GC-MS ANALYSIS OF BROMOXYNIL ESTERS - ANOMALOUS RESULTS EXPLAINED

Analytical confirmation of the presence of pesticide residues in environmental samples routinely requires the use of gas chromatography-mass spectrometry (GC-MS). While the electron impact (EI) mass spectra of bromoxynil octanoate and the free phenol, bromoxynil, in the NIST/FPA/NIH library are essentially the same, the mass spectra of bromoxynil esters are, in fact, substantially different from the spectrum of bromoxynil itself. an acylium ion is the major diagnostic species for the esters. Mass spectral libraries therefore need to be amended to reflect this information. The direct determination of bromoxynil ester residues by GC-MS is more difficult than that of bromoxynil itself. The fragment ions seen for the esters are explained.