Determination of Low Chlorine Content in Organic Compounds and Polymers Using an Expert-006 Coulometer

A method of visual mercurimetric titration of chloride ions is widely used in elemental microanalysis for determination of chlorine content in organic substances after their combustion in an oxygen-filled flask. However, when the chlorine content is less than 0.5%, the mercurimetric method fails to provide sufficient accuracy, and a more sensitive method of chlorine coulometric titration by electrogenerated silver ions appears preferable. We consider the possibility of determining microgram contents of chloride ions in solutions using a digital coulometric analyzer (Expert-006 produced by Econics-Expert (Moscow)) supplemented with an electrolytic cell with silver electrodes. The coulometer was tested in different operating modes to select the optimal electrochemical parameters of ion chloride titration and develop a technique for coulometric determination of chloride ions which in combination with the preliminary burning of the analyzed substances in an oxygen-filled flask provides determination of the residual chlorine in organic matrices at a level of 0.1–0.5%. The proposed technique was used to determine the residual chlorine in a number of polymers. The relative error did not exceed 5% at chlorine concentrations of 0.16–0.28%.