Multi-element Atomic Absorption Spectrometry Research Articles

Evaluation of internal standardization for the determination of semivolatile analytes in difficult matrices by simultaneous multielement atomic absorption spectrometry

The aim of the present work is to investigate the use of the internal standardization technique combined with permanent chemical modification for the determination of two semivolatile analytes, such as As and Se, in difficult matrices by electrothermal atomic absorption spectrometry. Bismuth and tellurium have been evaluated as internal standards to minimize matrix effects on the direct determination of selenium and arsenic in sediments, by simultaneous electrothermal atomic absorption spectrometry using graphite tubes with integrated platform, pre-treated with different masses of Zr and Ir as permanent modifier. A Perkin-Elmer SIMAA 6000 simultaneous multielement spectrometer was used to study the correlation between two integrated absorbance signals. Matrix effects were evaluated by calculating the slope ratio between the analytical curve obtained from reference solutions prepared in 1.0% (v/v) HNO3 and analytical curve obtained from IS additions in matrix solutions. The results showed that Te was the optimal internal standard and 200μg Zr and 20μg Ir was the optimal permanent chemical modifier for both analytes. The instrumental limits of detection for As and Se were 1.48 and 1.96μgL−1 without the use of an internal standard and 0.59 and 0.35μgL−1 when Te was used as an internal standard, respectively. Relative standard deviations for a sample with matrix effect containing 100μgL−1 As and 200μgL−1 Se were 1.3% and 2.3% (n=20) using 100μgL−1 Te, respectively, and for a standard solution sample containing 100μgL−1 As and 200μgL−1 Se were 3.0% and 1.2% (n=20) using 100μgL−1 Te, respectively. The accuracy of the proposed method was evaluated by an addition-recovery experiment and by the analysis of different certified reference materials. The recovered values were in the 95–100% range for both analytes.

Alternative approaches to correct interferences in the determination of boron in shrimps by electrothermal atomic absorption spectrometry

The aim of this study is to propose alternative techniques and methods in combination with the classical chemical modification to correct the major matrix interferences in the determination of boron in shrimps. The performance of an internal standard (Ge) for the determination of boron by the simultaneous multi-element atomic absorption spectrometry was tested. The use of internal standardization increased the recovery from 85.9% to 101% and allowed a simple correction of errors during sampling preparation and heating process. Furthermore, a new preparation procedure based on the use of citric acid during digestion and dilution steps improved the sensitivity of the method and decreased the limit of detection. Finally, a comparative study between the simultaneous multi-element atomic absorption spectrometry with a longitudinal Zeeman-effect background correction system, equipped with a transversely-heated graphite atomizer and the single element atomic absorption spectrometry with a D2 background correction system, equipped with an end-heated graphite atomizer was undertaken to investigate the different behavior of boron in both techniques. Different chemical modifiers for the determination of boron were tested with both techniques. Ni-citric acid and Ca were the optimal chemical modifiers when simultaneous multi-element atomic absorption spectrometry and single-element atomic absorption spectrometry were used, respectively. By using the single-element atomic absorption spectrometry, the calculated characteristic mass was 220pg and the calculated limit of detection was 370μg/kg. On the contrary, with simultaneous multi-element atomic absorption spectrometry, the characteristic mass was 2200pg and the limit of detection was 5.5mg/kg.

Concentration Levels of Trace Elements in Carrots, Onions, and Potatoes Cultivated in Asopos Region, Central Greece

The objective of the work was to investigate the correlation between the environmental pollution of Asopos river area in Viotia, Greece and the concentration of Ni, Cr, Cd, Pb, Cu, and As in specific crops (carrots, onions, and potatoes) produced in this region. Samples of these crops from Asopos and other Greek areas (control) were collected. For method accuracy, the Certified Reference Material, CRM 281 (trace elements in rye grass) was measured. Simultaneous multi-element graphite furnace atomic absorption spectrometry was used after a microwave acid digestion. The levels of Ni in Asopos food were found up to 9 times higher than control (e.g., Asopos potatoes had an average Ni content of 800 µg/kg compared to 78 µg/kg in control, whereas Asopos carrots had an average Ni content of 474 µg/kg compared to 93 µg/kg in control). Likewise, the levels of Cr were found to be about 2 times higher than control (e.g., Asopos carrots were found to have an average Cr content of 43 µg/kg compared to 20 µg/kg in control). The levels of Cd and Pb had a high variance in the Asopos sourced food. Arsenic was not detected in any sample. Our results indicate that the mean intake of trace elements (Ni, Cr, Pb, Cd, and Cu) by adults through consumption of crops from Asopos, for an average consumption pattern, generally is well below the Allowable Daily Intakes (ADIs). Comparison was also made with data from literature from Greece.

