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.     

Determination of mercury in sewage sludge by direct slurry sampling graphite furnace atomic absorption spectrometry

Ultrasonic slurry sampling electrothermal atomic absorption spectrometry (ETAAS) method was elaborated to the determination of Hg in sewage sludge samples with the use of KMnO₄+Pd modifier. The minimum sample amount required for slurry preparation with respect to sample homogeneity was evaluated by weighting masses between 3 and 30 mg directly into the autosampler cups. Validation of the proposed method was performed with the use of Certified Reference Materials of sewage sludge, CRM 007-040 and CRM 144R. Two sewage sludge samples from Poznañ (Poland) city were analysed using the present direct method and a method with sample digestion, resulting in no difference within statistical error.     

Sensitive Method for Trace Determination of Mercury in Wines Using Electrothermal Atomic Absorption Spectrometry

An accurate, simple and precise method for total mercury determination in wines is described. Liquid/liquid extraction of inorganic and organic mercury species directly from untreated wine samples is recommended as a preconcentration procedure prior to determination by electrothermal atomic absorption spectrometry (ETAAS). Ammonium pyrrolidinedithiocarbamate was used as complexation agent. The optimal instrumental parameters for ETAAS measurement of mercury species extracted are proposed. The detection limit for total mercury determination is 0.2µgL^–1. The relative standard deviation is 15–22% for mercury in wine in the range of 0.2–5µgL^–1. The proposed procedure has been successfully applied to the determination of mercury in bottled wines in Bulgaria and Macedonia.     

Flow injection method for the fluorimetric determination of Zn with 8-(benzenesulphonamido) quinoline

The development of a fluorimetric method for the determination of zinc, based on the fluorescence of the zinc-8-(benzenesulphonamido) quinoline chelate in a micellar medium of sodium dodecylsulfate, is reported. The detection limit is 0.2 g l^–1, the working range is 0.5–700 g l^–1, and the sample throughput is 145 h^–1. The method was evaluated for the determination of zinc in food samples.A batch procedure for the simultaneous determination of zinc and cadmium, based on the synchronous and derivative spectra, is also proposed.     

Contribution to the Development of Indirect Atomic Absorption Methods: Application of the Ion Pair 1,10-phenanthroline-mercury(II)-iodide to Iodide Determination in Water and Infant Formulae Samples

A method to determine iodide is developed, based on the formation of an ion pair between 1, 10-phenanthroline, mercury(II) and iodide that can be selectively extracted into IBMK. When the IBMK layer is analyzed by electrothermal atomic absorption spectrometry (ETAAS) for mercury, iodide can be quantified too. Parameters related to the preparation of the ion pair and to the measuring process are studied. Thus, 7.2–7.4 reveals to be the best pH interval to carry out the extraction, and 250 and 1000?°C, respectively, the mineralization and atomization temperatures for mercury determination by ETAAS. The procedure is applied to drinking tap water and commercial infant formulae milk samples. The accuracy of the method has been investigated by means of the analytical recovery for water samples (mean analytical recovery obtained at different concentration levels 98.1%) and by using the certified reference material BCR CRM No 151 Skim Milk Powder (Spiked) for the infant formulae (results within certification interval). The repeatability of the measurements at different concentration levels gave a RSD lower than 10% for both types of samples and the repeatability of the whole procedure for infant formulae shows a RSD of 1.33%. In addition, the limits of detection and quantification were 2.5?μg/L and 8.5?μg/L, respectively, for drinking water and 1.1?μg/g and 3.8?μg/g, respectively, for infant formulae.     

Determination of zinc in gallium arsenide by electrothermal atomic absorption spectrometry with the L''vov platform and matrix modification

Summary A method is described for the determination of zinc in gallium arsenide by ETAAS with platform atomization and matrix modification. The sample is decomposed with nitric and hydrochloric acids, ortho-phosphoric acid is added as a matrix modifier and the diluted solution is injected into the furnace. The optical correction of the nonspecific absorbance is readily achieved by means of a conventional deuterium lamp. Platform atomization improves the peak repeatability by a factor often in comparison with wall atomization. For a 40 mg sample, with reduced argon flow rate in the atomization step, the detection limit is 0.08 g Zn g^–1 (4×10¹⁵ atoms cm^–3). Results obtained by analysing Zn-doped GaAs samples are presented. The relative standard deviation of the overall procedure is 4–8%.

