Determination of monochloroacetic acid using a flow injection system featuring a flow through ion-selective electrode and an ion-exchange column for the minimization of interference by chloride.

An automated flow injection system for on-line monitoring of monochloroacetic acid (MCAA) in industrial processes for the production of zwitterionic surfactants (betaines) is developed, which can treat samples with chloride ion concentration up to 1 M. The system features an ion-exchange column for the separation of MCAA from the interferents in the complex sample. The sample is injected at low pH values so that interfering anions, mainly chloride, are retained in the ion exchange column. Detection is performed using specially constructed all-solid-state tubular flow-through ion selective electrodes sensitive to monochloroacetate. Selectivity data of the constructed electrodes are given, while their pH working range is 4.0–11.0 and their lifetime is greater than 30 days through a range between 10−4–10−1 M. Once applied to the treatment of real samples, the system developed can detect MCAA in the range between 5·10−3–10−1 M, with a maximum deviation of 5% when compared to standard photometric methods of analysis. The short time used in each determination (30 s) in addition to its simplicity, leads to an improvement of the techniques of analysis used until now.