DNA Adduct Formation in the Lungs and Brain of Rats Exposed to Low Concentrations of [13C2]-Acetaldehyde.

Air pollution is a major environmental risk for human health. Acetaldehyde is present in tobacco smoke and vehicle exhaust. In this study, we show that [13C2]-acetaldehyde induces DNA modification with the formation of isotopically labeled 1, N2-propano-2'-deoxyguanosine adducts in the brain and lungs of rats exposed to concentrations of acetaldehyde found in the atmosphere of megacities. The adduct, with the addition of two molecules of isotopically labeled acetaldehyde [13C4]-1, N2-propano-dGuo, was detected in the lung and brain tissues of exposed rats by micro-HPLC/MS/MS. Structural confirmation of the products was unequivocally performed by nano-LC/ESI+-HRMS3 analyses. DNA modifications induced by acetaldehyde have been regarded as a key factor in the mechanism of mutagenesis and may be involved in the cancer risks associated with air pollution.

Fast production of microfluidic devices by CO2 laser engraving of wax-coated glass slides.

Glass is one of the most convenient materials for the development of microfluidic devices. However, most fabrication protocols require long processing times and expensive facilities. As a convenient alternative, polymeric materials have been extensively used due their lower cost and versatility. Although CO2 laser ablation has been used for fast prototyping on polymeric materials, it cannot be applied to glass devices because the local heating causes thermal stress and results in extensive cracking. A few papers have shown the ablation of channels or thin holes (used as reservoirs) on glass but the process is still far away from yielding functional glass microfluidic devices. To address these shortcomings, this communication describes a simple method to engrave glass-based capillary electrophoresis devices using standard (1 mm-thick) microscope glass slides. The process uses a sacrificial layer of wax as heat sink and enables the development of both channels (with semicircular shape) and pass-through reservoirs. Although microscope images showed some small cracks around the channels (that became irrelevant after sealing the engraved glass layer to PDMS) the proposed strategy is a leap forward in the application of the technology to glass. In order to demonstrate the capabilities of the approach, the separation of dopamine, catechol and uric acid was accomplished in less than 100 s.

Unveiling the structure of polytetraruthenated nickel porphyrin by Raman spectroelectrochemistry.

The structure of polytetraruthenated nickel porphyrin was unveiled for the first time by electrochemistry, Raman spectroelectrochemistry, and a hydroxyl radical trapping assay. The electrocatalytic active material, precipitated on the electrode surface after successive cycling of [NiTPyP{Ru(bipy)2Cl}4](4+) species in strong aqueous alkaline solution (pH 13), was found to be a peroxo-bridged coordination polymer. The electropolymerization process involves hydroxyl radicals (as confirmed by the characteristic set of DMPO/(•)OH adduct EPR peaks) as reaction intermediates, electrocatalytically generated in the 0.80-1.10 V range, that induce the formation of Ni-O-O-Ni coordination polymers, as evidenced by Raman spectroelectrochemistry and molecular modeling studies. The film growth is halted above 1.10 V due to the formation of oxygen gas bubbles.

Graphite-polystyrene composite with enhanced electrochemical and electroanalytical performance.

A new composite electrode (G-PSE) was developed from graphite powder and expanded polystyrene (EPS, Styrofoam) by simply dissolving the foam in chloroform, incorporating the graphite particles under mixing and volatilizing the solvent at 80 °C. The resulting rigid black composite can be softened with acetone and so it can easily be molded to any shape, e.g., into a PTFE tube with an electric contact, to build the electrode. A 75% graphite content (w/w) was found appropriate for preparing the G-PSE with a working potential similar to that of carbon paste electrodes, superior mechanical stability and a much faster response to ferrocyanide, close to reversible and similar to that of the much more expensive glassy carbon electrode. Applications of the G-PSE to dipyrone and paracetamol quantification in pharmaceutical formulations were demonstrated. The results accomplished by flow injection analysis with amperometric detection at the G-PSE were successfully validated against standards methods.

Combined Colorimetric and Electrochemical Measurement Paper-Based Device for Chemometric Proof-of-Concept Analysis of Cocaine Samples.

