Statistical Evaluation of Bioavailability of Metals to Grapes Growing in Contaminated Vineyard Soils using Single Extractants

This article describes the statistical evaluation of concentrations of Cd, Co, Cr, Cu, Fe, Mn. Ni, Pb. Zn, Ca. and Mg metals determined in twenty-two grape and corresponding soil samples from around a zinc smelter in Kayseri. Turkey. In the analyses of soil samples. three different extraetants. 0.1 M HCl in 0.025 M H₂SO₄, 1 M NH₄OAc, and aqua regia (1HNO₃ + 3HCl), were used to extract and determine the leachable metal contents which are acid soluble, exchangeable, and total. respectively. A mixture of HNO₃ and HCIO₄ was used to dissolve grape samples. The determinations of metals were performed by flame atomic absorption spectrometry (FAAS). The analytical data were evaluated by using principal component analysis (PCA). hierarchial cluster analysis (HCA), correlation analysis (CA), and enrichment factors (EF). The relationship between the grapemetal and soil-extractable-metal concentrations was examined to evaluate the bioavailability of metals in soil to grape samples. As a consequence of statistical evaluations. Cd, Pb, Zn. Mn. and Fe labile levels in soil were related to total grape-metal contents indicating the method’s suitability for bioavailability studies in polluted soil–plant systems.     

The effect of sample preparation on metal determination in soil by FAAS

Different methods for the determination of several metals in soils by flame atomic absorption spectrometry (FAAS) were investigated. Different procedures for total dissolution of soil: I – HF+HClO₄, H₃BO₃, HCl digestion (conventional heating), II – HF+HClO₄, H₃BO₃ digestion followed by fusion with LiBO₂ (conventional heating) and III – HF+HCl+HNO₃, H₃BO₃ digestion (microwave heating), as well as a leaching procedure with HNO₃+HClO₄, HCl were tested and compared. For quality assessment, the certified reference material S-1 soil was used. For most of the investigated metals, the best accuracy and precision were achieved when the procedure I or III were used. The developed procedure was applied to the analysis of soil samples from crude oil refinery and dump of petroleum origin wastes regions.     

The effect of sample preparation on metal determination in soil by FAAS

Different methods for the determination of several metals in soils by flame atomic absorption spectrometry (FAAS) were investigated. Different procedures for total dissolution of soil: I – HF+HClO₄, H₃BO₃, HCl digestion (conventional heating), II – HF+HClO₄, H₃BO₃ digestion followed by fusion with LiBO₂ (conventional heating) and III – HF+HCl+HNO₃, H₃BO₃ digestion (microwave heating), as well as a leaching procedure with HNO₃+HClO₄, HCl were tested and compared. For quality assessment, the certified reference material S-1 soil was used. For most of the investigated metals, the best accuracy and precision were achieved when the procedure I or III were used. The developed procedure was applied to the analysis of soil samples from crude oil refinery and dump of petroleum origin wastes regions. Received: 22 Dezember 1997 / Revised: 9 February 1998 / Accepted: 12 February 1998     

Ultrasound-assisted extraction of gold and silver from environmental samples using different extractants followed by electrothermal-atomic absorption spectrometry

Ultrasound-assisted extraction combined with electrothermal-atomic absorption spectrometry has been applied to the determination of silver and gold at μg g^{− 1} levels in different environmental samples such as soil, sediment, fly ash and industrial sludge. Two different extraction systems have been tried, i.e. acid mixtures (HCl, HF, and HNO₃) and thiourea in diluted H₂SO₄ medium. In both cases, an efficient cup-horn sonoreactor was used as ultrasonic device to accelerate the extraction process. This ultrasonic processor allows the use of any extractant including HF and simultaneous treatment of up to six samples. Recovery ranged from 81% to 107% for silver, and from 91% to 105% for gold. Optimal acid mixtures were 25% v/v HNO₃ + 25% v/v HF for Ag and 25% v/v HNO₃ + 25% v/v HCl for Au. The thiourea method required 0.6% m/v thiourea + 2% v/v H₂SO₄. The latter method was considered advantageous since efficient Au and Ag extractions were obtained in a short time, and moreover, wastes generated were less harmful to the environment. Limits of detection for Ag and Au were 0.012 and 0.050 μg g^{− 1}, respectively. Repeatability expressed as relative standard deviation ranged from 2 to 10% for both metals. Both extraction methods were applied to the determination of Au and Ag in sediments and soils located at different sampling points from Galicia (Spain).     

