Determination of sinigrin in vegetable seeds by online microdialysis sampling coupled to reverse-phase ion-pair liquid chromatography.

A hollow fiber microdialysis sampling coupled online to ion-pair liquid chromatography was investigated as an alternative to sample pretreatment for the direct determination of sinigrin in cruciferous vegetables without desulfation. After microdialysis, the dialysate was online injected into the chromatographic system to analyze the sinigrin with UV detection at 227 nm. Parameters affecting the microdialysis efficiency, such as flow rate, polarity modifier, pH in perfusion stream, pH, and salt added in sample solution, were studied. Through ion suppression in the donor phase and ion-pair formation in the acceptor phase, the microdialysis efficiency of sinigrin was enhanced. Experimental results revealed that the microdialysis of a sample solution (pH 2.0) using 0.1 M tetrabutylammonium (pH 12) as a perfusate at 10 microL/min flow rate maximized the extraction efficiency. Detection was linear in the concentration of 1.0-100 mg/L with a detection limit of 0.3 mg/L. Three seed samples were analyzed, with sinigrin at 49.8 (3.15% RSD), 20.0 (4.43% RSD), and 19.8 mg/g (4.22% RSD) for brussels, cauliflower, and cabbage, respectively. When 40 mg/g sinigrin was spiked in brussels seed powder, the recovery was 102.4% with 3.15% RSD (n = 3). The proposed method was proven to provide a very simple, rapid, and eco-friendly procedure to determine sinigrin in the seeds of cruciferous vegetables.