All chemicals
were of analytical grade unless otherwise indicated. Potassium nitrate
(purity ≥99.0%) was purchased from Sinopharm (Beijing, China).
Lutein (HPLC ≥90%) and methanol (HPLC grade) were purchased
from Solarbio (Beijing, China) and Fisher Chemicals (Loughborough,
UK). Ultrapure water was produced by a Milli-Q purification system.
The SPE cartridge ProElut AC 250 mg/3 mL, ProElut C18 500 mg/3 mL,
ProElut CARB 250 mg/3 mL, ProElut CARB 500 mg/6 mL, ProElut NH2 500 mg/3 mL, ProElut PSA 500 mg/3 mL, ProElut CARB/NH2 500/500 mg/6 mL and ProElut CARB/PSA 500/500 mg/6 mL were
purchased from Dikma (Beijing, China).
were of analytical grade unless otherwise indicated. Potassium nitrate
(purity ≥99.0%) was purchased from Sinopharm (Beijing, China).
Lutein (HPLC ≥90%) and methanol (HPLC grade) were purchased
from Solarbio (Beijing, China) and Fisher Chemicals (Loughborough,
UK). Ultrapure water was produced by a Milli-Q purification system.
The SPE cartridge ProElut AC 250 mg/3 mL, ProElut C18 500 mg/3 mL,
ProElut CARB 250 mg/3 mL, ProElut CARB 500 mg/6 mL, ProElut NH2 500 mg/3 mL, ProElut PSA 500 mg/3 mL, ProElut CARB/NH2 500/500 mg/6 mL and ProElut CARB/PSA 500/500 mg/6 mL were
purchased from Dikma (Beijing, China).