Thermospray Flame Furnace Atomic Absorption Spectrometry Research Articles

Optimization of sample injection in TS-FF-AAS for determination of trace elements

In this work we present a proof of concept for the optimization of the analytical performance in ThermoSpray Flame Furnace Atomic Absorption Spectrometry (TS-FFAAS) by using different systems of sample injection. The influence of different operational variables was studied with emphasis on the characteristics of the ceramic capillary employed for sample introduction. The classic single hole capillary was compared to capillaries with different number of inner holes (one, four and six) and different spatial distribution. The influence on the analytical signal of a double simultaneous injection applied to different zones of the atomization furnace was also evaluated. Determination of elements with different atomization temperature (Ag, Cd and Se) was done, results shown an optimization of the figures of merit with respect to the TS-FF-AAS conventional assembly increased with the element volatility. Applications of Multi Injection (MI-TS-FF-AAS) was evaluated for determination of Cd in “yerba mate” samples; comparison of the obtained results using the proposed technique with other validated ones showed good agreement, and a reduction of amount of sample for the determination was achieved by using the multi-injection alternative. A discussion focused on the importance of an efficient sample introduction on the figures of merit attainable with TS-FFAAS and analytical applications of the technique is provided.

Investigation of thermospray flame furnace atomic absorption spectrometric determination of cadmium combined with ultrasound-assisted dispersive liquid-liquid microextraction

ABSTRACT Ultrasound-assisted dispersive liquid-liquid microextraction (UA-DLLME) was combined with thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) for the first time to develop a highly sensitive method for the determination of cadmium. Ultrasound was used to assist the liquid phase extraction, replacing the traditional disperser solvent. A self-assembled TS-FF-AAS instrument was adopted to improve the analytical performance of traditional flame atomic absorption spectrometry (FAAS), and the characteristic of micro-injection is fully suitable to be coupled with UA-DLLME. The developed combination significantly improved the analytical performance of TS-FF-AAS and traditional FAAS, while overcoming problems of nebulisation associated with the coupling of FAAS and liquid phase extraction methods. Some environmental water samples were collected and analysed by the developed coupling with satisfactory results.

Investigation of dispersive solid-phase extraction combined with slurry sampling thermospray flame furnace atomic absorption spectrometry for the determination of cadmium

In this work, a sensitive method for the determination of cadmium by flame atomic absorption spectrometry (FAAS) was established by combining dispersive solid-phase extraction (DSPE) with thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS). Nano-TiO2 was used as adsorbent, and the dispersive extraction simplified the operation procedure. Through the application of slurry sampling, the on-line combination of DSPE with TS-FF-AAS was established and the time-consuming elution step after DSPE was avoided. Problems of nebulization associated with previous methods based on the coupling of FAAS and SPE were overcome. DSPE combined with TS-FF-AAS significantly improved the analytical performance of the modified FAAS, which established a sensitive method for the determination of cadmium based on FAAS. Under the optimal conditions, the limit of detection (LOD) was 0.04 µg/L, which was better by an enhancement factor of 56. Compared to direct FAAS, the factor was 596. The method was applied to the determination of environmental water samples with satisfactory results.

Assessment of ultrasound-assisted extraction combined with supramolecular solvent-based microextraction for highly sensitive cadmium determination in medicinal plant sample by TS-FF-AAS

A new analytical method exploiting supramolecular solvent-based microextraction (SUPRAS) combined with ultrasound-assisted extraction to preconcentrate cadmium from medicinal plant, with further determination by thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS), is proposed. The proposed method is based on the cadmium ultrasound-assisted extraction from Ginkgo biloba L. leaf samples with diluted acid (0.10 mol L−1 HNO3), followed by the metal complexation with diethyl dithiophosphate and preconcentration using a supramolecular solvent composed of inverted hexagonal aggregates of dodecanoic acid arranged in tetrahydrofuran/water medium. The limits of detection (LOD) and quantification (LOQ) were found to be 0.11 μg L−1 and 0.36 μg L−1, respectively. Intraday and interday precision assessed in terms of relative standard deviations (RSD, %) were lower than 8.50% to 0.70, 1.75 and 5.00 μg L−1 cadmium solutions. The efficiency of ultrasound-assisted extraction was comparable to microwave-assisted digestion and the method accuracy was checked by analysis of certified reference material (Tomato Leaves, SRM 1573a). Samples of Ginkgo biloba L. were analyzed and cadmium contents between 0.21 and 0.33 μg g−1 were found, thereby showing clearly the importance of investigating toxic metals in medicinal plants. The proposed method is simple, highly sensitive, environmentally friendly and has great potential to be applied in the quality control of medicinal plants aiming trace cadmium determination.

