Determination of lead in plants in controlling phytoremediation processes using slurry sampling electrothermal atomic absorption spectrometry

The comparative determination of lead in plant samples by two atomic spectrometric techniques is reported. At first, slurry sampling electrothermal atomisation atomic absorption spectrometry (ETAAS) was applied. The results obtained were compared with those found after a wet digestion procedure by flame atomic absorption spectrometry (FAAS) or ETAAS. The accuracy of the studied methods was checked using a certified reference material (CL???1 CRM, Cabbage Leaves). The recovery of lead was 90% for slurry sampling ETAAS, and 86.6% for liquid sampling ETAAS. The advantages of the slurry sampling ETAAS method are the simplicity of sample preparation and very good sensitivity.     

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.     

Sample pre-treatment methods for the trace elements determination in seafood products by atomic absorption spectrometry

Different sample pre-treatments for seafood products have been compared with determine trace elements (As, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Se and Zn) by flame atomic absorption spectrometry (FAAS) and electrothermal atomic absorption spectrometry (ETAAS). Classic pre-treatments as microwave assisted-acid digestion and the slurry sampling technique were compared with new procedures such as microwave energy or ultrasound energy assisted-acid leaching process and enzymatic hydrolysis methodologies based on the use of pronase E. The methods were applied to DORM-1 and DOLT-1 reference materials with certified contents for the studied elements. The Student-Newman-Keuls (SNK) method was used to compare with element concentration means obtained with each sample pre-treatment and also the certified concentration means in both reference materials. Multivariate techniques such as principal components analysis (PCA) was also applied to comparative purposes.     

Determination of Bismuth in Sediment and Soil by Ultrasonic Slurry Sampling Electrothermal Atomic Absorption Spectrometry

The analytical conditions of the direct determination of bismuth in some certified reference material samples (soil and sediment) by slurry sampling Zeeman electrothermal atomic absorption spectrometry (ETAAS) with the use of automated ultrasonic slurry mixing are discussed. Palladium nitrate was used as a chemical modifier. With the use of this modifier it was possible to stabilize bismuth to the pyrolysis temperature of 1300 °C. Platform atomization was performed at 2050 °C. The results of determination are calculated from a simple, aqueous standards based calibration graph. Statistical evaluation of the results indicate that the slurry sampling method is reproducible and the accuracy of the proposed method is very good. This method is rather simple and its other advantages are good sensitivity and relatively short analysis time.     

Application of multivariate methods to scalp hair metal data to distinguish between drug-free subjects and drug abusers

Human scalp hair samples of drug-free subjects and drug abusers (heroin and cocaine-heroin abusers) were analysed for trace metals by flame atomic absorption spectrometry (FAAS), flame atomic emission spectrometry (FAES) and electrothermal atomic absorption spectrometry (ETAAS). The classification of drug-free subjects and drug abuses groups with four multivariate methods using the metal contents in hair samples as discriminant variables has been discussed. Principal component analysis (PCA), cluster analysis (CA), linear discriminant analysis (LDA) and soft independent modelling of class analogy (SIMCA) allow distinguishing the two groups correctly. However, predictions by SIMCA are less satisfactory. Thirteen elements (Ag, Al, Ca, Cd, Cr, Cu, K, Mg, Mn, Na, Ni, Pb, and Zn) were determined by FAAS/FAES/ETAAS in 53 hair samples (16 samples of drug-free people and 37 samples of drug abusers). Human hair samples were prepared as aqueous slurries as sample pre-treatment and they were analysed using the slurry sampling technique. The half-range central value transformation was novelty used as data pre-treatment to homogenise the data. Grouping in the samples (drug-free people and drug abusers) were observed by using PCA and CA (squared Euclidean distance between objects and Ward method as clustering procedure). The application of LDA gave a correct recognition assignation percentage of 91.7 and 100.0% for the drug-free people and drug abusers, respectively, at a significance of 5%, while SIMCA offered recognition percentages of 83.3 and 91.3% for drug-free people and drug abusers, respectively, also at 5%. Finally, some studies were developed to classify heroin abusers and polidrug abusers (cocaine-heroin abusers) by the cited multivariate statistical methods. Recognition percentages of 90.9 and 100.0% were reached for heroin abusers and polidrug abusers groups, respectively, after LDA, while these percentages decreased to percentages lower than 90.0% when SIMCA was applied.     

