Study on pretreatment methods for the simultaneous determination of three kinds of sugar alcohols in milk by gas chromatography

A novel method was developed for the determination of sugar alcohol contents in milk by gas chromato-graphy after freeze-drying, and the external standard method was used to determine. After removal of protein by zinc sulphate and barium hydroxide, the freeze-drying was used to dry samples. The sugar alcohols reacted with pyridine- acetic anhydride ( 1 ∶ 1, v / v) at 90 ℃ for 30 min. The sugar alcohol acetate derivatives were analyzed by gas chromatography with HP- 5 ( 30 m × 320μm × 0. 25μm) and with a flame ionization detector. The results showed that the recoveries of sugar alcohols treated by freeze-drying was higher than rotary evaporation. Under the optional chromatographic conditions, the calibration curve was linear in the range of 10⁹0μg/m L (r=0.9974⁰.9999) . The repeatability was reproducible (RSD=1.37%².04%) . The average recoveries were between 91.17% and 92.06%. This method was simple and fast so that it could be used to determine sugar alcohol contents in milk.