Simultaneous determination of cadmium and lead in wine by electrothermal atomic absorption spectrometry

A method has been developed for the direct simultaneous determination of Cd and Pb in white and red wine by electrothermal atomic absorption spectrometry (ET-AAS) using a transversely heated graphite tube atomizer (THGA) with longitudinal Zeeman-effect background correction. The thermal behavior of both analytes during pyrolysis and atomization stages were investigated in 0.028 mol l(-1) HNO3 and in 1 + 1 v/v diluted wine using mixtures of Pd(NO3)(2) + Mg(NO3)(2) and NH4H2PO4 + Mg(NO3)(2) as chemical modifiers. With 5 mug Pd + 3 mug Mg as the modifiers and a two-step pyrolysis (10 s at 400 degreesC and 10 s at 600 degreesC), the formation of carbonaceous residues inside the atomizer was avoided. For 20 mul of sample (wine + 0.056 mol l(-1) HNO3, 1 + 1, v/v) dispensed into the graphite tube, analytical curves in the 0.10-1.0 mug l(-1) Cd and 5.0-50 mug l(-1) Pb ranges were established. The characteristic mass was approximately 0.6 pg for Cd and 33 pg for Pb, and the lifetime of the tube was approximately 400 firings. The limits of detection (LOD) based on integrated absorbance (0.03 mug l(-1) for Cd, 0.8 mug l(-1) for Pb) exceeded the requirements of Brazilian Food Regulations (decree #55871 from Health Department), which establish the maximum permissible level for Cd at 200 mug l(-1) and for Pb at 500 mug l(-1). The relative standard deviations (n = 12) were typically < 8% for Cd and < 6% for Pb. The recoveries of Cd and Pb added to wine samples varied from 88 to 107% and 93 to 103%, respectively. The accuracy of the direct determination of Cd and Ph was checked for 10 table wines by comparing the results with those obtained for digested wine using single-element ET-AAS, which were in agreement at the 95% confidence level. (C) 2001 Elsevier B.V. B.V. All rights reserved.

Determination of selenium in nutritionally relevant foods by graphite furnace atomic absorption spectrometry using arsenic as internal standard

A method has been developed for the direct determination of Se in nutritionally relevant foods by graphite furnace atomic absorption spectrometry. Tungsten/rhodium carbide coating on the integrated platform of a transversely heated graphite atomizer or W coating with co-injection of Pd(NO3)(2) were used as a permanent modifiers. Samples and reference solutions were spiked with 500 mu g L-1 As and absorbance variations due to changes in experimental conditions were minimized. For 20 mu L aqueous analytical solutions delivered into the graphite tube, analytical curves in the 5.0-40 mu g L-1 with good linear correlation were established. Pyrolysis and atomization temperatures were evaluated using pyrolysis and atomization curves, respectively. The optimized heating program (temperature, ramp time, hold time) of the graphite tube of the Perkin-Elmer SIMAA 6000 atomic absorption spectrometer was: dry steps (110 degrees C, 5 s, 10 s; 130 degrees C, 15 s, 15 s); air-assisted pyrolysis step (600 degrees C, 20 s, 40 s; 20 degrees C, 1 s, 40 s); pyrolysis step (1300 degrees C, 10 s, 20 s); atomization step (2100 degrees C, 0 s, 4 s); clean step (2550 degrees C, 1 s, 5 s). The method was applied for Se determination in coconut water, coconut milk, soybean milk, cow milk, tomato juice, mango juice, grape juice and drinking water samples and four standard reference materials and results were in agreement at 95% confidence level. The lifetime of the tube was 500 firings and the relative standard deviations of measurements of typical samples containing 25 mu gL(-1) Se were 3.0% and 6.0% (n = 12) with and without internal standardization, respectively. The limits of detection were in the 0.35 mu g L-1-0.7 mu g Se L-1 range. The accuracy of the proposed method was evaluated by an addition-recovery experiment and all recovered values were in the 98-109% range. (c) 2004 Elsevier Ltd. All rights reserved.

The use of bioelectrical impedance to detect excess visceral and subcutaneous fat

objective: To analyze bioelectrical impedance performance in detecting the presence of excess visceral fat and overweight/obesity in young Brazilians and how its values are related with them.Methods: Study sample consisted of 811 adolescents of both genders (11 to 17 years of age). Nutritional status was determined based on triceps skinfold thickness (TSF), relative body fat (bioelectrical impedance), and excess visceral fat as determined by waist circumference. Statistical analysis was performed using means, standard deviations, linear correlation, Student's t test, and ROC curve.Results: Bioelectrical impedance achieved good performance in identifying excess visceral fat associated with overweight/obesity in both genders, and was found to be more specific (male 92.4% and female 93.8%) than sensitive (male 86.1% and female 71.8%).Conclusion: Our findings support the use of bioelectrical impedance to identify the presence of excess visceral and subcutaneous fat in adolescents.

