Extraction reference peak spiking

In-source transformation effects can only be perceived during method development if extracts of biological samples are analyzed under extended chromatographic runs. Interference by in-source transformation will not become evident if only spiked quality control materials are used which do not contain relevant metabolites. If one or more additional peak in the SRM trace of the target analyte is observed in comparison to analyte reference solutions, chromatography may only be accelerated to such degree that these peaks still remain baseline separated from the analyte. 

Fig. 15.8. Adsorption and elution of 100 pL of a placebo chewing gum extract spiked with nicotine (0.5 mg/mL) and /S-nicotyrine, cotinine and myosmine (0.05 mg/mL). The step elution was as follows MeCN 0-8 min, MeCN + 0.2 % TFA + 2.5% H2O 8-12 min, MeCN 12-15 min. The peak identity was established by separate injections and spectral analysis using a diode array detector. Rest refers to still not eluted -nicotyrine, cotinine and myosmine. In MISPE, only -nicotyrine could be detected in the adsorption and wash steps.

Here processed and unprocessed data refer to control matrix spiked with arralytical standard before and after extraction, respectively. Note that the ratios of the two peak areas represent a combination of extraction efficiency plus differences in matrix effects (if any). 

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