whey was obtained and low molecular weight protein separation was performed by size exclusion chromatography (SEC) with a TSK Gel SW glass guard (Waters) pre-column and a TSK-Gel G2000 glass (Toso Haas) column. After studying water as a possible mobile phase, this mobile phase was carefully selected in order to avoid alterations of the sample and to make subsequent iron determination in the protein fractions easier by ETAAS. The proposed method is sensitive (limit of detection [LOD] and LOQ 1.4 and 4.7 μg l⁻¹, respectively) and precise (relative standard deviation [RSD]<10%). Iron is principally found in the proteins of 3 and 76 kDa in breast milk, and it is irregularly distributed in infant formulas.     

电沉积-钨丝电热原子吸收光谱法测定水样中的铅

研制了一种便携式钨丝电热原子吸收光谱分析装置,其主要包括:钨丝电热原子化器、多道微型CCD光谱仪、仪器电源系统以及控制系统。并将电沉积分离富集技术与该钨丝电热原子吸收光谱分析仪器结合,完成环境水样中铅的现场分析。并对铅的电沉积条件作了研究,最佳电沉积电位为负650 mV(vs.SCE),方法检出限:0.20μg/L,线性范围:1~15μg/L,对4μg/L Pb标准溶液10次重复测试,RSD为4.4%。     

Determination of nickel in water by electrothermal atomic absorption spectrometry with preconcentration on a tungsten foil

A preconcentration method for nickel in waters involving adsorption on tungsten foil, followed by electrothermal atomic absorption spectrometry (ETAAS) with a tungsten tube atomizer is described. The most suitable pH for nickel adsorption was 5 and the optimum immersion time was 2 min. Severe interferences from co-existing elements (Al, Ca, Cu, Fe, K, Mg, Na, Pb and Zn) on the Ni AA signal were observed. Under optimal conditions, the preconcentration of nickel on W foil could eliminate interferences from these elements. The detection limit of nickel by preconcentration-ETAAS was 0.1 ng/ml (3S/N). The method with preconcentration on tungsten foil was applied to the determination of nickel in river water. The recovery of spiked nickel was 93–102%. The tungsten foil preconcentration method is sensitive, simple, and convenient. This adsorption method can be utilized inin situ-sampling of ultra-trace nickel in environmental samples (water). Furthermore, after sampling it is easy to carry and store the W-foil without contamination for long time.     

A simplified procedure for the determination of butyltin species in water

A method is described for the analysis of solutions containing inorganic tin and butyltin compounds. It can be used to determine total tin at a concentration of 20 ng dm^?3 using a 5 dm³ sample. The method is based on solvent extraction with dichloromethane containing tropolone and determination of the tin as inorganic tin by atomic absorption spectroscopy using electrothermal atomization. The extracted butyltin compounds can be separated by paper chromatography and the tin content of the individual spot determined as above. Observations on the stability of butyltin compounds in water at the ～2 mg dm^?3 (Sn) are included.     

Speciation of organotin compounds in water and sediments by gas chromatography/atomic absorption spectrometry (GC-AAS)

A commercially available atomic absorption detector coupled to a wide-bore column-containing gas Chromatograph (GC-AAS) was utilized to detect organotin compounds. Speciation was performed by pentane extraction of the organotin species as the corresponding sodium diethyldithiocarbamate complexes, enrichment by rotary evaporation, derivatization with Grignard reagent and finally the extracted water and sediment samples were separated and detected on the GC-AAS system.     

Separation and preconcentration by flow injection coupled to tungsten coil electrothermal atomic absorption spectrometry

A flow injection system coupled to a tungsten coil electrothermal atomizer has been developed for on-line separation and preconcentration, using lead as a model element. The system utilizes three-way solenoid valves for sampling, buffering, washing and reconditioning solution management, and the resin column is inserted in the tip of the autosampler arm of a Varian GTA-96. The solenoid valves and tungsten coil power supply were controlled by a computer program written in Visual Basic, interfaced with the built-in Varian software. The system performance was tested by loading the resin column with the sample flowing at 3 ml min⁻¹ for 60 s. Elution was performed automatically by sampling 20 μl of the eluent from a sample cup of the autosampler, and this aliquot was delivered into a 150 W tungsten coil. With Chelex-100 resin, the separation of concomitants was tested with lead in the presence of as much as 1000 mg l⁻¹ of Ca, Mg, Na or K. The model system presented an enrichment factor of 64 at a sampling rate of 30 samples per hour.     