Cloud point extraction of aluminum (III) in water samples and determination by electrothermal atomic absorption spectrometry,flame atomic absorption spectrometry and UV-visible spectrophotometry

Cloud point extraction was applied as a preconcentration step for the determination of trace level of Al(III) in water samples with electrothermal atomic absorption spectrometry (ETAAS), flame atomic absorption spectrometry (FAAS) and UV-visible spectrophotometry. The aluminum was extracted as aluminum-Eriochrome Cyanine R (ECR) complex, at pH 6 by micelles of the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114). The investigations showed that the same CPE procedure can be used for different detection techniques. The results obtained from these techniques were evaluated. Under the optimal conditions, limit of detection obtained with ETAAS, FAAS and UV-visible spectrophotometry were 0.03 ng mL^?1, 0.06 µg mL^?1 and 0.01 µg mL^?1, respectively. The accuracy of the procedure was tested by analysing certified reference material. The method was successfully applied to determination of aluminum in water samples and dialysis fluid.     

Selenium determination by electrothermal atomic absorption spectrometry in petroleum refinery aqueous streams containing volatile organic compounds

An electrothermal atomic absorption spectrometry (ETAAS) with polarized Zeeman background correction was used for determining selenium in petroleum refinery aqueous streams containing large amounts of volatile unknown organic compounds. Some parameters that might affect the measurement were investigated such as the amount of matrix modifier added, the temperature program and the calibration mode employed. Obtained results indicate that, in this kind of sample, selenium must be determined by standard addition procedure with a careful control of the dry step temperature and ramp pattern. Also, the results show that 2.5 μg of Pd must be added as matrix modifier to stabilize the analyte in the range of 2-20 ng Se. In order to evaluate the accuracy of the procedure, selenium was determined in 18 samples by ETAAS and hydride generation atomic absorption spectrometry (HGAAS) (as reference methodology). In both techniques the results agreed well.     

Determination of trace elements in biological materials using tetramethylammonium hydroxide for sample preparation

A method to prepare milk powder, bovine liver and bovine muscle samples for analysis by electrothermal atomic absorption spectrometry (ETAAS) is proposed. Samples are mixed with a small amount of tetramethylammonium hydroxide (TMAH) and a stable and homogeneous slurry is produced in ca. 2 h with heating at 60–70 °C. After such sample preparation and dilution with water, trace elements are determined in certified reference materials. Pyrolysis and atomisation temperatures are optimised for each element, and several modifiers are investigated. External calibration is used for every analyte. Limits of detection (LODs), precision and accuracy are reported for Cd, Pb, Ni, Cr, Cu and Ag and compared with those obtained after conventional acid digestion. The main advantages of the proposed method are the simplicity of sample preparation and the longer lifetime of the graphite tube.     

A direct solid sampling electrothermal atomic absorption spectrometry method for the determination of silicon in biological materials

A solid sampling electrothermal atomic absorption spectrometry method for direct determination of trace silicon in biological materials was developed and applied to analysis of pork liver, bovine liver SRM 1577b and pure cellulose. The organic matrix was destroyed and expelled from the furnace in the pyrolysis stage involving a step-wise increasing the temperature from 160 °C to 1200 °C. The mixed Pd/Mg(NO₃)₂ modifier has proved to be the optimum one with respect to the achievement of maximum sensitivity, elimination of the effect of the remaining inorganic substances and the possibility of using calibration curves measured with aqueous standard solutions for quantification. For the maximum applicable sample amount of 6 mg, the limit of detection was found to be 30 ng g^− 1. The results were compared with those obtained by different spectrometric methods involving sample digestion, by electrothermal atomic absorption spectrometry using slurry sampling, by wavelength dispersive X-ray fluorescence spectrometry and by radiochemical neutron activation analysis. The method seems to be a promising one for analysis of biological materials containing no significant fraction of silicon in form of not naturally occurring volatile organosilicon compounds. The still incessant serious limitations and uncertainties in the determination of trace silicon in solid biological materials are discussed.     

甲基异丁基甲酮萃取-火焰原子吸收光谱法测定氧化锑中的磷

研究了MIBK萃取-火焰原子吸收光谱法测定氧化锑中的磷。在盐酸介质中,磷酸根与钼酸铵形成磷钼物质的量之比为1∶12磷钼杂多酸,用酒石酸钾钠掩蔽锑,以甲基异丁基甲酮为萃取试剂,用火焰原子吸收光谱法测定有机相中磷钼杂多酸中的钼,据此建立了一种间接测定氧化锑中微量磷的新方法。在优化的实验条件下,当磷的含量在0.055~1.00 mg/L范围内时,其吸光度与浓度呈良好的线性关系;方法的检出限为0.011 mg/L;对4个样品进行测定的回收率在97.8%~106.2%之间;相对标准偏差为2.6%~4.2%。用于氧化锑中微量磷的测定,结果满意。     

