The optimized gradientfor dye separation is given
in Table 1. All experiments were performed at 25 ◦C at a flow rate
of 1 mL min−1. The time required for separation was 24 min and
the injection volume was 20 L. The detection wavelengths were
425 nm for TZ, 480 nm for SY and 520 nm for CR. These chromatographic
conditions involve minor modifications from the original
procedure [35].