Libert R, Van Hoof F, Schanck A, Hoffmann E
Biomed Environ Mass Spectrom. 1986 Nov;13(11):599-603. doi: 10.1002/bms.1200131104.
A previously unreported substance, detected by gas chromatography after oximation of urine from patients receiving valproic acid, was isolated and analysed by mass spectrometry and nuclear magnetic resonance spectroscopy. It was identified as the hydroxamate of valproic acid.