Comparison of Electrospray Mass Spectrometry of Chrysanthemic Acid Ester Pyrethroid Insecticides with Electron Ionization and Positive-ion Ammonia Chemical Ionization Methods
✍ Scribed by Ian A. Fleet; John J. Monaghan
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 187 KB
- Volume
- 11
- Category
- Article
- ISSN
- 0951-4198
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✦ Synopsis
The synthetic chrysanthemic acid ester pyrethroid insecticides empenthrin and prallethrin were studied by positive-ion electrospray mass spectrometry (ES-MS) in the presence of ammonium acetate and formic acid. Ammoniated molecule base-peak ions [M + NH 4 ] + and significant protonated molecule ions [M + H] + were observed at low electrospray source cone voltages for both insecticides. The effect of increasing the source cone voltage (from 10 to 40 V), in particular its influence on the extent of fragmentation arising from in-source collision-induced dissociation (CID), was also investigated and found to yield interpretable spectra. The associated increase in the population of low mass fragment ions following these CID experiments makes the monitoring of class-specific ions less attractive (poor sensitivity) than the monitoring of their respective protonated and/or ammoniated molecule ions. Key fragment ions in the ES mass spectra of both insecticides were found to be identical with those obtained under positive-ion electron ionization (EI) and positive-ion (ammonia) chemical ionization (proton transfer) conditions. Additionally, a number of these key ions have been examined by both EI tandem mass spectrometry (MS/MS) and positive-ion ES-MS/MS under low-energy collision induced dissociation (CID) conditions.