Full scan confirmation of tetrahydrophthalimide in whole milk using gas chromatography/ion trap mass spectrometry

The determination of tetrahydrophthalimide (THPI) in whole milk extracts by gas chromatography/ion trap mass spectrometry (GC/ITMS) in the full-scan, electron impact (EI) mode is presented. THPI is first isolated from whole milk by a procedure including protein precipitation, liquid-liquid partitioning, and 2 solid-phase extraction (SPE) cleanup steps. GC/ITMS in the EI mode is used for the determinative step. The average recovery of THPI at fortification levels ranging from 5 to 54 ppb was 85.6% (n = 16, coefficient of variation = 9.13%). Full-scan mass spectral confirmation of THPI in milk extracts was obtained at the 5 ppb fortification level. The limit of detection was estimated to be 0.5 ppb. Chemical ionization also was used for THPI determination in whole milk extracts. The simultaneous isolation and determination of captan and captofol in whole milk are also discussed.