Cloud point extraction for the determination of cadmium and lead employing sequential multi-element flame atomic absorption spectrometry

A cloud point extraction procedure for pre-concentration and determination of cadmium and lead in drinking water using sequential multi-element flame atomic absorption spectrometry is described. 4-(2-thiazolylazo)-orcinol (TAO) has been used as complexing agent and the micellar phase was obtained using the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) and centrifugation. The conditions for reaction and extraction (surfactant concentration, reagent concentration, effect of incubation time, etc) were studied and the analytical characteristics of the method were determined. The method allows the determination of cadmium and lead with quantification limits of 0.30 µg L−1 and 2.6 µg L−1, respectively. A precision expressed as relative standard deviation (RSD, n = 10) of 2.3% and 2.6% has been obtained for cadmium concentrations of 10 µg L−1 and 30 µg L−1, respectively, and RSD of 1.3% and 1.7% for lead concentrations of 10 µg L−1 and 30 µg L−1, respectively. The accuracy was confirmed by analysis of a natural water certified reference material. The method has been applied for the determination of cadmium and lead in drinking water samples collected in the cities of Ilhéus and Itabuna, Brazil. Recovery tests have also been performed for some samples, and results varied from 96 to 105% for cadmium and 97 to 106% for lead. The cadmium and lead concentrations found in these samples were always lower than the permissible maximum levels stipulated by World Health Organization and the Brazilian Government.

On-line simultaneous pre-concentration procedure for the determination of cadmium and lead in drinking water employing sequential multi-element flame atomic absorption spectrometry

An on-line pre-concentration system for the sequential determination of cadmium and lead in drinking water by using fast sequential flame atomic absorption spectrometry (FS-FAAS) is proposed in this paper. Two minicolums of polyurethane foam loaded with 2-(6-methyl-2-benzothiazolylazo)-orcinol (Me-BTAO) were used as sorptive pre-concentration media for cadmium and lead. The analytical procedure involves the quantitative uptake of both analyte species by on-column chelation with Me-BTAO during sample loading followed by sequential elution of the analytes with 1.0 mol L−1 hydrochloric acid and determination by FS-FAAS. The optimisation of the entire analytical procedure was performed using a Box–Behnken multivariate design utilising the sampling flow rate, sample pH and buffer concentration as experimental variables. The proposed flow-based method featured detection limits (3σ) of 0.08 and 0.51 µg L−1 for cadmium and lead, respectively, precision expressed as relative standard deviation (RSD) of 1.63% and 3.87% (n = 7) for cadmium at the 2.0 µg L−1 and 10.0 µg L−1 levels, respectively, and RSD of 6.34% and 3.26% (n = 7) for lead at the 5.0 µg L−1 and 30.0 µg L−1 levels, respectively. The enrichment factors achieved were 38.6 and 30.0 for cadmium and lead, respectively, using a sample volume of 10.0 mL. The sampling frequency was 45 samples per hour. The accuracy was confirmed by analysis of a certified reference material, namely, SRM 1643d (Trace elements in natural water). The optimised method was applied to the determination of cadmium and lead in drinking water samples collected in Santo Amaro da Purificação City, Bahia, Brazil.

In vitro evaluation of Cu and Fe bioavailability in cashew nuts by off-line coupled SEC–UV and SIMAAS

In this work Cu and Fe bioavailability in cashew nuts was evaluated using in vitro method. Extractions with simulated gastric and intestinal fluids and dialysis procedures were applied for this purpose. The proteins separation and quantification were performed by size exclusion chromatography (SEC) coupled on-line to ultra-violet (UV) and off-line to simultaneous multielement atomic absorption spectrometry (SIMAAS). The SEC–UV and SIMAAS profiles of the protein fractions obtained by alkaline extraction (NaOH) and precipitation with HCl indicated the presence of high and low molecular weight species in the range between >75 kDa and 9.3 kDa. Almost 83% of Cu and 78% of Fe were extracted during cashew nut digestion and 90% of both elements were dialyzed. With these results it is possible to assume that 75% of Cu and 70% of Fe present in cashew nut could be bioavailable. The SEC–UV and SIMAAS chromatographic profiles obtained after in vitro gastrointestinal digestion reveal that Cu and Fe not dialyzed can be associated to a compound of 9.2 kDa.

