Direct quantification of alkaloid mixtures by electrospray ionization mass spectrometry

✍ Scribed by Selby, D. S.; Guilhaus, M.; Murby, J.; Wells, R. J.

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 139 KB
• Volume: 33
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/(sici)1096-9888(199812)33:12<1232::aid-jms741>3.0.co;2-x

✦ Synopsis

For two-component mixtures, Kebarle and Tang observed that the ionization efficiency (i.e., yield of ions per unit concentration) depends strongly on the concentration and nature of other ionizable species and weakly on total concentration of ionized species. In this work, the model used by Kebarle and Tang was extended to several components. The extended model was tested in a study to determine whether analysis by extrospray ionization could be used as a fast method to screen and quantify Ðve alkaloids present in illicit heroin samples. The samples analysed included authentic standards. Solutions of the samples were infused directly into the electrospray ion source of a Finnigan TSQ 700 instrument. The resulting spectra contained a peak for each species at M + 1. No signiÐcant fragmentation was observed for any of the Ðve analytes. It was found that the "ionization efficienciesÏ (assumed constants in the Kebarle and Tang model) showed a dependence on total alkaloid concentration. In a blind study of 16 sample solutions, each containing Ðve alkaloids (one used as an internal standard), the error distributions for the 64 results obtained were skewed when calculated on the basis of a simple extension of the Kebarle model. When the variation of ionization efficiency with total alkaloid concentration was taken into account, the error distribution was normal. Errors were characterized (relative to total alkaloid mass) by an average error of Ô0.24% , a standard deviation of errors of 2.48% , a maximum error of 6.84% and a minimum error of Ô9.51% .