Electrothermal Atomic Absorption Spectrometry Determination Research Articles

ETAAS determination of nickel in serum and urine.

Methods for the direct determination of Ni in human blood serum and urine by electrothermal atomic absorption spectrometry (ETAAS) are described. Hydrogen peroxide was proposed as matrix modifier, assisting thermal decomposition of proteins during the ashing step. A pyrolysis temperature of 1,200 degrees C was found to be optimal while 2,100 degrees C and 2,200 degrees C were found to be optimal atomizing temperatures for Ni in serum and urine respectively. Calibration was performed by using a calibration curve prepared with aqueous standard solutions of Ni (glycine must be used as modifier for Ni in aqueous solutions). The limits of detection, defined as the blank values plus 3 times the standard deviation of the blank values, were 0.2 microg/L for both serum and urine samples. Relative standard deviations for serum samples with concentrations of Ni in the range 0.5-2 microg/L were 10-15% and for urine samples with Ni concentrations in the range 0.5-2.5 microg/L were 8-10%.

Sequential injection on-line matrix removal and trace metal preconcentration using a PTFE beads packed column as demonstrated for the determination of cadmium by electrothermal atomic absorption spectrometry

A sequential injection (SI) on-line matrix removal and trace metal preconcentration procedure by using a novel microcolumn packed with PTFE beads is described, and demonstrated for trace cadmium analysis with detection by electrothermal atomic absorption spectrometry (ETAAS). The analyte is initially complexed with diethyldithiophosphate (DDPA) and adsorbed onto the column, which is afterwards eluted with 50 µl of ethanol and subsequently introduced via air segmentation into the graphite tube for quantification. The ETAAS determination is synchronized with sample pre-treatment in the SI system. No flow resistance is encountered at a flow rate of 9.0 ml min−1 through the column. The preconcentration efficiency was improved significantly by using the packed column as compared with a knotted reactor. With a 40 s sample loading time at 4.5 ml min−1 along with a sampling frequency of 16 h−1, quantitative adsorption of cadmium (99% retention efficiency) and an enrichment factor of 59.4 were obtained, as compared with only 46.7% and 28.0 by using a knotted reactor of similar internal surface area as the packed column. The detection limits and precision (RSD, 0.1 µg l−1 Cd) are at the same levels, i.e., 1.3 ng l−1 (LOD), 1.3% (RSD) for the packed column, and 1.2 ng l−1 (LOD), 1.5% (RSD) for the knotted reactor. The practical applicability of the procedure is demonstrated by the determination of trace levels of cadmium in three certified reference materials.

Development of an automated sequential injection on-line solvent extraction-back extraction procedure as demonstrated for the determination of cadmium with detection by electrothermal atomic absorption spectrometry

An automated sequential injection (SI) on-line solvent extraction-back extraction separation/preconcentration procedure is described. Demonstrated for the assay of cadmium by electrothermal atomic absorption spectrometry (ETAAS), the analyte is initially complexed with ammonium pyrrolidinedithiocarbamate (APDC) in citrate buffer and the chelate is extracted into isobutyl methyl ketone (IBMK), which is separated from the aqueous phase by means of a newly designed dual-conical gravitational phase separator. A metered amount of the organic eluate is aspirated and stored in the PTFE holding coil (HC) of the SI-system. Afterwards, it is dispensed and mixed with an aqueous back extractant of dilute nitric acid containing Hg(II) ions as stripping agent, thereby facilitating a rapid metal-exchange reaction with the APDC ligand and transfer of the Cd into the aqueous phase. The aqueous phase is separated in a second dual-conical gravitational phase separator, and 30 μl of it is entrapped and metered in a sample loop (SL) and subsequently introduced via air segmentation into the graphite tube for analyte quantification. The ETAAS determination is performed in parallel with the separation/preconcentration process of the ensuing sample. An enrichment factor of 21.4, a detection limit of 2.7 ng l −1, along with a sampling frequency of 13 h −1 were obtained at a sample flow rate of 6.0 ml min −1. The precision (R.S.D.) at the 0.4 μg l −1 level was 1.8% as compared to 3.2% when quantifying the organic extractant directly. The applicability of the procedure is demonstrated for the determination of trace levels of cadmium in three certified reference materials.

