Sampling Electrothermal Atomic Absorption Spectrometry Research Articles

Rapid and sensitive determination of trace Cd in carbonate samples using direct solid sampling electrothermal vaporization atomic absorption spectrometry

The accurate determination of cadmium (Cd) hosted and accumulated in sedimentary carbonate remains challenging due to its low concentration (ng·g−1) and complex matrix. Conventional methods, such as inductively coupled plasma mass spectrometry (ICP-MS) and graphite furnace atomic absorption spectrometry (GF-AAS), which typically rely on liquid sampling and sample digestion, are tedious, labor-intensive and time-consuming. In this study, a rapid and sensitive method for the direct determination of carbonate-hosted Cd was developed based on solid sampling electrothermal atomic absorption spectrometry (SS-ETV-AAS). This method eliminates the need of acid digestion procedure, allowing the entire analysis, including sample preparation, to be completed within 10 min. To minimize the carbonate matrix effect, ethylene diamine tetra acetic acid disodium salt (EDTA-2Na) was proposed as matrix modifier to facilitate the release of Cd, enabling fast and accurate determination of trace Cd in carbonate samples. Under optimized conditions, the Cd detection limits was found to be as low as 0.17 ng·g−1, and repeatability (relative standard deviation, RSD) was better than 8 % (n = 7). The accuracy of the proposed SS-ETV-AAS was verified by analyzing five carbonate certified reference materials (GBW07127, GBW07129, GBW07130, GBW07135 and JDo-1), two soil certified reference materials (GBW07404a, GBW07405), as well as several actual carbonate samples. All these results demonstrate that the proposed SS-ETV-AAS method provides a simple, rapid and sensitive approach for measuring trace Cd in carbonates.

Fast Detection of Cadmium in Chocolate by Solid Sampling Electrothermal Vaporization Atomic Absorption Spectrometry and Its Application on Dietary Exposure Risk Assessment.

In this work, a rapid detection method using solid sampling electrothermal vaporization atomic absorption spectrometry (SS-ETV-AAS) was established for cadmium in chocolate. The instrumental system includes a solid sampling ETV unit, a catalytic pyrolysis furnace, an AAS detector, and a gas supply system with only an air pump and a hydrogen generator. Herein, MgO material with 1.0–1.5 mm particle size was first employed to replace the kaolin filler previously used to further shorten the peak width and to thereby improve the sensitivity. With 350 mL/min of air, a chocolate sample was heated for 25 s from 435 to 464 °C to remove water and organic matrices; then, after supplying 240 mL/min hydrogen and turning down air to 120 mL/min, a N2/H2 mixture gas was formed to accelerate Cd vaporization from chocolate residue under 465 to 765 °C. Under the optimized conditions, the detection limit (LOD) was obviously lowered to 70 pg/g (vs. previous 150 pg/g) with R2 > 0.999; the relative standard deviations (RSD) of repeated measurements for real chocolate samples ranged from 1.5% to 6.4%, indicating a favorable precision; and the Cd recoveries were in the range of 93–107%, proving a satisfied accuracy. Thus, the total analysis time is less than 3 min without the sample digestion process. Thereafter, 78 chocolate samples with different brands from 9 producing countries in China market were collected and measured by this proposed method. Based on the measured Cd concentrations, a dietary exposure assessment was performed for Chinese residents, and the target hazard quotient (THQ) values are all less than 1, proving no significant health risk from intaking chocolate cadmium for Chinese residents.

Novel solid sampling electrothermal vaporization atomic absorption spectrometry for fast detection of cadmium in grain samples

In this work, a novel and green solid sampling method of Cd in grain samples was established based on electrothermal vaporization atomic absorption spectrometry (ETV-AAS).

Rapid Screening Analysis of Methylmercury in Fish Samples Using Stannous Chloride Reduction and Direct Sampling Electrothermal Vaporization Atomic Absorption Spectrometry

Rapid Screening Analysis of Methylmercury in Fish Samples Using Stannous Chloride Reduction and Direct Sampling Electrothermal Vaporization Atomic Absorption Spectrometry

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.

