Development and Validation of a Standardized Method for the Determination of Morpholine Residues in Fruit Commodities by Liquid Chromatography–Mass Spectrometry

An analytical method was developed for the determination of morpholine on apples and citrus. The method utilized acidified methanol extraction, centrifugation, and determination by hydrophilic interaction liquid chromatography with electrospray ionization and tandem mass spectrometry (HILIC-ESI-MS/MS). Validation of the method occurred at the Pacific Agricultural Laboratory (PAL, Portland, OR, USA) and the Trace Analytical Laboratory (TAL, UC Davis, CA, USA). Method validation recoveries from control apple, orange, lemon, and grapefruit samples ranged from 84 to 120% over three levels of fortification (0.01, 0.04, and 0.2 μg/g). The limit of quantitation (LOQ) for all commodities was 0.01 μg/g, and the calculated method detection limit (MDL) ranged from 0.0010 to 0.0040 μg/g.