Determination of Cd(II) and Cd-metallothioneins in biological extracts using baker's yeast and inductively coupled plasma optical emission spectrometry

The use of Saccharomyces cerevisiae as a sorbent material to separate Cd(II) and Cd-metallothionein complex (Cd-MT) has been explored. Solid-liquid phase extractions were carried out in batch mode and the main parameters of the process (pH, temperature, time of incubation, amount of biomass and analyte) were evaluated. Under optimized conditions, the yeast quantitatively retain (94 +/- 5%) the Cd(II) while 97 +/- 2% of the Cd-MT remain in the supernatant. on base of the findings of this study, a simple method is proposed to determine Cd(II) and Cd-MT in cytosols extracted from mouse kidney and crab hepatopancreas. Inductively coupled plasma optical emission spectrometry was used to quantify the analytes in solid and liquid phase. Determination of Cd in the solid phase was carried out by introducing a slurry of the yeast (0.0625 g/10 mL) directly to the inductively coupled plasma optical emission spectrometer. Mixed standards solutions, which also have been submitted to the extraction procedure, were used to quantify the analytes in the samples. Thus, matrix effects due to nebulization of the slurry were overcame. Limits of detection (3 sigma) for Cd(II) and Cd-MT were 1.5 and 1.2 mu g L-1, respectively. Relative standard deviations of signals were 4.2% for measurements in the slurry of solid phase and 2.1% for measurements in the liquid phase. Recoveries of the analytes in cytosol samples were between 76 and 114%. The concentrations of Cd(II) (2.4 +/- 0.5 mu g L-1) and Cd-MT (3.0 +/- 0.5 mu g L-1) found by using the proposed approach were close to those found by tangential-flow ultrafiltration technique (2.6 +/- 0.7 mu g L-1 for Cd(II) and 3.7 +/- 1.7 mu g L-1 for Cd-MT).

Morphological characterization of Langmuir-Blodgett films from polyaniline and a ruthenium complex (Rupy): influence of the relative concentration of Rupy

We report on the use of dynamic scale theory and fractal analyses in a study of the growth stages of Langmuir-Blodgett (LB) films of polyaniline and a neutral biphosphinic ruthenium complex, namely mer-[ RuCl3 (dppb)(py)] (dppb = 1,4-bis(diphenylphosphine) buthane, py = pyridine), Rupy. The LB films were deposited onto indium-tin-oxide substrates and characterized with atomic force microscopy. From the granular morphology exhibited by the films one could infer growth processes inside and outside the grains. Growth outside was found to follow the Kardar-Parisi-Zhang model, with fractal dimensions of about 2.7. As one would expect, inside the grains the morphology is close to a Euclidian surface with fractal dimension of about 2.

A RELATIVE COHOMOLOGICAL INVARIANT FOR GROUP PAIRS

We define a cohomological invariant E(G, S, M) where G is a group, S is a non empty family of (not necessarily distinct) subgroups of infinite index in G and M is a F2G-module (F2 is the field of two elements). In this paper we are interested in the special case where the family of subgroups consists of just one subgroup, and M is the F2G-module F2(G/S). The invariant E(G, {S}, F2(G/S)) will be denoted by E(G, S). We study the relations of this invariant with other ends e(G) , e(G, S) and e(G, S), and some results are obtained in the case where G and S have certain properties of duality.

Amperometric differential determination of ascorbic acid in beverages and vitamin C tablets using a flow cell containing an array of gold microelectrodes modified with palladium

A simple and attractive method for quantification of ascorbic acid (AA) in beers, soda, natural juices and commercial vitamin C tablets was achieved by combining Bow injection analysis and amperometric detection. An array of gold microelectrodes electrochemically modified by deposition of palladium was employed as working electrode which was almost unaffected by fouling effects. Ascorbic acid was quantified in beverages and vitamin tablets using amperometric differential measurements. This method is based on three steps involving the flow injection of: 1) the sample plus a standard addition of AA, 2) the pure sample, and 3) the enzymatically-treated sample. The enzymatic treatment was carried out with Cucumis sativus tissue, which is a rich source of ascorbate oxidase, at pH 7. The calibration plots for freshly prepared ascorbic acid standards were very linear in the concentration range of 0.18-1.8 mg L-1 with a relative standard deviation (RSD) < 1%, while for real samples the deviations were between 2.7% to 8.9%.

