The vitamin C extraction method was adapted from Ross (1994).
Beverage sample (0.5 mL) and 10% meta-phosphoric acid (0.5 mL)
were mixed using a vortex (5 min) (final concentration of metaphosphoric
acid was 5%), centrifuged at 8500g for 10 min, and
injected onto the HPLC or UPLC column to determine AA content
(Gliszczyn´ ska-S´wigło & Tyrakowska, 2003). Before injection onto
UPLC column, the samples of fruit juices or drinks were diluted
1:50 or 1:10, respectively, using 10% meta-phosphoric acid.
The sum of AA and DHAA (vitamin C content; TAA) was determined
after reduction of DHAA to AA using DTT. The juice sample
(0.2 mL) and 5% DTT (0.2 mL) were mixed and diluted to 2 mL with
10% meta-phosphoric acid and injected onto HPLC or UPLC column
to determine vitamin C (Gliszczyn´ ska-S´wigło et al., 2006).
Vitamin C tablets were dissolved in 25 mL 10% meta-phosphoric
acid and treated as fruit beverages samples. Before injection onto
HPLC or UPLC column, the samples of tablets were diluted 1:50
or 1:150, respectively, using 10% meta-phosphoric acid. Three
independent extractions were carried out for all samples. The only
difference between sample preparation for HPLC and UPLC was the
magnitude of sample dilution before injection.
The vitamin C extraction method was adapted from Ross (1994).Beverage sample (0.5 mL) and 10% meta-phosphoric acid (0.5 mL)were mixed using a vortex (5 min) (final concentration of metaphosphoricacid was 5%), centrifuged at 8500g for 10 min, andinjected onto the HPLC or UPLC column to determine AA content(Gliszczyn´ ska-S´wigło & Tyrakowska, 2003). Before injection ontoUPLC column, the samples of fruit juices or drinks were diluted1:50 or 1:10, respectively, using 10% meta-phosphoric acid.The sum of AA and DHAA (vitamin C content; TAA) was determinedafter reduction of DHAA to AA using DTT. The juice sample(0.2 mL) and 5% DTT (0.2 mL) were mixed and diluted to 2 mL with10% meta-phosphoric acid and injected onto HPLC or UPLC columnto determine vitamin C (Gliszczyn´ ska-S´wigło et al., 2006).Vitamin C tablets were dissolved in 25 mL 10% meta-phosphoricacid and treated as fruit beverages samples. Before injection ontoHPLC or UPLC column, the samples of tablets were diluted 1:50or 1:150, respectively, using 10% meta-phosphoric acid. Threeindependent extractions were carried out for all samples. The onlydifference between sample preparation for HPLC and UPLC was themagnitude of sample dilution before injection.
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