Mn and Cu concentrations in mixed saliva of elementary school children in relation to sex, age, and dental caries

To examine the standard Mn and Cu concentrations in mixed saliva from children and the relationship between these levels and dental caries, resting mixed saliva samples obtained from 527 children of an elementary school in Kitakyushu City were collected at 10:00–11:30 a.m. during December 2004. The Mn and Cu concentrations were determined using simultaneous multi-element atomic absorption spectrometry. The standard Mn and Cu levels were 22.0±15.2 and 3.8±4.1 ng/mL, respectively, in the sound teeth group. Mn levels were significantly higher in boys (25.4±17.4 ng/mL) than girls (19.1±12.3 ng/mL) and also higher in upper (25.5±16.4 ng/mL) than lower (19.0±13.5 ng/mL) grades. The Cu level was unaffected by sex and age in the sound teeth group. The Cu level in children with caries experience (5.7±5.3 ng/mL) was significantly higher than that of the sound teeth group. Moreover, the Cu levels in children with untreated caries were significantly higher than that of the sound teeth group, and increased with the number of untreated teeth. No significant difference was found in the Cu concentrations between the group in which all decayed teeth were treated and the sound teeth group. The Mn levels were similar with or without caries and treatment. These findings indicate that the Mn level in mixed saliva depended on sex and age, and suggest the possibility of Cu dissolving into mixed saliva by demineralization due to dental caries.

Evaluation and application of bismuth as an internal standard for the determination of lead in wines by simultaneous electrothermal atomic absorption spectrometry.

A method for the direct determination of Pb in wines by simultaneous multi-element atomic absorption spectrometry (SIMAAS) using a transversely heated graphite atomizer, Zeeman-effect background corrector and internal standardization is proposed. Bismuth was used as an internal standard and Pd(NO3)2 plus Mg(NO3)2 as chemical modifier to stabilize both the analyte and the internal standard. The implementation of two pyrolysis steps avoided any build-up of carbonaceous residues on the graphite platform. All diluted samples (1 + 1 v/v) in 0.2% v/v HNO3 and reference solutions (5.0-50 microg l(-1) Pb in 0.2% v/v HNO3) were spiked with 25 microg l(-1) Bi. For a 20 microl aliquot dispensed into the graphite tube, a good correlation (r = 0.9997) was obtained between the ratio of the analyte signal to the internal standard signal and the analyte concentration of the reference solutions. The electrothermal behaviour of Pb and Bi in red, white and rosé wines were compared. In addition, absorbance variations due to changes in experimental conditions, such as atomizer temperature, integration time, injected sample volume, radiation beam intensity, graphite tube surface, dilution and sample composition, were minimized by using Bi as internal standard. Relative standard deviations of measurements based on integrated absorbance varied from 0.1 to 3.4% and from 0.5 to 7.3% (n = 12) with and without internal standard correction, respectively. Good recoveries (91-104%) for Pb spikes were obtained. The characteristic mass was 45 pg Pb and the limit of detection based on integrated absorbance was 0.9 microg l(-1) Pb. Internal standardization increased the lifetime of the tube by 25%. Direct determinations of Pb in wines with and without internal standardization approaches were in agreement at the 95% confidence level. The repeatability and the tube lifetime were improved when using Bi as internal standard. The improvement in accuracy using an internal standard was only observed when the analytical results were affected by errors.

An improved impaction-graphite furnace system for the direct and near real-time determination of cadmium, chromium, lead and manganese in aerosols and cigarette smoke by simultaneous multielement atomic absorption spectrometry

The design, operating characteristics, and preliminary evaluation of an improved impaction-graphite furnace system, based on a theoretical study of particle size collected, are presented. After direct collection, the graphite furnace from the system is inserted in an atomic absorption spectrometer for analysis by simultaneous multielement atomic absorption spectrometry. This system has the potential for the direct and near real-time (few minutes) determination of metals in aerosols. The system has been preliminarily evaluated using aqueous solutions of chromium, and has then been applied to the determination of cadmium, chromium, lead, and manganese in cigarette smoke. Results show an increase ranging from almost five (lead) to sixteen (cadmium) over background levels.

Frequency-modulated simultaneous multielement atomic absorption spectrometry using electrothermal atomizer and deuterium background correction

Characteristic data of the frequency-modulated simultaneous multielement atomic absorption spectrometry (FREMSAAS) using electrothermal atomizer with deuterium background correction, have been determined. The data obtained have been processed by using several statistical tests recommended for quality control purposes. The instrumentation has been presented as well as procedures of separating elements into measure groups and fixing of variable conditions. Detection limits, characteristic masses and working ranges have been given for the eleven elements examined. The data have been in good agreement to results obtained with conventional one-channel AAS instruments. The eleven elements have been simultaneously determined in a standard reference material (SRM) and all results are compatible with a 95% certainty with the certified values. FREMSAAS has been applied to a real sample.

