Optimized determination of iron in grape juice, wines, and other alcoholic beverages by atomic absorption spectrometry

This paper describes a study of the different methods of sample preparation for the determination of iron in grape juice, wines, and other alcoholic beverages by atomic absorption spectrometry with electrothermal atomization; results are also reported for the practical application of these methods to the analysis of commercial samples produced in Spain. The methods examined include dealcoholization and dry and wet mineralization treatment using different acids and/or mixtures of them, both with and without heating. The sensitivity, detection limit, accuracy, precision, and selectivity of each method were established. The best results were obtained for wet mineralization with heated acid (HNO3-H2SO4); the results for table wines had an accuracy of 97.5-101.6%, a relative standard deviation of 3.51%, a detection limit of 19.2 micrograms/L, and a determination limit of 32.0 micrograms/L. The method was also sufficiently sensitive and selective. It was applied to the determination of iron in grape juice, different types of wines, and beverages with high alcoholic content, all of which are produced and widely consumed in Spain. The values obtained ranged from 3.394 +/- 2.15 mg/L for the juice, 2.938 +/- 1.47 mg/L for the white wines, 19.470 +/- 5.43 mg/L for the sweet wines, 0.311 +/- 0.07 mg/L for the brandies, and 0.564 +/- 0.12 mg/L for the anisettes. Thus, the method is useful for routine analysis in the quality control of these beverages.     

Direct determination of Cd, Cu and Pb in wines and grape juices by thermospray flame furnace atomic absorption spectrometry

The applicability of thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) was evaluated for direct determination of Cu, Cd and Pb in wines and grape juices. The developed procedure does not require preliminary acid digestion of the samples. The optimum conditions for determination of Cu, Cd and Pb in wines were studied and the performance was compared to those typically obtained by flame atomic absorption spectrometry (FAAS). A sample volume of 150 microL was introduced into a heated nickel tube at a flow rate of 0.54 mLmin(-1) and 0.14 molL(-1) HNO(3) was used as sample carrier flowing at 2.5 mLmin(-1) for determining all analytes. The effect of ethanol concentrations on Cu, Cd and Pb absorbance signals were studied. All determinations were carried out by adopting optimized conditions and quantification was based on the standard additions method. Limits of detection (LOD) of 12.9, 1.8 and 5.3 microgL(-1) (n=14) for Cu, Cd and Pb, respectively, were obtained for wine samples (3sigma(blank)/slope, n=14). Relative standard deviations (R.S.D., %) of 2.7, 2.1 and 2.6 for Cu, Cd and Pb, were obtained (n=6) for wine samples. The values determined for grape juice samples were similar to these ones. The analytical throughput was 45 determinations h(-1) and accuracy was checked by addition-recovery experiments.     

Solid-phase microextraction for the determination of haloanisoles in wines and other alcoholic beverages using gas chromatography and atomic emission detection

A headspace solid-phase microextraction (HS-SPME) method for the determination of 12 haloanisoles in wine and spirit samples using gas chromatography with atomic emission detection (GC-AED) was developed. The different factors affecting the efficiency of the extraction were carefully optimized. The divinylbenzene/Carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber was the most suitable for preconcentrating the analytes from the headspace of the sample solution. Sample:water dilutions of 3:4 and 1:6 for wines and spirits, respectively, and the use of a mixed bromochloroanisole compound as internal standard allowed sample quantification against external standards prepared in the presence of 5% (v/v) ethanol. Detection limits ranged from 1.2 to 18.5ngL(-1), depending on the compound and the sample analyzed, with a fiber time exposure of 60min at 75 degrees C. The optimized method was successfully applied to different samples, and several of the studied haloanisoles were detected at concentration levels ranging from 10.3ngL(-1) to 1.14ngmL(-1).     

Determination of lithium in wines by atomic absorption spectrometry

Lithium (10–150 ng ml^?1) in wine is determined by atomic absorption spectrometry by direct nebulization and after digestion with mixed acids. The results of methods are similar. Thirty-four wines from various Spanish provinces are analysed.     

Direct determination of selenium in a wild fruit juice by electrothermal atomic absorption spectrometry

A matrix modifier composed of platinum and nickel is proposed for the determination of selenium in a wild fruit juice made from Lantingguo (Vuccinium uliginosam). Five matrix modifiers (copper/nickel, palladium/magnesium, platinum/magnesium, platinum/nickel and platinum/copper) for suppressing the interference effects of seven co-existing elements (potassium, phosphorus, calcium, magnesium, manganese, zinc and iron) in a wild juice were studied and a matrix modifier composed fro;m 10 mug of platinum and 200 mug of nickel was found to give the best performance. Selenium in three juices was determined by electrothermal atomic absorption spectrometry employing the proposed matrix modifier without matrix preseparation. The relative standard deviation was 14% for 0.20 mg l(-1) of selenium. The recoveries were 95-110%. A characteristic mass was 28 pg.     

