Note: Determination of effective gas diffusion coefficients of stainless steel films with differently shaped holes using a Loschmidt diffusion cell

In the past, some authors have not defined the diffusion coefficient appropriate to their experimental system, consequently, valuable data have been lost. We discuss the various diffusion coefficients referred to all possible frames of reference in relation to the choice of a suitable experimental system for the determination of gaseous diffusion coefficients in porous media. A modified Ney and Armistead type diffusion cell is described with an improved method of calculation of results from continuously monitored concentration changes in the diffusion cell.

Download Full-text

Determination of Sulfite in Food by Flow Injection Analysis

Journal of AOAC INTERNATIONAL ◽

10.1093/jaoac/69.3.542 ◽

1986 ◽

Vol 69 (3) ◽

pp. 542-546 ◽

Cited By ~ 2

Author(s):

John J Sullivan ◽

Thomas A Hollingworth ◽

Marleen M Wekell ◽

Richard T Newton ◽

Jack E Larose

Keyword(s):

Flow Injection ◽

Flow Injection Analysis ◽

Extraction Procedure ◽

Food Product ◽

Food Products ◽

Peak Height ◽

Gas Diffusion ◽

Diffusion Cell ◽

Low Concentrations

Abstract A method is described for the determination of sulfite levels in food products by flow injection analysis (FIA). The method is based on the decolorization of malachite green by S02, which is isolated from the flowing sample stream by means of a gas diffusion cell. The FIA method has a detection limit in food sample extracts of 0.1 ppm S02 (3 times peak height of blank), which corresponds to 1-10 ppm S02 in a food product, depending on the extraction procedure used. At the 5 ppm SO2 level in a food extract, the precision of replicate injections is ± 1-2%. The method was tested on a variety of both sulfite-treaied and untreated food products and the results compared favorably with those obtained by the Monier-Williams, colorimetric (pararosaniline), and enzymatic (sulfite oxidase) methods. The average differences from the FIA results were 19, 11, and 12%, respectively, for those samples (n = 12) above SO ppm S02. At lower levels the results were somewhat more erratic due to inaccuracies of the various methods at low concentrations.

Download Full-text

Total Volatile Acids: Temperature Dependent Decomposition Indicator in Halibut Determined by Flow Injection Analysis

Journal of Food Protection ◽

10.4315/0362-028x-57.6.505 ◽

1994 ◽

Vol 57 (6) ◽

pp. 505-508 ◽

Cited By ~ 1

Author(s):

THOMAS A. HOLLINGWORTH ◽

JAMES M. HUNGERFORD ◽

JAMES D. BARNETT ◽

MARLEEN M. WEKELL

Keyword(s):

Elevated Temperature ◽

Flow Injection ◽

Flow Injection Analysis ◽

Gas Diffusion ◽

Diffusion Cell ◽

Total Volatile ◽

Temperature Dependent ◽

Seafood Products

Total volatile acids (TVA) is a well known indicator for the decomposition of seafood products. A flow injection analysis (FIA) method, using a gas diffusion cell at elevated temperature, was developed for the determination of TVA in fish and applied to halibut. The FIA method is simple and rapid. The results of this study indicate that the correlation between levels of TVA and degree of decomposition is temperature dependent.

Download Full-text

Some Methodological Modifications of Determination of Diffusion Coefficients in Compacted Bentonite

MRS Proceedings ◽

10.1557/proc-932-11.1 ◽

2006 ◽

Vol 932 ◽

Cited By ~ 8

Author(s):

Dušan Vopálka ◽

Helena Filipská ◽

Antonín Vokál

Keyword(s):

Diffusion Coefficients ◽

Effective Porosity ◽

Diffusion Method ◽

Dry Density ◽

Diffusion Cell ◽

Compacted Bentonite ◽

Method Of Evaluation ◽

Exclusion Effect ◽

Positively Charged

ABSTRACTThe results of 3H, 36Cl and 137Cs diffusion experiments through compacted bentonite using a new design of diffusion cell and a new methodology of diffusion coefficients evaluation are presented. The diffusion cell was made from the stainless steel and enables to connect it directly to the input and/or output reservoirs without any tubing. The evaluation of diffusion coefficients utilizes a compartmental model developed in the environment of the GoldSim transport code. It enables to determine diffusion coefficients for various types of boundary conditions, including also input and output filters. The influence of the diffusion through filters on the determined values of both effective (De) and apparent (Da) diffusion coefficients was numerically demonstrated for the through diffusion method. This effect is most important for Da, the value of which would be underestimated using standard ways of evaluation for neutral and positively charged species, mainly in the case of high effective porosity.The comparison of standard and the newly developed method of evaluation of diffusion coefficients showed a significant influence of diffusion in filters for HTO. Contrary to the standard method of evaluation, the evaluation taking into account filters showed here no difference between total and effective porosity. The effect of filter resistance was negligible for Cl-, especially at high dry density of compacted bentonite, due to the anion exclusion effect. The numerical model developed enabled to determine Da values of Cs+ from the concentration change in the inlet reservoir.

Download Full-text