2.5. Analytical methods for sugars and inhibitors analysis
The prepared samples for carbohydrate and inhibitor analysis
were filtered through a 0.2 lm syringe filter into 200 lL HPLC vials.
Filtered liquid was injected into ion exclusion column HPX-87H or
HPX-87P. The HPX-87H column used 5 mM sulfuric acid as eluent
and operated at 50 C, while the HPX-87P column used water as eluent
and operated at 85 C. Carbohydrates were measured with a
refractive index detector (model 2414, Waters Corporation, Milford,
MA). HPLC detection limits of sugar and ethanol were 0.001% w/w.
2.6. Particle size analysis
Samples were diluted with DI water to 1 mg/ml for size analysis.
A particle size distribution range from 0.01 to 3500 lm was
measured using a laser diffraction size analyzer (Malvern Mastersizer
3000 with Hydro EV unit, Malvern, UK) with 100 measuring
points. Refractive index, absorption index and sample density were
set to 1.40, 2.8 and 3 lb/ft3
, respectively. Percent volume was
acquired and used to determine the average particle size.