New flow injection method for quality control of dietary supplements containing l-carnitine using extraction mediated by sodium taurodeoxycholate coacervate coupled to molecular fluorescence

• Novel method has been developed for l-Carnitine fluorescent quantification.
• On-line sodium taurodeoxycholate coacervate mediated extraction has been applied.
• It constitutes an alternative strategy to l-Carnitine conventional analysis.
• It is a green method considering the low volume consumption of reagents.

Carnitine (CAR) is an essential component of the tissue of animals, higher plants and many microorganisms; it plays an important role during the metabolism of the human body. CAR transfers fatty acids to the place of burning-mitochondria and aids in the transformation of fats into energy and in this way supports overweight reduction and immediate physical performance, increases resistance from physical load and protects heart from overload. In this study, a new methodology for the determination of L-CAR by molecular fluorescence is described, after derivatization with a fluorescence active substance, 9-fluorenylmethyl chloroformate. An on-line coacervation process was used in order to isolate the analyte of the complex matrix. The developed methodology was successfully applied to the control of carnitine content in dietary supplements. The detection limit and quantification obtained were 2.4 × 10− 8 mol L− 1 and 7.30 × 10− 8 mol L− 1; respectively. Recoveries between 82 and 103% were obtained. At optimized working conditions, the sample throughput was 30 samples h− 1 (without considering the required time for L-CAR derivatization). Thus short analysis and very low running costs compared with the LC/MS conventional methodology can be cited as the main advantages of the on-line coacervation with fluorescence detection proposed methodology.