HPLC analysis of liquid samples was performed on a
system consisting of a Varian 9010 Solvent Delivery System,
Waters 717plus Autosampler, Aminex HPX-87H column
(Biorad, Hercules, CA), Waters 2414 Refractive Index
Detector, Waters 2487 Dual k Absorbance Detector, and a
Hewlett Packard HP3396G Integrator. The mobile phase was 5 mM H2SO4 filtered through 0.2 lm nylon filter (Millipore)
and degassed. The mobile phase flow rate was
0.6 mL/min and the column temperature was maintained
at 60 C by an Eppendorf CH-30 Column Heater controlled
by an Eppendorf TC-50.