Critical comparison of wet and dry digestion procedures for trace metal analysis of meat and fish tissues

The efficiency of four methods of digestion was evaluated for trace metal analysis of pork meat and carp fish tissues. Two methods of dry and two methods of wet ashing were compared in terms of calculated variances. Mixtures of HCl+HNO₃ were applied for wet ashing of the samples at 100 °C, while dry ashing with or without H₂SO₄ at 450 °C were the alternative methods. The digests were subsequently analysed for Pb, Cd, Cu and Zn by graphite furnace atomic absorption spectrometry. Analysis of variance and Student's t-test were performed separately for meat and fish analytical results. Wet digestion with a (1+1) mixture of HCl+HNO₃ has given better recovery and repeatability for almost all metals than a (9+1) mixture of HCl+HNO₃. Also between the dry ashing methods, the use of H₂SO₄ has given better results than ashing of the tissues without H₂SO₄.     

Analytical evaluation of a cup-horn sonoreactor used for ultrasound-assisted extraction of trace metals from troublesome matrices

In this work, a sample preparation method based on ultrasound-assisted extraction of trace metals from a variety of biological and environmental matrices using a cup-horn sonoreactor is described. Diluted acids (HNO₃, HCl and HF) and oxidants (H₂O₂) were tried for extraction, the extracts being directly analyzed by electrothermal-atomic absorption spectrometry. The cup-horn sonoreactor combines the advantages of probe and bath sonicators, allowing a variety of conditions to be used for metal extraction from troublesome matrices. This system facilitates the use of HF to destroy the silicate lattice, application of simultaneous treatments of up to six samples and short treatment times. Quantitative metal recoveries are achieved from different matrices (animal and vegetal tissues, soil, sediment, fly ash, sewage sludge) under a set of extraction conditions ranging from the use of 3 min sonication time and 3% volume/volume HNO₃ for some animal tissues to 40 min sonication time along with 5% volume/volume HNO₃ + 20% volume/volume HF for sediment. Vegetal matter required the use of 5% volume/volume HNO₃ + 5% volume/volume HF for extraction of some elements.     

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.     

Determination of trace metals in Nile River and ground water by differential pulse stripping voltammetry

The determination of trace metals in river water and ground water by DPSV is seriously disturbed by the presence of organic complexes. The influence of these substances can be eliminated by acidification of the samples with acids. Cd, Pb and Cu were determined at pH 1.1 (HNO₃ medium) and Zn, Cd, Pb and Cu at pH 2 (HCl medium), in both the Nile river and ground water. Zn was determined at pH 3.5 in HCl and pH 4.5 in HNO₃, after neutralizing the samples with NH₃/NH₄Cl buffer. Manganese could then be determined, after further addition of ammoniacal buffer solution up to pH 7.5 and 8.5. Ni and Co were determined in the adsorptive mode after formation of dimethylglyoximates at pH 9.2. The effect of pH on the stripping peaks of manganese was studied. Good agreement was observed between DPSV and AAS results for Zn, Cd, Pb, Cu and Mn, but the concentrations of Ni and Co were below the detection limits for AAS. Good agreement was obtained between DPSV results in HCl and HNO₃ for Ni and Co. The results indicate that decomposition of organic complexes by acidification with HNO₃ is better than in the case with HCl for Zn, Pb, Cu, Ni and Co, but HCl is better than HNO₃ for Cd and Mn.     

Optimization studies for reliable trace metal analysis in sediments by atomic absorption spectrometric methods

Summary Sediments act as traps for metals introduced into the aquatic environment. Studies on the total metal contents have been performed with sediments from rivers, lakes, estuaries and coastal zones. The sediments were decomposed under pressure with a 31 mixture of HNO₃/HCl. The determinations were performed by atomic absorption spectrometry in appropriate specific modes (flame, graphite furnace, cold vapour mode, hydride system). The methods were optimized and verified with regard to precision and accuracy for the determination of 12 metals or metalloids by the use of some now available Control and Reference Materials.

