Linearity
The calibration curves were obtained by plotting the peak area
ratio between the derivatives of neutral sugar standards and that
of allose (IS) against their concentration ratio. The linearity was
studied by preparing nine concentration levels of sugar mixture
with 1 mg/mL internal standard as described in Table 1. The reasons
for choosing the calibration concentration at these levels
were: 1) the ratio of neutral sugars at each concentration level
was similar to the ratio in real food samples; 2) chromatography
following this ratio of neutral sugars at each concentration level
provided excellent separation of the peaks; 3) the sugar values of
test samples were in the mid-concentration levels of the calibration
range.
The data were subjected to statistical analysis using a
linear-regression model; the linear range, regression equation
and correlation coefficients are shown in Table 3. The calibration
plots show satisfactory linearity for all sugars as the coefficient
of determination (R2) are all higher than 0.99, ranging from
0.99816 to 0.99995.