Determination of chromium(III) and chromium(VI) in mineral water by bidirectional electrostacking and electrothermal atomic absorption spectrometry

A feasibility investigation was carried out on the use of bidirectional electrostacking for simultaneous separation and pre-concentration of Cr(III) and Cr(VI) and their electrothermal atomic absorption spectrometry (ETAAS) determination. The bidirectional electrostacking manifold was improved, and the effects of sample tube cross-section and electrostacking time on the pre-concentration factor were investigated. Results indicate that the sample tube cross-section and electrostacking time are the main influence factors on the electrostacking pre-concentration, as well as the electric field strength and ionic mobility. The method developed was suitable for the simultaneous separation and pre-concentration of micro- or trace cations and anions in low conductivity sample solutions. The dynamic calibration range for both, Cr(III) and Cr(VI), was from 0.5 to 10μgl−1 using 20μl sample volume and ETAAS determination. Standard addition method was used for the pre-concentration of Cr(III) and Cr(VI) in electrostacking procedure. The amounts of 100ngl−1 Cr(III) and Cr(VI) were added into one of twin samples, which were pre-concentrated in parallel, for the pre-concentration factor calculation. The limit of detection for Cr(III) and Cr(VI) was 6 and 5ngl−1, respectively, for three times standard deviation (S.D.) of blank values (n=7) and 10min electrostacking, providing pre-concentration factors of the order of 10 times. The method was applied to analyze a certified reference material of simulated fresh water, and results were coincident with its certified value.

Determination of trace metals in fish species of the Ria de Aveiro (Portugal) by electrothermal atomic absorption spectrometry

Cadmium, copper, nickel, lead and zinc were determined in fish samples from seven sampling stations of the Ria de Aveiro (Portugal). The species analyzed were Anguilla anguilla , Mullus surmuletus , Trigla lucerna, Mugil cephalus , Chelon labrosus , Liza aurata and Dicentrarchus labrax , all of which are used for human consumption. For this purpose, procedures for the electrothermal atomic absorption spectrometry determination of cadmium, copper, nickel and lead in these samples were developed, as well as a microwave digestion method for obtaining a fast dissolution of the samples. The concentrations of metals found in the muscle of the fish species were very low. The minor contents corresponded to cadium, lead and nickel with values smaller than 0.043, 0.15 and 0.14 μg/g (wet weight), respectively, except in the case of nickel in the Anguilla anguilla species where more elevated concentrations were found (between 0.16 and 0.40 μg/g). The contents of copper in the samples ranged from 0.5 to 1.1 μg/g (wet wt.). Zn is the most abundant element in all fishes, with concentrations around 20 μg/g (wet wt.) in the Anguilla anguilla samples and with values oscillating between 4.7 and 12 μg/g in the rest of the species studied. In all cases, the results obtained for all the elements were considerably lower than those recommended by specific legislation for these aquatic organisms. The accuracy of the analytical methodology employed was also evaluated through the analysis of two reference materials (NIST-1577b and IAEA-V10): good agreement was obtained between the experimental results and the certified values.

Flow-injection preconcentration and electrothermal atomic absorption spectrometry determination of manganese in seawater

A procedure for the determination of manganese in seawater by flow-injection preconcentration coupled to electrothermal atomic absorption spectrometry was developed. The analyte is complexed by 1-(1-hydroxy-2-naphthylazo)-6-nitro-2-naphthol-4-sulphonic acid (Eriochrome Black T), its complexes are retained onto an anion exchange resin, and eluted with hydrochloric acid. A software driven preconcentration apparatus was set up and a new housing for the enrichment column was designed and adopted. After studying the effect of acidity and ligand concentration, the accuracy of the procedure was assessed by analysis of certified seawater.

Coupling sequential injection on-line preconcentration by means of a renewable microcolumn with ion-exchange beads with detection by electrothermal atomic absorption spectrometry: Comparing the performance of eluting the loaded beads with transporting them directly into the graphite tube, as demonstrated for the determination of nickel in environmental and biological samples

