Determination of mitragynine in urine matrices by bar adsorptive microextraction and HPLC analysis

Bar adsorptive microextraction combined with liquid desorption followed by high performance liquid chromatography with diode array detection (BAμE-LD/HPLC-DAD) is proposed for the determination of the psychoactive alkaloid mitragynine (MG) in human urine matrices. By using a modified N-vinylpyrrolidone polymer (P2) sorbent phase, high selectivity and efficiency is achieved. Assays performed by BAμE(P2)-LD/HPLC-DAD on 25 mL water samples spiked at the 8.0 μg L^-1 level yielded average recoveries around 100% of MG, under optimized experimental conditions. The analytical performance showed good precision (RSD<15%), appropriated detection limits of 0.10 μg L^-1 and linear dynamic ranges (0.6-24.0 μg L^-1) with convenient determination coefficients of 0.9924. By using the standard addition method, the application of the present methodology for the determination of MG in human urine matrices after Kratom consumer, allowed very good performances. The proposed methodology proved to be a suitable alternative to monitor MG in biological fluid matrices, showing to be easy to implement, reliable, sensitive and requiring low sample volumes, when compared with other sorbent-based methods.