Multielement Atomic Absorption Spectrometry: A Historical Perspective

The development, performance, and application of multielement atomic absorption spectrometry from multielement hollow cathode lamps, continuum sources, and multichannel systems to current commercial systems are presented.

Background correction in frequency modulated simultaneous atomic absorption spectrometry

For a long time simultaneous multielement determination by AAS has been a subject of intensive research. In this work a simultaneous multielement atomic absorption spectrometry method is described in a special new arrangement, called frequency modulated simultaneous AAS (FremsAAS), using fiberoptics, interference filters and frequency modulation and demodulation by lock-in amplifiers as main devices. Purpose of this work was to equip the FremsAAS with a D2-background correction and to test it with certified reference materials. Mn, Cd, Pb, Cu, Ni, Cr and Zn had been determined simultaneously (three at a time) in sewage sludge (BCR/CRM 146), estuarine sediment (BCR/CRM 277) and phosphate rock (BCR/CRM 32) with good feasibility. Frequency modulated simultaneous AAS with background correction (FremsAASUK) represents an interesting alternative to known instruments.

A combination of a pulsed continuum light source, a high resolution spectrometer, and a charge coupled device detector for multielement atomic absorption spectrometry

This paper presents first results of atomic absorption measurements carried out for the development of a new multielement atomic absorption spectrometer. The results were obtained in the wavelength range 283–228 nm, using a flash lamp continuum of high intensity, a newly developed, advanced high-resolution echelle spectrometer and a charge coupled device (CCD) array as radiation detector arranged in the focal plane of the spectrometer. In this measuring method, each flash exposure yields the complete information for an absorption measurement including the background absorption. Because of the simultaneous measurement of the two intensity values I 0 and I these two quantities are processed with a correlation coefficient of r = 1. Using a graphite tube furnace as an absorber, characteristic masses of 0.6 and 18 pg are achieved for the elements Cd and Pb, respectively, which exceed those of line atomic absorption with the same absorption equipment by a factor of only 2 and 1.5, respectively. Absorption measurements were carried out on saturated Hg vapour in quartz cuvettes at room temperature. Owing to the high intensity of the continuum radiation at all wavelengths, appreciable stray light components occur in the echelle spectrometer, requiring a stray light correction of the measured intensity values.

Simultaneous multi-element analysis by continuum source atomic absorption spectrometry with a spatially and temporally isothermal graphite furnace

The performances of three furnace systems were compared with respect to conditions for multi-element atomic absorption spectrometry (AAS), interference effects and carry-over contamination, when operated with a simultaneous multi-element atomic absorption continuum source spectrometer (SIMAAC). The three systems were a Perkin-Elmer HGA-500, an integrated contact cuvette furnace (spatially isothermal) and a two-step atomiser (spatially and temporally isothermal). High atomisation temperatures must be used in multi-element AAS if non-volatile elements are to be included. Therefore the facility of the two-step atomiser for selecting optimum temperatures regardless of the volatility of an element cannot be fully exploited. However, by using a consecutive two-stage constant-temperature atomisation procedure, optimum sensitivity could be achieved for volatile as well as refractory elements. The two furnace systems providing spatial isothermality were in general less susceptible to interference effects and, in addition, offered a significant reduction in carry-over contamination. This is of special importance in the SIMAAC system in order to utilise its facility of a dynamic calibration range of 5–6 orders of magnitude for each element.

Human albumin as a reference material for trace elements

An investigation through interlaboratory comparison using different analytical techniques has been carried out in order to assess the suitability of a plasma protein solution as a source for a trace element reference material in clinical analysis. Reasonable agreement was obtained for a number of elements from the range studied: Al, Ba, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Se, Sr, V and Zn. The techniques used included flame and furnace atomic absorption spectrometry (FAAS and ETA-AAS), furnace atomic emission spectrometry (ETA-AES), inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), and simultaneous multi-element atomic absorption spectrometry (SIMAAC). Results indicated that this plasma protein solution may prove useful as a source for a reference material covering trace element levels outwith the range found in normal human plasma.

