Determination of traces of metals in wines from Macedonia

A new method for the determination of chromium and manganese in wines using square-wave voltammetry was developed. For chromium, acrylic acid was chosen as supporting electrolyte and for manganese a mixture of NH₄OH and NH₄Cl. The experimental conditions (initial and final potential, frequency, pulse height, scan increment, scan rate and equilibrium and deposition time) were optimized. Chromium and manganese were determined in the Macedonian wines Krato?ija, Kavadarka, Ohridija and Smederevka. The results agreed well with those obtained by standard UV/VIS spectrophotometry. A statistical treatment of the experimental data was performed using STATGRAPH and MATHCAD software packages.     

Determination of traces of heavy metals in positively charged inorganic colloids in fresh waters

Summary Determination of Traces of Heavy Metals in Positively Charged Inorganic Colloids in Fresh Waters After removal of suspended particulate matter by centrifugation followed by filtration through 0.4-m membrane filters, humic substances and other negatively charged species are sorbed on a small column of macroreticular weak-base anion exchanger DEAE-Sephadex A-25 at fast flow rates. Positively charged inorganic colloids pass through the column and are collected on a 0.015-m membrane filter, which is then ultrasonically treated with 1M nitric acid for the determination of copper, lead and cadmium by differential pulse anodic stripping voltammetry with a static mercury drop electrode. Up to O.2g 1^–1 of the heavy metals are found in positively charged inorganic colloids in river, pond and tap waters.     

Determination of six metals in galician red wines (in northwestern Spain) by capillary electrophoresis

A simple technique is described for the routine simultaneous capillary electrophoretic determination of 6 cations in wine. Separation was achieved on a fused silica capillary column with a UV-Cat-1, alpha-hydroxysobutyric acid and 18-crown-6-ether buffer at pH 4.5 and indirect UV detection at 214 nm. The content of magnesium, sodium, potassium, calcium, manganese, and lithium was determined. The method is quantitative, with recoveries in the 92-102% range, and linear over more than one order of magnitude. The precision is better than 2.5-3.4%. The method is sensible, with detection limits between 0.01 and 0.06 mg/L. Twenty-five red wines with a Certified Brand of Origin from Galicia (north-western Spain) were analyzed by the proposed method. Various wines showed very similar electrophoretic profiles, but significant quantitative differences were observed.     

Determination of allergy-causing metals from coins

Abstract  The majority of everyday items contain metals and their alloys, although many of them may be harmful to human health. Nickel, originating from different sources such as coins, jewelry, or buttons, represents the most common cause of contact allergy dermatitis. Therefore, the aim of this research work was to estimate the possible risk of allergy resulting from skin exposure to coins. In order to obtain information on the amounts of metals released by their daily use, extraction experiments of coins were performed applying an artificial acidic sweat solution during varying extraction periods. After extraction, the mass of the metals released (copper, iron, nickel, and zinc) were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES). The mass rate of Ni extracted per area considerably exceeded the permissible values according to the European norm: 50 times for 50-lipa coins, 80 times for 20-lipa coins, and 110 times for 1-kuna coins. This indicates that nickel-containing coins may represent a serious health hazard, especially to sensitive people. Graphical abstract        

Determination of traces of sulfur in titanium

Summary The sample is dissolved in hydrochloric acid, and the evolved hydrogen sulfide and sulfur dioxide are absorbed in hydrogen peroxide and sodium hydroxide solutions. After complete dissolution, the sulfur in the absorbents and that remaining in the sample solution are converted with a hydriodic acid-formic acid-red phosphorus reducing mixture to hydrogen sulfide, which is absorbed in a zinc acetate solution and determined by the photometric methylene blue method. A few ppm of sulfur in titanium is determined with an error of ± 10% within 4 to 5 hours.

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Zusammenfassung Die Probe wird in Salzsäure gelöst; Schwefelwasserstoff und Schwefeldioxid, die dabei entstehen, werden in Wasserstoffperoxid und Natronlauge absorbiert. Nach vollständiger Auflösung der Probe wird der Schwefel in den Absorptionslösungen und der in der Probelösung enthaltene Schwefel mit Hilfe eines reduzierenden Gemisches aus Jodwasserstoffsäure, Ameisensäure und rotem Phosphor zu Schwefelwasserstoff umgesetzt, der in Zinkacetat absorbiert und als Methylenblau photometrisch gemessen wird. Wenige ppm Schwefel in Titan können in 4 bis 5 Stunden auf ± 10% genau bestimmt werden.

     

Preconcentration and preseparation by electro-deposition of traces of metals

Several theoretical ideas on metal electro-deposition on inert solid electrodes, from solutions oftrace metal ion concentrations, are formulated. The results may be of importance in the application of electro-depositions as analytical preconcentration and preseparation methods.     

Collection of traces of metals on carboxy cellulose cation-exchanger

Carboxy cellulose ("C-cell") is a cation-exchanger based on cellulose and having carboxyl functional groups with pK 3.46 +/- 0.05 at 20 +/- 1 degrees in 1M sodium chloride. The capacity of the exchanger is pH-dependent and the maximum is 0.22 mequiv/g. The capacity is also influenced by the dielectric constant of the medium and by the swelling of the cellulose. C-cell is suitable for the collection of metal ion impurities from aqueous and non-aqueous media.     

Determination of traces of organic fluorine in hydrocarbons

Organic samples containing down to 0.2 ppm of fluorine may be analysed by first converting the organic fluorine into inorganic fluoride by treatment with sodium biphenyl, followed by removal of diverse cations with a cation-exchanger before conductometric titration with lanthanum acetate. Effect of variables, sources of error, and control of reagent blanks are evaluated. For the 0.2-1 ppm organic fluorine level in synthetic blends made from 1-fluoronaphthalene, the relative estimated standard deviation was 7.8%; the mean relative error was 6.2 %. Based on the mean range from duplicate analyses of catalytically processed samples in the C(12) boiling range, at the 1 ppm fluorine level the estimated standard deviation was 0.087 ppm of fluorine. One analyst can determine the fluorine content of about 12 samples in 8 hr.     

