Upon completion of acid hydrolysis, the sample
was neutralized by calcium carbonate and then diluted 50-fold,
filtered and injected into a high performance anion-exchange
chromatography (HPAEC) system (ICS 3000, Dionex, Sunnyvale,
CA, USA) equipped with an ion exchange Carbopac PA-1 column
(4 mm
×
250 mm) and a pulsed amperometric detector