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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Pilar Campins Falco

Abbrev:
Campins Falco, P.
Other Names:
Address:
Department of Analytical Chemistry, University of Valencia, 50 Dr. Moliner St., E-46100 Burjassot, Spain
Phone:
+34-96-354-3002
Fax:
+34-96-354-4436

Citations 8

"Influence Of Water Sample Storage Protocols In Chemiluminescence Detection Of Trace Elements"
Talanta 2003 Volume 60, Issue 2-3 Pages 257-268
Y. Moliner-Martínez, S. Meseguer-Lloret, L. A. Tortajada-Genaro and P. Campíns-Falcó

Abstract: This paper shows the influence of different sample storage protocols, on the chemiluminescence signal of some metal ions. The storage protocols studied were: acid addition (HCl or HNO3) and no reagent addition to filtered and refrigerated (T=4°C) samples. Light emission was produced for the chemiluminescence reaction between luminol and hydrogen peroxide in buffer carbonate conditions (pH 10.8) catalyzed by Cr(III), Co(II) and Cu(II). Batch and/or flow modes in different conditions were tested. Fe(II), Fe(III), Ni(II) and Mn(II) did not give chemiluminescence in the studied conditions. A parallel study of sensitivity and selectivity was performed. Then the presence or absence of the masking agent EDTA, added to samples or used in the carrier stream, is assayed. If the samples are acidified with HNO3, a previous neutralisation is needed using batch mode. The determination of Cr(III) is independent of storage protocol by flow injection (FI) method; however, the determination of Co(II) or Cu(II) or total determination of three metals requires the conditioning of standards. Detection limits achieved are ranged between 0.5 and 2 µg l-1. For batch mode, detection limits are better for unacidified samples and worse for carbonate-neutralised samples. The influence of storage protocols was validated using standard metal mixtures and calibration solutions. The use of standard reference material (SRM(c) 1640) (Trace elements in natural water) corroborates the previous statements and validates the accuracy of the different approaches underlined. This paper demonstrates that it is possible to determine Cr(III) selectively in natural waters.

"Creatinine Determination In Urine Samples By Batchwise Kinetic Procedure And Flow Injection Analysis Using The Jaffe Reaction: Chemometric Study"
Talanta 2001 Volume 55, Issue 6 Pages 1079-1089
P. Campins Falcó, L. A. Tortajada Genaro, S. Meseger Lloret, F. Blasco Gomez, A. Sevillano Cabeza and C. Molins Legua

Abstract: The classical Jaffe reaction for the determination of creatinine in urine samples is tested. A comparative study of the main analytical characteristics focussed to minimize the bias error and improve the precision, for the batchwise and flow injection (FI) methods is realized. Also, the effect of the albumin concentration in the determination of creatinine has been studied. Different analytical signals were studied. Absorbance increments at different times permit to estimate the creatinine concentration free from bias error in urine by the batchwise method using the calibration graph obtained with creatinine standards and no measurement of the blank solution is needed. The lineal interval was 0.92-50 mg L-1 and seven samples can be processed per hour by an operator. No previous treatment of the urine sample is necessary. The FI method provides also good results. The lineal interval was 30-100 mg L-1 and the sample rate was around 20 samples per hour. If increased albumin levels are detected in the urine, standard addition method or the calibration graphs with standards in presence of albumin are needed in order to obtain accurate results when FI method is employed. The obtained accuracy of the both methods allows its application as diagnostic tool to establish the urinary creatinine levels. (C) 2001 Elsevier Science B.V. All rights reserved.

"A Chemometric Study Of The Simultaneous Determination Of Calcium And Magnesium In Natural Waters"
Talanta 1999 Volume 49, Issue 1 Pages 155-163
F. Blasco Gómez, F. Bosch Reig and P. Campíns Falcó

Abstract: A method for the simultaneous spectrophotometric determination of calcium and magnesium in mineral waters with an FIA system is tested. The method is based on the reaction between the analytes and arsenazo(III) at pH 8.5. The calculations of the amounts of both analytes in the samples are carried out with the H-point standard addition method (HPSAM) for ternary mixtures, and with a partial least squares (PLS) model after a proper variable selection. The results obtained for the determination of calcium were comparable using both methods. The employment of the HPSAM brings to our attention the influence of the calcium concentration in the sample to the development of the reaction between magnesium and arsenazo(III). HPSAM also permits to estimate the concentration of magnesium in the samples.

"The H-point And Generalized H-point Standard Additions Methods For Flow Injection Procedures"
Talanta 1998 Volume 47, Issue 1 Pages 193-202
P. Campíns-Falcó*, F. Blasco Gómez and F. Bosch-Reig

Abstract: This paper establishes the fundamentals of the H-point standard additions method (HPSAM) and generalized H-point standard additions method (GHPSAM) in the flow injection technique. Two kinds of anal. signals can be employed, FIA peaks and spectra. Different anal. problems were studied: determinations of one analyte in the presence or absence of matrix effect when different blank features are present, and determination of two analytes in the presence of blank bias error affecting the development of one of them. The determination of chloride with Hg thiocyanate which presents a matrix effect, and the determinations of Ca and/or Mg with arsenazo III were examined The methods were compared with conventional data treatment and proved able to isolate the analyte signal from the global one, thus providing accurate and precise results in the determination of the above mentioned species in bottled waters. No additional experimental work is needed to apply the methods.
Chloride Calcium Magnesium Water Spectrophotometry Standard additions calibration Interferences