Development of a method for speciation of inorganic arsenic in waters using solid phase extraction and electrothermal atomic absorption spectrometry

A solid phase extraction (SPE) procedure based on Amberlite IRA 900 resin was developed for speciation and separation of inorganic arsenic species (III, V) and total As in water samples. The As species and total As in eluent solutions were determined by electrothermal atomic absorption spectrometry (ETAAS) using Ni chemical modifier with 1200°C pyrolysis temperature. Experimental parameters such as pH value, sample volume, flow rate, volume and concentration of eluent solution for As(V) were optimised and 98.0 ± 1.9% recovery was found at pH 4.0. Experimental adsorption capacity of the resin for As(V) was investigated and 229.9 mg g^–1 was found. Under optimised experimental conditions, instrumental parameters such as limit of detection (LOD) and limit of quantification (LOQ) found were 0.126 and 0.420 µg L^–1, respectively. Interference effects of coexisting ions in the sample matrix on the recovery of As(V) were investigated. Concentration of As(III) was obtained by subtracting As(V) concentration found at pH 4.0 from total As(III + V) found at pH 8.0. The accuracy of the method proposed by using the resin was tested for analysing As species in a waste water standard reference material (SRM, CWW-TM-D) and spiked real water samples with recovery above 95%. The method proposed was also applied to the determinations of As species and total As in underground hot waters and tap water with relative error below 3%.     

Determination of tributyltin oxide in coastal marine sediments and mussels by electrothermal atomic absorption spectrometry

We have devised a new method for bis(tributyltin)oxide (TBTO) determination in marine sediments and mussels. This technique involves an n-hexane/methylene chloride mixture extraction and extract purification with a sodium hydroxide wash in order to eliminate interfering compounds. TBTO is then extracted again by nitric acid and converted into an inorganic tin species; the analysis has been effected using Zeeman graphite furnace-atomic absorption spectrophotometry. The method detection limit for the matrices examined is 0.004 μg TBTO g^?1 (wet weight) and is sufficient for the analysis in real samples. The percentage recovery of TBTO from sediments and mussels samples is higher than 85% and 95% respectively. This method has been applied to TBTO level determination in sediments and mussels (Mytilus galloprovincialis) sampled in the harbour area in Taranto, where mussel culture activities are much developed; the TBTO levels obtained in sediments and mussels were in the range 15-47 ng g^?1 (wet weight) and 11-30 ng g^?1 (wet weight) respectively. Such values are comparable with those found in other harbour areas in the Mediterranean Sea.     

Determination of cadmium in slurries of marine sediment samples by electrothermal atomic absorption spectrometry using palladium and phosphate as chemical modifiers

A method for the determination of cadmium in slurries of marine sediment using palladium and phosphate as chemical modifier has been optimized. To stabilize the marine sediment slurry, Triton X-100 at 0.1% was used. To obtain a complete pyrolysis of the slurry sample two mineralization steps were used, the first at 480 °C and the second at 600 °C and 700 °C for phosphate and palladium, respectively. The precision and accuracy of the method have been studied by analyzing the Reference Material PACS-1 (marine sediment) of National Research Council Canada. The detection limits (LOD) were 11.9 g kg^–1 for phosphate and 42.0 g kg^–1 when palladium was used. These methods have been applied to the determination of cadmium in marine sediment samples from the Galicia coast and the results of both methods were compared; no significant differences were found between the two procedures.     

Speciation of butyltin compounds by on line HPLC-ETAAS

Speciation of butyltin compounds by liquid chromatography coupled to electrothermal atomic absorption spectrometry of toluene solutions containing tropolone is applied to sediment samples. Tributyltin and dibutyltin may be determined at concentrations as low as a few ng · g^–1. Monobutyltin is strongly retained, tetrabutyltin is not separated from tributyltin.     

电沉积-钨丝电热原子吸收光谱法测定地质样品中痕量金

以市售幻灯投仪卤钨灯泡钨丝为原子化器的钨丝电热原子吸收光谱分析仪(TC-AAS),功率小、仪器成本低[1,2],如用微型CCD光谱仪作检测系统,可以实现原子吸收光谱仪的小型化,甚至可用于野外现场分析[3,4].     

Study of parameters associated with the determination of cadmium in lake sediments by slurry sampling electrothermal atomic absorption spectrometry

