Simultaneous determination of Al, As, Cu, Fe, Mn, and Ni in fuel ethanol by GFAAS

A method has been developed for the simultaneous determination of Al, As, Cu, Fe, Mn, and Ni in fuel ethanol by graphite furnace atomic absorption spectrometry (GFAAS) using a transversely heated graphite atomizer (THGA) with longitudinal Zeeman-effect background correction. The thermal behavior of analytes during the pyrolysis and atomization stages using the mixture Pd(NO3)(2) + Mg(NO3)(2) as the chemical modifier was investigated in 0.028 mol L-1 HNO3, 0.14 mol L-1 HNO3, and diluted ethanol (1 + 1, v/v) containing different nitric acid concentrations. With 5 rhog Pd + 3 mug Mg as the modifiers, pyrolysis and atomization temperatures of the heating program of the atomizer were fixed at 1200 C and 2200degreesC respectively. For 20 muL of diluted sample (10 muL ethanol + 10 muL of 0.28 mol L-1 HNO3) dispensed into the graphite tube, analytical curves in the 2.0 - 50 mug L-1 Al, As, Cu, Fe, Mn, Ni ranges were established. The calculated characteristic masses were - 37 pg Al, 73 pg As, 31 pg Cu, 16 pg Fe, 9 pg Mn, and 44 pg Ni, and the lifetime of the tube was around 2 50 firings. The limits of detection (LOD) based on integrated absorbance were 1.2 mug L-1 Al, 2.5 mug L-1 As. 0.22 mug L-1 Cu, 1.6 L-1 Fe 0.20 mug L-1 Mn 1.1 mug L-1 Ni. The relatively standard deviations (n = 12) were less than or equal to 3%, less than or equal to 6%, less than or equal to 2%, less than or equal to 3.4%, less than or equal to 1.3%, and less than or equal to 2% for Al, As, Cu, Fe, Mn, and Ni, respectively, the recoveries of Al, As, Cu, Fe, Mn and Ni added to fuel ethanol samples varied from 77% to 112%, 92% to 114%, 104% to 113%, 73% to 116%, 91% to 122% and 93% to 116%, respectively. Accuracy was checked for Al, As, Cu, Fe, Mn, and Ni determination in 20 samples purchased at local gas stations in Araraquara city, Brazil. A paired t-test showed that the results were in agreement at the 95% confidence level with those obtained by single-element GFAAS.

Evaluation of Ir, Ru, and W as permanent modifiers for the simultaneous determination of As, Bi, Pb, Sb, and Se in natural water by electrothermal atomic absorption spectrometry

Iridium-, Ru-, and W-coated platforms were prepared by thermal treatment of the transversely heated graphite atomizer and investigated for the simultaneous determination of As, Bi, Pb, Sb, and Se in tap water by electrothermal atomic absorption spectrometry. The maximum pyrolysis temperature for As and Bi increased in a modifier sequence W < Ru < Ir. For Pb, Sb, and Se, this sequence was W < Ru, It. Calculated characteristic masses in the presence of It, Ru, and W were 35, 33, and 35 pg for As; 63, 51, and 52 pg for Bi; 50, 32, and 34 pg for Pb; 40, 35, and 31 pg for Sb; and 39, 39, and 93 pg for Se, respectively. Ruthenium was elected as the optimum modifier.Repeatability of the measurements was typically < 6%. Recoveries of As, Bi, Pb, Sb, and Se added to tap water samples varied from 79 to 109%. Accuracy was also checked by analysis of five certified reference materials (CRMs) from the National Institute of Standards and Technology (NIST1640 - Trace Elements in Natural Water; NIST 1643d Trace Elements in Water) and High Purity Standards (Trace Metals in Drinking Water Standards, lots #812708, #591107, and #710710). A paired t-test showed that the results for the CRMs were in agreement at the 95% confidence level with the certified values. The graphite tube lifetime was about 650 firings. multi-element determination is particularly challenging due to the necessity of carefully optimizing compromise conditions.Based on the considerations listed above, the aim of this paper was to evaluate the behavior of Ir, Ru, and W as permanent modifiers for the simultaneous determination of As, Bi, Pb, Sb, and Se. The performance of the proposed procedure was also verified after the ETAAS analysis of tap waters and reference materials.

