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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M. Lucia M.F.S. Saraiva

Abbrev:
Saraiva, M.L.M.F.S.
Other Names:
Maria Lúcia Marques Ferreira de Sousa Saraiva
Address:
Phone:
+351-22-2078939
Fax:
+351-22-2004427

Citations 10

"Fluorimetric Determination Of Aminocaproic Acid In Pharmaceutical Formulations Using A Sequential Injection Analysis System"
Talanta 2005 Volume 68, Issue 3 Pages 857-862
Paula C.A.G. Pinto, M. Lúcia M.F.S. Saraiva, João L.M. Santos and José L.F.C. Lima

Abstract: A sequential injection analysis (SIA) methodology for the fluorimetric determination of aminocaproic acid in pharmaceutical formulations is proposed. The developed analytical procedure is based on the derivatization reaction of the aminocaproic primary amine with o-phthalaldehyde (OPA) and N-acetylcysteine (NAC) and fluorimetric detection of the formed product (λex = 350 nm; λem = 450 nm). The implementation of a SIA flow system allowed for the development of a simple, fast and versatile automated methodology, which exhibits evident advantages regarding the US Pharmacopoeia 24 (USP 24) reference procedure. By combining the SIA time-based sample insertion with a subsequent zone sampling approach, which permitted to select for detection of a well-defined sample zone, it was possible to implement an on-line dilution strategy that enabled the expansion of the analytical working range of the methodology, and thus its application in dissolution studies, without manifold re-configuration.Linear calibration plots were obtained for aminocaproic acid concentrations up to 6 x 10^-5 mol l-1. The developed methodology exhibit a good precision, with a RSD < 2.0% (n = 15) and the detection limit was 2.5 x 10^-7 mol l-1. The obtained results complied with those furnished by the reference procedure with a relative deviation lower than 1.2%. No interference was found.

"Sensitive Sequential Injection Determination Of Naproxen Based On Interaction With -cyclodextrin"
Talanta 2005 Volume 68, Issue 2 Pages 226-230
Eftychia-Pavlina Zisiou, Paula C.A.G. Pinto, M. L&uacute;cia M.F.S. Saraiva, Christophe Siquet and Jos&eacute; L.F.C. Lima

Abstract: A sensitive sequential injection analysis (SIA) methodology for the fluorimetric determination of naproxen is proposed. The developed automatic analytical procedure is based on the complexation of naproxen with ?-cyclodextrin (?-CD) yielding an enhanced fluorimetric signal (?ex = 280 nm, ?em = 356 nm). Linear calibration plots were obtained for naproxen concentrations up to 1 x 10^-5 mol l-1. The developed methodology exhibited a good precision, with a RSD < 2.1% (n = 15). The detection limit of the determination was 1.9 x 10^-7 mol L-1 with a sampling rate of about 70 h-1. The automatic method was applied to the determination of naproxen in pharmaceutical formulations. The obtained results were compared with those furnished by the reference procedure and the relative deviations were lower than 3.6%. No interference was found from the excipients usually used in solid pharmaceutical formulations. © 2005 Elsevier B.V. All rights reserved.

"An Enzymatic Flow Analysis Methodology For The Determination Of Nitrates And Nitrites In Waters"
Int. J. Environ. Anal. Chem. 2005 Volume 85, Issue 1 Pages 29-40
Paula C. A. G. Pinto; Jos&eacute; L. F. C. Lima; M.L&uacute;cia M. F. S. Saraiva

Abstract: An enzymatic flow analysis approach, based on the Griess-Ilosvay reaction, was developed for the evaluation of nitrite and nitrate, aiming at an environmentally benign alternative reduction method using nitrate reductase and the development of an in-line dilution procedure for the analysis of water samples, with a wide range of nitrate concentrations. Nitrate concentrations up to 250 mg/L can be analyzed directly in the automatic system, by changing the aspirated sample volume or by applying the in-line dilution procedure provided by the automatic system. Under the optimum conditions, the calibration curves were linear up to 50 mg/L of nitrate and 3 mg/L of nitrite, with the detection limits being 0.73 mg/L and 0.03 mg/L, respectively. Nitrate and nitrite were determined in different water types by the flow method with rsd < 5%. Comparison with the reference methods showed no statistically significant differences for a 95% confidence level. © 2005 Taylor & Francis Group Ltd.

"Sequential Injection Analysis Of Nitrites And Nitrates In Human Serum Using Nitrate Reductase"
Clin. Chim. Acta 2003 Volume 337, Issue 1-2 Pages 69-76
Paula C. A. G. Pinto, Jos&eacute; L. F. C. Lima and Maria L&uacute;cia Marques Ferreira de Sousa Saraiva

Abstract: Background: Nitrates and nitrites, as products of nitric oxide in human serum, are currently used as markers in many diseases. A sequential injection analysis (SIA) flow system, for their determination in serum, is presented. The exact timing of fluidic manipulations and the small volumes used in the automated SIA systems provide exquisite control of the reaction conditions and an economy in the biological fluid and enzymes used. Methods: For nitrite determinations, 150 µl of sample and 50 µl of Griess reagent were sequentially aspirated to the system and sent to the detector. Nitrates were determined as nitrites after reduction through 0.09 U of nitrate reductase and 75 µl of NADPH. Results: Nitrates and nitrites were determined at concentrations up to 4 and 3 mg/l, respectively, with relative standard deviation (rsd) Conclusions: The automatic developed method seems to be a good alternative for routine implementation since it is four times faster, and it requires one third of sample and one half of nitrate reductase than the comparison batch procedure.

