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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Dual valve

Classification: Manifold component -> Dual valve

Citations 3

"Flow Injection System For Kinetic Determinations Based On The Use Of Two Serial Injection Valves"
Analyst 1987 Volume 112, Issue 6 Pages 803-807
Alfonso Fernández, María Dolores Luque de Castro and Miguel Valcárcel

Abstract: A flow injection configuration is described which inserts two zones of the same sample simultaneously into a channel to give two peaks at different residence times. The physical and physico-chemical behavior of the configuration was studied by injection of a dye and by the use of two chemical systems with different reaction rates. The manifold was applied to individual and differential kinetic determinations of Co and Ni, the latter based on their different complexation rates with 2-hydroxybenzaldehyde thiosemicarbazone. For individual kinetic determinations, peak area or height measurements made at two different reaction times were used to determine Co and Ni in the range 2 to 30 µg mL-1. The differential kinetic method was applied in the resolution of mixtures containing 5 to 50 µg mL-1 of each analyte. The coefficient of variation for mixtures of equal and extreme ratios of Co and Ni were 2.3% (n = 11) at a sampling rate of 15 h-1.
Cobalt Nickel Spectrophotometry

"Individual And Simultaneous Determination Of Ethanol And Acetaldehyde In Wines By Flow Injection Analysis And Immobilized Enzymes"
Anal. Chem. 1987 Volume 59, Issue 14 Pages 1859-1863
Fernando Lazaro, M. D. Luque de Castro, and Miguel Valcarcel

Abstract: Ethanol(I) and acetaldehyde(II) in wine were determined individually on a straightforward flow injection analysis manifold with a suitable enzyme reactor by using immobilized alcohol dehydrogenase and acetaldehyde dehydrogenase (NAD(P)+), respectively, and detection at 340 nm. For the simultaneous determination, a dual injection valve was used that inserted the sample into different length channels, each containing an enzyme reactor. One peak per analyte was obtained. Calibration graphs for I and II, respectively, were rectilinear from 2 to 14 ppm (v/v) and 0.5 to 11.0 µg mL-1, and corresponding coefficient of variation were 0.6 and 0.5%. Results compared favourably with those obtained by using a dissolved enzyme technique.
Acetaldehyde Ethanol Wine Spectrophotometry

"Simultaneous Determination Of Ascorbic Acid And Sulfite In Soft Drinks By Flow Injection Analysis"
Analusis 1987 Volume 15, Issue 4 Pages 183-187
Lazaro, F.;Luque De Castro, M.D.;Valcarcel, M.

Abstract: The method is based on the reactions of SO32- and ascorbic acid with chloramine T. By means of a dual valve system a portion of sample containing both analytes, together with KI and Na oxalate (stabilizer), is introduced into the system and yields a signal corresponding to both species; at the same time a second portion of sample is mixed with 0.1 M NaOH and heated to 45°C, thereby eliminating the ascorbic acid before reaction and thus producing a signal due almost entirely to SO32-. Four calibration graphs are prepared, corresponding to ascorbic acid and SO32- via each valve. Calibration graphs cover the range 4 to 140 µg mL-1. Advantages of this method are a high sampling frequency (90 h-1) and reduced sample and reagent consumption.
Ascorbic acid Sulfite Soft drink