Cocaine (COC) is one of the most widely consumed illegal drugs around the world. Street COC is commonly adulterated with pharmaceutical compounds that mimic or intensify the COC's sensory effect. Adulteration is performed to increase the profit of criminal organizations and each one has their own way of doing it. Therefore, determining the composition of seized COC samples (chemical profile) provides evidence for the police to track criminal organization networks and their activity patterns. Using filter paper as a substrate, we developed a multiple detection paper-based analytical device (PAD) that combines colorimetric and electrochemical measurements to discriminate COC samples according to adulterant's content. A regular graphite lead modified with a gold film made from Au leaf (graphite/Au) to improve electron transfer was used as a working electrode. Silver and Ag/AgCl were used as auxiliary and reference electrodes, respectively. The colorimetric device was patterned using a laser cutter and coupled to the electrochemical device using a double-sided tape, allowing simultaneous analysis to gather more analytical information about COC samples. Graphite/Au was characterized by scanning and transmission electron microscopies and electrochemical assays. The simultaneous colorimetric and electrochemical analyses combined to principal component analysis improved the analytical characterization of COC trial samples and provided a fast discrimination based on the assembled database.

Integrated instrumental analysis teaching platform with smartphone-operated fluorometer.

The present work describes an Integrated Teaching Tool (ITT) to facilitate the learning process in analytical chemistry. The first instrument integrated in the platform to demonstrate the concept is a wireless, portable fluorometer, produced by 3D printing. The low-cost instrument features a Teensy 3.1 board as the microcontroller, a high-power UV-LED, a secondary filter, a photodiode, and simple auxiliary electronic circuits. Modules of the ITT app were designed to manage the instrument and perform data acquisition remotely from any Android smartphone via Bluetooth, plot and transmit the results. Supporting the educational purpose of the platform, examples of basic concepts about fluorescence as well as technical information about the instrument are also provided to be considered for the app, which also allows instructors to assist and evaluate students through push notifications.

Exhaled breath acetone for predicting cardiac and overall mortality in chronic heart failure patients.

AIMS: Exhaled breath acetone (EBA) has been described as a new biomarker of heart failure (HF) diagnosis. EBA concentration increases according to severity of HF and is associated with poor prognosis, especially in acute decompensated HF. However, there are no data on chronic HF patients. The aim is to evaluate the role of EBA for predicting cardiac and overall mortality in chronic HF patients. METHODS AND RESULTS: In GENIUS-HF cohort, chronic patients were enrolled between August 2012 and December 2014. All patients had left ventricular ejection fraction ≤ 50%, and the diagnosis was established according to Framingham criteria. After consent, patients were submitted to clinical evaluation and exhaled breath collection. EBA identification and quantitative determination were done by spectrophotometry. The clinical characteristics associated with acetone were identified. All participants were followed for 18 months to assess cardiac and overall mortality. Around 700 participants were enrolled in the current analysis. Patients were 55.4 ± 12.2 years old, 67.6% male patients, and 81% New York Heart Association I/II with left ventricular ejection fraction of 32 ± 8.6%. EBA median concentration was 0.6 (0.3-1.2) ug/L. Acetone levels increased with the number of symptoms of HF and were associated with right HF signs/symptoms and liver biochemical changes. EBA at highest quartile (EBA > 1.2ug/L) was associated with a significantly worse prognosis (log rank test, P < 0.001). Cox proportional multivariable regression model revealed that EBA > 1.20ug/L was an independent predictor of cardiac (P = 0.011) and overall (P = 0.010) mortality in our population. CONCLUSIONS: This study shows that EBA levels reflect clinical HF features, especially right HF signs/symptoms. EBA is an independent predictor of cardiac and overall mortality in chronic HF patients.

Impact of Exhaled Breath Acetone in the Prognosis of Patients with Heart Failure with Reduced Ejection Fraction (HFrEF). One Year of Clinical Follow-up.