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Optimierungsstudien zur richtigen Metall-Spurenanalyse in Sedimenten mittels atomabsorptionsspektrometrischer Methoden

Zusammenfassung Sedimente speichern Metalle, die in die aquatische Umwelt eingebracht werden. Untersuchungen über die Metall-Totalgehalte wurden durchgeführt mit Fluß-, See-, Ästuar- und Küstensedimenten. Die Sedimente wurden einem Druckaufschluß mit einem 31-Gemisch von HNO₃/HCl unterworfen. Die Bestimmungen der Spurenmetalle erfolgten anschließend mit der Atomabsorptionsspektrometrie unter Anwendung geeigneter, spezifischer Techniken (Flamme, Graphitrohrküvette, Kaltdampfverfahren, Hydridsystem). Die Methoden wurden optimiert und bezüglich Präzision und Richtigkeit der Bestimmung von 12 Metallen oder Metalloiden verifiziert durch den Einsatz einiger jetzt verfügbarer Kontroll- und Referenzmaterialien.

     

Determination of nitrite with a nano-gold modified glassy carbon electrode by cyclic voltammetry

Abstract

Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) was employed to determine the concentration of rare earth elements (REEs) in plants and soils. Sample preparation and analytical conditions were investigated to set up a simple routine procedure for measuring rare earth elements. For prompt sample decomposition, a microwave digestion technique was successfully used with an acid mixture of HCl+HNO₃+HF. Detection limits, reproducibility, accuracy and possible interference were also studied. ICP-MS provided extremely low detection limits for REEs (0.6–6ng/l). Precision was typically better than 6% RSD (relative standard deviation) for soil and 10% for plant. The potential of the method was evaluated by analysis of standard reference materials of soils and plants. A good agreement between the experimental results and certified values was observed. The spectroscopic interference of Ba with Eu and light REEs(LREEs, La-Eu) with heavy REEs(HREEs, Gd-Lu) were eliminated by the algebra correction.

The results suggested that REEs in soil samples existed mainly as light REEs, and the same concentration distribution patterns of Oddo-Hakins law were observed, showing negative gradient from La to Lu concentrations. The REE contents in plants were very low, less than 20μg/g and varied with plant species. Apart from rape leaf(Brassica juncea), the REE distribution patterns in other plant leaves were consistent with soils, indicating that these plants generally absorbed REEs from soil without selectivity. Rape leaf showed selective absorption for LREEs, especially for La. The REE concentration distribution in parts of hot pepper(Capsicum annuum) was characteriaed by root>leaf>stem>fruit. The REEs absorbed by hot pepper concentrated mainly in roots and leaves, very little migrated into fruit. Transfer factors(TFs) of REEs in plants were very low. Although the contents of LREEs were relatively more than those of HREEs, no distinct difference of TFs between LREEs and HREEs was observed, meaning that LREEs and HREEs have the same abilities of transportation. However, for rape leaf, the TFs of LREEs were one or two orders of magnitude higher than those of HREEs.     

Multielement characterization of soil samples with ICP-MS for environmental studies

The recovery of trace elements of ecotoxic importance has been studied on certified soil and sediment reference samples after pressurized digestions with HNO₃, HNO₃+HF and HNO₃+HCl+HF mixtures, respectively. The acid digests have been analyzed by ICP-MS. The results indicate that digestion with nitric acid alone is satisfactory for the recovery of As, Cd, Co, Cu and Zn. Cr and Pb showed lower recoveries with HNO₃ alone but addition of HF improved their extraction. With appropriate corrections, ICP-MS can be used for the routine analysis of soils and sediments. These digestion procedures, evaluated based on reference samples, have been used for the trace element characterization of soil samples from the German Environmental Specimen Bank.     

Assessment of three digestion procedures for Zn contents in Pakistani soil by flame atomic absorption spectrometry

Evaluation of three different digestion procedures for accurate determination of elemental concentration in soils was undertaken. The digestion procedures, two leaching and a total dissolution processes were compared for twenty-one soil samples. The soil standard reference materials (SRMs), IAEA Soil-5 and IAEA Soil-7 were analysed for quality control purposes. Zinc (Zn) was analysed using flame atomic absorption spectrometry (FAAS). Precise analysis was accomplished in the SRM and soil samples, which was better than 4.7% for leaching and total dissolution procedure. Compared with the elemental concentration in soil samples, HF–HClO₄ procedure achieved greater accuracy, where as HNO₃–H₂O₂ and HNO₃–H₂SO₄–HCl procedures were comparable with slight variation in a few samples.     

