Electrothermal Atomization Atomic Absorption Spectrometry Research Articles

Sequential injection analysis of lead using time-based colorimetric detection and preconcentration on an anionic-exchange resin.

The development of a sequential injection analysis manifold for the colorimetric determination of lead in water samples is described The concentration of lead was assessed from its catalytic effect on the reaction of resazurine reduction caused by sulfide in an alkali medium. To that effect, the reaction zone was stopped at the detector, and the time interval required for the attainment of an absorbance decrease of 0.800 at the wavelength of 610 nm was estimated. Interference of other transition metals of the samples was minimized by adding potassium iodide to the sample and retaining the iodocomplexes formed in an on-line anionic resin (AGI X8). Elution was made with a 2 mol/L sodium hydroxide solution. The relationship [SIA] microg/L = 0.99 (+/- 0.11) x [ETAAS] microg/L + 0 (+/- 4) was obtained upon comparing the results given by the proposed system and by electrothermal atomization atomic absorption spectrometry (ETAAS) after the analysis of ten water samples.

Comparing several atomic spectrometric methods to the super stars: special emphasis on laser induced breakdown spectrometry, LIBS, a future super star

The “super stars” of analytical atomic spectrometry are electrothermal atomization-atomic absorption spectrometry (ETA-AAS), inductively coupled plasma-atomic emission spectrometry (ICP-AES) and inductively coupled plasma-mass spectrometry (ICP-MS). Many other atomic spectrometric methods have been used to determine levels of elements present in solid, liquid and gaseous samples, but in most cases these other methods are inferior to the big three super star methods. The other atomic methods include glow discharge emission, absorption and mass spectrometric methods, laser excited fluorescence emission and ionization methods, and flame and microwave plasma emission and mass spectrometric methods. These “lesser” methods will be compared to the “super star” methods based on a number of figures of merit, including detection power, selectivity, multi-element capability, cost, applications, and “age” of the methods. The “age” of the method will be determined by a modification of the well-known Laitinen “Seven Ages of an Analytical Method” (H.A. Laitinen, Anal. Chem., 1973, 45, 2305). Calculations will show that certain methods are capable of single atom detection, including several atomic absorption methods, as well as laser atomic ionization and fluorescence methods. The comparison of methods will indicate why the “super stars” of atomic spectrometric methods will continue to retain their status and what must be done for the lesser atomic methods to approach “super star” status. Certainly most of the lesser atomic spectrometric methods will have a limited place in the analytical arena. Because of the wide current interest and research activity, special emphasis will be placed on the technique of laser induced breakdown spectrometry (LIBS). Its current status and future developments will therefore be reviewed.

Determination of cadmium in tobacco smoke by electrothermal atomic absorption spectroscopy with electrostatic precipitation of samples on the graphite tube atomizer

The determination of Cd in ambient air, associated with tobacco smoke, has been carried out by electrostatic precipitation of Cd directly in a graphite tube, which was subsequently used as an atomizer in electrothermal atomization atomic absorption spectroscopy (ET-AAS). It is shown that graphite tube permanently modified with Ir allows carrying out pyrolysis of collected samples at 1000°C, leading to minimization of the blank. The combination of electrostatic precipitation of Cd from ambient air into the graphite tube with high efficiency of Cd determination by ET-AAS allows to trace Cd in ambient air for 25 min after the smoking a cigarette The limit of detection (LOD) of Cd determination was found to be 0.2 ng/m 3 . The results of investigations confirm the danger of passive smoking due to the presence of Cd in smoking areas.

Chromium determination in foods by quadrupole inductively coupled plasma–mass spectrometry with ultrasonic nebulization

The analytical issues connected with chromium determination in foodstuffs by quadrupole inductively coupled plasma–mass spectrometry (Q-ICP-MS) were addressed, including signal stability, spectral interferences and the use of mathematical correction equations. The analytical performance was compared to that of electrothermal atomisation–atomic absorption spectrometry (ETA-AAS), selected as reference method. Five food certified reference materials (CRMs), including two meat-based CRMs not previously characterized for their Cr content, were included in the study. The use of ultrasonic nebulization (UN) and the adoption of 53Cr as analytical mass allowed precise and accurate results to be obtained by Q-ICP-MS, with lower detection limits than ETA-AAS.