The design of a flow injection/sequential injection (FIA/SIA) on-line preconcentration system incorporating a renewable microcolumn with ion-exchange beads and interfaced with an electrothermal atomic absorption spectrometry (ETAAS) detector is described, and its practical applicability is demonstrated for the determination of trace level concentrations of nickel. The column is loaded with a defined volume of SP Sephadex C-25 cation-exchange resin beads and subsequently exposed to a metered volume of sample solution. The analyte loaded beads are afterwards eluted with 30 μl of diluted nitric acid, and the eluate transported via air segmentation into the graphite tube. The used beads are then discarded. The ETAAS determination is performed in parallel with the preconcentration process of the ensuing sample. An improved precision of R.S.D. 1.5% is obtained as compared to the 3.4% for the procedure in which the loaded beads are transported directly to the graphite furnace for pyrolysis and atomization, and even improved in comparison to the traditional unidirectional and bidirectional repetitive elution procedures which under comparable conditions yield R.S.D.-values of 5.8 and 4.9%, respectively. The tolerance limits for cations such as Pb(II), Zn(II), Co(II) and Mn(II) were improved up to 10–50-folds, and the linear calibration range extended to comprise 0.02–1.20 μg l −1. Because of lower operating temperature, the life time of the graphite tube is extended. An enrichment factor of 71.1 and a detection limit of 10.2 ng l −1 along with a sampling frequency of 12 h −1 were obtained, which are at the same levels as those for the previously described procedure without elution. The present approach was validated by determination of the nickel contents in two certified reference materials, an industrial waste water sample and a human urine sample.

Fractionation of elements by particle size and chemical bonding from aerosols followed by ETAAS determination

A simple sequential leaching procedure was applied to the determination of the distribution of elements in atmospheric aerosols collected on membrane filters in different particle size ranges. The three-stage sequential leaching procedure divides the elements into environmentally mobile, bound to carbonates and oxides, and bound to silicates and organic matter (environmentally immobile) fractions. Three particle size fractions were collected: fine, d 10 µm on membrane filters. The sampling site was set up in K-puszta, a Hungarian meteorological background station. The campaign involved the collection of samples every two days weekly for 13 consecutive months. Concentrations of ten elements were determined by electrothermal atomic absorption spectrometry (ETAAS). Dry deposition rates and enrichment factors (EF) were calculated for fine and coarse fractions, as well as the mobile portion of the chemical bonding of the elements. This approach opens a new dimension to understanding the dry deposition of aerosols containing toxic heavy metals. Results were compared with earlier findings from a sampling campaign at K-puszta and other studies at different sampling sites and conditions. Generally, it can be concluded that the pollution load characterizes well the background station and that aerosols are transported from long-range and originate from both anthropogenic and natural sources.

Coupling on-line preconcentration by ion-exchange with ETAAS: A novel flow injection approach based on the use of a renewable microcolumn as demonstrated for the determination of nickel in environmental and biological samples

A novel way of exploiting flow injection/sequential injection (FIA/SIA) on-line ion-exchange preconcentration with detection by electrothermal atomic absorption spectrometry (ETAAS) is described and demonstrated for the determination of trace-levels of nickel. Based on the use of a renewable microcolumn incorporated within an integrated micro FI-system, the column is loaded with a defined volume of small beads of an SP Sephadex C-25 cation-exchange resin and subsequently exposed to a metered amount of sample solution. However, instead of eluting the retained analyte from the organic ion-exchange resin, the beads are along with 30 μl of carrier (buffer) solution transported via air segmentation directly into the graphite tube, where they are ashed during the pyrolysis and atomization process. The ETAAS determination is performed in parallel with the preconcentration process of the ensuing sample. An enrichment factor of 72.1, a detection limit of 9 ng l −1, along with a sampling frequency of 12 h −1 were obtained with 150 s of sample loading time at a sample flow rate of 12 μl s −1 (corresponding to 0.72 ml min −1). The relative standard deviations were 3.4%. The procedure was validated by determination of the nickel contents in two certified reference materials and in a human urine sample.

Interfacing flow injection analysis (sequential injection analysis) and electro-thermal atomic absorption spectrometry determination of trace-levels of Cr(VI) via on-line pre-concentration by adsorption in a knotted reactor and by liquid–liquid extraction

