Ultrasound-assisted solubilization of trace and minor metals from plant tissue using ethylenediaminetetraacetic acid in alkaline medium

A simplified and fast sample pretreatment method based on ultrasound-assisted solubilization of metals from plant tissue with ethylenediaminetetraacetic acid in alkaline medium is described. Powdered unknown and certified plant samples (particle size < 50 μm) were slurried in the solubilization medium and subjected to high intensity ultrasonication by a probe ultrasonic processor (20 kHz, 100 W). Metal solubilization can be accomplished within 3 min using a 30% vibrational amplitude and 0.1 M EDTA at pH 10, the supernatant obtained upon centrifugation being used for analysis. The method is applied to several food plants with unknown metal contents and certified plant samples such as CRM GBW07605 tea leaves, BCR CRM 61 aquatic moss and BCR CRM 482 lichen, with good trueness and precision. Intensive treatments with concentrated acids involving total matrix decomposition can be avoided. Metal determination (Ca, Cd, Mg, Mn, Pb and Zn) in the alkaline extracts was carried out by flame and electrothermal atomic absorption spectrometry.     

Determination of trace alkaline earth metals in brines using chelation ion chromatography with an iminodiacetic acid bonded silica column

The chromatographic behaviour of alkaline earth metals on iminodiacetic acid bonded silica was studied. It was found that the ionic strength of the eluent greatly affected both retention time and selectivity by controlling the extent to which either simple ion exchange or surface complexation was responsible for retention. With a 0.1 M KNO3 eluent, the retention order was Mg(II), Sr(II), Ca(II) and Ba(II), indicating a strong contribution to retention from ion exchange. However, when using a 1.5 M KNO3 eluent, Ba(II) was found to elute first, indicating complexation to be more dominant under these conditions (pH 4.2). The effect of the ionic strength of the sample was also studied and it was found that by matching the eluent cation with that of the sample matrix, efficient separations of alkaline earth metals in 1.0 M NaCl and KCl brines could be obtained without matrix system peaks. Using post-column reaction with o-cresolphthalein complexone, trace levels of Ca(II) and Mg(II) were determined in medicinal NaCl saline solution and laboratory-grade KCl.     

Atomic absorption spectrometric determination of thirteen minor and trace metals in phosphate rock concentrates

Atomic absorption spectrometric methods are described for the determination of thirteen minor and trace elements in phosphate rock concentrates from Florida (U S.A.), Kola (U.S.S.R.) and Morocco. The techniques employed are atomization of solid or liquid samples in two types of graphite furnace, and conventional atomization in the flame or the cold-vapour cell.     

Determination of total mercury in biological samples using flow injection CVAAS following tissue solubilization in formic acid

Total mercury in biological samples was determined by flow injection (FI) cold vapour atomic absorption spectrometry (CVAAS) following tissue solubilization with formic acid. A mixture of potassium bromide and potassium bromate was used to decompose organomercury compounds prior to their reduction with sodium borohydride. A gold amalgam system was used to achieve lower detection limits when required. National Research Council Canada certified reference materials dogfish liver (DOLT-3), dogfish flesh (DORM-2) and lobster hepatopancreas (TORT-2), as well as oyster tissue (NIST SRM 1566b) and mussel tissue (NIST SRM 2976) were used to assess the accuracy of the method. The method of standard additions provided the most accurate results. Limit of detection (LOD) for Hg in the solid sample of 0.001 and 0.01 μg g⁻¹ were achieved with and without amalgamation, respectively. The precision of measurement for 1.6 ng ml⁻¹ methylmercury was 2.7% using the amalgam system.     