Monoterpenes in grape juice and wines

The importance of monoterpenes on varietal flavour of wines has been reviewed. These compounds were mainly found linked to sugar moieties in the grape juice and wines, showing no olfactive characteristics. In this way, mechanisms to liberate terpenes were studied, making a comparative study between acidic and enzymic hydrolysis of terpene glycosides. Finally, analytical techniques developed to study these compounds, in both free or glycosidically forms, and also to fractionate glycosidic precursors, have been discussed.     

Determination of lead in wines by hydride generation atomic absorption spectrometry.

The optimization of lead hydride generation in aqueous ethanolic media and the influence on its generation of the wine components, both white and red, have been studied. These interferences were overcome by careful control of the parameters affecting hydride generation and the procedure was applied to the determination of Pb in wines. The method is fast, accurate and sensitive and can be used to quantify 24 ppb of Pb in wines.     

Micelle mediated methodology for the determination of free and bound iron in wines by flame atomic absorption spectrometry

A methodology utilizing the cloud point phenomenon for the determination of free and tannin-bound iron in wines is presented. The method employs precipitation of the tannins and other phenolic and insoluble compounds in the micelles of a non-ionic surfactant mixture (TX-100 and TX-45) upon increase of the solution temperature, which are subsequently separated from the initial solution by centrifugation. The surfactant-rich-phase containing the tannins and the insoluble iron fraction is directly aspirated into the nebulizer of a flame atomic absorption spectrometer after its uptake with a methanolic solution of HNO₃. The supernatant is submitted to the same cloud point extraction procedure for the determination of free iron species in the presence of a chelating agent, ammonium pyrrolidine dithiocarbamate (APDC), in order to form water-insoluble complexes with free iron. The complexes are extracted in the micelles and directly analyzed after they are diluted in a methanolic solution as described above. The total content of iron was also determined by conventional methods for comparison, yielding satisfactory results.The calibration graph was rectilinear up to 0.35 mg l⁻¹ Fe, with detection limits of 0.02 mg l⁻¹ with a relative standard deviation of 2.4%. The method was successfully applied to red and white wines.     

The determination of gallium by atomic absorption spectrometry

The use of a nitrous oxide-acetylene flame for the determination of gallium by atomic absorption spectrometry was compared with the use of air-acetylene flames. The nitrous oxide method provided higher sensitivity and was much less sensitive to acid and base composition and to diverse added salts. Significant matrix and background effects, which occurred when gallium was determined in ore solutions with the air-acetylene flame, were eliminated with the nitrous oxideacetylene flame.     

Indirect determination of perchlorate by atomic absorption spectrometry

A liquid-liquid extraction and determination of perchlorate by atomic absorption spectrometry is described. The method involves extraction of perchlorate with the Schiffs base complex [Co(BPTC)₂]⁺, where BPTC = 2-benzoyl pyridine thiosemicarbazone, in methyl isobutyl ketone in acidic medium and subsequent analysis of cobalt in flame AAS, hence indirectly for perchlorate. The extraction efficiency is 98%. The calibration graph was found to be linear for 1.0–11.4 g ClO ₄ ^– per ml of solvent, and the limit of detection is 30 ng ml^–1. The present method is free from interference of large number of foreign ions. The method has been applied for determination of perchlorate in human blood serum samples spiked with perchlorate, urine and commercial potassium chlorate sample.     

Indirect determination of pilocarpine by atomic absorption spectrometry

Atomic absorption spectroscopic (AAS) method for microdetermination of pilocarpine alkaloid has been developed. The procedure is based upon the measurement of mercuric content of pilocarpine complex. The experimental conditions as well as the molar ratio were thoroughly studied. The percentage recovery of pilocarpine was found to be (99.15 ± 0.79). The proposed method was applied on pharmaceutical formulations and the results were satisfactory and in good agreement with that given by the official one.     

Indirect determination of vanadium by atomic absorption spectrometry

An indirect method for the determination of vanadium as vanadate by atomic absorption spectrometry is described. In neutral medium, vanadate forms a stable ion-association complex with copper (II) and biguanide, which is extractable into butanol with an efficiency higher than 99%. The copper content in the extract (and hence indirectly VO^?₃) is determined by aspirating it directly into an acetylene flame. The calibration graph is linear up to 3.4 μg ml^?1 of VO^?₃. The limit of detection is 16 ng ml^?1. Only chromium interferes.     

