Table S2 (in Supplementary data), the flow rate is reduced from
1.5 mL/min in the HC methods to 0.8 mL/min in the new method,
which further reduces solvent consumption. The flow rate can be
further reduced to 0.34 mL/min when a smaller inner diameter
column (2.1 mm ID) was used. The total running time per injection
is shortened by the new HPLC method to 34 min compared to
45 min in the HC HPLC methods. As demonstrated in Table 2 and
Fig. S3 (in Supplementary data), the sensitivity of the new method
is significantly improved compared to the traditional HPLC method
due to less dilution of analytes in the mobile phase (resulted from
the slower flow rate and smaller column) [26], the sharper analyte
peaks and optimized detector wavelengths in the new method.
Thus, a smaller amount of sample (10 L instead of 20 L as in HC
method) was injected by the new method, which can reduce sample
matrix effects on the analyses and enhance the lifetime of HPLC
systems (especially for HPLC columns).