UHPLC-MS/MS Determination of Rhodamine B in Edible Flavoring Oil by Solid Phase Extraction

Sample of edible flavoring oil was extracted with acetone, the extracting solution was taken for purification by MCX cation solid phase extraction column. The rhodamine B was eluted from column with a mixture of ammonia (aq.) and methanol (5+95), and evaporated to near-dryness by N2-blowing and made up to 2 mL with methanol. ACQUITY BHE C18 column was used as stationary phase, and the mixture of methanol and 0.1%(φ) formic acid solution with different ratio was used as mobile phase in gradient elution. ESI and multi-reactions monitoring mode were adopted in MS/MS. Linear relationship between values of peak area and mass concentration of rhodamine B was kept in the range of 1.00-100 μg·L-1, with values of detection limit (3S/N) of 0.003 mg·kg-1. Tests for recovery were made at the concentration levels of 0.01, 0.05, 0.20 mg·kg-1 of rhodamine B standard, giving values of recovery in the range of 82.1%-97.2%, with RSD′s (n=6) less than 9%.