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Bestimmung von Zink in Galliumarsenid durch ETAAS mit L'vov-Plattform und Matrixmodifizierung

     

Determination of Cd, Co, Cr, Cu, Fe, Mn, Ni and Pb in natural waters, alkali and alkaline earth salts by electrothermal atomic absorption spectrometry after preconcentration by column solid phase extraction

Methods are described for the determination of trace and ultra trace amounts of Cd, Co, Cr, Cu, Fe, Mn, Ni and Pb in natural waters, alkali and alkaline earth salts. Separation and preconcentration of trace metals is achieved by a column solid phase extraction procedure using silica gel modified with derivatives of dithiocarbamates — Na-DDTC (sodium diethyldithio-carbamate and HMDTC (ammonium hexamethylene-dithiocarbamate) as column packing material. The influence of the sorbent preparation procedure on the degree of sorption of the trace analytes is examined for different pH values of the sample solution. Isobutylmethyl ketone (IBMK) is proposed as an effective eluent for quantitative elution of retained metal ions. Optimal instrumental parameters for ETAAS determination of preconcentrated elements in organic eluate are presented. Practical application of sorbents in analysis of natural waters and alkali and alkaline earth salts is demonstrated. Proposed preconcentration procedure combined with ETAAS determination of trace analytes allows the determination of 0.04 g l^–1 Cd, 0.1 g l^–1 Cr, Cu, and Mn and 0.3 g l^–1 Co, Fe, Ni and Pb in natural waters and 1.10^–7% Cd, 3.10^–7% Cr and Mn, 7.10^–7% Co, Ni and Pb and 2.10^–6% Cu and Fe in alkali and alkaline earth salts.     

Selenium speciation by coupling vesicle mediated HPLC with off-line ETAAS and on-line focused microwave digestion HG-AAS detection

A novel High Performance Liquid Chromatography (HPLC) method for the separation of selenium species with specific detection by off-line Electrothermal Atomization Atomic Absorption Spectrometry (ETAAS) or on-line focused microwave digestion (MW) Hydride Generation Atomic Absorption Spectrometry (HG-AAS) is described. Vesicular mobile phases of the cationic surfactant didodecyldimethylammonium bromide (DDAB) have been evaluated for the liquid chromatographic separation of inorganic selenium (selenite and selenate) and different selenoaminoacids (selenocystine, selenomethionine and selenoethionine) on a C₁₈ reversed-phase column modified by DDAB molecules. The effects of different parameters (pH, buffer and vesicle concentrations) of the mobile phase on the retention times have been determined. The detection limit for selenium with the proposed off-line HPLC-ETAAS method has been found to be 5 g/L of Se. The detection limit using HPLC-on line focused microwave digestion-HG-AAS has been found to be 1 g/L of Se, with a precision (repeatability) better than ± 5%. The latter proved to be an exceptional on-line real-time chromatographic detector for selenium speciation purposes.     

Slurry Sampling Electrothermal Atomic Absorption Spectrometric Determination of Sodium and Iron Impurities in Optical Crystals of Rubidium Titanyl Phosphate

A simple and rapid slurry sampling electrothermal atomic absorption spectrometric (ETAAS) method was developed for the determination of traces of sodium and iron in single crystals of rubidium titanyl phosphate (RTP). The finely ground crystal material was dispersed in 5mL of 2% (v/v) HNO₃, containing 0.005% (v/v) Triton-X-100. The fast furnace ETAAS analysis was performed using a pyrolytic platform coated with titanium carbide. No matrix interference was registered for either of the analytes in slurries containing 4 to 10mgmL^–1 of RTP, which permitted simple calibration against aqueous solutions. The precision was about 2% RSD. The results for sodium and iron content in RTP were in good agreement with those obtained by flame AAS after sample digestion.     