Development of carbon paste electrode modified with cadmium ion-imprinted polymer for selective voltammetric determination of Cd2+

ABSTRACTA simple and fast voltammetric method based on a new electrode composed of carbon paste electrode/bifunctional hybrid ion imprinted polymer (CPE/IIP) was developed for the quantification of Cd2+ in water samples. The voltammetric measurements by Differential Pulse Voltammetry were performed by using CPE containing 11.0 mg of IIP under phosphate buffer solution at concentration 0.1 mol L−1 and pH 6.5. The electrochemical method was carried out by Cd2+ preconcentration at −1.2 V during 210 s, followed by anodic stripping. The performance of IIP towards Cd2+ determination was evaluated by comparison to non-imprinted polymer, whose detectability of IIP was much higher (45%). The sensitivity of the sensor was found to be 0.0105 µA/µg L−1. The limits of detection and limits of quantification were found to be 4.95 μg L−1 and 16.4 μg L−1, respectively. The developed method was successfully applied to Cd2+ determination in mineral, tap and lake water samples, whose results are in agreement with thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) used as reference analytical technique. According to achieved results, the developed method can be used for routine analysis of quality control of water samples from different sources.

Application of thermospray flame furnace atomic absorption spectrometry for investigation of silver nanoparticles.

Thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) was applied to investigate the time-dependent absorption peak profile of various forms of silver. The thermospray flame furnace was set up with a 10-cm-long nickel tube with six holes, each 2.0mm in diameter, to allow the flame to enter, and this nickel tube acted as a furnace. A sample of 300μL was introduced into this furnace by use of water as a carrier at a flow rate of 0.5mLmin-1 through the ceramic capillary (0.5-mm inner diameter and 2.0-mm outer diameter), which was inserted into the front hole of the nickel tube. The system was applied to examine atomization behaviors of silver nanoparticles (AgNPs) with particle sizes ranging from 10 to 100nm. The atomization rate of AgNPs was faster than that of the dissolved silver ion. With increased amount of silver, the decay time observed from the time-dependent absorption peak profile was shortened in the case of dissolved silver ion, but it was increased in the case of AgNPs. With the particle size ranging from 10 to 100nm, the detection sensitivity was indirectly proportional to the particle size, suggesting that TS-FF-AAS may offer insights into the particle size of AgNPs provided that the concentration of the silver is known. To obtain quantitative information on AgNPs, acid dissolution of the particles was performed before TS-FF-AAS analysis, and recoveries of 80-110% were obtained.

Development and feasibility of emulsion breaking method for the extraction of cadmium from omega-3 dietary supplements and determination by flow injection TS-FF-AAS

In the present study a new method for the determination of Cd2+ in omega-3 dietary supplement employing extraction induced by emulsion breaking (EIEB) and thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) was described. The method was based on the formation of a water-in-oil emulsion by the addition of extractor solution constituted by 3.54% (m/v) Triton X-114 and 1.16molL−1 HNO3 in the oil sample and further breaking of this emulsion by heating. Two well-defined phases were formed and the acid aqueous one containing the extracted cadmium ions was analyzed by TS-FF-AAS using a flow injection system. Different parameters that exert influence on the extraction efficiency of Cd2+ were optimized by means of chemometric tools. The limits of detection and quantification were found to be 2.5 and 8.3ngg−1, respectively using a calibration curve made in aqueous medium. The accuracy of the proposed method was assured by good agreement with the results achieved by microwave-assisted acid digestion procedure without statistical differences (confidence interval of 95%) and by spiking the samples with known concentrations of 50ngg−1 Cd2+. The content of Cd2+ in the samples was varied from 37.3 up to 54.5ngg−1.

A novel combination of experimental design and artificial neural networks as an analytical tool for improving performance in thermospray flame furnace atomic absorption spectrometry

In this work, we present the combined effect of artificial neural networks (ANN) and experimental design as a suitable analytical tool for improving the performance of thermospray flame furnace atomic absorption spectrometry (TS-FFAAS) using Mg as leading case.To this end, mixtures of different amounts of methanol, ethanol, and i-propanol in water were assayed as carriers at different flow rates and different flame stoichiometries (air/acetylene ratios). Different levels of these variables determined the experimental domain, consisting in a cube which was divided into eight identical cubical regions that allowed increase in the number of available experimental points. A Box–Behnken design (BBD) was employed in each one of the regions. The name Multiple Box–Behnken design (MBBD) was given to this new approach. Then, the features of ANN were exploited to find the optimum conditions for conducting Mg determination by TS-FFAAS.The prediction capability of ANN was examined and compared to the least-squares (LS) fitting when applied to the response surface method (RSM).The suitability of the new approach and the implications on TS-FFAAS analytical performance are discussed.