BACKGROUND: The identification of new biomarkers of heart failure (HF) could help in its treatment. Previously, our group studied 89 patients with HF and showed that exhaled breath acetone (EBA) is a new noninvasive biomarker of HF diagnosis. However, there is no data about the relevance of EBA as a biomarker of prognosis. OBJECTIVES: To evaluate whether EBA could give prognostic information in patients with heart failure with reduced ejection fraction (HFrEF). METHODS: After breath collection and analysis by gas chromatography-mass spectrometry and by spectrophotometry, the 89 patients referred before were followed by one year. Study physicians, blind to the results of cardiac biomarker testing, ascertained vital status of each study participant at 12 months. RESULTS: The composite endpoint death and heart transplantation (HT) were observed in 35 patients (39.3%): 29 patients (32.6%) died and 6 (6.7%) were submitted to HT within 12 months after study enrollment. High levels of EBA (≥3.7µg/L, 50th percentile) were associated with a progressively worse prognosis in 12-month follow-up (log-rank = 11.06, p = 0.001). Concentrations of EBA above 3.7µg/L increased the risk of death or HT in 3.26 times (HR = 3.26, 95%CI = 1.56-6.80, p = 0.002) within 12 months. In a multivariable cox regression model, the independent predictors of all-cause mortality were systolic blood pressure, respiratory rate and EBA levels. CONCLUSIONS: High EBA levels could be associated to poor prognosis in HFrEF patients.

Spectroelectrochemical determination of chlorpromazine hydrochloride by flow-injection analysis.

An original, simple and sensitive flow-injection spectroelectroanalytical method for the determination of chlorpromazine in pure form or in pharmaceutical formulations is described. The method is based on the formation of a stable cationic radical by electro-oxidation in sulfuric acid medium (0.1 mol l(-1)), monitored in situ at lambda=524 nm. The determination of chlorpromazine hydrochloride in pure form or in pharmaceutical formulations was explored, considering the amperometric and the absorptiometric signal. The association of these two signals enhanced the selectivity of the analysis and proved decisive when other electroactive compounds or excipients like ascorbic acid were present in the formulation. The analytical parameters have been evaluated and the results obtained using standard additions are in agreement with the reference methods.

Quantification of DNA adducts in lungs, liver and brain of rats exposed to acetaldehyde.

Air pollution is a major risk for human health. Acetaldehyde is an environmental pollutant present in tobacco smoke, vehicle exhaust and several food products. Formation of DNA adducts has been regarded as a critical factor in the mechanisms of acetaldehyde mutagenicity and carcinogenesis. Acetaldehyde reacts with 2'-deoxyguanosine in DNA to primarily form N(2)-ethylidene-2'-deoxyguanosine (N(2)-ethylidene-dGuo). The subsequent reaction of N(2)-ethylidene-dGuo with another molecule of acetaldehyde gives rise to 1,N(2)-propano-2´-deoxyguanosine (1,N(2)-propanodGuo). In this study, on-line reverse-phase high-performance liquid chromatography (HPLC) separation with tandem mass spectrometry detection was utilized for the accurate quantification of 1,N(2)-propanodGuo and 1,N(2)-etheno-2'-deoxyguanosine (1,N(2)-edGuo) in tissues of rats exposed to 12 ppb, 33 ppb and 96 ppb acetaldehyde in atmospheric air for 50 days. A significant increase in the levels of 1,N(2)-propanodGuo was observed in lung tissues of rats exposed to 12 ppb (7.8/10(8) dGuo); 33 ppb (8.9/10(8) dGuo) and 96 ppb (11.6/10(8) dGuo) compared to controls (4.2/10(8) dGuo). For comparative purposes, the levels of 1,N(2)-etheno-2'-deoxyguanosine (1,N(2)-edGuo), which is produced from a,b-unsaturated aldehydes formed during the lipid peroxidation process were also measured. Elevated levels of 1,N(2)-edGuo were observed only in lung tissues of animals exposed to 96 ppb acetaldehyde. 1,N(2)-propanodGuo also differed quantitatively in liver but not in brain. The monitoring of 1,N(2)-propanodGuo levels in tissues provides important information on acetaldehyde genotoxicity and may contribute to the elucidation of the mechanisms associated with acetaldehyde exposure and cancer risk. Supported byFAPESP:2011/10048-5, CAPES, INCT Redoxoma:573530/2008-4,NAP Redoxoma: 2011.1.9352.1.8, CEPID Redoxoma:2013/07937-8.