Determination of ultratrace elements in natural waters by solid-phase extraction and atomic spectrometry methods

A study was carried out on the preconcentration of ultratrace amounts of cadmium, lead, manganese, copper and iron from high-salinity aqueous samples and determination by atomic spectrometry methods. Sample volume, amount of resin, loading flow rate, and elution volume were optimized in order to obtain the simultaneous preconcentration of all the analytes. Quantitative recoveries were obtained by using 200 mg of iminodiacetic resin with a loading flow rate of 2 mL min(-1), elution volume of 3 mL and sample volume of 50-450 mL. Only copper in seawater samples was not completely retained by the resin (60-70% recovery), due to unfavorable competition of iminodiacetic-active groups with organically bound metal.To quantify the metals in the eluates, two atomic spectrometry techniques were compared: electrothermal atomization atomic absorption spectrometry (ETAAS) and inductively coupled plasma-optical emission spectrometry (ICP-OES) with simultaneous CCD detection system. Both techniques are suitable for sample analysis with detection limits of 1.0, 4.7, 3.3, 6.8, and 53 ng L(-1) using ETAAS and 12, 122, 3.4, 17, and 21 ng L(-1) using ICP-OES for Cd, Pb, Mn, Cu, and Fe, respectively. Relative standard deviations of the procedures ranged from 1.7 to 14% at the sub-microg L(-1) concentration level. The accuracy of both methods was verified by analyzing various certified reference materials (river water, estuarine water, coastal and off-shore seawater).

Determination of chromium in cerebrospinal fluid using electrothermal atomisation atomic absorption spectrometry

A rapid method to determine the chromium content of cerebrospinal fluid (CSF) samples using electrothermal atomization atomic absorption spectrometry (ETA-AAS) with deuterium-arc background correction is described. The chromium concentration in CSF was evaluated by the standard addition method. Sample dilution (1 + 1) with 0.25% (m/v) Triton X-100 and 4.5% (v/v) HNO 3 gave the best combination of sensitivity, reproducibility, and low blank reading compared with dilution using other solvents. Within-batch reproducibility was 3.2% for 20 CSF samples, between-batch reproducibility was 4.7%. CSF samples from 43 healthy volunteers collected in a manner designed to avoid contamination yielded chromium concentrations of 14.6 ± 6.3 ng mL −1.

Individual variability in human tibia lead concentration.

Our aims in this study were to determine proximal-distal variability in adult human tibia lead concentration via electrothermal atomization atomic absorption spectrometry (ETAAS) and to determine whether there were any differences between core and surface tibia lead concentrations. We analyzed duplicate core and surface tibia samples for lead at multiple proximal-distal sections on 10 adult human cadaver legs. Dried bone samples were digested in nitric acid using microwave-assisted heating, and lead content was determined by ETAAS with Zeeman background correction. Lead concentrations in nine tibiae (one tibia was excluded because some of the data were compromised) ranged from 3.1 to 27.9 microg lead/g of dry bone. Both core and surface tibia lead concentrations were lower at the proximal and distal ends of the tibia. Surface tibia lead was approximately 5 microg/g greater than core tibia lead in six tibiae with relatively low lead concentration, and 8 microg/g greater in three tibiae with relatively high lead concentration. The difference between core and surface tibia lead was independent of proximal-distal tibia location. We conclude that these nine human tibiae showed a greater surface tibia lead concentration than core tibia lead concentration. This observation has consequences for the noninvasive measurement of tibia lead via K-shell and L-shell X-ray fluorescence.

A model for the determination of the activation energy and the order of release of the atom formation in electrothermal atomization atomic absorption spectroscopy

A model for the atom formation in electrothermal atomization atomic absorption spectroscopy (ETAAS) is proposed. In this model, it is established that the activity of surface species is equated to the number of atoms with an energy value above the activation energy of the atom formation process. Dissipation of the analyte atoms is considered to be the result of diffusion, thermal expansion and redeposition processes. The new model based on Maxwell's theory can be used to determine the temperature-dependent activation energy and the order of release of the analyte atom formation process from one single absorbance–time profile and under non-isothermal conditions. An Arrhenius-type plot of Ln A i e + ∫ o t k 2iA i e dt T A p e −A i e + ∫ t t p k 2iA i e dt vs. 1/ T is used to determine the activation energy. Kinetics expressions are used to evaluate the order of the atom formation reaction, which can be deduced from the slope of the line obtained by plotting Ln dA i e dt +k 2 i A i e A p e −A i e + ∫ t t p k 2 i A i e dt T m+0.5 vs. Ln A p e −A i e + ∫ t t p k 2 i A i e dt T − E 0 kT . All calculations were carried out using the experimental absorbances data. A comparison with the previously developed models using the same earlier published experimental data sets for Cu, Ni and Au is made. The agreement found between the results derived from this work and those earlier published is satisfactory.