Relative contributions of beta-cell function and tissue insulin sensitivity to fasting and postglucose-load glycemia

We performed hyperglycemic clamps in 283 nondiabetic Caucasians and, with multiple linear regression, determined the contribution of beta-cell function and tissue insulin sensitivity to variations in glycemia and insulinemia during oral glucose tolerance tests (OGTTs). Impaired glucose tolerance (IGT) subjects had reduced insulin sensitivity(P < .02) and beta-cell function (P < .0001). Normal glucose tolerance (NGT) subjects with first-degree type 2 diabetic relatives had reduced first and second phase insulin secretion (both, P < .05), but normal insulin sensitivity(P = .37). beta-Cell function and insulin sensitivity accounted for one fourth of the variability in glucose tolerance. Fasting plasma glucose in subjects with NGT (n = 185) was a function of both phases of insulin secretion and of insulin sensitivity tall, P < .05), whereas, in IGT subjects (n = 98), it was a function of first phase insulin secretion and insulin sensitivity(P < .01). Two-hour glycemia was a function of second phase secretion and insulin sensitivity (P < .01). Fasting and 2-hour plasma insulin levels were determined by insulin sensitivity land glycemia) in NGT subjects (P < .001), but by second phase secretion in IGT (P < .001). We conclude that beta-cell function is reduced in subjects with IGT; glycemia and insulinemia are not regulated by the same mechanisms in IGT and NGT; insulin sensitivity does not contribute to insulinemia in IGT; family history of diabetes influences beta-cell function, but not insulin sensitivity in Caucasians. Copyright (C) 2000 by W.B. Saunders Company.

Direct determination of Al, As, Cu, Fe, Mn, and Ni in fuel ethanol by simultaneous GFAAS using integrated platforms pretreated with W-Rh permanent modifier together with Pd plus Mg modifier

A method is proposed for the simultaneous determination of Al, As, Cu, Fe, Mn, and Ni in fuel ethanol by electrothermal atomic absorption spectrometry (ETAAS) using W-Rh permanent modifier together with Pd(NO3)(2) + Mg(NO3)(2) conventional modifier. The integrated platform of a transversely heated graphite atomizer (THGA) was treated with tungsten, followed by rhodium, forming a deposit containing 250 mug W + 200 mug Rh. A 500-muL, volume of fuel ethanol was diluted with 500 muL, of 0.14 mol L-1 HNO3 in an autosampler cup of the spectrometer. Then, 20 muL, of the diluted ethanol was introduced into the pretreated graphite platform followed by the introduction of 5 mug Pd(NO3)(2) + 3 mug Mg(NO3)(2). The injection of this modifier was required to improve arsenic and iron recoveries in fuel ethanol. Calibrations were carried out using multi-element reference solutions prepared in diluted ethanol (1 + 1, v/v) acidified to 0. 14 mol L-1 HNO3. The pyrolysis and atomization temperatures of the heating program were 1200degreesC and 2200degreesC, respectively, which were obtained with multielement reference solutions in acidic diluted ethanol (1 + 1, v/v; 0. 14 mol L-1 HNO3). The characteristic masses for the simultaneous determination in ethanol fuel were 78 pg Al, 33 pg As, 10 pg Cu, 14 pg Fe, 7 pg Mn, and 24 pg Ni. The lifetime of the pretreated tube was about 700 firings. The detection limits (D.L.) were 1.9 mug L-1 Al, 2.9 mug L-1 As, 0.57 mug L-1.Cu, 1.3 mug L-1 Fe, 0.40 mug L-1 Mn, and 1.3 mug L-1 Ni. The relative standard deviations (n = 12) were 4%, 4%, 3%, 1.5%, 1.2%, and 2.2% for Al, As, Cu, Fe, Mn, and Ni, respectively. The recoveries of Al, As, Cu, Fe, Mn, and Ni added to the fuel ethanol samples varied from 81% to 95%, 80% to 98%, 97% to 109%, 85% to 107%, 98% to 106% and 97% to 103%, respectively. Accuracy was checked for the Al, As, Cu, Fe, Mn, and Ni determination in 10 samples purchased at a local gas station in Araraquara-SP City, Brazil. A paired t-test showed that at the 95% confidence level the results were in agreement with those obtained by single-element ETAAS.

Determination of the relative contribution of phenolic antioxidants in orange juice by voltammetric methods

The electrochemical oxidation of caffeic, chlorogenic, sinapic, ferulic and p-coumaric acids was investigated by cyclic voltammetry on acetate buffer pH 5.6 on glassy carbon electrode and modified glassy carbon electrode. According to their voltammetric behavior, the antioxidant activity of these phenolic acids was evaluated and the results pointed to the following sequence: caffeic acid (E-a = +0.31 V) > chlorogenic acid (+ 0.38 V) > sinapic acid (+ 0.45 V) > ferulic acid (+ 0.53 V) >p-coumaric acid (+ 0.73 V). The results were confirmed by DPPH test, which evidenced the strongest antiradical activity for compounds possessing the cathecol moiety (caffeic and chlorogenic acids). Linear calibration graphs were obtained for their determination at concentrations from 1 x 10(-4) to 1 x 10(-3) mol L-1. The method was applied to orange juice. Selectivity was illustrated by the analysis of caffeic and chlorogenic acids electrodeposited on a glassy carbon electrode previously modified by electrochemical activation in the presence of ascorbic acid. (C) 2003 Elsevier B.V. All rights reserved.