Preconcentration of trace metals from salt solutions using thiuram disulphide as collector

Traces of Fe, Co, Ni, Cu, Zn, Cd and Pb in salt solutions (e.g. KCl, Ca(NO₃)₂, A1₂(SO₄)₃, Cr₂(SO₄)₃, (NH₄)₂SO₄) are determined by flame AAS after preconcentration with thiuram disulphide (TDS) as collector precipitate. The preconcentration recovery is mainly influenced by pH, TDS amount and its aging in the sample solution. Conditions of an optimal preconcentration procedure were elaborated. Detection limits vary from 0.5 ng/ml (for Cd) to 8.3 ng/ml (for Pb) and the relative standard deviation is 2 to 6 %. The accuracy of the results was checked by differential pulse anodic stripping voltammetry and by electrothermal AAS.     

Determination of trace alkaline metals in quartz by flame atomic emission and atomic absorption spectrometry

Flame Atomic Emission Spectrometry (FAES) and Electrothermal Atomizer Atomic Absorption Spectrometry (ETA-AAS) were assessed for the determination of K and Na in quantities of less than 10 μg g⁻¹ in quartz. The advantages of the direct AAS technique (samples were atomized directly in solid form) are described as less time-consuming and do not require extensive sample preparation. The FAES technique was applied as the control method using water standard solutions for calibration. The results obtained by the two methods agree well in the concentration ranges from 0.5 to 20 μg ml⁻¹.     

Microdetermination of naturally occurring nodososide from Cassia nodosa, using chlorauric acid as oxidizing agent in alkaline medium

Nodososide, isolated from the flowers of Cassia nodosa, has been quantitatively determined by oxidizing with chlorauric acid in large excess of alkali. The oxidation reaction between nodososide and chlorauric acid is preceded by alkaline hydrolysis and is completed at 48 equivalence, resulting in the formation of sodium formate and acetate as main products. Maximum error observed was 1.4%. The method is accurate and gives reproducible results.     

Extraction of platinum metals from hydrochloric acid medium with triphenylphosphine solution in 1,2-dichloroethane

Extraction of platinum metals with TPP in 1,2-dichloroethane from hydrochloric acid medium has been examined. At hydrochloric acid concentrations higher than 6M, palladium, platinum and osmium are extracted, whereas at low acidity only palladium is quantitatively extracted. Addition of stannous chloride as labilizing agent makes possible a group separation of platinum metals (except osmium). Possible extraction mechanisms are discussed.     

Sequential extraction of trace metals from sediments

With the aim of harmonizing the methodology associated with the trace metal partitioning in sediments, a group of European researchers proposed a three-step sequential extraction scheme using acetic acid, hydroxylamine hydrochloride and ammonium acetate as extracting agents. The metal content in each extract is mainly determined by AAS or ICP.In this paper, the validation of chromium determination in the extracts by AAS is described. The optimum instrumental conditions and the matrix effects of the different reagents used in the extraction scheme are studied for Cr(III) and Cr(VI) solutions by FAAS and ETAAS techniques. The effect of the concomitant species are also studied in the different extracts. The interfering effects are minimized by means of releaser agent for FAAS.The addition of 1% oxine is recommended for acetic acid and hydroxylamine extracts, whereas for step 3 the use of a releaser agent is not necessary. For ETAAS, the use of a calibration graph with pyrolytically-coated tubes gave satisfactory results.The procedure of analysis is applied to chromium partitioning in two sediments with certified total chromium content and to different sediments from Rio dos Sinos of Brazil.From the results obtained it is recommended to measure chromium contents in steps 1 and 2 by ETAAS and the content of step 3 by FAAS.     

Determination of trace metals in water using x-ray fluorescence spectrometry

A simple, rapid and accurate method for water analysis is proposed. The analytical procedure for the determination of Fe, Mn, Zn, Cu, Cd, As, Pb and Se in water in concentrations as low as a few ppM involves precipitation with a carrier of the metals by diethyldithiocarbamate (DDTC) or 1-(2-pyridylazo)-2-naphthol (PAN) and filitration through a Millipore filter. The precipitates collected on the filter disc are examined by X-ray fluorescence analysis. PAN is excellent for the determination of several metal ions at the ppM level, and DDTC can be used with tartrate as a masking agent if water samples contain large amounts of iron(III).     