Ammonium Acetate Extracts and Their Analysis for the Speciation of Metal Ions in Soils and Sediments

Abstract

The use of ammonium acetate (1 mol/l at pH 7) extraction of soils and sediments for the speciation of metal ions is briefly discussed. Because the sensitivity of flame atomic absorption spectrometry (FAAS) is insufficiently sensitive for the determination of many of the heavy metals in ammonium acetate extracts of unpolluted, and even in some polluted soils, the use of electrothermal atomic absorption spectrometry (ETAAS) was studied. A general procedure, using graphite furnace atomisation and the “universal” matrix modifier, palladium, was developed, that was sufficiently sensitive for the determination of Cd, Cr, Cu, Ni, Pb and Zn even in unpolluted soils. The concentration of zinc, however, will almost always be high enough for determination of FAAS and this method is to be preferred to ETAAS for this element.

While, for Cr, Cu, Ni and Pb, direct calibration with external standard solutions is practicable, it is necessary to use the standard additions calibration method for cadmium, to avoid matrix interference effects. The standard additions technique is recommended, however, because it compensates for real differences in the operating parameters of different instruments set to the same nominal values. This is particularly important for interlaboratory comparisons or for certification analyses in the preparation of reference materials.     

Determination of Antimony in Sediments by Zeeman-Corrected Electrothermal Atomic Absorption Spectrometry with Ultrasonic Slurry Sampling

A method was developed for the determination of antimony in slurried sediments (on the basis of samples of three Certified Reference Materials) by electrothermal atomic absorption spectrometry (ETAAS) with Zeeman-effect background correction. Slurried samples were prepared in 6% nitric acid containing 0.02% of Triton X-100. A mixed palladium/magnesium chemical matrix modifier, L'vov platform atomization and a temperature-time program with a relatively short (10 s) sample pyrolysis stage were used. The results of the determinations by this technique are in very close agreement with certified values and the repeatability of this analytical procedure expressed in terms of relative standard deviation was typically better than 9% at the slurry concentration of approx. 90 mg/2 mL. The characteristic mass of Sb (at the spectral line 231.1 nm) was 25.6 pg and the limit of detection (calculated for 100 mg/2 mL slurry) was about 0. 04 μg/g.     

Determination of As,Cd, Cu,Hg and Pb in biological samples by modern electrothermal atomic absorption spectrometry

Pollution from heavy metals has increased in recent decades and has become an important concern for environmental agencies. Arsenic, cadmium, copper, mercury and lead are among the trace elements that have the greatest impact and carry the highest risk to human health. Electrothermal atomic absorption spectrometry (ETAAS) has long been used for trace element analyses and over the past few years, the main constraints of atomic absorption spectrometry (AAS) methods, namely matrix interferences that provoked high background absorption and interferences, have been reduced. The use of new, more efficient modifiers and in situ trapping methods for stabilization and pre-concentration of these analytes, progress in control of atomization temperatures, new designs of atomizers and advances in methods to correct background spectral interferences have permitted an improvement in sensitivity, an increase in detection power, reduction in sample manipulation, and increase in the reproducibility of the results. These advances have enhanced the utility of Electrothermal atomic absorption spectrometry (ETAAS) for trace element determination at μg L⁻¹ levels, especially in difficult matrices, giving rise to greater reproducibility, lower economic cost and ease of sample pre-treatment compared to other methods. Moreover, the recent introduction of high resolution continuum source Electrothermal atomic absorption spectrometry (HR-CS-ETAAS) has facilitated direct solid sampling, reducing background noise and opening the possibility of achieving even more rapid quantitation of some elements. The incorporation of flow injection analysis (FIA) systems for automation of sample pre-treatment, as well as chemical vapor generation renders (ETAAS) into a feasible option for detection of As and Hg in environmental and food control studies wherein large numbers of samples can be rapidly analyzed. A relatively inexpensive approach with low sample consumption provide additional advantages of this technique that reaches figures of merit equivalent to Inductively coupled plasma mass spectrometry (ICP-MS). Herein is presented an overview of recent advances and applications of (ETAAS) for the determination of As, Cd, Cu, Hg and Pb in biological samples drawn from studies over the last decade.     

