Document Detail

Progress in pulsed-current Karl Fischer coulometry using diaphragm-free cells.
MedLine Citation:
PMID:  11225824     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Factors influencing the accuracy of water determinations using diaphragm-free, pulsed current Karl Fischer (KF) coulometry were investigated with the new Metrohm 756 instrument. Results obtained with commercially available reagents from Riedel-deHaen and Merck were compared with home-made ones that were especially designed to minimize the formation of iodine-consuming reduction products generated in the cathode reaction. Positive errors in the range 2-5% were found for the commercial reagents as compared to 0.2-1% for the home-made ones which were buffered at about pH 10 containing modifiers like chloroform, hexanol or ethylene glycol. Except for the composition of the KF-reagent, the cathode current density and the titration rate were found to be critical parameters for the accuracy of the determinations. For all reagents investigated, the best results were obtained for the maximum generator current 400 mA (corresponding to a current density of 1,400 mA cm(-2)) in combination with a maximum titration rate of 2,000 microg min(-1). Surprisingly, the errors found under optimum conditions for the pulse technique were always somewhat larger than the corresponding values obtained with continuous coulometry.
U Nordmark; A Cedergren
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Fresenius' journal of analytical chemistry     Volume:  367     ISSN:  0937-0633     ISO Abbreviation:  Fresenius J Anal Chem     Publication Date:  2000 Jul 
Date Detail:
Created Date:  2001-02-27     Completed Date:  2001-04-05     Revised Date:  2003-10-31    
Medline Journal Info:
Nlm Unique ID:  9114077     Medline TA:  Fresenius J Anal Chem     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  519-24     Citation Subset:  -    
Department of Chemistry, Umeå University, Sweden.
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