Fig. 1. LC chromatogram of the 16 sleep inducers analysed in this study and the individual PDA spectra of each compound.
Fig. 2. XIC of a phenobarbital standard (a) and 500-fold diluted positive sample (b).
Fig. 3. Mass spectra of a phenobarbital standard (a) and a sample that contains phenobarbital (b).
Table 1. Recovery of each compound under different extraction conditions
Table 2. Summary of the calibration curves, limits of detection (LOD), and limits of quantification (LOQ) for 16 sleep inducers by UPLC
Table 3. Intra-and inter-day variation in the three concentrations of the 16 sleep inducers using UPLC
Table 3. Continued
Table 4. The recovery efficiency of the 16 sleep inducers from dietary supplement samples using UPLC
Table 5. Stability of the 16 sleep inducer compounds over 48 h analysed with UPLC.
Table 5. Continued