Slurry sampling and high-resolution continuum source flame atomic absorption spectrometry using secondary lines for the determination of Ca and Mg in dairy products

The present paper proposes a simple and fast analytical procedure for the sequential multi-element determination of Ca and Mg in dairy products employing sampling slurry and high resolution-continuum source flame atomic absorption spectrometry (HR-CS FAAS). Considering the high concentration of these species in these matrices, the analytical measurements were carried out at the secondary lines of 239.856 and 202.852 for Ca and Mg, respectively. The experimental conditions established for the preparation of the slurries during the optimization step were: 2.0 mol L^{− 1} hydrochloric acid, sonication time of 20 min and sample mass of 1.0 g for a slurry volume of 25 mL. Experiments demonstrated that the analytical curves can be established using the external calibration technique employing aqueous standards. The method allows the determination of Ca and Mg with limits of quantification of 0.038 and 0.016 mg g^{− 1}, respectively. The precision was evaluated under reproducibility and repeatability conditions and expressed as relative standard deviation. The results varied from 2.7 to 2.9% (all tests with n = 10) and using a yogurt sample containing Ca and Mg concentrations of 1.40 and 0.13 mg g^{− 1}, respectively.The accuracy was confirmed by the analysis of a certified reference material of non-fat milk powder furnished by the National Institute of Standard and Technology. The proposed method was applied for the determination of Ca and Mg in yogurt, cow milk and milk powder samples. The samples were also analyzed after complete acid digestion and Ca and Mg determination by HR-CS FAAS. No statistical difference was observed between the results obtained by both of the procedures performed.     

A direct solid sampling electrothermal atomic absorption spectrometric method for determination of trace elements in zirconium dioxide

A direct solid sampling electrothermal atomic absorption spectrometric method for determination of Cd, Co, Cr, Cu, Fe, Li, Mn, Ni and Zn in zirconium dioxide has been developed. Using optimised experimental conditions, very effective in-situ analyte/matrix separation was achieved without any chemical modification. After the measurement, the matrix residue could easily be tipped out from the platform. In the determination of Cr, before sampling, the platform bottom was covered with carbon powder. Quantification was performed using calibration curves measured with aqueous standard solutions pipetted onto the matrix residue from a previous sample run. Sample amounts between 0.5 and 40 mg were applied for each analysis cycle. The accuracy was determined by comparison of the results with those obtained by radiochemical neutron activation analysis and by electrothermal atomic absorption spectrometry using liquid sampling of digests and slurry sampling. For the nine elements assayed, the limits of detection achievable by this method are between 0.06 ng g^–1 (Cd) and 2.3 ng g^–1 (Fe).Dedicated to the memory of Wilhelm Fresenius     

Determination of tin and titanium in soils, sediments and sludges using electrothermal atomic absorption spectrometry with slurry sample introduction

Fast-heating programmes for determining titanium and tin in soils, sediments and sludges using electrothermal atomic absorption spectrometry (ETAAS) with slurry sampling are developed. For titanium determination, suspensions are prepared by weighing 5-40 mg of sample and adding 25 ml of a solution containing 50% (v/v) concentrated hydrofluoric acid. For tin determination, suspensions are prepared by weighing up to 300 mg of sample and then adding 1 ml of a solution containing 25% (v/v) concentrated hydrofluoric acid. Palladium (30 μg) and ammonium dihydrogen phosphate (7% w/v) are used as matrix modifiers for titanium and tin, respectively. Prior mild heating in a microwave oven is recommended for titanium determination. Calibration is carried out using aqueous standards. The tin and titanium contents of a number of samples obtained by using the slurry approach agree with those obtained by means of a procedure based on the total dissolution of the samples using microwave oven digestion. The reliability of the procedures is also confirmed by analysing several certified reference materials.     

Reduction of interferences in graphite furnace atomic absorption spectrometry by multiple linear regression modelling

The multivariate effects of Na, K, Mg and Ca as nitrates on the electrothermal atomisation of manganese, cadmium and iron were studied by multiple linear regression modelling. Since the models proved to efficiently predict the effects of the considered matrix elements in a wide range of concentrations, they were applied to correct the interferences occurring in the determination of trace elements in seawater after pre-concentration of the analytes. In order to obtain a statistically significant number of samples, a large volume of the certified seawater reference materials CASS-3 and NASS-3 was treated with Chelex-100 resin; then, the chelating resin was separated from the solution, divided into several sub-samples, each of them was eluted with nitric acid and analysed by electrothermal atomic absorption spectrometry (for trace element determinations) and inductively coupled plasma optical emission spectrometry (for matrix element determinations). To minimise any other systematic error besides that due to matrix effects, accuracy of the pre-concentration step and contamination levels of the procedure were checked by inductively coupled plasma mass spectrometric measurements. Analytical results obtained by applying the multiple linear regression models were compared with those obtained with other calibration methods, such as external calibration using acid-based standards, external calibration using matrix-matched standards and the analyte addition technique. Empirical models proved to efficiently reduce interferences occurring in the analysis of real samples, allowing an improvement of accuracy better than for other calibration methods.     

