HPLC Determination of 3 Monascus Pigments in Cooked Meat Products with Automatic-SPE

The meat sample (5.000 g) was extracted ultrasonically with 25.0 mL of ethanol-H₂O (85+15) solution for 15 min, and the mixture was centrifuged at 4℃ for 10 min at high speed. The supernatant (10.0 mL) was taken and added with 30 mL of ethanol. The solution was evaporated to near-dryness at (60±2)℃. The residue was taken up with 2 portions of methanol-H₂O (20+80) solution, using 2.5 mL in each dissolution. The analytes of 3 monascus pigments in the methanol solution were then purified and enriched by passing the solution through Oasis HLB SPE column (500 mg/6 mL) of the automatic-SPE installation and operated according to the program automatically. The eluate was collected and evaporated to near-dryness by N₂-blowing at 40℃. The residue was dissolved with 2.0 mL of C₂H₅OH-H₂O (85+15) solution and after filtering through 0.22 μm filtering membrane, the filtrate was used as testing solution for HPLC analysis. Waters SunFire C₁₈ chromatographic column (250 mm×4.6 mm, 5 μm) was used as stationary phase and mixtures with various ratios of methanol and 20 mmol·L^-1 NH₄OAc solution were used as mobile phases in the programed gradient elution for separation of the 3 monascus pigments and their determinations with diode array detector, at wavelengths of 264 nm for monascorubramine and at 390 nm for both monascin and monascorubrin. Linearity ranges between definite mass concentrations of the 3 monascus pigments were obtained having their correlation coeffcients greater than 0.999 5. Detection limits (3S/N) found for the 3 monascus pigments were 0.20, 0.060, 9.9 mg·kg^-1 respectively. Test for recovery was made by standard addition method using a blank sample as matrix, the results obtained were in the range of 92.9%-100%. Values of RSDs (n=6) were found range from 1.3%-3.7%.