Absorption Spectra of Reaction System of Tetracaine Hydrochloride with Erythrosin and Its Analytical Application

Abstract

In a Britton-Robinson ( BR) buffer solution of pH = 4. 0,erythrosine reacted with tetracaine hydrochloride( TC.HCl) to form a 1∶1 ion-association complex. As a result the absorption spectra of solution changed,and an obvious fading peak at 516 nm and a coloring revealing peak at 558 nm appeared. In the range of 0. 1 × 10 -6 to 7. 2 × 10 -6 g/mL,there is linearity between the concentration of TC.HCl and absorbency of the solution at the fading peak and coloring revealing peak. Based on it,a new spectrophotometry for the determination of TC.HCl was proposed. The molar absorptivity is 3. 30 × 104 L/( mol.cm) for the fading method,2. 22 × 104 L/( mol.cm) for the revealing method and 5. 52 × 104 L/( mol.cm) for the dualwavelength method. The optimum reaction conditions and primary chemistry characteristics were discussed. The reaction mechanism was dicussed by quantum chemistry AM1 method. The method has been applied to the determination of TC.HCl in human serum and urine samples with satisfactory results. The mean recovery is from 98. 1% to 103. 3%.