Direct determination of sinigrin in mustard seed without desulfatation by reversed-phase ion-pair liquid chromatography

Reversed-phase ion-pair liquid chromatography has been investigated for directly analyzing sinigrin in mustard seed without desulfatation. After extraction by phosphate buffer (pH 7.0) from the grind-pastes of inactivated-myrosinase mustard seeds, sinigrin was first isolated through deproteinization and centrifugation, followed by filtration and injection into the chromatographic system. A reversed-phase C18 column was used to separate the sinigrin with an eluent of acetonitrile (ACN)-water (20:80) containing 0.02 M tetrabutylammonium (TBA) as the counter ion at pH 7.0. Detection was carried out with an UV detector operated at 227 nm. Factors affecting the chromatographic separation and quantitative determination, such as concentrations of TBA and ACN, and pH, were studied. The linear dynamic range is larger than three orders of magnitude and the detection limit is 0.045 mg/L. The RSD is around 3% and the recovery is 85% (3% RSD, n = 3).