Towards broadening thermospray flame furnace atomic absorption spectrometry: Influence of organic solvents on the analytical signal of magnesium

This study demonstrates the influence of the solvent when thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) is employed for the determination of elements of low volatility, taking magnesium (Mg) as leading case. Several organic solvents/water solutions of different characteristics (density, surface tension, viscosity, etc.) and proportions were employed for the TS-FF-AAS analytical determination. To this end, solutions containing methanol, ethanol and isopropanol in water were assayed. Measurements were performed at different acetylene/air ratios of the combustion flame and then, the corresponding response surfaces were obtained. Methanol/water 75% v/v as carrier and a fuel rich flame were found as the most sensitive alternative.In the light of these findings and in order to explain the changes on the analytical signal, the influence of the solvent characteristics, the sample droplet size and the redox environment was studied. An estimation of the temperature of different zones of the heated flame furnace based on a modified signal ratio pyrometry method was analyzed for comparative purposes. A full discussion is provided throughout the paper.Once obtained the best conditions for analysis, Mg was determined in samples of effervescent vitamin tablets comparing two different solvents. The tablets were dissolved in methanol/water 75% v/v and ethanol/water 75% v/v and then, directly introduced in the TS device. The methanol/water 75% v/v dissolution yielded a slightly higher sensitivity when compared to ethanol/water and thus, the latter was selected due to its lower toxicity. The obtained figures of merit are: LOD (3σb): 0.021mgL−1; LOQ (10σb): 0.068mgL−1, sensitivity: 0.086Lmg−1; RSD%: 3.55, dynamic linear range 0.068–5mgL−1. Comparison of the results was performed by flame atomic absorption spectrometry (FAAS), showing a good agreement (95% confidence level, n=5). Whilst the FAAS approach needed sample mineralization as no complete solubility was attained with both alcohol/water solvents, TS allowed direct introduction of the sample with an excellent recovery of the analyte after spiking. The whole TS procedure was more economic (lower amount of reagents and wastings, lower time of operation) and faster (60h−1 sampling throughput) than FAAS.Nonetheless, the main objective of this work is to show that an analytical signal different from zero can be obtained for Mg via TS by simply choosing the adequate operational variables that allow an optimization of the mass transfer of the analyte into the atomizer and a favorable dynamics of desolvation/atomization.This approach could broad TS analytical capabilities to other elements of lower volatility as it is shown here for the case of Mg.

Enhancement effect of room temperature ionic liquids on the chemical vapor generation of lead, cadmium and bismuth for thermospray flame furnace atomic absorption spectrometric determination

A novel method was developed for the chemical vapor generation (CVG) of lead, cadmium and bismuth based on the enhancement effect of room temperature ionic liquids followed by thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) determination. Room temperature ionic liquids (RTILs) and ammonium pyrroldinedithiocarbamate (APDC) were used as enhancement reagents and chelating reagents for the CVG of lead, cadmium and bismuth, respectively. TS-FF-AAS was used for the determination of lead, cadmium and bismuth. The addition of RTILs led to an improvement of 3.5, 3.0 and 4.0 times the CVG efficiencies of Pb, Cd and Bi, respectively. The efficiencies for the CVG of Pb, Cd and Bi in the presence of RTILs and APDC were 55%, 46% and 60%, respectively. Volatile species of Pb, Cd and Bi were effectively generated through reduction of acidified analyte solutions with KBH4 in the presence of 0.02% (m/v) APDC and 0.1% (v/v) 1-butyl-3-methylimidazolium tetrafluoroborate ([C4MIM]BF4). Some parameters that influenced CVG and the subsequent determinations were evaluated in detail, such as the concentrations of RTILs, APDC, HNO3 and KBH4; the flow rates of the carrier gas, lengths of the reaction tube and transfer tube, as well as interferences. Under optimized conditions, the detection limits for Pb, Cd and Bi were 8, 1 and 5 ng mL−1, respectively. Relative standard deviations for five replicate determinations of a standard solution containing 200 ng mL−1 Pb, Cd and Bi were 4.5%, 5.5% and 5.2%, respectively. The proposed method was successfully applied in the determination of Pb, Cd and Bi in certified environmental reference materials with satisfactory results.