Cadmium concentration in lake sediments is determined by suspending the solid samples in a solution containing 5% (v/v) concentrated nitric acid and 0.1% (v/v) Triton X-100. Three modifiers were tested for the direct determination. The furnace temperature programmes and appropriate amount for each modifier were optimised to get the highest signal and the best separation between the atomic and background signals. The drying stage is performed by programming a 400 °C temperature, a ramp time of 25 s and hold time of 10 s on the power supply of the atomiser. No ashing step is used and platform atomisation is carried out at 2200 °C. W–Rh permanent modifier combined with conventional modifier by delivering 10 μl of 0.50% (w/v) NH₄H₂PO₄ solution was the best chemical modifier for cadmium determination. This modifier also acts as a liquid medium for the slurry, thus simplifying the procedure. Calibration is performed using aqueous standards in the 1–5 μg l⁻¹ range. The optimised method gave a limit of detection of 0.56 ng ml⁻¹, characteristic mass of 10.1±0.8 pg for aqueous standard, 9.6±0.7 pg for slurry samples containing different Cd concentrations and good precision (7.6–5.2%). The method was validated by analysing four certified reference lake sediment materials: LKSD-1, LKSD-2, LKSD-3 and LKSD-4; satisfactory recoveries were obtained (90.0–96.3%) and no statistical differences were observed between the experimental and the certified cadmium concentration. The developed methodology was used to determine cadmium in three ‘real’ sediment samples from lakes in the area of Wielkopolski National Park, Poland.     

Speciation of butyltin compounds in oyster samples

Experimental instrumentation for the speciation of butyltin compounds by hydride generation and gas chromatography-quartz furnace atomic absorption spectrometry is described. Evaluation of a number of extraction methods revealed that simple acid leaching of oyster samples gave adequate recoveries. The levels of each butyltin species in oyster flesh and gill are reported together with the tentative identification of a mixed methylbutyltin compound.     

Ultrasonic assisted deep eutectic solvent liquid–liquid microextraction using azadipyrromethene dye as complexing agent for assessment of chromium species in environmental samples by electrothermal atomic absorption spectrometry

A novel type of solvent named deep eutectic solvent (DES) has been considered as a green ionic liquid analogue. A novel method was developed for enrichment and speciation of chromium ion from water and food samples based on deep eutectic solvent and ultrasonic extraction. The procedure for this method was comprised of Cr(III) complex formation with a hydrophobic complexing agent (Z)‐N‐(3,5‐diphenyl‐1H‐pyrrol‐2‐yl)‐3,5‐diphenyl‐2H‐pyrrol‐2‐imine (azadipyrromethene dye). Metal complex was entrapped in a deep eutectic solvent as an extracting solvent. While Cr(III) recovery was quantitative, the recovery of Cr(VI) was found 5%. After reduction of Cr(VI) to Cr(III), the method was applied for determination of total chromium(III) ion. The amount of Cr(VI) was calculated as subtracting of Cr(III) from total chromium ion. Various analytical parameters were optimized. The certified reference materials were analyzed and standard addition method also carried out to real samples to check the accuracy of the developed method. Preconcentration factor was found to be 50. The limit of detection of chromium(III) was found to be 4.3 ng l^‐1. The precision of developed method as the relative standard deviation (RSD) was found as 3.5 %. The developed method was applied successfully for the speciation of chromium ions in water and food samples.     

Preconcentration of trace heavy metals in water by coprecipitation with magnesium oxinate for electrothermal atomic absorption spectrometry

Nanogram quantities of heavy metals in 200 ml of water were quantitatively preconcentrated by coprecipitation with magnesium oxinate at pH 9–9.5. The precipitate was collected on a 1-m Nuclepore membrane filter and then dissolved in 5 ml of 1 mol/l nitric acid. After diluting to 10 ml with water, a 10- or 20-l aliquot of the solution was directly analyzed by electrothermal atomic absorption spectrometry using deuterium background correction. The background absorption due to the collector magnesium oxinate was negligibly small. The optimized coprecipitation technique has been applied to the determination of cobalt, nickel, copper, cadmium and lead at the ppt level in river and seawater. The relative standard deviations were within 10% and the detection limits were 0.025 (for Co), 0.019 (for Ni), 0.006 (for Cu), 0.001 (for Cd) and 0.017 g/l (for Pb). Blanks through the whole procedure were not detectable.     

Selenium determination by electrothermal atomic absorption spectrometry in petroleum refinery aqueous streams containing volatile organic compounds

An electrothermal atomic absorption spectrometry (ETAAS) with polarized Zeeman background correction was used for determining selenium in petroleum refinery aqueous streams containing large amounts of volatile unknown organic compounds. Some parameters that might affect the measurement were investigated such as the amount of matrix modifier added, the temperature program and the calibration mode employed. Obtained results indicate that, in this kind of sample, selenium must be determined by standard addition procedure with a careful control of the dry step temperature and ramp pattern. Also, the results show that 2.5 μg of Pd must be added as matrix modifier to stabilize the analyte in the range of 2-20 ng Se. In order to evaluate the accuracy of the procedure, selenium was determined in 18 samples by ETAAS and hydride generation atomic absorption spectrometry (HGAAS) (as reference methodology). In both techniques the results agreed well.