Resonance Rayleigh scattering technique as a detection method for the RP‐HPLC determination of local anaesthetics in human urine

A highly selective and sensitive method of reversed phase high‐performance liquid chromatography (RP‐HPLC) coupled with resonance Rayleigh scattering (RRS) was developed for the determination of procaine, bupivacaine and tetracaine. Separation of three local anaesthetics was achieved at 35 °C on a C₁₈ column. The mobile phase was 30: 70 (v/v) acetonitrile/triethylamine–phosphoric acid buffer (pH 2.9) at flow rate of 0.3 mL/min. The RRS detection was conducted by taking advantage of the strong RRS enhancement of the local anaesthetics with erythrosine reaction in an acidic medium. Under optimum conditions, the limit of detection (S/N = 3) values were in the range of 2.4–11.2 ng/mL. Recoveries from spiked human urine samples were 95.8%–104.5%. The proposed method applied to the determination of local anaesthetics in human urine achieved satisfactory results. In addition, the mechanism of the reaction is fully discussed. Copyright © 2016 John Wiley & Sons, Ltd.