Does Deconvolution Help to Disentangle the Complexities of Mammal Odors?
Mammal odors (in the broad sense) are notorious for chemical complexity and small quantities of individual components. No single chromatographic separation can resolve all the components, and so some of them are partially or completely obscured by others. I have tested how useful deconvolution (AnalyzerPro, SpectralWorks; http://www.spectralworks.com/analyzerpro.html) is for detecting hidden components in GC–MS data from methanol extracts of African wild dog (Lycaon pictus) urine and preputial gland secretion.
Deconvolution is better and much faster than an experienced human at finding hidden peaks, but when low detection limits and maximum separation are prioritized, shortcomings in analytical repeatability confound consistent component assignments across samples. In addition to random variation and drift in retention times, and increased retention due to overloading, some compounds showed marked changes in relative retention. As chromatographic peaks get smaller, minor fragments in their mass spectra are lost in the noise, and this affects the matches between spectra. Fluctuating background that coincides with the elution of real peaks generates false components.
To get the best from deconvolution, separations need repeatable retention times, similar peak sizes in different samples, and low and consistent background noise. Deconvolution is an extremely powerful tool, but it does not fix analytical shortcomings, and the results from real data need to be checked and refined manually.
KeywordsRelative Retention Time Cyanuric Acid Baseline Drift Asian Elephant Peak Size
I am very grateful to John Moncur of SpectralWorks who provided AnalyzerPro free of charge, the Paul G. Allen Family Foundation which funded the research by a grant to the Botswana Predator Conservation Trust, Tico McNutt, director of the Trust, Neil Jordan and Geoff Gillfillan who collected most of the samples and Lesego Mmualefe who analyzed many of them. Permission to conduct research in Botswana was granted by the Department of Wildlife and National Parks under permit number EWT 3/3/8 XXIV.
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