Table 2 Comparison between the BfR method and the proposed PA method
Pretreatment processing | BfR-PA-Tea (BfR, 2014) | Current PA method |
|---|---|---|
Samples (g) | 2.0 | 2.0 |
Extraction | 0.05 M H2SO4 20 mL | 50% MeOH included 0.05 M H2SO4 40 mL |
Sonication for 15 min | Shaking for 30 min, | |
Centrifugation | 10 min, (4 ℃, 3800×g) | 10 min, (4 ℃, 3230×g) |
Filtering etc | Repeat 2 times, neutralization of supernatant with ammonia soln, pH 7 | Filtering supernatant |
Cartridge purification | DSC-C18 (500 mg, 6 cc) | SPE-MCX (150 mg, 6 cc) |
Activation | MeOH 5 mL, D.W 5 mL | MeOH 3 mL, D.W 3 mL |
Loading | Supernatant 10 mL | Supernatant 2 mL |
washing (using pump) | D.W 10 mL | D.W 4 mL |
Elution | MeOH soln included 2.5% ammonia 10 mL, or MeOH 10 mL | MeOH soln included 5% ammonia 4 mL |
Nitrogen concentration | 50–55 ℃ | |
Dissolving and filtering | 5% MeOH, 1 mL, with 0.2 μm syringe range filter | |
LC–MS/MS analysis | ||