Optimisation of flame parameters for simultaneous multi-element atomic absorption spectrometric determination of trace elements in rocks

A study is described that identifies the optimum operating conditions for the accurate determination of Co, Cu, Mn, Ni, Pb, Zn, Ag, Bi and Cd using simultaneous multi-element atomic absorption spectrometry. Accuracy was measured in terms of the percentage recoveries of the analytes based on certified values in nine standard reference materials. In addition to identifying optimum operating conditions for accurate analysis, conditions resulting in serious matrix interferences and the magnitude of the interferences were determined. The listed elements can be measured with acceptable accuracy in a lean to stoicheiometric flame at measurement heights ⩽5–10 mm above the burner.

高周波誘導結合プラズマを原子化源とし，水銀キセノンランプを光源とする原子吸光分光分析法

Simultaneous multielement atomic absorption spectrometry using a mercury-xenon lamp and inductively coupled plasma (ICP) was studied. The ICP was used for the atomization and ionization of analytes, and the mercuryxenon lamp was used as a light source which provided a strong continuum emission spectrum over a wide wavelength range.Effects of the carrier gas flow rate, rf power and the height of optical axis on the absorbed spectral intensity were investigated. Detection limits of Ni, Fe, V, Sn, Si and Pb were lower than those obtained by ICP-atomic emission spectrometry. Linear dynamic ranges of typically three orders of magnitude were observed.

Determination of metals at the microgram-per-liter level in blood serum by simultaneous multielement atomic absorption spectrometry with graphite furnace atomization.

A method is described for the simultaneous determination of seven metals - Al, Co, Cr, Mn, Mo, Ni, and V - in blood serum using a simultaneous, multielement atomic absorption spectrometer (SIMAAC) and graphite furnace atomization. Our original intention was to determine two additional metals - Pb and Sn - however, the high ashing temperature needed resulted in premature loss of these volatile metals. Serum samples (2 mL) are dry-ashed with 20 ..mu..L of Mg(NO/sub 3/)/sub 2/.6H/sub 2/O (20 g/L) as an ashing aid/matrix modifier. The organic-free residue is reconsituted with 0.5 mL of nitric acid (50 mL/L), allowing for a fourfold concentration step. The addition of Mg(NO/sub 3/)/sub 2/ permits a graphite furnace ashing temperature of 1300/sup 0/C. Atomization from a L'vov platform with a fast heating rate and the use of peak area measurements permit calibration with acidifed aqueous standards. A well-characterized bovine serum pool is used to establish the accuracy and precision of the method. Serum samples from 30 fasting adult volunteers, drawn under controlled conditions, are analyzed to assess the efficacy of this method to determine these seven metals over the ranges normally encountered in human sera. 16 references, 1 figure, 8 tables.

Simultaneous multielement analysis of microliter quantities of serum for copper, iron, and zinc by graphite furnace atomic absorption spectrometry

A method is described for the simultaneous determination of Cu, Fe, and Zn in 25 ..mu..L of serum, using simultaneous, multielement atomic absorption spectrometry (SIMAAC) and graphite furnace atomization. Peak height measurements are more adversely affected than peak area measurements by both the organic and inorganic constituents in serum. Peak area measurements are significantly more precise and accurate than peak height measurements. Determinations are carried out at a 1:21 dilution of serum, in the concentration range with the optimum precision and minimum carryover contamination and memory effects for these elements, using SIMAAC. The serum specimens are diluted with Triton X-100 (10 mL/L), 10 mM nitric acid, and 30 mM ammonium nitrate. The use of peak area measurements and atomization from a L'vov platform permits calibration with acidified aqueous standards. A commercially available, protein-based reference material, Cation-Cal (American Dade) and a bovine serum pool are used as controls. The method is shown to have good correlation to comparative methods (single-element flame AAS after deproteinization) for the analysis of 37 serum samples.

Analysis of blood serum for essential metals by simultaneous multielement atomic absorption spectrometry with flame atomization.

Blood serum is analyzed for Na, K, Ca, Mg, Fe, Cu, and Zn by using a simultaneous, multielement, atomic absorption spectrometer with a continuum source (SIMAAC). Because of the extended range capabilities of the SIMAAC system, analyses can be carried out on a single 5-fold dilution. Standards and samples are matched in appropriate concentrations for the major, minor, and trace elements. The SI-MAAC results show excellent agreement with the certified values for the National Bureau of Standards serum reference material and the manufacturer's values of a commercially available calibration material, Cation-Cal (American Dade). The relative standard deviations of day-to-day precision studies range from 1.4% for Na to 11.1% for Fe. Good correlations are obtained between the values obtained by SIMAAC and comparative clinical methods. 20 references, 2 figures, 4 tables.