"Application Of Sequential Injection Analysis To The Determination Of Cationic Surfactants Based On The Sensitized Molybdenum-Bromopyrogallol Red Reaction"
Anal. Sci. 2005 Volume 21, Issue 12 Pages 1509-1514
Marieta L. C. Passos, M. L&uacute;cia M. F. S. Saraiva And Jos&eacute; L. F. C. Lima

Abstract: The aim of this work was to develop a simple, automatic system for the evaluation of cationic surfactants by combining sequential injection analysis and the sensitized effect of cationic surfactants on the reaction between metal ions and chelating dyes. This reaction is based on the increase in absorbance of the complex formed among molybdenum, bromopyrogallol red and increasing concentrations of cationic surfactants. Under optimum conditions, two calibration plots were obtained for a concentration range between 2.50 x 10^-7 mol L-1 (detection limit) and 5.00 x 10^-4 mol L-1 of cetylpyridinium chloride, used as standard. Solubilization of water insoluble complexes formed for concentrations of cationic surfactants greater than 1.00 x 10^-4 mol L-1 were successfully achieved with Triton X-405. RSD values lower than 5.0% were obtained in all cases. The quality of the results obtained for 18 water samples were evaluated by comparison with conventional methods, with no statistically significant differences for a 95% confidence level.
Surfactants, cationic Environmental Spectrophotometry Triton X Method comparison Optimization Sequential injection

"Determination And Antioxidant Activity Evaluation Of Etodolac, An Anti-inflammatory Drug, By Sequential Injection Analysis"
Anal. Chim. Acta 2006 Volume 573, Issue 1 Pages 371-375
Julia B. Garcia, M. L&uacute;cia M.F.S. Saraiva and Jos&eacute; L.F.C. Lima

Abstract: A robust, accurate and sensitive automated procedure for the determination of etodolac, an anti-inflammatory drug, in pharmaceutical formulas by sequential injection analysis, is reported. The same system was also applied to evaluate the antioxidant activity of the drug expressed as Trolox equivalent antioxidant capacity (TEAC). The methodology is based on measuring at 734 nm the decay of absorbance of a solution with the radical 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS+) after its reduction by etodolac. Optimum ABTS+-etodolac reaction was achieved with 0.329 mL of sample and 0.205 mL of ABTS+ solution. Etodolac was determined at concentrations up to 4.5 x 10^-5 mol L-1. A solution detection limit of 6.6 x 10^-6 mol L-1 was obtained under the optimized experimental conditions. A relative standard deviation (n = 10) lower than 4.7% with a sample throughput of more than 21 samples/h was obtained. No interference from excipients was observed. The developed methodology was applied in the analysis of pharmaceutical preparations and the obtained results were in good agreement with those furnished by the reference procedure with relative deviations lower than 1.4%.

"A Flow Sampling Strategy For The Analysis Of Oil Samples Without Pre-treatment In A Sequential Injection Analysis System"
Anal. Chim. Acta 2006 Volume 555, Issue 2 Pages 377-383
Paula C.A.G. Pinto, M. L&uacute;cia M.F.S. SaraivaCorresponding Author Contact Information, E-mail The Corresponding Author and Jos&eacute; L.F.C. Lima

Abstract: The present work describes a sequential injection analysis (SIA) system adapted to direct analysis of oil samples. In this way, the flow system was designed by incorporation, in the SIA system, of an injection valve that was responsible for the sample insertion. With the developed sampling strategy the sample pre-treatment outside the flow system is avoided and also the problems associated with viscous samples in flow systems. The developed SIA system was applied to the determination of iron (Fe(III)) in edible oil samples and was based on the formation of a red complex (? = 510 nm) between Fe(III) and thiocyanate in organic medium. A mixture of methanol:chloroform (85:15) was used as carrier solution and possible refractive index associated with the spectrophotometric detection was avoided by introduction of a mixing chamber in the flow system. The presented methodology produced 4.2 mL of effluent and consumed 150 µL of sample and 0.95 mg of thiocyanate per determination. Linear calibration plots were obtained for Fe(III) concentrations up to 25 mg L-1 and the detection limit of the determination was 0.31 mg l -1. The developed methodology exhibited a good precision, with an RSD < 3.5% (n = 15) and a determination frequency of 20 determinations h-1. The results of the analysis were evaluated by recovery studies (96.5-104.5%) and by the analysis of two AOCS reference samples. © 2005 Elsevier B.V. All rights reserved.