Exhaled acetone as a new biomaker of heart failure severity.

BACKGROUND: Heart failure (HF) is associated with poor prognosis, and the identification of biomarkers of its severity could help in its treatment. In a pilot study, we observed high levels of acetone in the exhaled breath of patients with HF. The present study was designed to evaluate exhaled acetone as a biomarker of HF diagnosis and HF severity. METHODS: Of 235 patients with systolic dysfunction evaluated between May 2009 and September 2010, 89 patients (HF group) fulfilled inclusion criteria and were compared with sex- and age-matched healthy subjects (control group, n = 20). Patients with HF were grouped according to clinical stability (acute decompensated HF [ADHF], n = 59; chronic HF, n = 30) and submitted to exhaled breath collection. Identification of chemical species was done by gas chromatography-mass spectrometry and quantification by spectrophotometry. Patients with diabetes were excluded. RESULTS: The concentration of exhaled breath acetone (EBA) was higher in the HF group (median, 3.7 µg/L; interquartile range [IQR], 1.69-10.45 µg/L) than in the control group (median, 0.39 µg/L; IQR, 0.30-0.79 µg/L; P < .001) and higher in the ADHF group (median, 7.8 µg/L; IQR, 3.6-15.2 µg/L) than in the chronic HF group (median, 1.22 µg/L; IQR, 0.68-2.19 µg/L; P < .001). The accuracy and sensitivity of this method in the diagnosis of HF and ADHF were about 85%, a value similar to that obtained with B-type natriuretic peptide (BNP). EBA levels differed significantly as a function of severity of HF (New York Heart Association classification, P < .001). There was a positive correlation between EBA and BNP (r = 0.772, P < .001). CONCLUSIONS: EBA not only is a promising noninvasive diagnostic method of HF with an accuracy equivalent to BNP but also a new biomarker of HF severity.

Flow injection analysis of ethyl xanthate by gas diffusion and UV detection as CS2 for process monitoring of sulfide ore flotation.

A sensitive and robust analytical method for spectrophotometric determination of ethyl xanthate, CH(3)CH(2)OCS(2)(-) at trace concentrations in pulp solutions from froth flotation process is proposed. The analytical method is based on the decomposition of ethyl xanthate, EtX(-), with 2.0 mol L(-1) HCl generating ethanol and carbon disulfide, CS(2). A gas diffusion cell assures that only the volatile compounds diffuse through a PTFE membrane towards an acceptor stream of deionized water, thus avoiding the interferences of non-volatile compounds and suspended particles. The CS(2) is selectively detected by UV absorbance at 206 nm (epsilon=65,000 L mol(-1) cm(-1)). The measured absorbance is directly proportional to EtX(-) concentration present in the sample solutions. The Beer's law is obeyed in a 1x10(-6) to 2x10(-4) mol L(-1) concentration range of ethyl xanthate in the pulp with an excellent correlation coefficient (r=0.999) and a detection limit of 3.1x10(-7) mol L(-1), corresponding to 38 microg L(-1). At flow rates of 200 microL min(-1) of the donor stream and 100 microL min(-1) of the acceptor channel a sampling rate of 15 injections per hour could be achieved with RSD<2.3% (n=10, 300 microL injections of 1x10(-5) mol L(-1) EtX(-)). Two practical applications demonstrate the versatility of the FIA method: (i) evaluation the free EtX(-) concentration during a laboratory study of the EtX(-) adsorption capacity on pulverized sulfide ore (pyrite) and (ii) monitoring of EtX(-) at different stages (from starting load to washing effluents) of a flotation pilot plant processing a Cu-Zn sulfide ore.

Versatile microanalytical system with porous polypropylene capillary membrane for calibration gas generation and trace gaseous pollutants sampling applied to the analysis of formaldehyde, formic acid, acetic acid and ammonia in outdoor air.