A comparative study of standards for determinations of trace wear metals in jet engine oils

The feasibility of using acid-treated metal powder standards for the determination of trace wear metals in spent jet engine oils is evaluated. The addition of 2:3:3 (v/v/v) HF—HCl—HNO₃ mixture to used lubricating oils did not cause any statistically reliable differences from results obtained with organometallic standards. Two sets of six correlation samples, one set being acid-treated, were analyzed for Cu, Cr, Mg, Fe, Mo and V by flame atomic absorption and flame atomic fluorescence spectrometry against each set of standards.     

Application of Metalfix Chelamine prior to the determination of noble metals by the inductively coupled plasma atomic emission spectrometry

Metalfix Chelamine chelating resins of two different bead sizes (150-300 and 40-80 μm) were examined and compared regarding their application for sorption of Au, Ir, Pd, Pt, Rh and Ru ions from medium of HCl, HNO₃ and mixtures of HCl and HNO₃. The quantitative enrichment of Au, Ir, Pd and Pt was established for the resin of 150-300 μm particle size and for solutions acidified with HCl and HNO₃ (3:1) up to the concentration of 0.50 mol l⁻¹. In the case of Rh and Ru, the uptake of these metals by the resin was lower than 50%. For the elution, solutions of different reagents, i.e. HCl, HNO₃, KCN, KI, KSCN and (NH₂)₂CS, were studied with respect to the complete release of the analytes retained by the resin. In addition, influence of various base metals, i.e. Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn, on the retention of the noble metals was investigated. Under the selected conditions for the retention and elution of Au, Ir, Pd and Pt, the analytical performance of the proposed pre-concentration procedure was evaluated and it was applied to the determination of these noble metals in anodic sludge sample.     

Rapid dissolution of large environmental samples for the determination of fission products

The dissolution of large environmental samples was investigated using a microwave autoclave, capable of digestion conditions of 300 °C and 200 bar, for the application of rapid determination of radionuclides. Six samples of up to 5 g plant material were digested, also eliminating predigestion steps such as ashing and grinding. Batches of forty 1 g samples of plant leaves were also completely digested in 75 minutes. Quantitative recovery of ⁹⁰Sr from 5 g soil samples by leaching with 8M HNO₃ at 200 °C was achieved, whereas ¹³⁷Cs was not completely recovered from the large soil samples using total digestion or leaching (HCl:HNO₃) techniques, but quantitative recovery was achieved using fusion and sinter procedures.     

Selectivity of glassy type mixed zirconium-titanium phosphate toward rare earth metal ions

The selectivity of glass type mixed Zr+Ti phosphates with various Ti contents has been investigated toward rare earth metal ions. The k_d values were determined by radiotracer technique both in HCl and HNO₃ solutions of various concentrations. At room temperature and at pH=4 the following selectivity orders were found: Yb>TmEu>Sm>La (HCl) and Eu>La>Sm>Yb>Tm (HNO₃).     

Electrochemical hydride generation for the determination of hydride forming elements by atomic fluorescence spectrometry

The determinations of As, Bi, Ge, Sb and Se were performed by atomic fluorescence spectrometry following their electrochemical hydride generation. An electrochemical hydride generator based on a screw-thread seal arrangement, working in a continuous flow mode was used. The effects of cathode material, shape and area of material, catholyte, sample flow rate, applied current, catholyte solution concentration and interference of transition metals on signal intensity were studied. Five kinds of materials including lead, graphite, copper, tungsten and platinum with different shapes were tested as cathode materials. The signal obtained from a 3-dimensional electrode was higher than that from a 2-dimensional electrode under the same conditions. The signal intensity of Ge in HNO₃ medium within a narrow concentration range of 0.05–0.10 mol L^{− 1} was stronger than that in other acidic medium, such as HCl and H₂SO₄. However, the signal intensity of Ge was rapidly decreased with HNO₃, HCl and H₂SO₄ concentration increasing, and then reached approximately zero. In general, limits of detection and a precision were improved using a graphite cathode in H₃PO₄ medium. The analysis of the reference materials showed good agreement with the certified values for As, Bi, Ge, Sb and Se. The method was successfully applied in the determination of As, Bi, Ge, Sb and Se in traditional Chinese medicine samples.     

