University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Email: schalk@unf.edu
Website: @unf

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Marcelo Blanco

Abbrev:
Blanco, M.
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Address:
Departamento de Química, Unidad de Química Analítica, Universidad Autónoma de Barcelona, E-08193 Bellaterra, Barcelona, Spain
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Citations 8

"Kinetic Spectrophotometric Determination Of Gallium(III) - Aluminum(III) Mixtures By Stopped-flow Injection Analysis Using Principal Component Regression"
Talanta 1993 Volume 40, Issue 2 Pages 261-267
M. Blanco*, J. Coello, H. Iturriaga, S. Maspoch, J. Riba and E. Rovira,

Abstract: Fourteen solution were prepared, containing Ga(III) (0 to 5 mg l-1) and Al(III) (0 to 130 mg l-1). Seven of these solution, together with the pure metal ion solution, were used as calibration samples and the remaining seven were used as quantitation samples. Portions of the solution were injected into the carrier stream, merged with the borate buffer of pH 8.5 and the reagent [1 mM 4-(2-pyridylazo)resorcinol]. The injection valve and the pump were computer-controlled to stop the flow when the plug reached the detector cell. Spectra were recorded at 2-s intervals for 60 s, with an integration time of 0.3 s. Data at six wavelengths were processed by a principal components regression program, using the NIPALS algorithm. The seven sample mixtures were then analyzed. With one exception (Al content 20 mg l-1), the errors were 10%. The mean coefficient of variation were 0.8% for Ga(III) and 1.6% for Al(III). The most accurate results were obtained when Al(III) was in excess.
Gallium(3+) Aluminum(III) Spectrophotometry Kinetic Stopped-flow Principal component analysis

"Diode-array Detectors In Flow Injection Analysis. Mixture Resolution By Multi-wavelength Analysis"
Talanta 1987 Volume 34, Issue 12 Pages 987-993
M. Blanco*, J. Gene, H. Iturriaga, S. Maspoch and J. Riba

Abstract: In the use of diode-array spectrophotometry for multi-component determination by flow injection analysis, aspects considered are(I) the recording of reproducible spectra at max. sensitivity and(II) the mathematical processing of the spectral data to determine the various components. Three data processing procedures are assessed, viz: (a) a linear simultaneous-equation system, (b) a multi-component analysis computation program (Hewlett-Packard), and (c) graphical multi-wavelength linear regression analysis. The test analysis was simultaneous determination of Fe(II) and Fe(III) with 1,10-phenanthroline - sulfosalicylic acid reagent with measurements at 486 and 510 nm. Data processing procedures (b) and (c) yielded similar and satisfactory results.
Iron(2+) Iron(III) Spectrophotometry Calibration Computer Multicomponent Speciation

"Modification Of A Commercial Dual Channel Valve To Be Used In A Stopped-flow Injection Analysis System"
J. Flow Injection Anal. 1990 Volume 7, Issue 1 Pages 3-10
Marcelo Blanco(*), Jordi Coelio, Hortensia Iturriaga, Santiago Maspoch and Joaquim Riba

Abstract: The bypass loops of a variable-volume dual-channel Tecator V-200 injection valve were modified for stopped-flow use. Good precision was achieved, the coefficient of variation being >1% only when the flow was stopped at the end of the tail of the peak. The behavior of the modified valve was comparable with any injection valve suitable to be used in stopped-flow flow injection analysis.
Tecator Stopped-flow Valve

"Diode-array Detectors In Flow Injection Analysis. Simultaneous Determination Of Rare Earth Metals With Arsenazo III"
Fresenius J. Anal. Chem. 1990 Volume 338, Issue 7 Pages 831-835
M. Blanco, J. Coello, J. Gené, H. Iturriaga and S. Maspoch

