University of North Florida
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Contact Info

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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Mabel B. Tudino

Abbrev:
Tudino, M.B.
Other Names:
Address:
Departmento de Quimica e Organica Analitica, University of Buenos Aires, Pabellon 2, Ra-1428 Buenos Aires, Df Argentina
Phone:
+54-1145763360
Fax:
+54-1145763341

Citations 8

"Determination Of Selenite And Selenate In Drinking Water: A Fully Automatic On-line Separation/pre-concentration System Coupled To Electrothermal Atomic Spectrometry With Permanent Chemical Modifiers"
Anal. Chim. Acta 2004 Volume 502, Issue 1 Pages 99-105
Jorge Stripeikis, Juana Pedro, Adrián Bonivardi and Mabel Tudino

Abstract: A time-based flow injection (FI) separation pre-concentration system coupled to an electrothermal atomic absorption spectrometer (graphite furnace) has been developed for the direct ultra-trace determination of selenite and selenate in drinking water. The pre-concentration of both forms of selenium is carried out onto a micro-column packed with an anionic resin (Dowex 1X8) that is placed in the robotic arm of the autosampling device. Selenite and selenate are sequentially eluted with HCl 0.1 M and HCl 4 M, respectively. The interference of large quantities of chloride during selenium atomisation is prevented by using iridium as a 'permanent' chemical modifier. The features of the pre-concentration separation system for both species are: 53% efficiency of retention and an enhancement factor of 82 for a pre-concentration time of 180 s (sample flow rate=3 mL min-1) with HCl elution volumes of 100 µl. The detection limit (3 s) is 10 ng L-1 for the two species and the relative standard deviation (n=10) at the 200 ng L-1 level is 3.5% for selenite and 5.6% for selenate. The addition of selenite and selenate stock standard solutions to tap water samples yields a 97-103% recovery of both species.

"Mass Distribution In A Dynamic Sample Zone Inside A Flow Injection Manifold: Modelling Integrated Conductimetric Profiles"
Anal. Chim. Acta 2003 Volume 477, Issue 1 Pages 59-71
Fernando A. Iñón, Francisco J. Andrade and Mabel B. Tudino

Abstract: A mathematical model for fitting the experimental ICM (integrated conductimetric method) curves developed by the authors in a previous work, is presented for the first time in this study. The proposed model fits the experimental curves with great precision and allows to predict physical dispersion for single-line flow injection system. The correlation of the model's parameters with typical reactionless FIA peak parameters is also assessed. The IDQ coefficient--a novel dispersion estimator previously reported by the authors--can also be predicted when operational FIA variables are changed. Experimental and modelled profiles are compared as a function of the system's variables, showing an excellent agreement.

"Multicomponent Kinetic Determination Of Cu, Zn, Co, Ni And Fe At Trace Levels By First And Second Order Multivariate Calibration"
Anal. Chim. Acta 2001 Volume 433, Issue 1 Pages 119-134
Facundo M. Fernández, Mabel B. Tudino and Osvaldo E. Troccoli

Abstract: A flow injection system coupled to a photodiode array spectrophotometer (FI-PDA) for the multicomponent kinetic determination of Cu, Zn, Co, Ni and Fe at trace levels is presented. The substitution reaction of metal-nitrilotriacetic complexes (M-NTA) by 4-(2-pyridilazo) resorcinol (PAR) instead of the direct complexation of the free ions with PAR is employed. In this way, the spectral differences between the colored complexes are combined with the different reaction rates of the ions producing a more specific lambda -time region for each metal enhancing the selectivity. Since the NTA-M-PAR system is fast and the pure analyte profiles appear partially overlapped in the time and lambda -axis, temporal and spectral information were added to PLS and PCR models to improve results and to increase the number of metals to be determined. The developed method provides the fast and cheap determination of the five metals at the sub ppm range and demonstrates that the use of temporal and spectral information increases the number of analytes to be simultaneously determined, improving the analytical figures of merit as well.
Multivariate calibration

"Flow Injection-hydride Generation Atomic Absorption Spectrometric Determination Of Se(VI) And Se(IV): Utility Of A Conventionally Heated Water Bath For The On-line Reduction Of Se(VI)"
Anal. Chim. Acta 2000 Volume 408, Issue 1-2 Pages 191-197
Jorge Stripeikis, Pablo Costa, Mabel Tudino and Osvaldo Troccoli

Abstract: A simple how injection manifold coupled to a hydride generation atomic absorption spectrometer has been designed for Se(VI) and Se(IV) determination. On-line reduction of Se(VI) is performed by passing the sample, in 6.8 M hydrochloric acid, through a conventionally heated water bath. Complete conversion into Se(IV) is achieved in about 1 min. Conventional on-line heating has proved to be a good alternative for the fast conversion of Se(VI) into Se(IV). Its performance, in comparison to microwave heating, is discussed. Reaction kinetic parameters have been obtained via on-line experiments for the first time. A comparison with those values already reported is also presented. A limit of detection of 0.05 ng mL-1 (n = 10, 3 s) is obtained for both forms, with a precision (relative standard deviation, n = 10, 3 s) better than 3%. The sample throughput is 60 samples/h, better than other flow injection systems reported up to date.
Selenium(IV) Selenium(VI) Spectrophotometry Speciation Volatile generation Online digestion Microwave Review