Closed-vessel miniaturised microwave-assisted EDTA extraction to determine trace metals in plant materials

The demonstration of an innovative miniaturised closed-vessel microwave-assisted extraction (µMAE) method under the use of EDTA (µMAE-EDTA) for determination of trace metal contents in grassland (Lolio-Cynosuretum) was examined by ICP-OES. The evaluation of the method was done by comparison of the results with another miniaturised closed-vessel microwave HNO₃ method (µMAE-H) and with a macro-scale microwave procedure (MAE-H). Concerning their homogeneity certified plant reference materials (CRMs) were used for validation of the applicability of µMAE-EDTA procedure. For CRMs and 72 real plant samples, no significant differences were found between µMAE-EDTA and MAE-H in the determination of Cd, Co, Cu, Mn, Ni, Pb, and Zn contents. Recovery rates achieved from µMAE-EDTA for CRMs ranged between 100.0–102.6% for the investigated elements. The key characteristics of µMAE-EDTA for determination of trace metal contents in plant samples are: (i) suitability as a high-throughput procedure; (ii) consumption of minimum volume of extracting agent and minimum amount of sample; and (iii) combination of fast, safe and environmentally friendly extraction procedure.     

Preparation of stable colloidal solution of cadmium sulfide CdS using ethylenediaminetetraacetic acid

By the method of chemical condensation a stable aqueous colloidal solution of nanoparticles of cadmium sulfide was obtained. The solution obtained in the daylight had a bright lemon-yellow color. For the temporary stabilization of the solution was used an organic complexone, disodium ethylenediaminetetraacetate (EDTA), that prevented coagulation of colloidal particles up to several months at 4°C. At room temperature, the solution remained stable during a month. The structure and properties of the disperse phase were studied by the X-ray diffraction, optical fluorescence, and electron microscopy. The solid particles size is about 3 nm, they have a disordered close-packed structure with the space group P6mm and possess the photoluminescence color from green to orange depending on the duration of keeping the solution. The size of coagulates was 10 nm, 100 nm, and 1 μm after keeping for 1, 2, and 4 months, respectively.     

Concentration and separation of trace metals with an arsonic acid resin

Macroporeus arsonic acid resins with different pore sizes and surface areas were prepared and the properties compared. One of the resins was used for concentration of trace metal ions from dimineralized water, tap-water, and sea-water. The effect of pH and complexing agents on the recovery of metal ions was studied. A method for separation of uranium(VI) and thorium(IV) from each other and from other metal ions was developed.     

Selected minor and trace elements from water bodies of western Paraguay

Minor and trace elements composition of bottom sediments from water bodies in Western Paraguay have been investigated by XRF techniques to determine their correlation as well as provenance. The analysis of complex spectra was performed by the AXIL software and the quantitative analysis by the QAES software. Analyzed trace elements were the refractory elements Rb, Sr, Y, Zr, Nb, Ba, La, Ce, Pr, Nd, Zr, y and other HFSE as Cr, Ni, Cu, together with Zn. Minor elements were Ti, Mn, Fe which are often to the above refractories related. According to their normalized spidergrams two sets of sediments can be differentiated. Those from Pilcomayo and Verde rivers as well as from km164-Wetland show light rare earth elements (LREE) enrichment, negative Nb and Ti anomalies and no spike at Zr. On the other hand, sediments from Confuso, Aguaray(Jehe), Negro and Montelindo rivers have spidergrams very alike, with strong negative anomalies at Nb, Nd and Ti whereas a positive at Zr. Further, in the former there is a strong correlation of Fe versus the refractory elements; such a correlation does not exist in the latter. The sediments from the Pilcomayo & Verde Rivers and from the km164-Wetland evolved as the sub-Andean/Andean metamorphic/sedimentary materials.     

Decomposability in hydrofluoric acid of the main and some minor and trace minerals of silicate rocks

The decomposability in hydrofluoric acid of a selection of 28 main and some minor and trace minerals of silicate rocks was investigated. 21 minerals were decomposed successfully by heating on the water bath ; the remainder - with the exception of topaz-were found to be decomposable at the higher temperatures of a teflon-lined bomb. The results indicate that hydrofluoric acid alone is more effective as decomposing agent than a mixture containing another mineral acid.     