Determination of manganese in brain samples by slurry sampling graphite furnace atomic absorption spectrometry

A simple procedure for the determination of manganese in different sections of human brain samples by graphite furnace atomic absorption spectrometry has been developed. Brain sections included cerebellum, hypothalamus, frontal cortex, vermix and encephalic trunk. Two sample preparation procedures were evaluated, namely, slurry sampling and microwave-assisted acid digestion. Brain slurries (2% w/v) could be prepared in distilled, de-ionized water, with good stability for up to 30 min. Brain samples were also digested in a domestic microwave oven using 5 ml of concentrated HNO₃. A mixed palladium+magnesium nitrate chemical modifier was used for thermal stabilization of the analyte in the electrothermal atomizer up to pyrolysis temperatures of 1300 °C, irrespective of the matrix. Quantitation of manganese was conducted in both cases by means of aqueous standards calibration. The detection limits were 0.3 and 0.4 ng ml⁻¹ for the slurry and the digested samples, respectively. The accuracy of the procedure was checked by comparing the results obtained in the analysis of slurries and digested brain samples, and by analysis of the NIST Bovine Liver standard reference material (SRM 1577a). The ease of slurry preparation, together with the conventional set of analytical and instrumental conditions selected for the determination of manganese make such methodology suitable for routine clinical applications.     

Determination of sodium, potassium, calcium, magnesium, zinc, and iron in emulsified egg samples by flame atomic absorption spectrometry

In this study, oil-in-water formulations were optimized to determine sodium, potassium, calcium, magnesium, zinc, and iron in emulsified egg samples by flame atomic absorption spectrometry (FAAS). This method is simpler and requires fewer reagents when compared with other sample pre-treatment procedures and allows the calibration to be carried out using aqueous standards. Different oily phases such as corn oil, decyl oleate and octyl stearate were tested, as well as Tween 80, Triton X-100 and Triton 114 were analyzed as surfactants. The optimum type and proportion of formulations were determined and their use depended on the element studied. The emulsion preparation was performed by a conventional method that involves mixing both phases at 60 °C by magnetic stirring and phase inversion to change the water-to-oil ratio by increasing the volume of the surfactant-water external phase and correspondingly decreasing the volume of internal phase. The accuracy of the method was further confirmed by determining the metals in a whole egg powder CRM and recoveries ranged from 97.5% for Mg to 102.2% for Na, with relative standard deviations lower than 2.3%. The precision of the procedures was determined through repeatability (intra-day precision) and intermediate precision (inter-day). The repeatability presented RSD values lower than 4.2%. The intermediate precision was evaluated using the RSD and F-test. The RSD values to intermediate precision was lower than 5.3% and the computed F-values were lower than tabulated F-values, indicating no significant difference between the results obtained on different days. The proposed method including, sample emulsification for subsequent metal determination for FAAS, has proved to be sensitive, reproducible, simple and economical.     

Vapor phase matrix extraction of high purity di-boron trioxide and trace analysis using electrothermal AAS

A method has been developed for the determination of Al, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Sb, Sn and Zn at trace levels in high purity di-boron trioxide using ETAAS. The boron trioxide matrix was eliminated as trimethyl borate ester in a multiplex vapor phase matrix extraction (MVPME) device using a mixture of glycerol and methanol. In this MVPME device, in situ reagent purification, sample digestion and simultaneous matrix elimination were achieved by a single step in closed condition, which in combined effect reduce the process blanks. The matrix extraction procedure allows determination of trace elemental impurities by electrothermal atomic absorption spectrometry (ETAAS) with fast furnace analysis (without an ashing step and modifier) and calibration against aqueous standards. The performance and accuracy of the vapor phase matrix elimination technique are compared to those of suprapur grade hydrofluoric acid solution in two ways; (i) matrix separation as BF₃ over hot plate and (ii) in situ matrix elimination inside graphite furnaces. The method detection limits calculated from blank samples are in the range of 0.5 (Ni) and 2.9 (Al) ng g⁻¹. Thus the MVPME-based sample preparation approach is well suited for the trace analysis of high purity di-boron trioxide used in microelectronics applications.