Determination of traces of perchlorate in chlorate solutions

Perchlorate present in chlorate solutions is determined gravimetrically as tetraphenylphosphonium perchlorate after destruction of chlorate by addition of hydrochloric acid. Interference of Fe(III) and Cr(III) is prevented by complexing with tarartic acid. Replicate analyses of a sodium chlorate solution containing NaClO(3), NaCl, Na(2)Cr(2)O(7), and 390 ppm NaClO(4) showed 405 ppm NaClO(4) (standard deviation 19 ppm, 12 results).     

Determination of traces of polychlorinated biphenyls in pigments

PCB patterns in a new pigment brand are characterized using GC-MS in the single ion monitoring (SIM) mode. Specific PCBs are then used as external standards for GC-ECD quantification. The following PCB isomers or groups of isomers have to be determined (CB = chlorobiphenyl): total diCBs, 3,3′ diCB, 2,4,5-triCB, 2,2′,4,4′-tetraCB, 2,2′,5,5′-tetraCB, total pentaCB, total hexaCB. Capillary gas chromatography is performed on preseparated solutions (LC) of pigment. An electron caputure detector (ECD) is used for PCB detection and quantification. Calibration is based on the peak areas of external standards and the PCB isomers in the samples, all normalized for internal standard peak areas. Total concentrations of diCB, hexaCB, or pentaCB in a sample are calculated by summing the individual PCB isomer concentrations within the correcsponding elution ranges. Determination limits lie in the range of 1 mg/PCB-isomer/kg pigment.     

Determination of traces of hydrogen in fluoro-organic compounds

The determination of traces of hydrogen in highly fluorinated compounds has been studied. Nitrogen and sulphur in the sample interfere slightly in the pyrolytic method of Miller etal. A straightforward combustion method is proposed in which the sample is burned in oxygen over magnesium oxide at 900° and the water formed is determined either gravimetrically or titrimetrically.     

Determination of lithium in wines by ion chromatography

Lithium ion can be added as a denaturing agent to wines unsuitable for consumption. Accuracy of flame atomic emission spectroscopy with direct nebulization, which is commonly adopted for discovering illegal use of denatured wines, was found to be compromised by Na+, K+, NH4+, Mg2+, Ca2+ and ethanol contained in wine. Ion chromatography (IC) was tested in order to propose an alternative method for legal controls. Experimental design was used to investigate the influence on the accuracy of the determination of Li+ at ppb levels, of Na+ and ethanol content of wine and of fluctuations of eluent flow-rate and composition. It turned out that IC quantification of Li+ can be affected by eluent parameters rather than by wine composition. Since the former can be maintained under the operators control, while the latter cannot, IC was judged preferable to AES for legal controls of Li+ in wines.     

Spectrophotometric extractive titrations for the determination of traces of metals

A modification of extractive titrations, spectrophotometric end-point determination, is proposed. There is no need to discard the organic layer after each extraction because specially constructed titration cells are used. Precise, rapid and selective determination of microgram amounts of single cations, and in favourable cases pairs of cations, is possible.     

Determination of volatile phenols in fino sherry wines

An easy, fast and reliable analytical method is proposed to determine the concentration of volatile phenols (ethyl- and vinylphenols) in fino sherry wines. The technique employed is a single stage sample treatment by solid-phase extraction (SPE) following a simple, fast procedure that enables 12 samples to be extracted simultaneously and requires a small volume sample and little time. Subsequently, the extracts are analyzed by gas chromatography (GC) with flame ionization detection. The method proposed has been applied to the study of fino sherry wines affected by microbial contamination with yeasts of the Brettanomyces genus, and the relationship of these yeasts with the concentrations of volatile phenols present in this wine.     

Simultaneous determination of traces of heavy metals by solid-phase spectrophotometry

A coupling sensitive solid phase spectrophotometric (SPS) procedure for determination of traces of heavy metals (Me-SPS) and multicomponent analysis by multiple linear regressions (MA), a simple methodology for simultaneous determination of metals in mixtures was inaugurated. The Me-SPS procedure is based on sorption of heavy metals on PAN-resin and direct absorbance measurements of colour product Me-PAN sorbed on a solid carrier in a 1-mm cell. This methodology (Me-SPS-MA) was checked by simultaneous determination of metals in synthetic mixtures with different compositions and contents of metals important in pharmaceutical practice: Zn, Pb, Cd, Cu, Co, and Ni. Good agreement between experimental and theoretical amounts of heavy metals is obtained from the recovery test (78.3–110.0%). The proposed method enables determination of particular metal ion at the ng mL⁻¹ level and it was successfully applied to the determination impurities from heavy metal traces in pharmaceutical substances (Cu in ascorbic acid, Pb in glucose, and Zn in insulin). The proposed procedure could be possible contribution to the development of pharmacopoeial methodology for a heavy metals test.     

Flotation of traces of heavy metals coprecipitated with aluminum hydroxide from water and sea water

Microgram quantities of heavy metals in 1-l samples of water and sea water are quantitatively coprecipitated with aluminum hydroxide at pH 9.5. The precipitate is floated with the aid of sodium oleate and small nitrogen bubbles, separated and dissolved in 2 M nitric acid, and the heavy metals are determined by atomic-absorption spectrometry. The method is rapid and applicable to 9 heavy metals at the low p.p.b. level.