Abstract: Ore (1 g) was treated with 20 mL of concentrated HNO3 and heated to dryness. The residue was treated with 20 mL of concentrated HCl and heated to dryness. The residue was resuspended in 0.1 M HCl, filtered, washed and the filtrate was diluted to 100 mL with 0.1 M HCl. A 25 mL aliquot was treated with 0.1 M NH3 and the ppt. was filtered off, washed and dissolved in 0.1 M HCl. The solution was mixed with 10 mL of tartaric acid and diluted to 100 mL with 0.1 M HCl. A portion of this solution was injected into a carrier stream of 1 M acetic acid - sodium acetate buffer (pH 4; 1.2 mL min-1), mixed with a reagent stream containing 0.3 mM arsenazo III and the absorbance of the solution was measured between 600 and 720 nm with use of a diode array detector. Binary mixtures of 0.5 to 2.5 µg g-1 of tervalent rare-earth-metal cations and 1.4 to 4.3 µg g-1 of U were accurately resolved with use of univariate calibration. The presence of Th (2.8 to 7.0 µg g-1) required use of multivariate calibration. Results obtained for the determination of Th and U in pitchblende agreed well with the certified values.
Metals, rare earth Uranium Thorium-232 Pitchblende Spectrophotometry Buffer Reference material Multivariate calibration Interferences

"Isomeric Transformation Of 4-aminobiphenyl By UV Radiation And Its Influence On The Determination By Flow Injection Analysis With Amperometric And Spectrophotometric Detection"
Anal. Lett. 1995 Volume 28, Issue 15 Pages 2683-2697
Hernandez Blanco, M.;Quintana, M.C.;Hernandez, P.;Vicente, J.;Hernandez, L.

Abstract: Sample (200 µL) containing 4-aminobiphenyl (I; 0.1-1 µg/ml in methanol) was injected into a carrier stream (5.5 ml/min) containing 0.04 M Britton-Robinson buffer of pH 8 via a single-flow injection manifold. The streams were mixed in a reactor (20 cm x 0.5 mm i.d.) before amperometric detection in a wall-jet flow-cell with a working electrode potential of +0.9 V. Vitreous C, Ag/AgCl and Au were used as working, reference and auxiliary electrodes, respectively. Spectrophotometric measurements were performed similarly except that a 400 µL sample (containing 0.8-24 µg/ml of I in methanol) and a 0.02 M buffer of pH 10 were used. Detection was at 274 nm. For amperometric detection the calibration graph was linear from 0.1-1 µg/ml of I; quantitation and detection limits were 0.11 and 0.05 µg/ml, respectively. RSD were 2.5%. For the spectrophotometric method, the linear calibration range was 0.8-24 µg/ml of I; quantitation and detection limits were 0.4 and 0.05 µg/ml, respectively. RSD were 2.4%. Sample throughputs were 200 and 240 samples/h for amperometric and spectrophotometric detection, respectively. The methods were applied to the determination of I in food colorings. Two flow injection methods for the determination of 4-aminobiphenyl by amperometry (glassy carbon electrode) and spectrophotometry are proposed. A sample volume of 200 or 400 µl containing an analyte concentration of 0.1-1.0 µg mL-1 or 0.8-24.0 µg mL-1 for amperometric or spectrophotometric detection, respectively, is injected into a carrier stream containing 0.04 or 0.02 M Britton-Robinson buffer at pH 10.0 or 8.0, respectively. (11 References)
4-Aminobiphenyl Food Amperometry Electrode Spectrophotometry Photochemistry

"Artificial Neural Networks For Multicomponent Kinetic Determinations"
Anal. Chem. 1995 Volume 67, Issue 24 Pages 4477-4483
Marcelo Blanco, Jordi Coello, Hortensia Iturriaga, Santiago Maspoch, and Miguel Redon

