Determination of cyanamide residue in grapes and cherries by liquid chromatography-tandem mass spectrometry coupled with precolumn derivatization

Abstract

A method was developed for the quantitative determination of cyanamide in grapes and cherries by liquid chromatography-tandem mass spectrometry (LC-MS/MS) coupled with dansyl chloride (DNS) precolumn derivatization. First, the samples were homogenized, and then extracted with ethyl acetate under ultrasonication. The water was removed using anhydrous sodium sulfate, and the extract was concentrated and derivatized with dansyl chloride under alkaline condition. The separation was performed on a Shimadzu Shim-pack XR-ODS column (75 mm×2.0 mm, 1.6 μm) with the mobile phases of methanol and 2 mmol/L ammonium acetate aqueous solution (containing 0.05% (v/v) formic acid) in a gradient elution mode. The identification and quantification of cyanamide were carried out by MS/MS in positive electrospray ionization (ESI+) and multiple reaction monitoring (MRM) mode. The calibration curves showed good linearities in the range of 0.01-1.0 mg/L with the correlation coefficients not less than 0.9990. The average recoveries of cyanamide spiked at 0.01, 0.05 and 1.0 mg/kg in cherries and grapes were between 75% and 81%, and the relative standard deviations (RSDs) were between 6.5% and 9.8%. Both the limits of quantification (LOQs) of the analytes were 0.01 mg/kg. The method is simple, rapid, accurate and suitable for the confirmation and quantification of cyanamide in cherries and grapes.