University of North Florida
Browse the Citations
-OR-

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

View Stuart Chalk's profile on LinkedIn

Commercial product

Citations 4

"Determination Of Phosphate Species In Nutrient Solutions And Phosphorus In Plant Material As Phosphovanadomolybdic Acid By Flow Injection Analysis"
Anal. Chim. Acta 1985 Volume 178, Issue 2 Pages 217-221
Oddvar Røtset

Abstract: A flow injection spectrophotometric method is described for the determination of PO43- by absorbance measurement at 400 nm of its yellow molybdovanadophosphoric acid complex. The detection limit is 0.1 mg L-1 of PO43-; the calibration graph is rectilinear for up to 30 mg L-1 of P and up to 240 samples per h can be analyzed. Up to 0.1 g L-1 of Fe and SiO2 and up to 1.0 g L-1 of other common cations and anions do not interfere. The method is used to determine P in plant nutrient solution and in digested plant material and is also applied to separation of free PO43- from acid-labile aluminum phosphate colloids in nutrient solution.
Phosphate Sample preparation Spectrophotometry Interferences Tecator

"Versatile Manifold For The Simultaneous Determination Of Ions In Flow Injection Analysis"
Analyst 1988 Volume 113, Issue 10 Pages 1551-1555
Peter C. Hauser, Susie S. Tan, Terence J. Cardwell, Robert W. Cattrall and Ian C. Hamilton

Abstract: A flow injection analysis system is described for the simultaneous determination in plant nutrient solution of K+, Ca(II), NO3- and Cl- by potentiometry, and NH4+ and PO43- by spectrophotometry. Diagrams of the manifold and the spectrophotometric transducer are given. Potentiometric measurements were made with PVC-based ion-selective membranes; the carrier stream was 0.2 M Na acetate buffer. Ammonium ion was determined by the gas diffusion method with use of cresol red and thymol blue. Absorbance was measured at 605 nm. The calibration graph covered the range from 0.5 to 25 mg L-1 as N. Phosphate was determined by the molybdenum blue method, with absorbance measurement at 820 nm; the calibration graph covered the range from 0.5 to 25 mg l-1. Results agreed well with expected values.
Potassium Calcium Ammonium Chloride Nitrate Phosphate Electrode Electrode Electrode Electrode Potentiometry Spectrophotometry Gas diffusion Simultaneous analysis

"Determination Of Trace Inorganic Selenium In Organoselenium (selenosugar) Oral Nutrition Liquids By Graphite Furnace Atomic Absorption Spectrometry With Hydride Generation"
Fresenius J. Anal. Chem. 1997 Volume 359, Issue 6 Pages 492-496
Zhang De-qiang A, Sun Han-wen A, Yang Li-li

Abstract: A method has been proposed for the determination of trace levels of inorganic selenium in organoselenium (selenosugar) oral nutrition liquids using hydride generation-graphite furnace atomic absorption spectrometry (HG-GFAAS), taking advantage of the fact that this organic selenium compound did not generate volatile hydride upon reduction. K2S2O8 was selected for the decomposition of the compound in a boiling water bath. Selenium was found to give a sharp analytical signal upon reduction with NaBH4 in 1.0 mol L-1 HCl medium. The characteristic mass giving an integrated absorbance of 0.0044 s was 21 pg. An absolute detection limit (3s) of 36 pg was obtained. The recovery was in the range of 94.2-102.1%. Less than parts per million levels of inorganic Se in the presence of organic selenium can be determined.
Selenium, inorganic Selenium, organic Spectrophotometry Speciation

"Enzymic Determination Of Nitrate By Flow Injection Analysis"
LaborPraxis 1991 Volume 15, Issue 6 Pages 479-481
Kuecke, M.

Abstract: The procedure described is based on the reduction of NO3- to NO2- by E. coli cells, chromogenic reaction with sulfanilamide and N-(1-naphthyl)ethylendiamine dihydrochloride, and spectrophotometric detection. Details are given of the preparation of the cell suspension. For analysis of water, the suspension (20 ml) was diluted with 0.1 M phosphate buffer (pH 7.2) (400 ml), whereas for Ca-containing extracts the cell suspension (15 to 25 ml) was centrifuged and the cells were suspended in 0.2 M borate buffer (pH 7.2) (400 ml). Continuous-flow injection analysis was performed by mixing the cell suspension with the sample in phosphate buffer solution (pH 7.2) in a coil (6 m x 0.7 mm) at 37°C, followed by mixing with the color reagent in another coil (30 cm x 0.7 mm) and detection at 540 nm. The procedure is suitable for the analysis of waters, wines, nutrient solution and similar samples.
Nitrate Spectrophotometry Buffer Heated reaction Enzyme