Estimation of chromium bioavailability from the diet by an in vitro method

An in vitro method was used to study the dialysable fraction of chromium (Cr) from the diet which simulates human gastric and intestinal digestion. The percentage of dialysed Cr was used to assess the bioavailability. The duplicate diet approach was used to obtain ten different sets of samples each representative of the normal diet consumed in southern Spain. In each case triplicate analysis of Cr was carried out by electrothermal atomization-atomic absorption spectrometry in acid-mineralized samples. The Cr dietary intake ranged from 16 to 117 μg/day, and the dialysable Cr fraction ranged from 0.4% to 1.6%. The Cr absorption was higher for low levels of daily dietary mu intake of Cr (lt; 40 μg) than for levels of 40–80 μg; for mu high levels (> 80 μg) there was an increase in the dialysable fraction. The energy and nutrient intake of these diets was also evaluated.

Tungsten coil devices in atomic spectrometry: absorption, fluorescence, and emission.

In this work, tungsten coil (W-Coil) devices are used as atomizers for electrothermal atomization atomic absorption spectrometry (ETAAS), electrothermal atomization laser excited atomic fluorescence spectrometry (ETA-LEAFS), and electrothermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES). For most cases in ETAAS and ETA-LEAFS, limits of detection (LODs) using the W-Coil are within a factor of ten of those observed with commercial graphite furnace systems. LOD for Cd by W-Coil AAS is 10 pg, while LODs for As, Se, Cr, Sb and Pb by W-Coil LEAFS are 950, 320, 1400, 330, and 160 fg, respectively. The compact W-Coil device makes it an ideal atomizer for portable atomic spectrometry instrumentation, especially when coupled with a miniature charge coupled device spectrometer. Alternatively, the atomizer can be used as an inexpensive, modular add-on to an existing commercial ICP-AES system; and the thermal separation of Pb with interference elements Al, Mn, and Fe is demonstrated.

Determination of butyltin compounds by high-performance liquid chromatography-hydride generation-electrothermal atomization atomic absorption spectrometry

An ultrasensitive method for the determination of butyltin compounds has been developed coupling liquid chromatography with electrothermal atomization atomic absorption spectrometry by means of a hydride generation-in situ trapping system. The eluent coming out from the HPLC column was mixed in a tee piece assembly with hydrochloric acid and sodium tetrahydroborate; the reacting solution was carried through the mixing coil to the gas–liquid separator and the generated hydrides were stripped from the solution, introduced into the graphite atomizer through the quartz tube and collected on a Pd-treated platform. The quartz tube was then removed from the injection hole of the graphite tube and the atomic absorbance measured. For each considered tin species (inorganic tin, monobutyltin, dibutyltin, tributyltin) hydride generation conditions were studied in a multivariate way by a suitable experimental design. The resulting analytical performance of the HG-in situ trapping-ETAAS set-up was adequate for the determination of organotin species in environmental samples and therefore it was used as a metal-specific detector for HPLC analysis of this class of compounds. Detection limits of 0.84, 1.66 and 20.4 ng were obtained for mono-, di- and tributyltin, respectively. The system has been used for the determination of butyltin species in certified reference materials of marine samples such as mussel tissues and sediments.

Direct determination of trace elements in terephthalic acid by laser induced breakdown spectroscopy

The feasibility of laser induced breakdown spectroscopy (LIBS) as an online tool for trace metal analysis in terephthalic acid (TA) was evaluated. Millions of metric tonnes of TA are produced each year as a raw material for various kinds of polyesters used to make many consumer and industrial products. The conventional techniques used for trace metal analysis in TA are electrothermal atomization atomic absorption spectrometry (ETA-AAS) and inductively coupled plasma optical emission spectroscopy (ICP-OES). However, these techniques require digestion of the sample and dissolution and so are very time consuming and are not suitable for online analysis. LIBS, if it meets the sensitivity and accuracy requirements, will be a very effective tool for online analysis of the production of terephthalic acid and other organic particles. In this work, the main elements of interest, including Mn, Co, Fe, and Na, were studied. The strongest emission line of each element was chosen to obtain the best detection limit. The experimental parameters, including delay time, gate time, sample stage moving speed, and laser repetition rate, were optimized to maximize the signal-to-noise and signal-to-background ratios. Two sampling methods were studied: compressed pellet and loose powder on sticky tape. The preliminary results indicated that there was no difference between these two sampling methods in term of sensitivity and precision. Therefore, the loose powder on sticky tape was preferred for making online analysis of loose powders possible. One unknown and two certified samples were used to determine the accuracy of the method, and the results were compared to those obtained by ICP-OES.