Evaluation of high-pressure microwave digestion methods for hydride generation atomic absorption spectrometric determination of total selenium and arsenic in sediment

Five closed-vessel microwave digestion methods were compared for the accurate determination of arsenic and selenium in NIST SRM 1645 River Sediment by flow-injection hydride-generation atomic absorption spectrometric methods. The digestion methods using five different acid mixtures (HNO₃/ H₂SO₄, HNO₃/HCl0₄, HNO₃/HCl, HNO₃/HCl/HF, HNO₃/H₂SO₄/HClO₄) were all found to be reliable for the determination of the analytes. Taking into consideration the safety and suitability for the analysis of other metals, the methods based on the use ofaqua regia are recommended for closed vessel microwave digestion with pressure control. Using the quick digestion program, the presence of up to 10% organic content in soil samples did not adversely affect the closed vessel digestion and did not cause the loss of volatile analytes. After digestion, opening the vessel under an inner pressure of below 345 kPa (50 psi) had no effect on the accuracy of the results. The recommended digestion methods (HNO₃/HCl and HNO₃/ HCl/HF) for the reliable determination of arsenic and selenium in different sediment samples were demonstrated. The calculated detection limits (3 _b ) were less than 0.030 g/g and 0.033 g/g for arsenic and selenium, respectively. All analytical results for arsenic and selenium in SRM 1645 River sediment, NRCC BCSS-1 Marine Sediment and NIES CRM Pond Sediment were within or near the certified and reported ranges, with the exception of selenium in NIES CRM No. 2 Pond Sediment.     

Validation of a digestion system using a digester block/cold finger system for the determination of lead in vegetable foods by electrothermal atomic absorption spectrometry

This paper presents the validation of a system for sample digestion using a digester block/cold finger to determine the lead content in vegetables by electrothermal atomic absorption spectrometry (ETAAS). After mineralization, lead contents were determined by ETAAS using a calibration curve based on aqueous standards prepared in 2.60 M nitric acid solutions containing 5 microg ammonium phosphate as chemical modifier. A pyrolysis temperature of 900 degrees C and atomization temperature of 2000 degrees C were used. This method allowed the determination of lead with a characteristic mass of 35 pg; LOD and LOQ of 0.6 and 2 nglg, respectively, were found. The precision was investigated in terms of reproducibility and repeatability. Reproducibility was estimated by analysis of nine different portions of a certified reference material (CRM) of spinach leaves, and the repeatability was determined through the analysis of nine aliquots of the same solution. The reproducibility and repeatability were found to be 4.27 and 2.94% RSD, respectively. The accuracy was confirmed by analysis of whole meal flour, spinach leaves, and orchard leaves CRMs, all furnished by the National Institute of Standards and Technology. Lead contents were measured using the newly developed technique in 11 different potato samples. The lead contents ranged from 12.80 to 69.27 ng/g, with an average value of 28.59 ng/g. These values were in agreement with data reported in the literature.     

Determination of impurities in silicon carbide powders

Summary The analysis of SiC powders used for the production of high-performance ceramics was investigated by combined procedures as well as by a direct technique including atomic spectrometric detection. For the combined chemical procedure, SiC powders (0.25 g) were completely dissolved in a mixture of HNO₃, HF and fuming H₂SO₄ in an autoclave at 240°C within 8 to 20 h. In the final 0.5% w/v solution 13 elements were determined by electrothermal atomic absorption spectrometry (ETAAS) and by inductively coupled plasma atomic emission spectrometry (ICP-AES). With acid decomposition the detection limits for Ca, Cd, Cr, Cu, Mg, Mn and Zn were found to be in the range of 0.1–1 g/g; those for Al, B, Fe, Ni, Ti and V are at the 1–5 g/g level. With a Babingtontype nebulizer 1% slurries of SiC can be directly analyzed by ICP-AES. Calibration was performed by standard addition of aqueous solutions of the elements to be determined and the detection limits are close to those of ETAAS subsequent to pressure decomposition. The required analysis time was reduced from approx. 24 h to 30 min. First results for Ca, Cr, Cu, Mg, Mn, Ti and V as well as the needs to overcome systematic errors of this method, e.g. for Fe, are communicated.Part of this paper was presented at XI. International Symposium of Microtechniques, Wiesbaden, FRG, Aug. 28th–Sept. 1st 1989     

