The quantitative determination of compounds in analytical samples typically relies on calibration curves of known standards in order to provide reliable comparative data. Unfortunately, for most natural products, standards of analytically pure materials are not readily available and of course, for novel compounds, no such standards could exist. Chromatography-mass spectrometry are commonly used for identifying natural products in extracts. However, mass spectrometry, particularly electron impact (EI) is generally viewed as being unreliable without standards because of variation in ion yields and fragmentation probabilities. Chemical ionization methods (ammonia chemical ionization in GC-MS and electrospray and atmospheric pressure chemical ionization in LC-MS) are better but also suffer from ion yields, proton exchange and ion-molecule reactions. We are examining a variety of alkaloids related to our work with poison frogs to develop a reliable quantitation method that takes these factors into account based on structure and concentration by preparing an alkaloid-like library of cyclic aliphatic amines. Our results to date will be presented, including a discussion of structural influences on response factors in CI-(NH<sub>3</sub>)-GC-MS, LC-ESI-MS and LC-APCI-MS.

Evaluation of chemical ionization methods for standard-free quantitative analysis of alkaloids in poison frogs

2019 Spring National Meeting

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