"Analyser Of Chromium And/or Cobalt"
Anal. Chim. Acta 2003 Volume 488, Issue 2 Pages 243-254
L. A. Tortajada-Genaro, P. Campíns-Falcó and F. Bosch-Reig

Abstract: Two stopped-flow manifolds have been proposed for individual or simultaneous determination of chromium and cobalt in water samples. Automated procedures based on multicommutation systems have emphasised the differences of their catalytic effect in luminol-hydrogen peroxide chemiluminescence reaction. A more rapid decay of signal was observed for Co for both configurations (flow injection or continuous injection). The influence of chemical and hydrodynamic variables has been studied in order to establish the robustness of method. The analysis rate was lower 1.5 min per replicate.Chemometric tools have been employed for the resolution of their contributions. Partial least squares (PLS) and H-point standard additions method (HPSAM) were used as multivariate calibration models. The percentages of explained variance were 97-99% (two factors). PLS and HPSAM obtained similar results. HPSAM provided a simple calibration model contributing to develop an analyzer. for chromium and/or cobalt.Standard mixtures, spiked samples and a certified reference material validated the proposed strategy. The applicability has been demonstrated by the determination of Cr and Co concentration in different water samples. The best results have been obtained for continuous injection providing more robust predictions. The achieved detection limit was 0.2 µg/l for both metals.

"Multivariate Versus Univariate Calibration For Nonlinear Chemiluminescence Data - Application To Chromium Determination By Luminol-hydrogen Peroxide Reaction"
Anal. Chim. Acta 2001 Volume 450, Issue 1-2 Pages 155-173
L. A. Tortajada-Genaro, P. Campíns-Falcó, J. Verdú-Andrés and F. Bosch-Reig

Abstract: Multivariate calibration is tested as an alternative to model chromium(III) concentration versus chemiluminescence registers obtained from luminol-hydrogen peroxide reaction. The multivariate calibration approaches included have been: conventional linear methods (principal component regression (PCR) and partial least squares (PLS)), nonlinear methods (nonlinear variants and variants of locally weighted regression) and linear methods combined with variable selection performed in the original or in the transformed data (stepwise multiple linear regression procedure). Both the direct and inverse univariate approaches have been also tested. The use of a double logarithmic transformation previous to the linear regression has been also evaluated. A new double logarithmic transformation previous to the linear regression is proposed in order to avoid the effect of the noise in the calibration model. Pre-processing, optimization and prediction ability of the multivariate calibration models has been studied at nine different experimental conditions including batch and FIA measurements. Box-plots, PCA and cluster analysis have been employed to test the prediction ability of the different models tested. Nonlinear PCR and nonlinear PLS provide the best results. Real samples have been analyzed and compared with the reference method. The results confirm the successful use of the proposed methodology.

"Calibration Transfer In Chemiluminescence Analysis - Application To Chromium Determination By Luminol-hydrogen Peroxide Reaction"
Anal. Chim. Acta 2001 Volume 446, Issue 1-2 Pages 383-390
L. A. Tortajada-Genaro, P. Campíns-Falcó and F. Bosch-Reig

Abstract: Direct standardization (DS) and piecewise direct standardization (PDS) methods are applied to multivariate standardization of chemiluminescence signals using PLS model as the calibration model. The linear concentration interval of the chemiluminescence determination was determined. This interval was located using univariate robust calibration by least median of squares (LMS) method. The linear calibration model was corroborated by conventional least-squares method. The standardization subset and window size were optimized by means of the prediction residual error sum of squares. Several instrumental sources of variability have been studied: the detection cell, instrument, batch versus flow injection (FI) modes, time and their possible combinations. This study shows the calibration transfer can be employed successfully. The proposed strategy was used in the chemiluminescence determination of Cr(III), Cr(VI) and total Cr in water samples by means of a calibration transfer. The obtained results are in agreement with reference method values and known spiked amounts, and are independent of the standardization factors.

"Standard Addition Method In FIA. Comparison Between Different Assemblies"
Anal. Chim. Acta 1999 Volume 379, Issue 1-2 Pages 89-97
P. Campíns-Falcó, F. Bosch-Reig and F. Blasco-Gómez

Abstract: A comparison between the different proposed methods to perform the standard addition in an online way (flow injection analysis) is made. The different assemblies (reverse and conventional FIA) and the employed standards in every method are compared. Three analyzes were carried out, two of them were analyzes of samples of pH indicators (methylorange and chlorophenol red) prepared at an acid pH, while the standards were prepared at a basic pH. The third analysis was the analysis of chloride in different synthetic waters with a perfectly known composition for all the ions present in the samples. Besides a new method to perform the online standard addition is proposed, trying to reduce the consumption of reagents and sample. This new method makes use of a 6-port multiposition valve electrically actuated.
Methylorange Chlorophenol Red Chloride Water Spectrophotometry Standard additions calibration Manifold comparison Reverse