Determination of copper in powdered chocolate samples by slurry-sampling flame atomic-absorption spectrometry

Chocolate is a complex sample with a high content of organic compounds and its analysis generally involves digestion procedures that might include the risk of losses and/or contamination. The determination of copper in chocolate is important because copper compounds are extensively used as fungicides in the farming of cocoa. In this paper, a slurry-sampling flame atomic-absorption spectrometric method is proposed for determination of copper in powdered chocolate samples. Optimization was carried out using univariate methodology involving the variables nature and concentration of the acid solution for slurry preparation, sonication time, and sample mass. The recommended conditions include a sample mass of 0.2 g, 2.0 mol L^–1 hydrochloric acid solution, and a sonication time of 15 min. The calibration curve was prepared using aqueous copper standards in 2.0 mol L^–1 hydrochloric acid. This method allowed determination of copper in chocolate with a detection limit of 0.4 g g^–1 and precision, expressed as relative standard deviation (RSD), of 2.5% (n=10) for a copper content of approximately 30 g g^–1, using a chocolate mass of 0.2 g. The accuracy was confirmed by analyzing the certified reference materials NIST SRM 1568a rice flour and NIES CRM 10-b rice flour. The proposed method was used for determination of copper in three powdered chocolate samples, the copper content of which varied between 26.6 and 31.5 g g^–1. The results showed no significant differences with those obtained after complete digestion, using a t-test for comparison.     

Voltammetric determination of uranium in rocks, soils and sediment by using the catalytic nitrate reduction

The differential pulse voltammetry with a hanging drop mercury electrode using catalytic reduction was used to determine uranium at trace level in rocks, soils and sediments. Some the instrumental parameters were established at optimal conditions. A softer digestion than the normal high pressure method was applied to dissolve the samples. A liquid liquid extraction procedure was used to separate the uranium from matrices. The precision and accuracy of method were evaluated, using certified Soil-7, 312 and 314 samples from IAEA which uranium concentrations lie from 2 to 60g/g. The results are in good agreement with those obtained from other techniques and reference materials.     

Comparison of procedures for correction of matrix interferences in the multi-element analysis of soils by ICP-AES with a CCD detection system

Three procedures, matrix matching, plasma optimisation and single-point standard-addition, have been evaluated to ascertain the best procedure for simultaneous multi-element analysis of industrial soils by ICP-AES with CCD detection. A standard reference material, CRM143 from the Bureau Communautaire de Réference (BCR), has been analysed for Cd, Cr, Cu, Mn, Ni and Pb using the three different matrix interference correction procedures. All three procedures give comparable results which are in good agreement with the BCR values, except for Cr. The single-point standard addition procedure was chosen, on the basis of economy and ease of implementation, to correct for matrix interferences in the determination of Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Sn and V in soil samples collected from an industrial site in England. Concentrations of some of the elements were found to vary greatly with sampling depth. For example, the concentration of Mn, determined using the atomic line at 279.920 nm, increased from 426 ± 3 g/g at a depth of 18–28 cm to 5996 ± 144 g/g at 60–85 cm.     

Ultrasound assisted pseudo-digestion for determination of iron and manganese in citric acid fermentation mediums by electrothermal atomic absorption spectroscopy

A sensitive, simple and rapid method for ultra-trace determination of iron and manganese based on ultrasound assisted pseudodigestion in citric acid fermentation medium samples (beet and cane molasses and raw sugar based mediums) is described. Parameters influencing pseudo-digestion, such as sonication time, sample mass and solvent system were fully optimized. Final solutions obtained upon sonication were analyzed by electrothermal atomic absorption spectrometry (ETAAS). The best conditions for metal pseudo-digestion were as follows: a 25, 30 and 20 min sonication time for beet molasses, cane molasses and raw sugar based medium samples, respectively, 0.7 g sample mass of raw sugar based samples, 0.5 g sample mass of molasses based samples and an extraction mixture of concentrated HNO₃-H₂O₂, in 25 mL of solvent. Analytical results obtained for the two metals by ultrasound assisted pseudo-digestion and conventional wet digestion methods showed a good agreement. This method reduces the time required for all treatments (heating to dryness, cooling and separation) in comparison with conventional wet digestion method. The accuracy of the method was tested by comparing the obtained results with that of conventional wet digestion method.      

