equipped with Waters 1525 binary HPLC pump and UV detector at 284
nm) was utilized to analyze the yields of HMF and furfural. The column
was thermostated at 30 °C. The eluent CH3OH/H2O (0.2:0.8, v/v) was run at a flow rate of 0.8 mL min–1.
The carbohydrates (Glc, Fru, and furfural)
and organic acid content were analyzed using a liquid chromatography
system Agilent 1200 equipped with Aminex HPX-87H as a stationary phase
and a refractive index detector. The column was thermostated at 65
°C. The eluent (0.05 M H2SO4) was run at
0.55 mL min–1 flow rate. The amount of Cr3+ ions in a water solution collected after the reaction was quantified
by ICP-AES (IRIS Intrepid II XSP). HMF and side products were also
quantified using MS (Thermo Fisher ITQ-1100). The HMF yield from Glc
was calculated as