Flow injection hydride generation electrothermal atomic absorption spectrometry with in-atomizer trapping for the determination of lead in calcium supplements

Lead hydride was generated from acid solution, containing potassium ferricyanide as an oxidizing agent, by the reaction with alkaline borohydride solution. The effects of reaction conditions (hydrochloric acid, ferricyanide and borohydride concentrations), and the lengths of reaction and stripping coils were studied. The effects of trapping temperature and argon flow rate were also investigated. Under the conditions giving the best peak area sensitivity, the detection limit (concentration giving a signal equal to three S.D. of the blank signal) was 0.12 μg l −1 for a 1000 μl injection volume. The detection limit was improved to 0.03 μg l −1 when the ferricyanide was purified by passage through a cation-exchange resin. Two calcium supplement materials were analyzed by the flow injection (FI)-hydride generation (HG)-electrothermal atomization atomic absorption spectrometry (ETAAS) method, giving values of 0.55 and 0.66 μg g −1, in agreement with results obtained by previously validated methods. For a 500-mg sample the limits of detection and quantification were 0.006 and 0.02 μg g −1, respectively.

Aluminum Content in Foods and Beverages Consumed in the Spanish Diet

A reliable and rapid method for determining aluminum content in foods and beverages was developed using electrothermal atomization-atomic absorption spectrometry (ETA-AAS) using previous optimization of the time-temperature program for the graphite furnace. The samples were subjected to acid mineralization with HNO 3 and V 2 O 5 . The technique used slurries for assay in samples of dairy products. The detection limit was 4.0 pg. The mean recovery obtained ranged from 98.5% to 99.0%. The variation coefficient ranged from 3.2% to 5.2%. The results obtained ranged from 1.362 to 6.610 μg/g in seafood, 0.171 to 29.688 μg/g in vegetables, 19.560 to 70.100 μg/g in olive oil, 0.424 to 6.430 μg/g in dairy products and 25.600 to 58.057 μg/g in stimulant drinks and infusions. This study contributes new data on the Al content of a variety of foods and beverages in Spain and such data are important for composition tables. The higher presence corresponded to seafood, vegetables and dairy products. Their contribution to Al dietary intake were estimated.

Chromium levels in spices and aromatic herbs

We determined the presence of chromium in a total of 72 samples of 17 different spices and aromatic herbs. Electrothermal atomization atomic absorption spectrometry (ETA-AAS) was used to determine Cr content in the samples mineralized with HNO 3 and V 2O 5. The analytical characteristics of the proposed method were tested, and the accuracy and precision was also verified against an NBS-certified reference material. Chromium concentrations ranged from not detectable to 1.42 μg/g (dry wt.) and Cr presence was detected in 95% of samples. Spices and aromatic herbs are widely consumed in the Spanish diet and in the Mediterranean diet, in general.

Electrothermal atomization atomic absorption spectrometry for the determination of lead in urine: results of an interlaboratory study

Results of an interlaboratory study are reported for the determination of lead in urine. Two levels of a lyophilized material containing biologically-bound lead were prepared using pooled urine obtained from lead-poisoned children undergoing the CaNa 2EDTA mobilization test. The materials were circulated to a group of reference laboratories that participate in the `New York State Proficiency Testing Program for Blood Lead'. Results of the initial round-robin gave all-method consensus target values of 145±22 μg/l (S.D.) for lot 17 and 449±43 μg/l (S.D.) for lot 20. The interlaboratory exercise was repeated some 5 years later and consensus target values were re-calculated using the grand mean (excluding outliers) of results reported by laboratories using electrothermal atomization atomic absorption spectrometry (ETAAS). The re-calculated target values were 139±10 μg/l (S.D.) and 433±12 μg/l (S.D.). The urine reference materials were also analyzed for lead by several laboratories using other instrumental techniques including isotope dilution (ID), inductively coupled plasma (ICP) mass spectrometry (MS), flame atomic absorption with extraction, ICP-atomic emission spectrometry, ID-gas chromatography MS and flow injection-hydride generation AAS, thus providing a rich source of analytical data with which to characterize them. The materials were also used in a long-term validation study of an ETAAS method developed originally for blood lead determinations that has since been used unmodified for the determination of lead in urine also. Recently, urine lead method performance has been tracked in a proficiency testing program specifically for this analysis. In addition, a number of commercial control materials have been analyzed and evaluated.