Assessment of cadmium and iron adsorption in sediment, employing a flow injection analysis system with on line filtration and detection by flame atomic absorption spectrometry and thermospray flame furnace atomic absorption spectrometry

This work presents an evaluation of iron and cadmium adsorption in sediment of the Furnas Hydroelectric Plant Reservatory located in Alfenas, Minas Gerais (Brazil). The metal determination was done employing a flow injection analysis (FIA) with an on-line filtering system. As detection techniques, flame atomic absorption spectrometry (FAAS) for iron and thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) for cadmium determinations were used. The developed methodology presented good limits of detection, being 190μgL−1 for iron and 1.36μgL−1 for cadmium, and high sampling frequency for both metals 144 and 60 readings h−1 for iron and cadmium, respectively. Both metals obey the Langmuir model, with maximum adsorptive capacity of 0⋅169mgg−1 for iron and 7⋅991mgg−1 for cadmium. For iron, a pseudo-first-order kinetic model was obtained with a theoretical Qe=9⋅8355mgg−1 (experimental Qe=9⋅5432mg g−1), while for cadmium, a pseudo-second-order kinetic model was obtained, with a theoretical Qe=0.3123mgg−1 (experimental Qe=0⋅3052mgg−1).

Evaluation of quartz tubes as atomization cells for gold determination by thermospray flame furnace atomic absorption spectrometry

This work describes the development of a new analytical procedure able to determine gold by thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) using nickel tubes (NiT) and quartz tubes (QT) as atomization cells. Experiments involving changes in the flow injection operational parameters, reagent concentrations and sizes of the QT were performed in order to optimize sensitivity. Under the same operational conditions, it was observed that the employment of QT increases the sensitivity of gold determination when compared to the nickel tube. Since solutions of highly concentrated hydrochloric acid showed the best performance as carriers, quartz tubes were also preferred due to its greater tolerance to corrosion by mineral acids in comparison to NiT. In addition, changes in the internal diameter of the QT revealed an important improvement in sensitivity for smaller tubes.Under optimized conditions the main figures of merit showed values close to that of graphite furnace atomic absorption spectrometry with the addition of an excellent improvement of the sample throughput. They are: LOD (3s): 0.004μgmL−1, sensitivity: 0.306 (μgmL−1)−1, RSD% (n=10, 1μgmL−1): 2.5, linear range: 0.01–4μgmL−1 and sample throughput: 72h−1.This new method was employed for the determination of gold in homeopathic medicines with no need of sample digestion. Validation of the analytical results will be shown.A full discussion of the most relevant findings regarding the role of the atomization cell as a strategic key for improving sensitivity will be also provided.

The coupling of rapidly synergistic cloud point extraction with thermospray flame furnace atomic absorption spectrometry

Rapidly synergistic cloud point extraction (RS-CPE) was coupled with thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) to result in new CPE patterns and accelerated (1 min) protocols. It is demonstrated, for the case of copper (II) ion, that TS-FF-AAS improves the sampling efficiency and the sensitivity of FAAS determinations. Problems of nebulization associated with previous methods based on the coupling of FAAS and RS-CPE are overcome. TS-FF-AAS also improves sensitivity and gives a limit of detection for copper of 0.20 μg L-1, which is better by a factor of 32. Compared to direct FAAS, the factor is 114.

Determination of Cd levels in smoke condensate of Brazilian and Paraguayan cigarettes by Thermospray Flame Furnace Atomic Absorption Spectrometry (TS-FF-AAS)

In this study, the concentrations of Cd in smoke condensate of Paraguayan and Brazilian full flavor normal size cigarettes were determined. A “fishtail” chimney was used to confine and direct cigarette smoke to an impaction trap followed by 3 MCE (mixed cellulose ester) filters for smoke collection. The smoke condensate collected at the first two collection stages (chimney and impactor) was prepared as Triton X-100 slurry samples and the 3 MCE filters (third collection stage) used to collect smoke were microwave digested. Samples were analyzed by Thermospray Flame Furnace Atomic Absorption Spectrometry (TS-FF-AAS) for Cd and the results obtained were compared with Graphite Furnace Atomic Absorption Spectrometry (GFAAS). No significant differences were found between the values obtained with TS-FF-AAS and GFAAS at a 95% confidence level. The total concentration of Cd in the smoke of Brazilian and Paraguayan cigarettes tested ranged from 187 to 281ng/cigarette and from 176 to 271ng/cigarette, respectively. The LODs for Cd using TS-FF-AAS and GFAAS, were 5.8 and 1.5ng/cigarette, respectively, for the analysis of smoke condensate from 1 cigarette. The main advantages of using the simple TS-FF-AAS system are its low running costs and the analysis time when compared to GFAAS.

