Spectrophotometric determination of polyquaternium-1 with trypan blue by a difference procedure

Abstract

A spectrophotometric method is described for the determination of polyquaternium-1 in a pharmaceutical solution. This method is based on a bathochromic shift of the trypan blue absorption which occurs when it is complexed with polyquaternium-1. The difference in absorption is measured at 680 nm with an apparent average molar absorptivity of 1.5 × 10⁵ l mol^–1 cm^–1. Linearity is observed over the range 5–15 µg ml^–1.