The analytical determination of atmospheric pollutants still presents challenges due to the low-level concentrations (frequently in the µg m(-3) range) and their variations with sampling site and time. In this work, a capillary membrane diffusion scrubber (CMDS) was scaled down to match with capillary electrophoresis (CE), a quick separation technique that requires nothing more than some nanoliters of sample and, when combined with capacitively coupled contactless conductometric detection (C(4)D), is particularly favorable for ionic species that do not absorb in the UV-vis region, like the target analytes formaldehyde, formic acid, acetic acid and ammonium. The CMDS was coaxially assembled inside a PTFE tube and fed with acceptor phase (deionized water for species with a high Henry's constant such as formaldehyde and carboxylic acids, or acidic solution for ammonia sampling with equilibrium displacement to the non-volatile ammonium ion) at a low flow rate (8.3 nL s(-1)), while the sample was aspirated through the annular gap of the concentric tubes at 2.5 mL s(-1). A second unit, in all similar to the CMDS, was operated as a capillary membrane diffusion emitter (CMDE), generating a gas flow with know concentrations of ammonia for the evaluation of the CMDS. The fluids of the system were driven with inexpensive aquarium air pumps, and the collected samples were stored in vials cooled by a Peltier element. Complete protocols were developed for the analysis, in air, of NH(3), CH(3)COOH, HCOOH and, with a derivatization setup, CH(2)O, by associating the CMDS collection with the determination by CE-C(4)D. The ammonia concentrations obtained by electrophoresis were checked against the reference spectrophotometric method based on Berthelot's reaction. Sensitivity enhancements of this reference method were achieved by using a modified Berthelot reaction, solenoid micro-pumps for liquid propulsion and a long optical path cell based on a liquid core waveguide (LCW). All techniques and methods of this work are in line with the green analytical chemistry trends.

Environmental formaldehyde analysis by active diffusive sampling with a bundle of polypropylene porous capillaries followed by capillary zone electrophoretic separation and contactless conductivity detection.

Compared to other volatile carbonylic compounds present in outdoor air, formaldehyde (CH(2)O) is the most toxic, deserving more attention in terms of indoor and outdoor air quality legislation and control. The analytical determination of CH(2)O in air still presents challenges due to the low-level concentration (in the sub-ppb range) and its variation with sampling site and time. Of the many available analytical methods for carbonylic compounds, the most widespread one is the time consuming collection in cartridges impregnated with 2,4-dinitrophenylhydrazine followed by the analysis of the formed hydrazones by HPLC. The present work proposes the use of polypropylene hollow porous capillary fibers to achieve efficient CH(2)O collection. The Oxyphan fiber (designed for blood oxygenation) was chosen for this purpose because it presents good mechanical resistance, high density of very fine pores and high ratio of collection area to volume of the acceptor fluid in the tube, all favorable for the development of air sampling apparatus. The collector device consists of a Teflon pipe inside of which a bundle of polypropylene microporous capillary membranes was introduced. While the acceptor passes at a low flow rate through the capillaries, the sampled air circulates around the fibers, impelled by a low flow membrane pump (of the type used for aquariums ventilation). The coupling of this sampling technique with the selective and quantitative determination of CH(2)O, in the form of hydroxymethanesulfonate (HMS) after derivatization with HSO(3)(-), by capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C(4)D) enabled the development of a complete analytical protocol for the CH(2)O evaluation in air.

Flow injection analysis of ethyl xanthate by in-line dialysis and UV spectrophotometric detection.

A simple and sensitive spectrophotometric flow method for determination of low concentrations of the flotation collector O-ethyldithiocarbonate (ethyl xanthate, CH(3)CH(2)-O-CS(2)(-)) in solutions is described. The method is based on ethyl xanthate detection at 301nm in medium of NaOH 50mmolL(-1). By injection of 200muL of sample, the analytical method shows linear response for the ethyl xanthate concentration from 0.5 up to 500mumolL(-1). Successive injections of 4mumolL(-1) ethyl xanthate (n=23) show a coefficient of variation lower than 0.6%, denoting high repeatability. The detection limit is 0.3mumolL(-1). At a flow rate of 2.0mLmin(-1), a frequency of 120injections/h of ethyl xanthate can be attained. By introduction of a tangential dialysis cell in the FIA system, the manual sample filtration step with 0.22mum filter was eliminated and the residual interference of suspended material, was completely overcome even for unfiltered sludge suspension samples, an important advantage that compensates for the frequency reduction to 25injections/h elevation and detection limit elevation to 2mumolL(-1), still outreaching for many applications. Potential applications of the method embrace the at line determination of ethyl xanthate in the ore processing industry, control of the concentration at its optimal level during the flotation process, as well as monitoring of residues in the effluents.