"Novel Application And Comparison Of Multivariate Calibration For The Simultaneous Determination Of Cu, Zn And Mn At Trace Levels Using Flow Injection Diode Array Spectrophotometry"
Anal. Chim. Acta 1999 Volume 398, Issue 1 Pages 93-102
Maia Azubel, Facundo M. Fernández, Mabel B. Tudino and Osvaldo E. Troccoli

Abstract: Three different calibration approaches: Partial Least Squares, Unfold Partial Least Squares and n-way Partial Least Squares are compared in terms of explained variance, root mean square error of calibration and root mean square error of cross-validation. Attention is also focused on the application of genetic algorithms to spectral data as a way to obtain an improvement in calibration accuracy. Influence of initial starting conditions for the genetic algorithms (population size, mutation probability, % initial terms etc.) was investigated by means of factorial experimental designs. A simple flow injection manifold coupled to a diode array spectrophotometer and multivariate calibration were employed in order to determine Ni, Cd, Pb, Cu, Zn and Mn. Calibration was not successful for the three first elements. Rapid determination of the microamounts of Cu, Zn and Mn was performed in the presence of concomitant ions with a sample throughput of 180 samples h-1. Since three metals were simultaneously determined, this corresponds to 540 determinations h-1. The effect of different matrix interferences (Fe, Al, Ca, Mg, Cr, Sr, Co) was studied in natural and synthetic water samples. Chemical masking with NaF was assayed for the interferent ions Fe and Al. The typical recoveries ranged from 91 to 94% with typical relative standard deviation between 5 and 10 %.

"Integrated Conductimetric Detection: Mass Distribution In A Dynamic Sample Zone Inside A Flow Injection Manifold"
Anal. Chim. Acta 1999 Volume 379, Issue 1-2 Pages 99-106
Francisco J. Andrade, Fernando A. Iñon, Mabel B. Tudino and Osvaldo E. Troccoli

Abstract: The insights provided by integrated detection (conductimetric) as a novel approach to follow physical dispersion in continuous-flow manifolds are presented. This approach replaces the conventional instantaneous detection and permits to follow the dispersion phenomena, including details of the radial component as the sample plug travels the manifold. Integrated detection permits to look at the radial dispersion in a detailed manner inaccessible to instantaneous detection. The effect of different experimental parameters affecting mass distribution was studied (e.g., flow rate, tube length and diameter, injected sample volume, and reactor type) and their effects on integrated response curves are discussed. A single channel manifold employing aqueous nitric acid as the conducting carrier, and water injected as sample plug, and playing the role of an insulator, provided the physicochemical model for the reported studies.
Conductometry Dispersion Modeling Simulation

"Kinetic Control Of Reagent Dissolution For The Flow Injection Determination Of Iron At Trace Levels"
Analyst 2002 Volume 127, Issue 7 Pages 990-994
Hernán A. Bruno, Francisco J. Andrade, Pablo C. Luna and Mabel B. Tudino

Abstract: A novel methodology for the determination of iron at the ppb level by spectrophotometric flow injection analysis is described. The method is based on the control of the flow dissolution of the colorimetric reagent 1,10-phenanthroline. This is achieved by means of the minimization of the area of contact between the carrier and the solid reagent, thus allowing the use of the fairly soluble organic compound without affecting the reactor lifetime. The reagent is melted inside an acrylic column (3.0 X 0.5 cm id) in such a way that a hollow space is left in the center after cooling. This new design improves some aspects of the performance of the classical solid-phase reactors as no problems related to the increase in the backpressure of the system are evidenced. Furthermore, the total reagent loading of the column is increased as no inert support is needed. A comparison between the performance of this novel methodology and that of the conventional packed reactor was performed and several advantages were observed: the use of higher flow rates, an increase in the reactor lifetime and a decrease in reagent consumption. A mathematical model to fit the concentration profiles of the dissolved reagent as a function of the residence time of the sample within the column is presented. The application of this strategy to the determination of Fe(II) improves the figures of merit in comparison to those obtained with a single-line homogeneous system: the limit of detection is 2 µg Fe L-1 (3s) and the sensitivity is similar to that of the batch procedure. Results obtained for the determination of iron in natural waters are also presented.
Reactor

"Oscillatory Control Of Sample Dispersion In A Continuous Flow System"
Analyst 2001 Volume 126, Issue 3 Pages 394-398
H. Bruno, F. Andrade, F. Iñón, M. Tudino and O. Troccoli

Abstract: A new strategy for the instrumental control of sample dispersion in continuous flow systems is presented. The method is based on shaking a loosely held straight reactor while the sample travels through the flow injection manifold. This external disturbance yields a sample transport more similar to the plug flow type because of the changes promoted on the flow pattern. Up to a three-fold increase in peak height, a comparable reduction in peak width and a more Gaussian peak profile are observed when the signals obtained with the shaken reactor are compared with those obtained with the same reactor but static. Improvements in the analytical performance as a function of different operational variables are shown for systems with or without a chemical reaction. Analytical implications and possible uses are discussed since this strategy allows the control of dispersion by simply selecting the frequency and amplitude of oscillation.