GC/MS analysis of toxaphene: A comparative study of different mass spectrometric techniques.

Electron capture negative ion (ECNI) mass spectrometry has been recognized as the most sensitive and specific method for toxaphene analysis. Our recent analysis of 17 individual chlorobornane congeners indicated that the production of [M-Cl]- from some congeners was highly susceptible to ECNI conditions and may result in very weak or totally absent responses in selected ion monitoring (SIM) mode. These congeners have two common features : all have 2,2,5,5-chlorine substitutions and no chlorine substitution at C-3 and C-6 positions. On the other hand, electron impact ionization combined with high resolution mass spectrometry (EI-MS) produces responses (based on the characteristic ions at m/z 159, 161 and 163) similar to that from the electron capture GC for all congeners. Evidence will be presented to illustrate the difference in responses between these two mass spectrometric methods from a nonachlorobornane (congener #62, based on Parlar's numbering system) which is one of the abundant congeners in cod liver oil, fish, as well as monkey blood/tissues in our toxicology studies. Advantages and disadvantages of both methods in trace analysis of toxaphene are discussed.