Potentiometric determination of <scp>L</scp>‐dopa, carbidopa, methyldopa and aspartame using a new trinitrobenzenesulfonate selective electrode

Abstract

Abstract A selective PVC membrane electrode based on the ion‐pair of cetylpyridinium (CP + ) and 2,4,6‐trinitrobenzenesulfonate (TNBS − ) as the electroactive species was developed. The electrode exhibits a rapid and Nernstian response to TNBS − from 5.0 × 10 −5 to 1.0 × 10 −2 M at 25 ± 0.1°C. The response is unaffected by the change of pH over the range 2–12. Selectivity coefficients for a larger number of organic and inorganic anions and sugars are given. The electrode has been successfully applied to the determination of L ‐dopa, carbidopa, methyldopa and aspartame in pure solutions and in their pharmaceutical formulations with a precision and accuracy of 0.9–1.3% without interference from excipients.