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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Blackcurrent

Classification: Fruit -> juice -> blackcurrent

Citations 2

"Application Of Square-wave Voltammetry For The Determination Of Ascorbic Acid In Soft Drinks And Fruit Juices Using A Flow Injection System"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 375-380
Ying-Sing Fung* and Song-Ying Mo

Abstract: A portion (100 µL) of test solution was injected into a stream of the supporting electrolyte (Britton - Robinson buffer) for transfer to a thin-layer electrochemical cell (volume 16 µL) equipped with vitreous-carbon working, stainless-steel counter and Ag - AgCl reference electrodes. The normal flow rate was 0.5 mL min-1, and the potential of the working electrode was scanned from +0.2 to +0.7 V in 1 s, with application of a computer-generated square waveform and measurement of the oxidation peak current at +0.46 V. The buffer pH was 2.87 to stabilize the ascorbic acid. The peak signal was rectilinearly related to ascorbic acid concentration. from 2 µM to 6 mM; food additives at normal concentration. levels did not interfere. Results obtained on blackcurrant juice, lemon tea, sugar-cane juice and apple juice were satisfactory. The application of square-wave voltammetry for detection in the flow injection determination of ascorbic acid in soft drinks and fruit juices was investigated. The pH of the solution was buffered at 2.87 to stabilize the ascorbic acid prior to anal. Parameters such as scan rate, square-wave amplitude, step height and flow-rate of electrolyte were found to have little effect on the potential, but a significant effect on the current. The anal. current is only slightly affected by the flow-rate of the electrolyte and a max. scan rate of 0.5 V/s can be used. As a compromise between sensitivity and selectivity, 40 mV was chosen as the amplitude of the square wave and 10 mV as the potential step height. Similarly, a flow-rate of 0.5 mL/min and an injection volume of 100 µL were chosen as a compromise between the sensitivity and resolution of the FIA method. With these procedures, the max. number of samples that could be analyzed was 120/h. The linear calibration range was from 2 x 10^-6 to 6 x 10^-3 M and the determination limit (10s) was 2 x 10^-7M. No significant interference was found from additives commonly found in juice and drink samples within their normal concentration. ranges. Four juice samples were analyzed using the developed method and the results were compared with those given by the established AOAC method. No significant difference was observed between the two methods used for the four samples studied.
Ascorbic acid Voltammetry Electrode Standard method Method comparison Interferences

"Determination Of Total Acidity In Wines And Fruit Juices By Flow Injection Analysis"
GBF Monogr. Ser. 1989 Volume 11, Issue 1 Pages 277-280
Flossdorf, Josef; Wansheng, Yang (SFS)

Abstract: Procedures developed by J. Ruzicka were used for flow-injection anal. of total acidity in beverages. Agreement with the standard method is better than ±2%. Up to 30 determinations per h are possible with each 100-150 µL sample volume (SFS)
Acidity, total