Two time-based flow injection pre-concentration procedures are described for the analysis of ultra-trace-level concentrations of metal ions, as exemplified for the determination of Cr(VI). While the first approach exploits pre-concentration by on-line formation and extraction into MIBK of the non-polar complex formed of Cr(VI) ions with ammonium pyrrolidine dithiocarbamate (APDC), the second one is based on formation of the same complex compound and adsorption of it in an incorporated knotted reactor which is subsequently eluted by a discrete volume of ethanol. In both cases, the detection of the analyte in the eluent is executed by electrothermal atomic absorption spectrometry (ETAAS). Using a newly developed syringe pump based FI-system, FIAlab-3500, the present communication discusses and emphasizes the performance of these on-line pre-concentration/separation procedures. Particularly, the interface between the FI-system and the detector ensuring reliable, effective and robust operation of the automated combination is detailed, because this calls for an intelligent coupling of the continuously operating FI-system with the discontinuously working ETAAS instrument. In this context, a unique application of the liquid–liquid separator used is described. The operational characteristics obtained were as follows. For the FI-system with liquid–liquid extraction the enhancement in sensitivity of Cr(VI) for 99 s sample aspiration at a flow rate of 5.5 ml min −1 was 18-fold as compared to direct introduction of 40 μl samples, yielding a detection limit (3 σ) of 3.2 ng l −1. The sample frequency was 10.9 h −1. By employing the adsorption procedure the enhancement in sensitivity of Cr(VI) was 19-fold as achieved after pre-concentration for 60 s at a sample flow rate of 5.0 ml min −1 as compared to direct introduction of 40 μl samples, yielding a detection limit (3 σ) of 6.7 ng l −1. The sample frequency was 13.8 h −1. The procedures were applied for the assay of Cr(VI) in a NIST reference material with good recoveries in both instances.

Use of nitric acid in sample pretreatment for determination of trace elements in various biological samples by ETAAS

Trace elements in liquid biological samples may be determined by direct electrothermal atomic absorption spectrometry (ETAAS). In our previous work it was found that samples containing proteins or DNA may leak out of the graphite tube before the drying step, despite the addition of various modifiers. In order to keep the sample to the graphite tube, samples were diluted before analysis 1+1 with 32% v/v nitric acid, or 5 μl of 32% v/v nitric acid was added to the graphite tube before ETAAS determination. Applying the proposed procedure, the concentrations of lead in eluted fractions after gel chromatographic separation of human cerebellar nucleus dentatus supernatant and platinum in isolated DNA samples were determined. The use of nitric acid in sample pretreatment prevent sample leakage out of the graphite tube, provided for even drying and considerably reduced nonspecific absorption in lead determination. The repeatability of measurements was better than ±6%. The accuracy of the procedure was checked by spiking samples. The recoveries for both elements lay between 93–104%. Nitric acid was found to be a better modifier than TRITON X-100.

Flow Injection On-Line Two-Stage Solvent Extraction Preconcentration Coupled with Et-Aas for Determination of Bismuth in Biological and Environmental Samples

ABSTRACT A robust flow injection/sequential injection(FIA/SIA) on-line two-stage solvent extraction separation/preconcentration procedure coupled to electrothermal atomic absorption spectrometry (ETAAS) is described and demonstrated for the determination of trace-levels of bismuth. In 1-4% (v/v) nitric acid medium, diethyldithiophosphate (DDPA) chelates bismuth and the chelating complex formed is extracted into isobutyl methyl ketone (IBMK), which is separated from the aqueous phase by means of cavity gravitational phase separation. Both single and two-stage separations are used. In each case, 40 μl of the concentrate is entrapped and metered in a loop, and subsequently delivered via air-segmentation into a pyrolytically coated graphite tube. The ETAAS determination is performed in parallel with the preconcentration process of the ensuing sample. Enrichment factors of 17.8 and 31.5, detection limits of 12 ng 1−1 and 10.5 ng 1−1 for single and two-stage extractions, respectively, along with a sampling frequency of 13 h−1 were obtained with 100 s of sample loading time at a sample flow rate of 5.4 ml min−1. The relative standard deviations were 2.8% and 1.9% for single and two-stage extractions, respectively. The procedure was validated by determining the bismuth content in a certified reference material and i8543220 human urine samples.

