Molecularly imprinted polymer-coated paper as a substrate for highly sensitive analysis using paper spray mass spectrometry: quantification of metabolites in urine

Here, we proposed an analytical approach based on the use of a molecularly imprinted polymer-coated paper substrate (MIP-CPS) for paper spray ionization mass spectrometry (PS-MS) to improve its specificity. The new substrate developed was applied to detect and quantify dopamine, sarcosine, and butyric acid in synthetic human urine without derivatization or complex sample pre-treatments. The urinary levels of these metabolites can be correlated with several pathological conditions including heart disease, stress, neurological disorders, cancerous tumors, and AIDS. Calibration curves exhibited R-2 > 0.99 for dopamine, sarcosine, and butyric acid. LODs and LOQs were found at mu g L-1 (parts-per-billion) for dopamine and sarcosine, and pg L-1 (parts-per-trillion) for butyric acid. Precision and accuracy showed coefficients of variation and relative errors less than 18% for almost all analyses. Recovery test results ranged between 95.5 and 117.7%. Finally, we compared the analytical performance of the MIP-CPS with a traditional paper substrate and ESI. The MIP-CPS showed a superior performance in detecting dopamine and avoiding the ionization suppression commonly observed during the analysis of complex biological samples such as urine.