On-line determination of Sb(III) and total Sb using baker's yeast immobilized on polyurethane foam and hydride generation inductively coupled plasma optical emission spectrometry

The yeast Saccharomyces cerevisiae was immobilized in cubes of polyurethane foam and the ability of this immobilized material to separate Sb(III) and Sb(V) was investigated. A method based on sequential determination of total Sb (after on-line reduction of Sb(V) to Sb(III) with thiourea) and Sb(Ill) (after on-line solid-liquid phase extraction) by hydride generation inductively coupled plasma optical emission spectrometry is proposed. A flow system assembled with solenoid valves was used to manage all stages of the process. The effects of pH, sample loading and elution flow rates on solid-liquid phase extraction of Sb(III) were evaluated. Also, the parameters related to online pre-reduction (reaction coil and flow rates) were optimized. Detection limits of 0.8 and 0.15 mu g L-1 were obtained for total Sb and Sb (III), respectively. The proposed method was applied to the analysis of river water and effluent samples. The results obtained for the determination of total Sb were in agreement with expected values, including the river water Standard Reference Material 1640 certified by the National Institute of Standards and Technology (NIST). Recoveries of Sb(III) and Sb(V) in spiked samples were between 81 19 and I I I 15% when 120 s of sample loading were used. (c) 2006 Elsevier B.V. All rights reserved.

Direct determination of arsenic in sugar by GFAAS with transversely heated graphite atomizer and longitudinal Zeeman-effect background correction

A method has been developed for the direct determination of As in sugar by graphite furnace atomic absorption spectrometry with a transversely heated graphite atomizer (end-capped THGA) and longitudinal Zeeman-effect background correction. The thermal behavior of As during the pyrolysis and atomization steps was investigated in sugar solutions containing 0.2% (v/v) HNO3 using Pd, Ni, and a mixture of Pd + Mg as the chemical modifiers. For a 60-muL sugar solution, an aliquot of 8% (m/v) in 0.2% (v/v)HNO3 was dispensed into a pre-heated graphite tube at 70 degreesC. Linear analytical curves were obtained in the 0.25 - 1.50-mug L-1 As range. Using 5 mug Pd and a first pyrolysis step at 600 degreesC assisted by air during 40 s, the formation of a large amount of carbonaceous residue inside the atomizer was avoided. The characteristic mass was calculated as 24 pg As and the lifetime of the graphite tube was around 280 firings. The limit of detection (L.O.D.) based on integrated absorbance was 0.08 mug L-1 (4.8 pg As) and the typical relative standard deviation (n = 12) was 7% for a sugar solution containing 0.5 mug L-1. Recoveries of As added to sugar samples varied from 86 to 98%. The accuracy was checked in the direct analysis of eight sugar samples. A paired t-test showed that the results were in agreement at the 95% confidence level with those obtained for acid-digested sugar samples by GFAAS.

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.

Solid-phase extraction of sugar cane soot extract for analysis by gas chromatography with flame ionisation and mass spectrometric detection

The incomplete combustion of biomass is one of the most important sources of emissions of organic compounds into the atmosphere, like polycyclic aromatic hydrocarbons (PAHs) which show genotoxic activity. Since environmental samples generally contain interferents and trace amounts of PAHs of interest, concentration and clean-up procedures are usually required prior to the final chromatographic analysis. This paper discusses the performance of Sep-Pak cartridges (silica gel and RP18) on clean-up of sugar cane soot extract. The best results were obtained with a silica Sep-Pak cartridge. The recoveries ranged from 79% (benzo[b]fluoranthene) to 113% (benzo[e]pyrene). (C) 2000 Elsevier B.V. B.V. All rights reserved.

Speciation analysis of Sn(II) and Sn(IV) using baker's yeast and inductively coupled plasma optical emission spectrometry

The use of Saccharomyces cerevisiae as a substrate to selectively retain Sn(II) and Sn(IV) has been investigated. Several factors affecting the retention of the analytes by yeast, such as pH, amount of biomass, temperature and time of contact were evaluated. Based on this study, a method for determination of Sn(II) and Sn(IV) combining inductively coupled plasma optical emission spectrometry (ICP OES) and solid phase extraction using Saccharomyces cerevisiae is proposed. The procedure consists of the selective retention of Sn(IV) by yeast at pH = 2.0 while Sn(II) remains in solution. Determination of tin in the solid phase was easily carried out by submitting a slurry of the yeast (0.5 g/40 mL) directly to ICP OES. The precision of the extraction procedure was characterized by an RSD lower than 4%. The detection limits of tin (3 sigma) in the solid phase and the liquid phase were 1.1 and 0.7 mu g L-1, respectively. The proposed approach was evaluated for determination of Sn(II) and Sn(IV) in spiked river water and real samples of industrial waste water (untreated and treated). For all samples, recoveries of spiked Sn(II) and Sn(IV) were between 85 and 112%.