"A Pulsed Sequential Injection Analysis Flow System For The Fluorimetric Determination Of Indomethacin In Pharmaceutical Preparations"
Anal. Chim. Acta 2005 Volume 539, Issue 1-2 Pages 173-179
Paula C.A.G. Pinto, M. L&uacute;cia M.F.S. SaraivaCorresponding Author Contact Information, E-mail The Corresponding Author, Jo&atilde;o L.M. Santos and Jos&eacute; L.F.C. Lima

Abstract: This works reports the development of a pulsed flow sequential injection analysis (SIA) system based on the utilisation of pulse generating solenoid micro-pumps, which replace the conventional solutions propelling units commonly used in SIA systems. The influence on sample/reagent zones interpenetration and reaction zone formation of the reproducible pulsed flow produced by micro-pumps operation, which is characterized by a chaotic solutions movement, was comparatively evaluated with the typical laminar flow conditions of conventional SIA systems. The enhanced sample/reagent mixing provided by the controlled pulsed flow was favourably applied in the implementation of a SIA methodology for the fluorimetric determination of indomethacin in pharmaceutical preparations upon alkaline hydrolysis in micellar medium. Linear calibration plots were obtained for indomethacin concentrations up to 10^-5 mol L-1 with a 3? detection limit of about 1.6 x 10 -8 mol l-1. The obtained results complied with those furnished by the reference procedure (RD ? 2.3%) and exhibited good reproducibility (RSD < 1.2%, n = 15). Sampling rate was about 30 samples per hour. © 2005 Elsevier B.V. All rights reserved.

"Automatic Sequential Determination Of The Hydrogen Peroxide Scavenging Activity And Evaluation Of The Antioxidant Potential By The 2,2- Azinobis(3-ethylbenzothiazoline-6-sulfonic Acid) Radical Cation Assay In Wines By Sequential Injection Analysis"
Anal. Chim. Acta 2005 Volume 531, Issue 1 Pages 25-32
Paula C.A.G. Pinto, M. L&uacute;cia M.F.S. SaraivaCorresponding Author Contact Information, E-mail The Corresponding Author, Salette Reis and Jos&eacute; L.F.C. Lima

Abstract: An automatic system that performs two analytical procedures, allowing the evaluation of the relative antioxidant capacity of wine samples, was developed. Automation was carried out using a sequential injection analysis (SIA) system that allowed, thanks to its versatility, the development of two methodologies. One is based on the decolorization assay of the 2,2?-azinobis(3- ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical, using a spectrophotometric detector. A second methodology allowed the evaluation of the hydrogen peroxide scavenging activity by measuring the oxidation of homovanylic acid (HVA) to its fluorescent dimer, using a fluorescent detector. The developed automatic methodologies were evaluated using trolox as standard and subsequently using other antioxidant substances as gallic acid, caffeic acid, ascorbic acid, catechin and taxifolin which are abundant in wine and whose antioxidant activities were compared to that shown by trolox. The spectrophotometric and fluorimetric assays showed linearity intervals between 0.001 and 0.01 mM, and 0.001 and 0.008 mM of trolox, respectively. The evaluation of the antioxidant power of 20 white and red wine samples, from different Portuguese wine producing regions, was carried out sequentially, in the automatic system. The results were expressed in trolox equivalent antioxidant capacity (TEAC) and presented, for the ABTS and hydrogen peroxide scavenging activity methodologies, detection limits of 8.4 x 10^-7 and 1.4 x 10^-4 mM and relative standard deviation (RSD (%)) in the range 0.6-2.4 and 1-1.8, respectively. © 2004 Elsevier B.V. All rights reserved.

"A New Approach To Dialysis In Sequential Injection Systems: Spectrophotometric Determination Of L(+)-lactate In Wines"
Am. J. Enol. Vitic. 1997 Volume 48, Issue 4 Pages 428-432
Alberto N. Ara&uacute;jo, Jos&eacute; L.F.C. Lima, M. L&uacute;cia M.F.S. Saraiva, and Elias A.G. Zagatto

Abstract: A sequential injection analysis (SIA) system for the spectrophotometric determination of L(+)-lactate using lactate oxidase/peroxidase was developed and applied to wine analysis. It incorporates a dialysis unit between the pump and the selecting valve to provide online dilution and interference minimization of the sample matrix. A volume of 100 µL of carrier solution trapped in one channel of the dialysis unit, acts as donor and acceptor solution. With an assay cycle of 262 seconds, the system allows a sample throughput of 14 samples per hour and yields precise results (rsd < 2%). Peroxidase (0.0512 IU) and 0.0384 IU of lactate oxidase promote the conversion of L(+)-lactate in 160 µL of sample, allowing its determination within the 0.25 to 2.5 g/L range. A detection limit of 0.074 g/L was calculated. Results are in good agreement with those obtained with the conventional method (Boehringer UV-Kit).
l-Lactate Wine Spectrophotometry Sequential injection Interferences Dilution Method comparison Dialysis