Calibration possibilities and modifier use in ETV ICP OES determination of trace and minor elements in plant materials

The possibilities for universal calibration based on multi-element aqueous standard solutions and graphite laboratory reference materials (graphite standards) for the electrothermal vaporization inductively coupled plasma optical emission spectrometric (ETV ICP OES) determination of Al, B, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, P, Pb, S, Sr, Ti, V, and Zn in plant materials were investigated. A commercially available state-of-the-art ETV device was coupled with an Echelle ICP spectrometer equipped with a charge-injection-device (CID) camera for spectral detection. The transition area between transport tube and ETV graphite tube and the gas streams for inner gas, bypass gas, and modifier gas were optimized to achieve best transport efficiencies. The influence of four gaseous modifiers (CCl₄, CHCl₃, CCl₂F₂, and C₃H₈) added to the inner gas was studied. Five reference materials (RM P-Alfalfa, Lucerne; NIES CRM No.9 “Sargasso”; CTA-VTL-2 Virginia Tobacco Leaves; NIST SRM 1515 Apple Leaves; IAEA-V-10 Hay Powder) were used for method validation. If certified reference materials are not available, calibration against graphite standards or dried aqueous standard solutions is possible. Three carbonization procedures as sample pretreatment for the plant materials were investigated. Figure Picture of the ETV system (sample changer and graphite-tube furbace) used in this work Presented at the European Symposium on Atomic Spectrometry (ESAS) September 28-October 1, 2008, Weimar, Germany.     

Separation of four platinum metals by anion-exchange in hydrobromic acid medium

Distribution coefficients of Pt, Ir, Pd and Rh in the systems Dowex 1 [Br^?]?HBr plus 0.0035M bromine and Dowex 1 [Br^?]?HBr plus 2% N₂H₄·HCl, were determined with the aid of radioactive tracers by batch equilibration for the resins of nominal cross-linking 2, 4 and 8, respectively. Column experiments showed that Dowex 1X4 should be used for separations because of the favourable dynamics of the column process. Elution conditions for the quantitative separation of both trace and milligram amounts of Ir?Pt, Rh?Pt, Pd?Pt and Ir?Pd?Pt mixtures are given. Some data on the effect of temperature upon the quality of separation are also presented.     

Simultaneous determination of some trace metals in plant materials by energy-dispersive X-ray fluorescence method

Energy dispersive X-ray fluorescence method with chemical preconcentration has been worked out for Mn, Fe, Ni, Cu and Zn determination in plant materials. The analytical procedure involves wet digestion of organic matter, precipitation of metal ions with NaDDTC and the measurement of K emission lines of the elements to be determined. The overall precision of the method ranges from 3 to 7% /one relative S.D./ depending on the element.     

Determination of heavy metals and other trace elements in lake sediments from a sewage treatment plant by neutron activation analysis

Instrumental neutron activation analysis (INAA) was used to determine metals (Ba, Co, Cr, Cs, Fe, Hf, Rb, Sc, Zn), semi-metals (As, Sb), actinides (U, Th) and rare earth elements (La, Ce, Nd, Sm, Eu, Tb, Yb and Lu) in bottom sediments from one of the ponds of the Sewage Treatment Plant (STP) in São Paulo, Brazil. The results obtained were compared with the concentration determined in a soil profile and in a rock sample, in natura, representing the lithologies of the region, and indicated that only As, Cr and Zn can have their origin associated with the residues disposed around the pond.     

Effect of ozone on the corrosion of metals in an acid medium

The corrosion-electrochemical behavior of steels and metals in sulfuric, hydrochloric, and acetic acids in the presence of ozone was studied.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 11, 2004, pp. 1819–1825.Original Russian Text Copyright © 2004 by Tatarchenko.