Electrochemical hydride generation for the determination of hydride forming elements by atomic fluorescence spectrometry

The determinations of As, Bi, Ge, Sb and Se were performed by atomic fluorescence spectrometry following their electrochemical hydride generation. An electrochemical hydride generator based on a screw-thread seal arrangement, working in a continuous flow mode was used. The effects of cathode material, shape and area of material, catholyte, sample flow rate, applied current, catholyte solution concentration and interference of transition metals on signal intensity were studied. Five kinds of materials including lead, graphite, copper, tungsten and platinum with different shapes were tested as cathode materials. The signal obtained from a 3-dimensional electrode was higher than that from a 2-dimensional electrode under the same conditions. The signal intensity of Ge in HNO₃ medium within a narrow concentration range of 0.05–0.10 mol L^− 1 was stronger than that in other acidic medium, such as HCl and H₂SO₄. However, the signal intensity of Ge was rapidly decreased with HNO₃, HCl and H₂SO₄ concentration increasing, and then reached approximately zero. In general, limits of detection and a precision were improved using a graphite cathode in H₃PO₄ medium. The analysis of the reference materials showed good agreement with the certified values for As, Bi, Ge, Sb and Se. The method was successfully applied in the determination of As, Bi, Ge, Sb and Se in traditional Chinese medicine samples.     

Study of the suitability of HNO<Subscript>3</Subscript> and HCl as extracting agents of mercury species in soils from cinnabar mines

The aim of this study was to compare the influence and feasibility of two common extracting agents (50% v/v HCl and 50% v/v HNO₃) on the leaching of Hg from soils. The solubility of a number of Hg species in each acid solution was evaluated under selected conditions. Most species were quantitatively dissolved in both acids with the exception of HgS. The application of both acid solutions to a soil sample from the Almaden mining area provided different recoveries of Hg: about 5% in 50% v/v HNO₃ and 50% in 50% v/v HCl. The following experiments were designed and developed in order to evaluate the matrix influence on HgS solubility and leaching: (1) study of the solubility of HgS in the presence of different potential interfering compounds such as FeCl₃, KCl, KI, Fe₂O₃, CuSO₄, FeSO₄, MnO₂ and NaNO₃; (2) study of the recovery of HgS spiked in soil samples; (3) study of the extraction process in soil samples spiked with the critical interfering compounds. Results showed the existence of a greater matrix influence with the HCl solution, since much higher Hg recoveries were obtained with this reagent. In addition, the presence of nitrates and Mn oxides drastically promotes the solubility of HgS in an HCl solution. On the other hand, halide compounds drastically enhanced the extractability of Hg in the HNO₃ and they must be considered as potential interfering compounds when this acid solution is used as extracting agent. In summary, neither acid is totally free of matrix effects from common soil constituents; conclusions about mercury mobility resulting from the general application of these extraction procedures must therefore be made with caution.     

Digests or extracts?—Some interesting but conflicting results for three widely differing polluted sediment samples

Three sets of samples have been investigated in some detail. One set is from a river polluted by mine workings, containing substantial levels of Fe, Mn,Cu, Zn and Ni with traces of many other metals. The second set consists of typical estuarine sediments contaminated from a wide range of industrial sources, and the third set consists of oily drilling cuttings from the sea bottom in the vicinity of a North Sea oil production platform.These samples have been subjected to treatment 1) with EDTA at two different pH's (extracts) 2) with HNO₃/H₂O₂ 3) with HNO₃/HCl and 4) with HNO₃/HCl/HF (digests). EDTA recoveries, compared toaqua regia digests, are often very reproducible, not dependent on pH, and usually significantly low. Nitric/peroxide andaqua regia digests often give very close results suggesting that these are meaningful values indicating the maximum levels of polluting metals in the sediments. However, the triple acid digest with HF does sometimes give higher values (and reasonable agreement for CRM's such as MESS-1) but with poorer reproducibility.