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
Website: @unf

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Classification: Fruit -> citrus -> juice

Citations 5

"Flow Injection Fluorimetric Determination Of Thiourea"
Talanta 1995 Volume 42, Issue 3 Pages 391-394
Tomás Pérez-Ruiz*, Carmen Martínez-Lozano, Virginia Tomás and Rocio Casajús,

Abstract: A flow injection configuration for the fluorimetric determination of thiourea is presented. The method is based on the rapid oxidation of thiourea by Tl(III) with resultant formation of fluorescent Tl(I), which was measured at 419 nm (excitation at 227 nm). The calibration graph was linear from 0.5-10 µM with a sampling rate of 90 samples/h. RSD were 1.2-2.3% (n = 10). The method was applied to the determination of thiourea in citrus fruit juices and fruit peels. Recoveries were 95.6-100.5%.
Thiourea Fluorescence Indirect

"Flow Injection For The Determination Of Selenium(IV) And Selenium(VI) By Hydride-generation Atomic Absorption Spectrometry With Microwave-oven Online Prereduction Of Selenium(VI) To Selenium(IV)"
Spectrochim. Acta B 1996 Volume 51, Issue 14 Pages 1837-1847
J. L. Burguera, P. Carrero, M. Burguera, C. Rondon, M. R. Brunetto and M. Gallignani

Abstract: The manifold is based on an Ismatec IPC eight-channel peristaltic pump and incorporates the time-based injector, controlled by a Gralab model 900 programmable timer, described previously (Carrero et al., Talanta, 1993, 40, 1967; Burguera et al., Anal. Chim. Acta, 1995, 308, 339), a Prolabo MW Microdigest oven mode l 301, and the gas-phase separator of Burguera etal. (Ibid., 1991, 261, 105). The carrier is 1% HCl and the 0.5% NaBH4 reductant solutions for Se(IV) and Se(VI) are in 4 M and 12 M HCl media, respectively. Further NaBH4 solution is added downstream of the microwave oven to keep the baseline stable. Se is determined at 196 nm. The response is linear for up to 120 µg/l of Se(IV) and 100 µg/l of Se(VI), and the detection limits are 1 and 1.5 µg/l, respectively. The RSD were 2.0-2.5% and the recoveries of Se(IV) and Se(VI) were 96-98% and 94-98%, respectively. The method has been applied to geothermal water and citrus juice.
Selenium Sample preparation Spectrophotometry Microwave Online digestion Speciation Phase separator

"Study On The Sourness Of Food And Its Electrochemical Measurement. 7. Conductometric Flow Injection Analysis Of The Organic Acid Content In Citrus Fruits"
Agric. Biol. Chem. 1984 Volume 48, Issue 9 Pages 2211-2215
Kiyoshi MATSUMOTO, Koh-ichi ISHIDA, Takakazu NOMURA and Yutaka OSAJIMA

Abstract: A flow injection system, incorporating a flow-through four-electrode cell for controlled-potential conductance measurements, is described. For the analysis, a sample (35 µL) of pure centrifuged fruit juice was injected into the carrier stream (flow rate 20 mL min-1), and the mixing-coil length was 100 cm. There was good correlation (r = 0.992) between peak conductance and acid content (as shown by addition of malic and citric acids to the juice). By this method, 50 samples could be analyzed in 1 h, and the coefficient of variation of the results for any given juice was 0.5% (n = 20). To reduce the viscosity of the juice, dilution (1:3 or 1:4) before injection is recommended.
Acids, carboxylic Conductometry Electrode Conductometry Standard additions calibration Viscosity

"Kinetic Determination Of Ascorbic Acid In Fruit Juices"
An. Quim. 1991 Volume 87, Issue 5 Pages 683-686
Erroz, C.L.;Hernandez Cordoba, M.;Sanchez Pedreno, C.

Abstract: Ascorbic acid was determined spectrophotometrically (600 nm) by measuring the initial rate of reaction at 25°C with 5-[N-(3,5-dichloroquinoniimine)]-8-hydroxyquinoline in a reaction mixture containing 20% EtOH and 0.08 M Britton-Robinson buffer (pH 5.5). This procedure was appropriate for the determination of 10^-5 - 4 x 10^-4 M ascorbic acid. The relative standard deviation was ≤4.2%. Good agreement with the AOAC procedure was obtained when the new method was applied to pineapple, pear, and peach nectars, and to apple juice. (SFS)
Ascorbic acid HPLC Kinetic

"Flow Injection Analysis System For Conductometric Measurement Of Sugar Content. Study On Electrochemical Measurement Of Sugar Content Of Food, Part VII "
Nippon Shokuhin Kagaku Kogaku Kaishi 1985 Volume 32, Issue 8 Pages 576-581
Takakazu NOMURA, Hiroyuki UKEDA, Kiyoshi MATSUMOTO, Yutaka OSAJIMA

Abstract: A conductometric flow injection analysis system for measuring sugar content in food was constructed and several component of this system were investigated. The controlled-current four-electrode method was used for conductance measurements, and then the cell constant of this system was not affected by flow rate (0-5 mL min-1). The most preferrable conditions for optimum operation of the system were as follows: mixing coil length 80 cm (i.d.=0.8 mm), injection volume 0.68 ml, flow rate 2.3 mL min-1. Over the range of 5 to 30% (w/w), the linear response was obtained and the coefficient of variation was 0.20% at 20% (w/w) sucrose for 10 successive assays. The measuring time was about 3 min for each of these assays. The sugar content in citrus juice estimated with this system agreed with that obtained from phenol-sulfuric acid method within an error of 0.20% (w/w).
Sucrose Conductometry Method comparison