Ultra-trace determination of Pb(II) and Cd(II) in drinking water and alcoholic beverages using homogeneous liquid-liquid extraction followed by flame atomic absorption spectrometry

The determination of Pb(II) and Cd(II) in different sample matrices, including drinking water, distilled spirits and fruit wine, was carried out by flame atomic absorption spectrometry (FAAS) after pre-concentration using homogeneous liquid-liquid extraction (HLLE). First, the HLLE method was optimised with lead diethyldithiocarbamate (Pb-DDTC) complex which was extracted with a perfluorooctanoate anion (PFOA^?) dissolved in lithium hydroxide under acidic conditions. The optimum extraction conditions, using 0.01 M DDTC, 0.05 M PFOA^?, 3 M HCl and 1 mL of 30 vol. % acetone, were obtained. The Pb-DDTC complex in the nitric acid digest of the samples (50–150 mL) was extracted quantitatively into a drop of 100 μL of sediment phase. The sediment phase dissolved in 1 vol. % HNO₃ with at least 3–5 mL of the final volume was then determined by FAAS, affording a pre-concentration factor of 10–50. Hence, the HLLE method afforded an increase in both sensitivity and selectivity for the metal determination by conventional FAAS, resulting in ultra-trace level detection of Pb(II) in all samples analysed (drinking water, 9.2–23 ng mL^?1; distilled spirits, 23–50 ng mL^?1; fruit wine, 24–53 ng mL^?1). In addition, the proposed method could successfully be applied to Cd(II) determination in these samples.     

间接原子吸收法测定乳酸环丙沙星

研究了在弱酸性介质中，乳酸环丙沙星与雷氏盐定量生成缔合物的反应条件，以及通过原子吸收法测定沉淀中Cr的含量而间接测定乳酸环丙沙星含量的分析方法。线性范围在5－40mg/L，相对标准偏差为2．5％，回收率在98％－101％之间。     

The determination of manganese in urine by atomic absorption spectrometry

Urine samples were digested with a mixture of nitric, sulfuric, and perchloric acids containing molybdate as catalyst. A two-point standard addition technique involved extracts of buffered, digested aliquots containing 10- and 20-p.p.b. manganese(II) in the aqueous phase. The extraction system was MIBK-cupferron. Of the substances tested only bismuth, antimony, and thallium interfered. From the same subject, five morning urine samples averaged 3.0 p.p.b. of manganese with a range of 2.0–4.2 p.p.b.; the average deviation was 0.6 p.p.b.     

The determination of lead in petrol by atomic absorption spectrometry

The lead compounds are extracted into aqueous iodine monochloride, converted to lead nitrate by digestion with nitric acid, and determined by atomic absorption spectrometry against aqueous lead nitrate standards. The procedure is accurate, precise and rapid.     

Indirect flow-injection determination of methadone by atomic absorption spectrometry

A simple continuous redox flow system coupled on-line with an atomic absorption spectrometer for the determination of methadone at the ng ml^?1 level is described. It is based on the reduction of the keto group of the analyte in a camium or zinc microcolumn and determination of the metal ions formed. The drug can be determined in the range 5–50 ng ml^?1 with a relative standard deviation between 1.8 and 2.5% at a sampling frequency of 150 h^?1. The selectivity of the method allows the analyte to be determined in the presence of other drugs.     

The determination of selenium by atom-trapping atomic absorption spectrometry

The application of atom-trapping atomic absorption spectrometry to the determination of selenium has been studied in detail. The optimum experimental parameters were established and the interference of major elements on the determination of selenium was studied using collection on a cold silica tube. The atom-trapping atomic absorption technique gives a detection limit of 0.03 ppm after 2-min collection on silica in an air—acetylene flame. This compares with ca. 1 ppm by the conventional absorption technique at the same 196.1-nm line. Methods to minimize interferences were examined, including the use of a double tube arrangement, an aluminium oxide-coated silica tube and ion-exchange separation. A combination of combustion in an oxygen flask and collection from an air—acetylene flame on the aluminium oxide-coated silica tube yielded satisfactory results in the analysis of four plant tissue samples.     

The determination of sulphate in fertilizers by atomic absorption spectrometry

Methods are described for the determination of sulphate in superphosphate fertilizers. Barium sulphate precipitated from an acidified EDTA solution is filtered onto a membrane filter and redissolved in ammoniacal EDTA, and the barium equivalent to the sulphate is determined by atomic absorption spectrometry. Alternatively, after precipitation of calcium as oxalate during sample solution preparation, and by following a similar sulphate precipitation technique, excess of barium is determined in the filtrate. No interferences were encountered when a nitrous oxide—acetylene flame was used with a potassium ionization buffer.