Determination of capsaicin and dihydrocapsaicin in some hot chilli varieties by RP-HPLC-PDA after magnetic stirring extraction and clean up with C18 cartridge

Reversed phase-HPLC separation of capsaicin and dihydrocapsaicin in some hot chilli varieties was achieved using photodiode array (PDA) detector. Under optimum conditions, their analytical figures of merit for the HPLC method were validated. The linearity range of calibration curve was 1.0-25 μg/mL with multiple determination coefficients higher than 0.995. Limits of detection and quantitation were 0.5 and 1.0 μg/mL, respectively. The repeatability and reproducibility of both retention time and peak area for these compounds were in good precision with their relative standard deviations (RSDs) lower than 1% and 4%, respectively. Solvent extraction using methanol for both compounds were conducted by magnetic stirring extraction (MSE) method and then cleaned up with C18 solid-phase extraction (SPE) prior to analysis by HPLC. Recoveries of SPE of all sample extracts spiked with 16 μg of each capsaicin and dihydrocapsaicin were ranged from 90.0-95.0% and 87.8-95.7%, respectively. The optimized conditions were applied for the determination of both capsaicinoids in ten varieties of the chilli samples. Total contents of the capsaicinoids were found in the range of 1,758.2-7068.9 μg/g DW with corresponding to their Scoville heat unit (SHU) obtained in the range of 26,400-106,000. Additionally, the contents of capsaicinoids determined by external calibration method comparing with those of standard addition were not significantly different, indicating less matrix effect. Mostly, the average amounts of capsaicin (62%) found in these real samples were rather higher than those of dihydrocapsaicin (38%).