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: Environmental -> water -> canal

Citations 2

"Determination Of Total Ammoniacal Nitrogen In Water By Flow Injection Analysis And A Gas Diffusion Membrane"
Anal. Chim. Acta 1983 Volume 153, Issue 1 Pages 271-275
M. van Son, R. C. Schothorst and G. den Boef

Abstract: The sample (29 µL) is injected into a 10 mM NaOH carrier stream (0.72 mL min-1) and passes to a dialyser module fitted with a PTFE gas-permeable membrane. The NH3 released diffuses through the membrane and is absorbed in a parallel stream of 0.1 mM bromothymol blue (pH 6.5), and the absorbance of the resulting solution is measured at 620 nm. The change in absorbance of the indicator solution varies rectilinearly with the concentration. of NH3 in the sample within the range 1 µM to 0.1 mM, and the limit of detection is ~1 µM. Results for canal water (~65 µM-NH3) agreed well with those by the Nessler method. The sampling rate is 100 h-1. Carbon dioxide interferes seriously, but the method has the advantage that clarification of turbid samples is unnecessary.
Ammonium, nitrogen Spectrophotometry Interferences Gas diffusion Teflon membrane

"Chemical Oxygen Demand Determination In Well And River Waters By Flow Injection Analysis Using A Microwave Oven During The Oxidation Step"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 295-299
M. L. Balconi, M. Borgarello and R. Ferraroli*, F. Realini

Abstract: The sample (0.25 ml) is injected into water as carrier and, after mixing, the stream is treated with oxidizing solution prepared by adding dropwise, with vigorous stirring, 10 mL of aqueous 12% K2Cr2O7 to 300 mL of concentrated H2SO4 and diluting the cooled solution to 1 l with concentrated H2SO4. The resulting solution passes through a reaction coil (10 m) enclosed by a microwave oven operated at 180 W and then through a cooling coil and a de-bubbler before absorbance measurement at 445 nm. Under optimum conditions (described), the calibration graph is rectilinear for COD up to 100 mg l-1, and the detection limit is 1.5 mg l-1. The coefficient of variation was 2.1% (n = 20) at 40 mg l-1. Results obtained on well, river and canal water, sewage and food industry waste agreed with those by a standard method. A flow injection method based on the use of a microwave oven to maximize the rate of the oxidation step is described. The flow system consists of 2 lines (water as carrier and K dichromate-H2SO4 mixture as reagent), 3 coils, of which the intermediate one (wound around a special strong microwave absorber support) acts as reaction coil, a membrane degassing unit, and a spectrophotometric detector. Optimal parameters includes the oven capacity at 180 W, application range in 0-100 mg/L COD, relative standard deviation 2.12% at 40 mg/L COD, and detection limit 1.5 mg/L COD. Preliminary applications were made to well water, river water (with low COD levels), and wastewaters. The results obtained are in good agreement with those given by the manual reference method.
Chemical oxygen demand Spectrophotometry Microwave Method comparison Optimization Standard method