Electronic micropipettor: a versatile fluid propulsion and injection device for micro-flow analysis.

The shortage of ready to use small sized liquid propulsion and switching devices for microfluidic cells (micro-cell) is a bottleneck in the dissemination of micro-flow analysis (mu-FA), now that microfluidic electrochemical cells can be designed and assembled in any laboratory by thermal transfer of laser printed masks and CD-Rs. Microprocessor-controlled electronic pipettors, commercially available with minimum capacity of 10 microL, represent a compromise solution between oversized peristaltic pumps and tiny "on a chip" micropumps and valves. The versatility of the electronic pipette coupled with the mu-cell (13-microm deep longitudinal channel) was demonstrated in three operation modes: SIA like, FIA like and direct injection analysis (DIA). Injections of 100 nL K4Fe(CN)6 (0.1 mol L(-1) KCl) define a linear analytical curve (r=0.999) in the range of 5 x 10(-7) to 1.0 x 10(-3) mol L(-1) for flow amperometry at a gold electrode potentiostated at 0.4V versus Ag/AgCl. Methods for the amperometric mu-flow determination of promethazine (FIA like), dipyrone (SIA like) and chlorpromazine (DIA) in pharmaceutical formulations were developed and applied to real samples. Excellent linearity of analytical curves and high repeatability (R.S.D.<3.0%) at the low picomole range was obtained and all results for real samples were in agreement with reference methods. The results reflect the stability and the reliability of the setups envisioned for the electronic pipette coupled with amperometric mu-cell and the validity of the mu-FA methods.

Trace analysis of acids and bases by conductometric titration with multiparametric non-linear regression.

A chemometric method for analysis of conductometric titration data was introduced to extend its applicability to lower concentrations and more complex acid-base systems. Auxiliary pH measurements were made during the titration to assist the calculation of the distribution of protonable species on base of known or guessed equilibrium constants. Conductivity values of each ionized or ionizable species possibly present in the sample were introduced in a general equation where the only unknown parameters were the total concentrations of (conjugated) bases and of strong electrolytes not involved in acid-base equilibria. All these concentrations were adjusted by a multiparametric nonlinear regression (NLR) method, based on the Levenberg-Marquardt algorithm. This first conductometric titration method with NLR analysis (CT-NLR) was successfully applied to simulated conductometric titration data and to synthetic samples with multiple components at concentrations as low as those found in rainwater (approximately 10 micromol L(-1)). It was possible to resolve and quantify mixtures containing a strong acid, formic acid, acetic acid, ammonium ion, bicarbonate and inert electrolyte with accuracy of 5% or better.

Simultaneous determination of three surfactants and water in shampoo and liquid soap by ATR-FTIR.

It is demonstrated for the first time that the principal constituents of a shampoo as well as of a liquid soap -three surfactants and water- can be determined directly, simultaneously and quickly in undiluted samples by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy in the middle infrared region, despite the broad absorption bands of the solvent. Two of the surfactants, sodium lauryl ether sulfate (SLES) and cocoamidopropyl betaine (CAPB), are common to both formulations; alkylpolyglucoside (APG) is the third surfactant of the liquid soap and cocodiethanolamide (CDEA), the corresponding ingredient of the shampoo. Absorbance data of the undiluted samples and of the calibration standards was collected in the middle infrared region of the spectrum (800-1600 and 1900-3000cm(-1)). Two methods of multivariate quantification were compared: classical least squares (CLS), where absorbance data measured at 200 wavenumbers was processed, and inverse least squares (ILS), where data at 10 selected wavenumbers was analyzed. A spectra normalization procedure, based on a dominating water band, was examined. Twenty-seven standard mixtures were used for each application, consisting of all combinations at three concentration levels of each surfactant, respectively the lower limit, the expected value and the upper limit accepted in quality control. By favoring wavenumbers where absorption bands of the minor components (APG in the liquid soap and CDEA in the shampoo) are more intense, good results were obtained for 18 simulated samples of shampoo and 18 samples of liquid soap, no matter if calculations were made by CLS or ILS. The relative errors for water (major component, 84-88%) and SLES (7-10%) were always below 2%; for CAPB (2-4%), APG (<2%) and CDEA (<2%), they occasionally reached 5% of the component, an uncertainty of less than 0.07% in terms of the sample weight.