Determination of Cu, Cd, Pb and Cr in yogurt by slurry sampling electrothermal atomic absorption spectrometry: A case study for Brazilian yogurt

A slurry sampling electrothermal atomic absorption spectrometric method is proposed for the determination of trace elements such as Cu, Cr, Cd and Pb in yogurt. The main factors affecting the slurry preparation were optimized: nature and concentration of acid solution and sonication time. The analytical method was validated in-house by calibration, linearity, limits of detection and quantification, precision and accuracy test obtaining satisfactory results in all cases. The proposed method was applied for the determination of Cd, Cr, Cu and Pb in some Brazilian yogurt samples. For these samples, the concentrations ranged from 2.5±0.2 to 12.4±0.2ngg−1; 34±3 to 899±7ngg−1; <8.3 to 12±1ngg−1; and <35.4 to 210±16ngg−1 for Cd, Cu, Cr and Pb, respectively. The daily intake of Cd, Cu, Cr and Pb via consumption of these samples was estimated.

Heated Slurry Sampling for the Determination of Cadmium in Food by Electrothermal Atomic Absorption Spectrometry

A heating procedure is reported with slurry sampling electrothermal atomic absorption spectrometry to improve the accuracy of cadmium determination in food. In comparison to conventional slurry sampling, the heating significantly increased cadmium recovery and improved the precision. For the optimized procedure, 25–250 mg of food were treated with 2% HNO3 and 1% H2O2 with heating at 120°C for 20 min, followed by the addition of 50 µL of 10% Triton X-100, and homogenization in an ultrasonic bath prior to analysis. Tungsten and rhodium were employed as a permanent modifier with optimum pyrolysis and atomization temperatures of 500°C and 1500°C. Calibration with aqueous standards resulted in good agreement between certified or information values and measured results at the 95% confidence level. A characteristic mass of 0.8 ± 0.1 pg and a detection limit of 0.7 ng g−1 for a 2% slurry were obtained. The method was employed for the direct determination of cadmium in food certified reference materials.

Determination of cadmium and lead in urine samples after dispersive solid–liquid extraction on multiwalled carbon nanotubes by slurry sampling electrothermal atomic absorption spectrometry

A new method for the determination of Cd and Pb in urine samples has been developed. The method involves dispersive solid-phase extraction (DSPE), slurry sampling (SS), and subsequent electrothermal atomic absorption spectrometry (ETAAS). Oxidized multiwalled carbon nanotubes (MWCNTs) were used as the sorbent material. The isolated MWCNT/analyte aggregates were treated with nitric acid to form a slurry and both metals were determined directly by injecting the slurry into the ETAAS-atomizer. The parameters that influence the adsorption of the metals on MWCNTs in the DSPE process, the formation and extraction of the slurry, and the ETAAS conditions were studied by different factorial design strategies. The detection and quantification limits obtained for Cd under optimized conditions were 9.7 and 32.3ngL−1, respectively, and for Pb these limits were 0.13 and 0.43μgL−1. The preconcentration factors achieved were 3.9 and 5.4. The RSD values (n=10) were less than 4.1% and 5.9% for Cd and Pb, respectively. The accuracy of the method was assessed in recovery studies, with values in the range 96–102% obtained for Cd and 97–101% for Pb. In addition, the analysis of certified reference materials gave consistent results. The DSPE–SS–ETAAS method is a novel and useful strategy for the determination of Pb and Cd at low levels in human urine samples. The method is sensitive, fast, and free of matrix interferences, and it avoids the tedious and time-consuming on-column adsorption and elution steps associated with commonly used SPE procedures. The proposed method was used to determine Cd and Pb in urine samples of unexposed healthy people and satisfactory results were obtained.

Direct determination of cadmium in geological samples by slurry sampling electrothermal atomic absorption spectrometry

An accurate and high throughput method involving slurry sampling ETAAS was developed to detect trace Cd content in various geological samples.

Direct determination of Cd, Pb and Cr in honey by slurry sampling electrothermal atomic absorption spectrometry

Slurry sampling electrothermal atomic absorption spectrometry was used for direct determination of Cr, Pb and Cd in honey without sample pretreatment. The honey slurries were prepared in aqueous solution containing hydrogen peroxide and nitric acid. The slurries were directly introduced in the pyrolytic graphite tubes. Pd–Mg was used as a chemical modifier only for Cd determination. Analytical curves were performed with aqueous standards for Pb and Cr and with addition of fructose for Cd. The quantification limits for Cd, Pb and Cr were 2.0, 5.4 and 9.4ngg−1, respectively. Acceptable precision of the methodology was obtained through repeatability and intermediate precision. In the accuracy study, recoveries were satisfactory (94–101%) for the three elements. The methodology was applied in honey from Paraná (Brazil). The concentrations of Pb, Cd and Cr ranged from 141 to 228ngg−1, <2.0 to 8ngg−1 and 83 to 94ngg−1, respectively.