Determination of Cd in Water Samples by Hollow-Fiber–Supported Liquid-Membrane Extraction Coupled with Thermospray-Flame–Furnace Atomic-Absorption Spectrometry

ABSTRACT A new method of hollow-fiber–supported liquid-membrane extraction (HF-SLME) coupled with thermospray-flame–furnace atomic-absorption spectrometry (TS-FF-AAS) for the determination of cadmium in water samples was developed. 1-Octanol was immobilized in the pores of the polypropylene hollow fiber as liquid membrane and used as the acceptor solution. Cd was selectively extracted from water samples into 1-octanol that filled the inner part of hollow fiber as the acceptor solution. The authors evaluated in detail some parameters that influence extraction and determination, such as the concentration of sodium diethyldithiocarbamate (DDTC), pH of samples, stirring rate, extraction time, flow rate of the pump, and interferences. Under optimized conditions, an enrichment factor of 146 could be obtained. In combination with thermospray-flame–furnace atomic-absorption spectrometry, a very low limit of detection (LOD) (5 ng L−1) was achieved. The relative standard deviation (RSD) was 4.3% for five determinations of 0.1 ng mL−1 cadmium. The accuracy of this method was validated by determination of certified reference water samples (GBW(E) 08607 and GSBZ(E) 50009-88). The proposed method was also applied to the determination of cadmium in tap water and river water, with the recoveries in the range of 90–96% for spiked samples.

Hollow fiber supported liquid membrane extraction coupled with thermospray flame furnace atomic absorption spectrometry for the speciation of Sb(III) and Sb(V) in environmental and biological samples

A new method of hollow fiber supported liquid membrane extraction (HF-SLME) coupled with thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) for the speciation of Sb(III) and Sb(V) in environmental and biological samples has been developed. The method is based on the complex of Sb(III) with sodium diethyldithiocarbamate (DDTC). The formed hydrophobic complex is subsequently extracted into the lumen of hollow fiber, whereas Sb(V) is remained in aqueous solutions. The extraction organic phase was injected into TS-FF-AAS for the determination of Sb(III). Total Sb concentration was determined after reduction of Sb(V) to Sb(III) in the presence of l-cysteine and the extraction procedure mentioned above. Sb(V) was calculated by subtracting of Sb(III) from the total Sb. DDTC was used as complexing reagent. 1-Octanol was immobilized in the pores of the polypropylene hollow fiber as liquid membrane and also used as the acceptor solution. Some parameters that influenced extraction and determination were evaluated in detail, such as concentration of sodium diethyldithiocarbamate (DDTC), type of organic solvent, pH of samples, stirring rates, extraction time, as well as interferences. Under optimized conditions, a detection limit of 0.8 ng mL −1 and an enrichment factor of 160 were achieved. The relative standard deviation (RSD) was 6.2% for Sb(III) (50 ng mL −1, n = 5). The proposed method was successfully applied to the speciation of Sb(III) and Sb(V) in environmental and biological samples with satisfactory results.

Liquid carbon dioxide for improvements in online preconcentration and sample introduction in AAS,

In this work liquid carbon dioxide in a flow system for better sample introduction and online preconcentration of copper, by means of Thermospray Flame Furnace-Atomic Absorption Spectrometry (TS-FF-AAS) has been used. Liquid carbon was used as pressure pump, liquid carrier, eluting solvent and nebulizer gas in the flow system. The flow restrictor consisted of a fused silica capillary (optimal i.d. 75 μm, 5 cm length) which is used for maintaining carbon dioxide in liquid state under subcritical conditions (58.5 bar and room temperature). Regarding the aerosol formation mechanism by aqueous samples, the CO2-saturated sample is decompressed from 58.5 to 1 bar producing CO2 vaporization which expands the liquid jet and forms a conic wet aerosol cloud that is rapidly vaporized in the atomizer. In other cases, by elution of preconcentrated complexed metals from a column (C18), CO2-dissolved compounds became rapidly desolvated by CO2 vaporization, forming a dry aerosol of gaseous metal complexes which became thermally decomposed and atomized in the Ni-tube. The detection limit by means of liquid carbon dioxide have improved by a factor ca. 3 and 10, in comparison with TS-FF-AAS and Flow Injection Flame Atomic Absorption Spectrometry (FI-FAAS), respectively. Preconcentration of copper 8-hydroxyquinoleine complex in a C18 mini column and its elution with liquid carbon dioxide resulted in an enrichment factor of 24 and a detection limit of 2 μg L−1. This innovative system of sample pretreatment and nebulization envisages novel applications in atomic spectrometry avoiding the use of organic solvents and consequently the generation of toxic residues.