Microfluidic cells with interdigitated array gold electrodes: Fabrication and electrochemical characterization.

Microfluidic flow cells combined with an interdigitated array (IDA) electrode and/or individually driven interdigitated electrodes were fabricated and characterized for application as detectors for flow injection analysis. The gold electrodes were produced by a process involving heat transfer of a toner mask onto the gold surface of a CD-R and etching of the toner-free gold region by short exposure to iodine-iodide solution. The arrays of electrodes with individual area of 0.01cm(2) (0.10cm of lengthx0.10cm of width and separated by gaps of 0.05 or 0.03cm) were assembled in microfluidic flow cells with 13 or 19mum channel depth. The electrochemical characterization of the cells was made by voltammetry under stationary conditions and the influence of experimental parameters related to geometry of the channels and electrodes were studied by using K(4)Fe(CN)(6) as model system. The obtained results for peaks currents (I(p)) are in excellent agreement with the expected ones for a reversible redox system under stationary thin-layer conditions. Two different configurations of the working electrodes, E(i), auxiliary electrode, A, and reference electrode, R, on the chip were examined: E(i)/R/A and R/E(i)/A, with the first presenting certain uncompensated resistance. This is because the potentiostat actively compensates the iR drop occurring in the electrolyte thin layer between A and R, but not from R to each E(i). This is confirmed by the smaller difference between the cathodic and anodic peak potentials for the second configuration. Evaluation of the microfluidic flow cells combined with (individually driven) interdigitated array electrodes as biamperometric or amperometric detectors for FIA reveals stable and reproducible operation, with peak heights presenting relative standard deviations of less than 2.2%. For electrochemically reversible species, FIA peaks with enhanced current signal were obtained due to redox cycling under flow operation. The versatility of microfluidic flow cells, produced by simple and low-cost technique, associated with the rich information content of electrochemical techniques with arrays of electrodes, opens many future research and application opportunities.

A new electrolytic dissolution of aluminum alloys and determination of some constituents by inductively coupled plasma optical emission spectrometry.

The new electrolytic dissolution in batch of aluminum alloys samples as grains or turns and the determination of Fe, Cu, Mn, Mg, Cr, Ni, Zn, Pb and Ti by ICP OES was investigated. In on-line electrodissolution procedures described in the literature, samples were restricted to be in the form of solid blocks or plates with one polished flat face. Here, the sample was loaded in the barrel of a modified disposable syringe (the anodic semi-cell) and pressed with a modified plunger fitted with a platinum disk to establish electrical contact with the analyte. This arrangement was introduced in a beaker containing the electrolyte (1 mol L(-1) HNO(3)) and a platinum wire as the cathode. The resulting solution from electrodissolution (0.6A) was used for the ICP OES determinations. The influence of the aluminum concentration increase on the determination of the elements was evaluated. Electrodissolution of certified reference materials and commercial samples revealed relative errors lower than 10% for the elements Fe, Cu, Mg, Ni, Cr, Zn and Ti (when their content is above 0.1%). Higher inaccuracies (>10%) were observed for Mn and for Fe in B.C.S. 268/1 reference material certified. The proposed method presented a relative standard deviations (R.S.D.) lower or circa 10% to all of the elements (except Pb). In comparison with traditional acid dissolution, the proposed electrodissolution method is relatively fast (about 30 min), it is clean (there is no projection of solution) and simple (heating and fumes exhaust system were not necessary).