Simultaneous determination of quinoline and pyridine compounds in gasoline and diesel by differential pulse voltammetry

The presence of trace basic organonitrogen compounds such as quinoline and pyridine in derivative petroleum fuels plays an important role in maintaining the engines of vehicles. However, these substances can contaminate the environment and so must be controlled because most of them are potentially carcinogenic and mutagenic. For these reasons, a reliable and sensitive method was developed for the determination of basic nitrogen compounds in fuel samples such as gasoline and diesel. This method utilizes preconcentration on an ion-exchange resin (Amberlyte IR - 120 H) followed by differential pulse voltammetry (DPV) on a glassy carbon electrode. The electrochemical behavior of quinoline and pyridine as studied by cyclic voltammetry (CV) suggests that their reduction occurs via a reversible electron transfer followed by an irreversible chemical reaction. Very well resolved diffusion-controlled voltammetric peaks were obtained in dimethylformamide (DMF) with tetrabutylammonium tetrafluoroborate (TBAF(4) 0.1 mol L-1) for quinoline (-1.95 V) and pyridine (-2.52 V) vs. Ag vertical bar AgCl vertical bar KClsat reference electrode. The proposed DPV method displayed a good linear response from 0.10 to 300 mg L-1 and a limit of detection (LOD) of 5.05 and 0.25 mu g L-1 for quinoline and pyridine, respectively. Using the method of standard additions, the simultaneous determination of quinoline and pyridine in gasoline samples yielded 25.0 +/- 0.3 and 33.0 +/- 0.7 mg L-1 and in diesel samples yielded 80.3 +/- 0.2 and 131 +/- 0.4 mg L-1, respectively. Spike recoveries were 94.4 +/- 0.3% and 10 +/- 0.5% for quinoline and pyridine, respectively, in the fuel determinations. This proposed method was also compared with UV-vis spectrophotometric measurements. Results obtained for the two methods agreed well based on F and t student's tests.

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).

Direct and simultaneous determination of As, Cu, and Pb in Brazilian sugar cane spirits by graphite furnace AAS using Tungsten permanent modifier with Co-injection of Pd/Mg(NO3)(2)

A method was developed using the multi-element graphite furnace atomic absorption spectrometry technique for the direct and simultaneous determination of As, Cu, and Pb in Brazilian sugar cane spirit (cachaqa) samples. Also employed was the end-capped transversely heated graphite atomizer (THGA) with platforms pre-treated with W permanent modifier and co-injection of Pd/Mg(NO3)(2). Pyrolysis and atomization temperature curves were established in a cachaqa medium (1+1; v/v) containing 0.2% (v/v) HNO3 and spiked with 20 mu g L-1 As and Pb and 200 mu g L-1 Cu. The effect of the concentration of major elements usually present in cachaqa matrices (Ca, Mg, Na, and K) and ethanol on the absorbance of As, Cu, and Pb was investigated. Analytical working solutions of As, Cu, and Pb were prepared in 10% (v/v) ethanol plus 5.0 mg L-1 Ca, Mg, Na, and K. Acidified to 0.2% (v/v) HNO3, these solutions were suitable to build calibration curves by matrix matching. The proposed method was applied to the simultaneous determination of As, Cu, and Pb in commercial sugar cane spirits. The characteristic mass for the simultaneous determination was 16 pg As, 119 pg Cu, and 28 pg Pb. The pretreated tube lifetime was about 450 firings. The limit of detection (LOD) was 0.6 mu g L-1 As, 9.2 mu g L-1 Cu, and 0.3 pig L-1 Pb. The found concentrations varied from 0.81 to 4.28 mu g L-1 As, 0.28 to 3.82 mg L-1 Cu and 0.82 to 518 mu g L-1 Pb. The recoveries of the spiked samples varied from 94-112% (As), 97-111% (Cu), and 95-101% (Pb). The relative standard deviation (n=12) was 6.9%, 7.4%, and 7.7% for As, Cu, and Pb, respectively, present in a sample at 0.87 mu g L-1, 0.81 mg L-1, and 38.9 mu g L-1 concentrations.

Indirect polarographic and cathodic stripping voltammetric determination of cefaclor as an alkaline degradation product

Cefaclor is not reducible at a mercury electrode, but it can be determined polarographically and by cathodic stripping voltammetry as its initial alkaline degradation product which is obtained in high yield by hydrolysis of cefaclor in Britton-Robinson (B-R) buffer pH 10 at 50 degrees C for 30 min (reduction peak at pH 10, -0.70 V). Differential pulse polarographic calibration graphs are linear up to at least 1 x 10(-4) mol l(-1). Recoveries of 93% of the cefaclor (n = 3) were obtained from urine spiked with 38.6 mu g ml(-1) using this polarographic method with 1 ml urine made up to 10 ml with pH 10 buffer. Using cathodic stripping voltammetry and accumulating at a hanging mercury drop electrode at -0.2 V for 30 s, linear calibration graphs were obtained from 0.35 to 40 mu g ml(-1) cefaclor in B-R buffer pH 10. A relative standard deviation of 4.2% (eta = 5) was obtained, and the limit of detection was calculated to be 2.9 ng ml(-1). Direct determination of cefaclor in human urine (1 ml of urine was made up to 10 ml with pH 10 buffer) spiked to 0.39 mu g ml(-1) was made (recovery 98.6%). (C) 1999 Elsevier B.V. B.V. All rights reserved.

