Determination of Captopril in Biofluids by Luminol–Chloroauric Acid–Lysozyme Chemiluminescence

Abstract

A rapid and sensitive method for determining captopril by flow injection chemiluminescence is reported. It was found that captopril quenched the chemiluminescence of the luminol–chloroauric acid–lysozyme system. The decreased chemiluminescence was linear with the logarithm of captopril concentration between 0.1 and 50.0 ng · mL⁻¹ with a detection limit of 0.03 ng · mL⁻¹ (3σ). At a flow rate of 2.0 mL · min⁻¹, one analysis cycle including sampling and washing was accomplished within 36 s. The chemiluminescence method was successfully applied to the continuous monitoring of captopril in human urine after oral intake over a period of 7.5 hr. Captopril reached a maximum concentration in urine at 1.5 hr and the total elimination ratio was 48.70 ± 0.09%. The pharmacokinetic parameters of absorption rate constant (2.81 ± 0.05 h⁻¹), elimination rate constant (0.88 ± 0.02 h⁻¹), and elimination half–life time (0.79 ± 0.01 h) were obtained. The possible chemiluminescence mechanism of lysozyme/captopril reaction was obtained with molecular docking methods.

Keywords:

• captopril
• chemiluminescence
• chloroauric acid
• flow injection
• lysozyme
• pharmacokinetic