The study of nonionic ethoxylates determination according to Czech standard ČSN ISO 7875, part 2 (Determination of nonionic surfactants using Dragendorff reagent – so-called BiAS method) is main subject of the experimental part. Three possible final determination of bismuth concentration are compared. The Bi content can be measured by potentionmetric titration with pyrrolidine dithiocarbamate, by atomic absorption spectroscopy or by ultraviolet spectrophotometry. Analogous method is given in the Standard Methods for Examination of Water and Wastewater. Nonionic surfactants react with cobalt thiocyanate reagent forming a Co – complex, in which cobalt concentration is determined by VIS spectrophotometry (CTAS method). The differences between BiAS and CTAS method are studied in this work.
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