Determination of cadmium and lead in fresh fish samples by direct sampling electrothermal atomic absorption spectrometry

The determination of cadmium and lead in fish samples has large analytical interest due to the potential toxicity of these elements. The development of fast and reliable analytical methods is extremely important for an effective control of contamination. In this work, the feasibility of Cd and Pb determination in fresh fish samples using direct sampling by electrothermal atomic absorption spectrometry (DS-ET AAS) was investigated. For optimization of the furnace temperature program, pyrolysis and atomization curves with TORT-2 and DORM-3 certified reference materials were carried out using chemical modifier (0.05% Pd + 0.03% Mg + 0.05% Triton X-100). The figures of merit obtained were: characteristic mass of 1.0 pg and 16 pg and limit of detection (LOD) of 0.2 μg kg−1 and 1.0 μg kg−1 for Cd and Pb, respectively, based on 8 mg of sample mass. The results obtained for certificated references materials were statistically not different from the certified values at 95% confidence level, using the calibration with aqueous standards, showing that this calibration method is suitable for this application. For assessment of the accuracy of the method, fresh fish samples were digested. The results obtained with direct determination of Cd and Pb in fresh fish samples and with microwave assisted acid digestion were statistically accordant. The developed method for analysis of fresh fish samples is accurate, simple, fast and suitable for routine application, avoiding digestion procedures or the drying/lyophilization and grinding procedures, usually used in DS analysis, reducing the preparation time, risk of contamination and costs.

Direct solid sampling electrothermal atomic absorption spectrometric determination of toxic and potentially toxic elements in certified reference materials of brown coal fly ash

This work describes a method for the direct determination of Bi, Cd, Cr, Ni, Pb, Sb, Sn and Zn in reference materials of brown coal fly ash, using solid sampling electrothermal atomic absorption spectrometry. The use of chemical modifiers was found to be necessary for obtaining reproducible and sufficiently sensitive signals for the analytes under study. The mixture of Pd and Mg(NO3)2 was used for the determination of Bi, Cd, Pb, Sb, Sn and Zn, W (permanent modifier) in combination with Mg(NO3)2 (as aqueous modifier) provided well-defined signal profiles for Cr and Ni determination in coal fly ash samples. A systematic study focused on the use of alternative (less sensitive) lines for obtaining sufficient sensitivity. The following analytical lines were used: Bi 306.8nm, Cd 326.1nm, Cr 520.6nm, Ni 305.1nm, Pb 205.3nm, Sb 206.8nm, Sn 300.9nm, Zn 307.6nm. The limits of detection were 0.057μg g−1 for Bi, 0.21μg g−1 for Cd, 1.1μg g−1 for Cr, 1.4μg g−1 for Ni, 4.0μg g−1 for Pb, 0.13μg g−1 for Sb, 0.33μg g−1 for Sn and 16μg g−1 for Zn, respectively.

Stabilizing Agents for Calibration in the Determination of Mercury Using Solid Sampling Electrothermal Atomic Absorption Spectrometry

Tetramethylene dithiocarbamate (TMDTC), diethyldithiocarbamate (DEDTC), and thiourea were investigated as stabilizing agents for calibration purposes in the determination of mercury using solid sampling electrothermal atomic absorption spectrometry (SS-ETAAS). These agents were used for complexation of mercury in calibration solutions and its thermal stabilization in a solid sampling platform. The calibration solutions had the form of methyl isobutyl ketone (MIBK) extracts or MIBK-methanol solutions with the TMDTC and DEDTC chelates and aqueous solutions with thiourea complexes. The best results were obtained for MIBK-methanol solutions in the presence of 2.5 g L−1 TMDTC. The surface of graphite platforms for solid sampling was modified with palladium or rhenium by using electrodeposition from a drop of solutions. The Re modifier is preferable due to a higher lifetime of platform coating. A new SS-ETAAS procedure using the direct sampling of solid samples into a platform with an Re modified graphite surface and the calibration against MIBK-methanol solutions in the presence of TMDTC is proposed for the determination of mercury content in solid environmental samples, such as soil and plants.