Comparative sediment quality assessment in different littoral ecosystems from Spain (Gulf of Cadiz) and Brazil (Santos and Sao Vicente estuarine system)

The goal of this work was to establish comparisons among environmental degradation in different areas from Southern Spain (Gulf of Cadiz) and Brazil (Santos and Sao Vicente estuary), by using principal component analyses (PCA) to integrate sediment toxicity (amphipods mortality) and chemical-physical data (Zn, Cd, Pb; Cu, Ni, Co, V, PCBs, PAHs concentrations, OC and fines contents). The results of PCA extraction of Spanish data showed that Bay of Cadiz, CA-1 did not present contamination or degradation; CA-2 exhibited contamination by PCBs, however it was not related to the amphipods mortality. Ria of Huelva was the most impacted site, showing contamination caused principally by hydrocarbons, in HV-1 and HV-2, but heavy metals were also important contaminants at HV-1, HV-2 and HV-3. Algeciras Bay was considered as not degraded in GR-3 and -4, but in GR-3' high contamination by PAHs was found. In the Brazilian area, the most degraded sediments were found in the stations situated at the inner parts of the estuary (SSV-2, SSV-3, and SSV-4), followed by SSV-6, which is close to the Submarine Sewage Outfall of Santos - SSOS. Sediments from SSV-1 and SSV-5 did not present chemical contamination, organic contamination or significant amphipod mortality. The results, of this investigation showed that both countries present environmental degradation related to PAHs: in Spain, at Ria of Huelva and Gudarranque river's estuary areas; and in Brasil, in the internal portion of the Santos and Sao Vicente estuary. The same situation is found for heavy metals, since all of the identified metals are related to toxicity in the studied areas, with few exceptions (V for both Brazil and Spain, and Cd and Co for Brazilian areas). The contamination by PCBs is more serious for Santos and Sao Vicente estuary than for the investigated areas in Gulf of Cadiz, where such compound did not relate to the toxicity. (c) 2006 Elsevier Ltd. All rights reserved.

Methods for determination of hexachlorobenzene and pentachlorophenol in soil samples

The efficiency of methods for the determination of hexachlorobenzene (HCB) and pentachlorophenol (PCP) in soil samples was evaluated. An on-line method was applied for HCB determination. Soil samples were transferred to chromatographic columns prepacked with alumina. The HCB elution was processed with n-hexane. The PCP was extracted from soil samples with n-hexane-acetone in an ultrasonic bath. After re-extraction with K2CO3 solution PCP was acetylated with acetic anhydride. The pentachlorophenyl acetate derivative was then extracted with n-hexane. The HCB and PCP derivative were analyzed by gas chromatography with electron capture detection (GC-ECD). Mean recoveries obtained from soil samples fortified at levels of 0.5; 4 and 20 ng g(-1) ranged from 91 to 100% for HCB, and for PCP, at levels of 10; 40 and 200 ng g(-1), ranged from 88 to 101%. These results demonstrated the efficiency of the proposed methods. (C) 1998 Elsevier B.V. B.V. All rights reserved.

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.

Reversible intermittent flow-injection determination of mercury in sediments and vinasses by cold vapor atomic absorption spectrometry

A reversible intermittent pow-injection procedure is proposed for the automated determination of mercury in sediments and vinasses by cold vapor atomic absorption spectrometry, CVAAS. Solutions of sample and stannous chloride are carried by two air streams and sequentially injected into the generator/separator chamber in a segmented asynchronous merging zone configuration. The intermittent flow in the forward direction carries the mercury vapor through the flow cell, and in the backward direction, if aspirates the the remaining solution from the vessel to waste. We investigated composition and concentration of reagents, pow rates, commutation times, reactor configuration, and conditions for mercury release. The accuracy was checked by mercury determination in a certified sediment and spiked vinasses and river waters. The system handles about 100 samples per hour (0.50-5.00 mu g L-1), consuming ca. 2.5 mL of sample and 50 mg of SnCl2 per determination; Good recoveries (92-103%) were obtained with spiked samples. Results are precise (RSD <3% for 2.5 mu g Hg L-1, n = 12) and in agreement with values for certified reference material at 95% confidence level. (C) 1999 John Wiley & Sons, Inc.