Abstract: An artificial neural network (ANN) procedure that uses the scores of a principal component model as input data was tested for calibration in the resolution of binary mixtures from kinetic measurements. The results thus obtained are compared with those provided by partial least-squares (PLS) regression and principal component regression (PCR). The ANN was first applied to simulated single wavelength kinetic curves. The effect of experimental variability was considered by assuming rate constants to fit a normal distribution curve. An amount of instrumental noise was also added to the simulated curves. Both linear and nonlinear systems were tested. Non-linearity was assumed to result from interactions between analytes and modeled by introducing a multiplicative term in the rate equation. The results provided by the three methods on linear systems were comparable; in the presence of interactions between analytes, however, the ANN method clearly outperformed the other two. The ANN method was also used to resolve mixtures of Fe(III), Co(II), and Zn(II) by displacement from their EGTA complexes with 4-(2-pyridylazo)resorcinol (PAR) using a stopped-flow injection assembly including a diode array detector. Preliminary experiments revealed the Co(II) and Zn(II) displacement reactions to be pseudo-first-order and that of Fe(III) to be a multistep process that departed from the linear behavior of the other two. Again, the results obtained with ANN were better than those provided by PCR and PLS.
Cobalt(II) Iron(2+) Zinc(II) Spectrophotometry Neural network Indirect Kinetic Stopped-flow Principal component analysis Partial least squares

"Kinetic Spectrophotometric Method For Analysing Mixtures Of Metal Ions By Stopped-flow Injection Analysis Using Partial Least-squares Regression"
Anal. Chem. 1994 Volume 66, Issue 18 Pages 2905-2911
M. Blanco, J. Coello, H. Iturriaga, S. Maspoch, and J. Riba

Abstract: Binary and tertiary mixtures of Co(II), Zn(II) and Fe(III) were analyzed using a stopped-flow injection manifold, in which they were merged with streams of 0.625 mM EGTA in 0.1 M Tris buffer of pH 8.05, water, and 1 mM 4-(2-pyridylazo)resorcinol (PAR). A diode-array detector recorded absorbances at various wavelengths simultaneously. In the first mode, the metal ion solutions were directly injected into the flow stream, where EGTA complexes were formed and the chelator was competitively displaced by PAR. In the second mode, metal-EGTA complexes were formed prior to injection into the flow system; only ternary mixtures were analyzed in this mode. The data from the spectrophotometer were reduced to the absorbances recorded at 500-540 nm at 15 reaction times from 10^-150 s and processed by PC. Partial least-squares (PLS) regression was used to resolve the mixtures on the basis of the differences in the rate of displacement of EGTA by PAR. The data from mode 2 showed that displacement of EGTA was pseudo first-order whereas in mode 1, the displacement rates from the Co and Zn complexes were the same but those for Fe were not first order. In both modes, PLS calibration allowed satisfactory measurement of the transition metal ions.
Cobalt(II) Iron(2+) Zinc(II) Spectrophotometry Stopped-flow Partial least squares Calibration Complexation Signal processing Kinetic

"Multicomponent Analysis Of Concentrated Solutions By Flow Injection Analysis With Zone Sampling And Partial-least-squares Resolution"
Anal. Chim. Acta 1992 Volume 259, Issue 2 Pages 219-224
M. Blanco*, J. Coello, H. Iturriaga, S. Maspoch, M. Redón and J. Riba

Abstract: A description is given of an automated flow injection dilution system based on zone sampling with use of a variable-volume, dual-channel bypass injection valve (Tecator V-200). The performance of the method was assessed by applying it to the spectral resolution of mixtures of complexes of Cu(II) and Zn(II) with 4-(2-pyridylazo)resorcinol. The combined spectra were recorded at the max. of the flow injection peaks and were resolved into the individual components by the partial-least-squares method. The coefficient of variation of the results for each metal were in general 4%. Results are also presented for the analysis of two brasses. The potential of a flow injection zone sampling system equipped with a diode-array spectrophotometric detector for the simultaneous determination of metal ions in mixtures was studied. Zone sampling was accomplished by using a commercial available, variable-volume, dual-channel bypass injection valve. The mixed spectra were recorded at the max. of the flow injection peaks and were resolved into the individual components by using a partial least-squares method. The method was applied to the determinations of Cu(II) and Zn(II) in mixtures with 4-(2-pyridylazo)resorcinol as reagent.
Copper(II) Zinc(II) Spectrophotometry Multicomponent Tecator Partial least squares Zone sampling