Determination of impurities for controllable growth of high quality optical fluorite

AbstractNatural fluorite is used for growing CaF2 boules from melt by an improved technique. Chemical treatment of the starting ore decomposes the accessory minerals, thus producing small amounts of the oxides of Si, Al, and Fe insoluble in the melt, whereas the overall content of rare earth elements (REEs) of hundreds of μg g−1, remains unchanged. Analytical techniques and optical measurements provide for assessing the concentration range and trends in the distribution of residual metal impurities along the height of the boules. Solid sampling electrothermal atomic absorption spectrometry (SS-ETAAS) gives good reproducibility for impurities’ distribution within a large concentration range of 0.1–10 μg g−1. The concentrations of Zn and Cu determined were found to vary within the lowest tenths of μg g−1 range in the starting portions of chemically treated fluorspar and a batch of boules produced subsequently. The concentrations of both elements show a decreasing trend towards the top section within the confidential interval, the width of which confirms the definite in homogeneities in their distribution at those concentration levels. The Fe occurs in the boules below the detection limit, while the content of lead diminishes rapidly towards their upper section, probably due to a shorter path in the liquid phase before any vapour phase transition proceeds. A satisfactory correlation is found between the Pb concentration in ng g−1-range and light-absorption peak intensity at 204 nm, the precise determination of which is impeded due to the overlapping bands and the light-scattering effect. Reliable determination of impurities enables optimisation of the basic purification — growing stages for the production of high grade crystals.

Comparison of chemical modifiers for direct determination of Cd, Cu and Zn in food stuffs by solid-sampling-ETAAS

In this work, the capability of different chemical modifiers (Pd, Pd/Mg(NO3)2, Pd/NH4NO3, NH4H2PO4, NH4H2PO4/Mg(NO3)2) to eliminate the matrix effects in the direct determination of Cd, Cu and Zn in food-stuffs by solid sampling-electrothermal atomic absorption spectrometry was compared. The alternative analytical lines were used for determination of Cu (327.4nm) and Zn (307.6nm) in order to allow the introduction of reasonably high sample mass into the furnace. Mixed modifiers containing palladium were useful to eliminate the matrix effect in Cd determination. For Cu and Zn determination the application of Pd shows satisfactory analytical performance. In the determinations of Cd and Zn the phosphate containing modifiers shows elimination of matrix effects only when applying them to a partially pyrolysed sample (at 400°C). The achievable limits of detection for Cd, Cu and Zn in solid samples were 0.279ngg−1; 0.020μgg−1 and 2.04μgg−1, respectively.

Determination of metal impurities in carbon nanotubes by direct solid sampling electrothermal atomic absorption spectrometry

Metal impurities (Al, Cd, Co, Cr, Cu, Mg, Mn and Pb) were determined in carbon nanotubes (CNTs) by direct solid sampling electrothermal atomic absorption spectrometry (DSS-ET AAS, deuterium lamp background corrector). Parameters as pyrolysis and atomization temperatures, use of Pd as chemical modifier, feasibility of calibration using aqueous standard solutions and maximum sample mass were investigated. Results obtained by the proposed method were compared with those obtained by neutron activation analysis (NAA) and also by inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectrometry (ICP OES) after high-pressure microwave assisted wet digestion and microwave-induced combustion methods. No significant differences were observed between the results obtained by DSS-ET AAS, ICP-MS and ICP OES after both digestion methods and also by NAA. Calibration was performed using aqueous standards. Background signals were always lower than 0.02 (peak height) and no chemical modifier was used. The proposed method allowed the determination of all elements in CNTs with lower limits of detection in comparison with other techniques.

