Qp2010 gc system

Chromatography was performed by a GC-MS QP2010 GC system (Shimadzu) equipped with an RXI-5 SIL MS column (30 m × 0.25 mm, 250 μm) (Agilent 19091J-413) under the following conditions: starting at a temperature 120 °C, then raised to 250 °C at a rate of 3 °C min⁻¹ and held for 5 min. The injector and detector temperatures were both set at 250 °C. The flow rates of H2 and air were 30 mL min⁻¹ and 400 mL min⁻¹, respectively. The carrier gas was He, and the flow rate was up to 1.0 mL min⁻¹. GC analysis was employed to detect the monosaccharide composition of MHHP.
A MHHP sample (2 mg) was hydrolyzed in trifluoroacetic acid (TFA) (2 M, 1 mL) at 120 °C for 90 min. The hydrolysate was repeatedly concentrated with methanol (2 mL) until dried and reduced by adding double-distilled water (2 mL) and sodium borohydride (100 mg) at room temperature, then neutralized by acetic acid. The reduzate was repeatedly concentrated with methanol (3 mL) until dried again and acetylated by 1 mL acetic anhydride at 100 °C for 1 h. Then, the sample was cooled down and repeatedly concentrated with methylbenzene (3 mL) to remove excess anhydride. The acetylated derivative was dissolved in chloroform (3 mL), transferred into a separating funnel and shaken with distilled water 5 times. The chloroform layer was dehydrated by anhydrous sodium sulfate, and the final volume was increased to 10 mL for analysis.