Determination of fluquinconazole, pyrimethanil, and clofentezine residues in fruits by liquid chromatography with ultraviolet detection

A simple method was developed for the determination of fluquinconazole, pyrimethanil, and clofentezine in whole fruit; peel; and pulp of mango, apple, and papaya. These compounds were extracted from fruit samples with a mixture of ethyl acetate-n-hexane (1 + 1, v/v). An aliquot (2 mL) of the extract was evaporated to near dryness under a stream of nitrogen, and the residue was dissolved with 2 mL methanol. The analysis was performed by means of liquid chromatography with ultraviolet detection at 254 nm using a gradient solvent system. The method was validated with fortified fruit samples at concentration levels of 0.05, 0.10, 0.20, and 0.50 mg/kg. Average recoveries (4-8 replicates) ranged from 80 to 95% with relative standard deviations between 3.5 and 12.7%. Detection limits ranged from 0.03 to 0.05 mg/kg for fruit pulp and 0.03 mg/kg for whole fruit. The quantitation limits ranged from 0.05 to 0.10 mg/kg for fruit pulp and 0.05 mg/kg for whole fruit. The analytical method was applied to fruit samples obtained from local markets.

RELATIVE GROWTH OF THE SPECKLED SWIMMING CRAB ARENAEUS-CRIBRARIUS (LAMARCK, 1818) (BRACHYURA, PORTUNIDAE), NEAR UBATUBA, STATE OF SAO-PAULO, BRAZIL

Arenaeus cribrarius is a mainly tropical crab that occurs in the Western Atlantic Ocean, Brazil being its type-locality. The species ranges from Vinevard Sound, Massachusetts, USA to La Paloma, Uruguay. Information about this species is scarce. The relative growth of A. cribrarius was analyzed, based on some morphometric relations, where the carapace width, excluding lateral spines (CW), was used as an independent variable. A total of 403 specimens (189 males and 214 females), was collected in Ubatuba, State of São Paulo, Brazil, with otter-trawls. The animals were sexed and sorted to maturation phase (juvenile or adult). Some measurements were made: carapace (length and width excluding lateral spines), abdomen (greatest width of the fifth somite in females and the sixth in males) and major chela (greatest length, width and height, dactylus length). This study was made by the application of the power function (y=a.x(b)) which was fitted to the data and the pattern of growth established for each parameter by the ''b''-value (constant of allometry), as positive allometry (b>1), negative allometry (b<1) or isometry (b=1). The morphometric relations of the carapace showed a tendency to isometry. In females, the abdominal width grew in positive allometry, higher in juveniles (b=1.33) than in adults (b=1.18). In this case, an overlap and discontinuity was noticed between the phases over a carapace width range of 55 to 70 mm, where the puberty molt occurs. The majority of relationships showed that the major chela of the males grew in positive allometry, however, the greatest allometric difference between the phases was observed towards the propodus length with 1.09 as juvenile and 1.26 as adult ''b''values. In the males, this variable showed an inflection between the CW range of 45' to 55 mm, where the transition to the maturation phase occurs. The relative growth of this species is similar to those of previously studied species. This indicates, that the propodus length and the abdominal width are the morphometric variables most appropriate to estimate the size of the beginning of the sexual maturity for males and females of this species, respectively.

Relative growth of spider crab Acanthonyx scutiformis (Dana, 1851) (Crustacea, Decapoda, Majidae)

The dimensions of chelar propodus and abdomen were utilized for the morphometric analysis about the relative growth studies of Acanthonyx scutiformis (Dana, 1851). A total of 297 specimens (114 males and 183 females), was collected in Ubatuba, State of São Paulo, Brazil. The animals were sexed and soarted to maturation phase (immature and mature). The following measurements were made: carapace (length and width), abdomen width and chelar propodus (length and height). In this study was applicated the power function (y= a.x(b)), in which the growth was considered positive allometric with isometric with b=1, and negative allometric with b<1. The alometry becomes isometric, when the results concerning immature and mature females and males are analysed. In the Brachyura male chelipeds are utilized in territorial defense, fight, display and courtship and female abdomens are utilized as a chamber that protect and incubate the eggs.