Highly efficient and sensitive screening of ractopamine in foodstuffs by HPLC-FLD using fluorescent labeling and ultrasonic-assisted dispersive liquid–liquid microextraction

Abstract

A simple, low-cost, rapid, sensitive and specific analytical method for ractopamine (RAC) screening in foodstuffs based on fluorescent labeling coupled with ultrasonic-assisted dispersive liquid–liquid microextraction (UA-DLLME) was established by high-performance liquid chromatography (HPLC) with fluorescence detection (FLD). In this study, 2-(11H-benzo[a]carbazol-11-yl)ethyl chloroformate (BCEC-Cl) was first employed as the labeling reagent for RAC, and the labeled sample was directly submitted to UA-DLLME. In order to obtain optimal experimental conditions, several important parameters including the kinds of extraction and dispersive solvent, pH of the solution, salt effect and the volume of sample solution affecting the UA-DLLME were optimized systematically. Moreover, the main parameters including ultrasonic time (T), extraction solvent volume (EV) and disperser solvent volume (DV) were further optimized by response surface methodology (RSM) based on a Box–Behnken design (BBD). Under the optimal conditions, the quantitative linear range of the targeted analyte was 2–100 ng mL⁻¹, and the correlation coefficient was 0.9995. The low limit of detection (LOD) and limit of quantification (LOQ) for RAC were 0.4 ng mL⁻¹ and 1.3 ng mL⁻¹, respectively. The developed method combining the merits of fluorescent labeling and UA-DLLME facilitated high-sensitivity and high-throughput sample screening. The novel method was successfully applied to trace RAC screening in foodstuffs with excellent applicability and good reproducibility. This method was proven to be inexpensive, sensitive, efficient, accurate and reliable for trace RAC screening.