title: A novel cation exchange polymer as a reversed-dispersive solid phase   extraction sorbent for the rapid determination of rhodamine B   residue in chili powder and chili oil.
abstract: This paper presents a new analytical method for the determination of rhodamine B (RB) residue in chili powder and chili oil based on a novel reversed-dispersive solid phase extraction (r-dSPE) and ultra high performance liquid chromatography–high resolution mass spectrometry (UHPLC–HRMS). Chili powder and chili oil samples were first extracted with acetonitrile/water (1:1, v/v) and acetonitrile, respectively. Then, RB from the extract was adsorbed to the polymer cation exchange (PCX) sorbent with the characteristics of ion exchange and reversed-phase retention. Subsequently, the analyte in PCX sorbent was eluted with ammonium hydroxide/methanol (1:99, v/v) through a simple unit device equipped with 1 mL syringe and 0.22 μm nylon syringe filter. All of the samples were analyzed by UHPLC–HRMS/MS on a Waters Acquity BEH C18 column with 0.1% formic acid and 4 mM ammonium formate in water/acetonitrile as the mobile phase with gradient elution. The matrix effect, recovery, and repeatability, within laboratory reproducibility, and the LODs and LOQs of the r-dSPE cleanup method were investigated. The method showed a good linearity (R2 > 0.999) in the ranges of 0.01–1 μg/L and 1–100 μg/L for the analyte. The LODs of RB for chili powder and chili oil samples were 0.5 μg/kg. The average recoveries of RB from the samples spiked at four different concentrations (2, 20, 500 and 5000 μg/kg) were in a range from 76.7 to 104.9%. Results showed that the proposed method was simple, fast, economical and effective for the determination of RB in chili powder and chili oil. Considering the excellent sorptive performance of PCX for RB, further work should be done to evaluate the usefulness of the PCX in r-dSPE for the clean-up and analyses of other trace-level alkaline contaminants.
authors.affiliation: Key Laboratory of Food Safety Risk Assessment, Ministry of Health, China National Center for Food Safety Risk Assessment, Beijing 100021, China.
authors.forename: Dawei
authors.initials: D
authors.lastname: Chen
authors.affiliation: Key Laboratory of Food Safety Risk Assessment, Ministry of Health, China National Center for Food Safety Risk Assessment, Beijing 100021, China.
authors.forename: Yunfeng
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Key Laboratory of Food Safety Risk Assessment, Ministry of Health, China National Center for Food Safety Risk Assessment, Beijing 100021, China. Electronic address: miaoh@cfsa.net.cn.
authors.forename: Hong
authors.initials: H
authors.lastname: Miao
authors.affiliation: Key Laboratory of Food Safety Risk Assessment, Ministry of Health, China National Center for Food Safety Risk Assessment, Beijing 100021, China.
authors.forename: Yongning
authors.initials: Y
authors.lastname: Wu
mesh_terms: D002212:Capsicum / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation / Q000379:methods*; D057230:Limit of Detection; D013058:Mass Spectrometry / Q000379:methods; D011108:Polymers / Q000737:chemistry; D015203:Reproducibility of Results; D012235:Rhodamines / Q000032:analysis*; D052616:Solid Phase Extraction / Q000379:methods; D017365:Spices; D013997:Time Factors
chemical_list: D011108:Polymers; D012235:Rhodamines; C029773:rhodamine B