A rapid method for the determination of Pb, Cu and Sn in dried tomato sauces with solid sampling electrothermal atomic absorption spectrometry

In this work, lead, copper and tin were determined in tomato sauces by solid sampling graphite furnace atomic absorption spectrometry (SS-GFAAS) and the results were compared with those obtained after sample digestion. The tomato sauce samples were dried at 90°C for 12h and directly introduced into the graphite furnace by means of solid auto sampler. Alternatively the dried samples were digested with concentrated HNO3 (65%) and pipetted into the graphite furnace. After the optimization of the experimental parameters, the average lead, copper and tin concentrations found by the solid sampling and digestion methods in 10 different kinds of tomato sauce samples were not significantly different at 95% confidence level. For solid sampling technique, the limits of detection (LOD) for Cu, Sn and Pb were 10.4, 3.2 and 0.4ng/g, respectively. Whereas for digestion method, for Cu, Sn and Pb were 6.7, 2.7 and 0.3ng/g, respectively. The proposed solid sampling technique was fast, simple, the risks of contamination and analyte loss were low.

A study of the direct determination of Cd, Cr, Cu, Pb and Zn in certified reference materials of soils by solid sampling electrothermal atomic absorption spectrometry

A simple and rapid method for the direct determination of Cd, Cr, Cu, Pb and Zn in soil was developed. The method was developed using three certified reference materials of soil: Eutric Cambisol, Orthic Luvisols and Rendzina, which differed in their matrix composition. Chemical modifiers were essential to achieve reproducible and interference-free signals for the analytes studied. The best results were obtained with a Pd/Mg(NO 3) 2 admixture for the determination of Cd, Pb and Zn and NH 4F for Cu. The combination of W (as a permanent modifier) and Mg(NO 3) 2 provided well-defined signal profiles for Cr. The following spectral lines were used: Cd 228.8 nm, Cr 520.6 nm, Cu 218.2 nm, Pb 205.3 nm and Zn 307.6 nm. The limit of detection was 4.2 ng g − 1 for Cd, 1.1 μg g − 1 for Cr, 0.5 μg g − 1 for Cu, 1.3 μg g − 1 for Pb and 8.6 μg g − 1 for Zn for the maximum sample mass used. Under optimized conditions, the analyte and matrix were separated effectively in situ, and aqueous standards could be used for calibration.

Electrochemical Modification of a Graphite Platform for a Solid Sampling Electrothermal Atomic Absorption Spectrometry of Mercury

An electrodeposited palladium and iridium/gold mixture has been investigated as a chemical modifier for mercury determination in environmental samples by solid sampling electrothermal atomic absorption spectrometry. Electrochemical procedures of platform surface modification performed in a cell with 20 ml of solution, and in a drop of modifier solution have been optimized. Simple electrolysis in a drop was found to be the most consistent, taking the reproducibility as the major criterion. A total mass of 250 µg of electrodeposited palladium or an iridium/gold mixture was used. The lifetime of 60 - 70 firings for a deposited iridium/gold mixture was smaller than that for palladium with a lifetime of 100 - 120 firings. The detection limit was 120 pg Hg. Different sample masses of between 0.1 and 10 mg were weighed into modified platforms according to the mercury content. The results obtained for mercury in environmental samples as soils, sediments and plant, using solid sampling and calibration against aqueous standards stabilized by potassium permanganate, were in good agreement with those achieved by using the thermal deposition of modifiers and with measurements by pyrolysis atomic absorption spectrometry with gold amalgamation.

A practical solid sampling method for the determination of lead in chewing gum by electrothermal atomic absorption spectrometry

In this study, the lead concentrations of chewing gum samples having different compositions were determined by solid sampling electrothermal atomic absorption spectrometry. In order to optimise the experimental conditions, the effects of pyrolysis temperature, atomization temperature, sample amount and sample thermal pre-treatment, on the analyte sensitivity were investigated. The samples were ashed at 400 °C for 2 h prior to directly determined by SS-ETAAS applying 600 °C of pyrolysis and 1600 °C of atomization temperatures without to add a modifier, acid and/or surfactant. The relationship between sample mass and integrated absorbance was linear up to 1.2 mg of sample; for higher sample mass the relationship was no longer linear, irrespective of the lead content. In addition, the thermally treated chewing gum samples were digested using concentrated HNO 3. The lead concentrations found by the two methods in 27 different kinds of samples were not significantly different at 95% confidence level. The proposed solid sampling technique was fast, simple, the risks of contamination and analyte loss were low. Detection limit (3 σ) for lead was 0.017 ng/g.