Thallium determination in biological materials by radiochemical neutron activation analysis

Summary The determination of thallium in biological materials sometimes cause problems because of the low concentrations of this toxic element. In the present work a method is described which optimizes the parameters affecting the specificity and sensitivity of the radiochemical NAA of thallium in biological samples. High thermal neutron flux, complete decomposition of the organic matter by pressurized digestion, TlI precipitations, liquid extraction of HTlBr₄ and La(OH)₃ scavenging purification are the steps leading to the final homogeneous preparation of Tl₂CrO₄ for -activity measurement. The method was applied to various materials as bovine liver, bone and nails. Good agreement was found between certified and determined thallium concentrations of the reference material CRM 176. The chemical yield comes to about 80%, with low deviations. The sensitivity of the method is about 10^–3 g/g, the standard deviations being in the range of 3.6% (CRM 176), 14% (bovine liver), and 17% (bone). Detailed working instructions are given.     

Electrothermal atomic-absorption determination of Ti in polypropylene in the presence of Al and Mg

A method is proposed for the determination of low concentrations of Ti (< 2 microg g(-1)) in polypropylene in presence of Al and Mg by ETAAS after elimination of the polymer matrix and Si. The optimum instrumental conditions for the determination of Ti are presented. Interferences of Al and Mg in the determination of Ti and some necessary precautions providing better accuracy and precision for the determination of Ti by ETAAS are discussed. A simple procedure for sample preparation is proposed. The detection limit of the method is 12 ng g(-1). The method developed has been applied to real polypropylene samples.     

Determination of selenium in blood serum by ICP-OES including an on-line wet digestion and Se-hydride formation procedure

Summary An analytical procedure for the determination of Se, as well as of other trace elements of clinical interest, in undiluted blood serum samples is presented. This procedure allows the on-line wet ashing of the sample, the hydride generation and the determination of the SeH₂ formed in one step. For this purpose, carrier solution and the injected sample (300 l) were merged with an acid stream (80% H₂SO₄, 12% HClO₄, 8% HNO₃) and passed through a reaction coil heated up to 240°C. To increase the dispersion, the wet digestion was carried out in an ultrasonic field. After trapping of the gas bubbles, 5 mol/l HCl and 0.053 mol/l NaBH₄ solutions were added via T-junctions for Se-hydride generation. The nebulizing system of the ICP-OES was used as gas/liquid separator. The hydride was swept from the spray chamber into the plasma by an argon gas flow with droplets containing other sample constituents. This allows the simultaneous determination of other trace elements of clinical interest, for example Fe, Cu and Zn. The relative detection limit for Se in blood serum was 5 g/l. The quality of the developed procedure was verified in two ways: by measuring SRM Seronorm 116 and by comparing the results for different serum samples with the results obtained with ETAAS. Our results were in good agreement in both cases.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday     

Stopped-flow determination of paracetamol and oxyphenbutazone alone and in mixtures by a differential reaction rate method

Summary A stopped-flow method for the determination of paracetamol and oxyphenbutazone individually and in mixtures with no prior separation is proposed. The method is based on the oxidation of these drugs by the tris(2,2-bipyridine)-iron(III) complex in an acid medium. The reactions are monitored by measuring the rate of appearance of the absorbance of the ferroin complex ( _max=490 nm). The calibration graphs for the individual determination of the two drugs are both linear in the range 5–40 g ml^–1, and the precision (R.S.D.) is about 2%. A linear graphical differential reaction rate method is used for the resolution of mixtures of these drugs at the g ml^–1 level at paracetamol/ oxyphenbutazone ratios from 61 to 12. The proposed method is practically free from interferences.

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Stopped-Flow-Bestimmung von Paracetamol und Oxyphenbutazon allein und in Mischungen mit Hilfe einer kinetisch-photometrischen Methode