A comparative study of the different analytical methods for analysis of S-allyl cysteine in black garlic by HPLC

A sensitive and reproducible analytical method to measure S-allyl cysteine (SAC) in black garlic was developed using the HPLC-FLD (fluorescence detection) with prior derivatization with AccQ-Fluor Reagent. The results were then compared with those from obtained using the HPLD-UVD (ultraviolet detection) that has been conventionally used for measuring SAC in raw garlic. The SAC content in raw garlic measured by the HPLC-FLD and the HPLD-UVD were 21.52 and 22.73μg/g, respectively. And these results were satisfactory with %CV (coefficient of variation) less than 2%. However, the application of the HPLC-UVD for the determination of SAC in black garlic was limited due to the high %CV that arose from the unstable baseline. However, the HPLC-FLD could be applied to the measurement of SAC in black garlic with satisfactory %CV. The HPLC-FLD method was validated by determining the linearity, limit of detection, limit of quantification, accuracy and precision. This method showed excellent linearity with a coefficient of determination (R²) greater than 0.998. The limits of detection (LOD) and the limit of quantification (LOQ) were 6.28 and 19.02μg/mL, respectively. The accuracy ranged from 98.51 to 102.08%, and the precision of the method was found to be less than 2%.