Cloud point extraction for determination of cadmium in soft drinks by thermospray flame furnace atomic absorption spectrometry

Cloud point extraction (CPE) is proposed as a preconcentration procedure for the determination of Cd in soft drinks by thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS). The cadmium reacted with pyridyl-azo-naphthol (PAN) to form hydrophobic chelates, which were extracted into the micelles of Triton X-114 in a solution buffered at pH 9. NaCl was used for the phase separation. The variables which affect the preconcentration were optimized using a 2 3 factorial design and central composite design (CCD). A response surface maximum point was obtained, and the critical values were a concentration of 0.13 mmol L − 1 PAN, 0.03% m/v Triton X-114 and 2.3% m/v NaCl. Under the optimized conditions, after the extraction and preconcentration steps, a sample volume of 100 μL was introduced into the hot Ni tube using water as the carrier at a flow rate of 0.4 mL min − 1 . The values obtained for the detection limit, relative standard deviation and preconcentration factor were 0.0178 μg L − 1 , 4.1% (n = 8) and 55.5, respectively. The accuracy of the proposed method was demonstrated by performing addition-recovery experiments. Recoveries varied from 88 to 104%.

Evaluation of the mineral profile of textile materials using inductively coupled plasma optical emission spectrometry and chemometrics

The content of Al, Ba, Ca, Cr, Cu, Fe, Ni, P, Zn, Cd and Pb was determined in textile material samples after microwave-assisted decomposition in a cavity oven and extraction with an artificial sweat solution. Radial viewing inductively coupled plasma optical emission spectrometry (ICP OES) was the main detection technique, but Cd and Pb were determined by thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) to increase the sensitivity. Principal components analysis (PCA) was applied to the data sets to characterize the samples with respect to their geographic origin and color difference. The PCA for Brazilian single-color samples showed separation, with one group consisting of blue and green textiles and another with all the other materials evaluated. The geographic origin study showed a clear separation between Brazilian and Chinese textiles. The metals amount extracted with sweat extractable solution were lower than limits values pointed by the International Testing and Certification System for Textiles, Öko Tex Standard 100, in the all considered classes. Recoveries varied from 85 to 112% for additions ranging from 3.0 to 25 mg kg −1 for Ca and from 0.3 to 7.0 mg kg −1 for all other analytes through the microwave-assisted decomposition procedure.

Ti and Ni tubes combined in thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) for the determination of copper in biological samples

This study presents an evaluation of Cu determination in thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) using Ni and Ti metal tube atomizers. The TS-FF-AAS system was equipped with Ti tubes inserted inside Ni tubes (called Ni/Ti), and also different configurations of Ti tube atomizers placed on an oxidizing air/acetylene flame. This new arrangement combining both tubes permitted an increased sensitivity (approximately 4 times) when it was compared with single Ni or Ti tubes. This high sensitivity is due to the formation of TiO 2 inside the Ti tubes (shown by X-ray diffractometry and microanalyses), improving the Cu atomization through the corresponding oxide. The estimated gaseous phase temperatures for the tubes (Ni, Ti and Ni/Ti) were of the same magnitude (varied from 1400 to 1800 °C). Tests with concomitants (Na, K, Ca and Mg) showed similar behavior of Ni and Ni/Ti tubes. The differences between Ni and Ni/Ti tube atomizers for Cu sensitivity were not related to differences between the tube atomizers' internal volumes. The method accuracy was verified using certified reference materials (CRM's) of biological samples prepared with a closed-vessel microwave system using diluted HNO 3. A 2 µg L − 1 Cu detection limit was obtained using a Ni/Ti tube atomizer. The recoveries for Cu from the CRM's were about 100%. Finally, the use of a Ti tube inside a Ni tube increased the Ti tube lifetime.