Direct solid sampling ETAAS determination of cadmium in equine muscle

Direct solid sampling by means of electrothermal atomic absorption spectrometry ( ETAAS) was evaluated as a rapid proccdure for the determination of Cd in equine muscle tissue with respect to the introduction of a legal limit for Cd in cquine muscle tissue in Germany. Analysis of the distribution of Cd within individual muscles of horses showed the variance component 'heterogeneity' (relative standard deviation, RSD: 16%) to be clearly dominated by residual analytical variance ( RSD 24%). Error of mean value estimation can be reduced by increasing the number of samples-each taken from different sampling sites-from approximately 30% (n=1) to 11%(n=6). In a comparison between solid sampling ETAAS and a conventional compound procedure as reference (regression analysis, n = 394), the Cd content ranged from 0.01 to 0.9 μg g -1 fresh substance. Results were found to be closely correlated (r = 0.98) and proved to be analytically and statistically (P > 0.10) of no relevant difference. Ranges of erroneous classification were calculated, which allow the identification of transgressing samples. For the legal limit of 0.2 μg g -1 fresh substance, erroneous classification (false positive and false negative) ranged from 0.14 to 0.27 μg g -1 frcsh substance. Limits for the 1% range of crroneous classification were calculated to range from 0.13 to 0.32 μg g -1 fresh substance. Based on these results, a model strategy is proposed for the application of direct solid sampling analysis as a rapid in-process screening procedure within the scope of meat hygiene regulations.

Direct electrothermal atomic absorption spectrometry determination of nickel in sea water using multiple hot injection and Zeeman correction

Methods for the direct determination of Ni in sea water samples by ETAAS were developed using Zeeman effect background correction system (ZEBC) and a multi-injection technique. A mass of palladium nitrate of 2.5 μg (for an injection volume of 100 μl) was used as chemical modifier. The optimum pyrolysis and atomization temperatures were 1700 and 2100°C, respectively. The characteristic mass ( m 0) and characteristic concentration ( C 0), precision and accuracy were studied for different injection volumes (20, 100 and 200 μl). For an injection volume of 100 μl (five 20 μl aliquot) of sample the accuracy analysis of different certified materials (saline and non saline water) was agreeable. The total time of the proposed procedure is 6 min. A m 0 and C 0 of 34.5 pg and 0.3 μg l −1, respectively were obtained for this injection volume (100 μl). Finally, interferences from major and minor components of sea water was studied.

MG-W Cell—Electrothermal Atomic Absorption Spectrometry—Determination of Gold in Environmental Samples

An electrodeposition method of trace elements using a Mg-W cell is reported. This method does not need a power supply (electric source) like a potentiostat or a battery. Some elements electrodeposited on a W sheet were detected by electrothermal atomic absorption spectrometry (ETAAS) with a tungsten atomizer. The detection limits of Au, Sb, Te and Tl by Mg-W cell-ETAAS were 55, 48, 47 and 880 pg/mL, respectively. The severe interferences of Al, Ca, Cu, Fe, K, Na, Pb and Zn on Au-AAsignal, which were observed in AAS, were eliminated by use of the Mg-W cell. The Mg-W cell electrodeposition method was applied to the determination of Au in sea and surface water samples. The recovery of gold in spiked environmental samples was in the range of 91 to 104%.

The atomization of cadmium in graphite furnaces

The effect of the atomization temperature on the analysis of cadmium in graphite furnaces has been studied. A comparison of the electrothermal atomic absorption spectrometry (ETAAS) determination of total Cd in animal tissues was carried out with Zeeman effect and deuterium background corrections. A detailed study of the atomic absorption profile and background correction of cadmium, as well as the variation of absorbance values at different atomization temperatures, in both peak-height and integrated modes, has been made. The accuracy of the ETAAS determination of Cd in tissue samples, using various atomization temperatures, has also been evaluated, having found that an atomization temperature equal or higher than 1600 °C is necessary in order to obtain accurate and reproducible results. The use of low atomization temperatures, suggested in some published works, makes it possible to obtain accurate results, but the slow production of gaseous atoms of cadmium can affect the precision of the absorbance measurements and strongly affects the peak area values. On the other hand, the use of atomization temperatures higher than 2000 °C produces bad recoveries of cadmium in the analysis of certified tissue samples.

Electrothermal AAS determination of bismuth, antimony and tin in high-purity WO3

Four methods for the bulk trace determination of Bi, Sb and Sn in WO3 were developed and tested. In all cases, the final determination is carried out by graphite furnace atomic absorption spectrophotometry. The limits of detection range from 1 μg/g for a very fast and simple method to 50 ng/g for a method comprising a trace-matrix separation by sorption and complexation on activated carbon powder loaded with TMDTC. A way of preparation of standard reference WO3-samples doped with varying amounts of Bi, Sb and Sn traces is also described.