Table 1. Operating conditions of HPLC for the analysis of sinapine contents in not-purified, purified surface-active substances and residues

Instrument	Agilent Technologies 1200 series
Column	Capcell PAK C18 column
	(4.6 × 250 mm, 5 μm; Shiseido, Tokyo, Japan)
Wavelength	350 nm
Injection volume	10 μL
Oven temperature	40°C
Flow rate	1.0 mL/min
Mobile phase	Solvent A
	MeOH:water:acetic acid = 5:92.5:2.5, (v/v/v)
	Solvent B
	MeOH:water:acetic acid = 95:2.5:2.5, (v/v/v)
Gradient condition	0.1 min, solvent B 0%
	10.0 min, solvent B 20%
	15.0 min, solvent B 40%
	20.0 min, solvent B 40%
	25.0 min, solvent B 50%
	28.0 min, solvent B 50%
	30.0 min, solvent B 100%