Comparative determination of Ba, Cu, Fe, Pb and Zn in tea leaves by slurry sampling electrothermal atomic absorption and liquid sampling inductively coupled plasma atomic emission spectrometry

The comparative determination of barium, copper, iron, lead and zinc in tea leaf samples by two atomic spectrometric techniques is reported. At first, slurry sampling electrothermal atomization atomic absorption spectrometry (ETAAS) was applied. The results of Ba and Pb determination were calculated using the method of standard additions, and results of Cu, Fe and Zn from the calibration graphs based on aqueous standards. These results were compared with the results obtained after microwave-assisted wet (nitric+hydrochloric+hydrofluoric acids) digestion in closed vessels followed by inductively coupled plasma-atomic emission spectrometric (ICP-AES) determination with the calibration by means of aqueous standards. The exception was lead determined after a wet digestion procedure by ETAAS. The accuracy of the studied methods was checked by the use of the certified reference material Tea GBW-07605. The recoveries of the analytes varied in the range from 91 to 99% for slurry sampling ETAAS, and from 92.5 to 102% for liquid sampling ICP-AES. The advantages of slurry sampling ETAAS method are simplicity of sample preparation and very good sensitivity. Slurry sampling ETAAS method is relatively fast but if several elements must be determined in one sample, the time of the whole microwave-assisted digestion procedure and ICP-AES determination will be shorter. However, worse detection limits of ICP-AES must also be taken into the consideration in a case of some analytes.

On atomization of uranium in plutonium matrix using ETA-AAS

Atomization processes for uranium in aqueous media and in the presence of a plutonium matrix have been studied and a chemical mechanism is proposed. These studies have been utilized for the determination of uranium in plutonium by Electrothermal Atomization- Atomic Absorption Spectrometry (ETA-AAS) within the constraints of its stable carbide forming tendency and complexity caused by formation of plutonium suboxide at high temperatures. In spite of these limitations the analytical range obtained for determination of uranium is 2.5–100 ng with a sample aliquot of 5 μL containing 5 mg/mL plutonium concentration. The precision of the method is evaluated as 9% RSD.

Determination of Co and Ni in soils and river sediments by electrothermal atomic absorption spectrometry with slurry sampling

Cobalt and nickel were determined in slurry samples of soils and river sediments by electrothermal atomization atomic absorption spectrometry (ETAAS) with Zeeman effect background correction. It is suggested that cobalt and nickel can be determined simultaneously by slurry sampling ETAAS. The results of determinations with the use of slurry sampling technique and aqueous standards are in good agreement with certified values, and the repeatability of the over-all analytical procedure expressed as relative standard deviation is less than 8.8% for Ni and 6.9% for Co. The characteristic mass is 7.5 pg and 14.1 pg for Co and Ni, respectively. The analytical results are also compared with the results obtained by sample microwave assisted wet digestion followed by inductively coupled plasma – atomic emission spectrometry (ICP-AES) determination. The influence of sample grinding and sample homogeneity is discussed as well.

Investigation of the interaction of molybdenum with a graphite surface by electrothermal atomization atomic-absorption spectroscopy and scanning tunnelling microscopy

The Mo memory effect usually observed during electrothermal atomization is explained in terms of a complex mechanism which involves both interaction with strong adsorption sites on the graphite substrate and a diffusion process. There is no correlation between the number of adsorption sites and the number of retained Mo atoms. The effect of HCl concentration on the Mo absorbance signal shows that Mo solutions containing 4–10% v v HCl give signals 1.4 times the average signals given by aqueous (non-acidic) solutions. Removal of Mo species occurs due to the presence of acid, and this in turn leads to a decrease in the observed memory effect. However, results indicate that there is a limiting acid concentration at which most Mo species are removed from the graphite. Results on the role of H + on the molybdenum electrothermal atomization lead to the conclusions: 1. 1. The presence of the acid does not permanently modify the graphite sites on which Mo will be adsorbed. 2. 2. There is no evidence that H + can compete with Mo for adsorption sites. 3. 3. The analyte and the acid (H +) must be combined in solution or on the surface in order to cause signal enhancement. 4. 4. The effect of the acid may favour the formation of aggregates by vacancy creation by protons in the liquid phase as well as at the liquid-solid interface. STM studies reveal that most adsorption in non-acidic solutions is on dislocations or rough areas, in which the analyte-surface interaction is stronger (a large retention effect). In acidic solutions the cluster distribution occurs on flat and rough areas of the graphite surface, in good agreement with the assumption that aggregates are formed in the liquid phase or at the liquid-surface interface.