Heating paper spray mass spectrometry for enhanced detection of propranolol in dried blood samples

Paper spray mass spectrometry (PSMS) has been widely used for rapid analysis of complex samples, particularly in rapid analysis of clinical samples for point-of-care diagnostics. In this study, heating PSMS was developed for enhanced detection of propranolol in dried blood samples (DBS). Prepared DBS were first placed on an aluminum plate and organic solvent was added. The plate was then heated using a heating probe. Heating was revealed to play two roles in detection of propranolol in DBS: (1) improving the diffusion of propranolol from paper to solvent and (2) improving release of propranolol from protein–propranolol complex. Heating efficiency evaluated at different temperatures showed that detection of propranolol in DBS significantly improved (about 30 times) under optimized temperature. Using an isotopic internal standard, the limit of detection (LOD) and limit of quantitation (LOQ) of propranolol were found to be less than 0.4 ng mL−1 (S/N > 3) and less than 1 ng mL−1 (S/N > 10), respectively. The dynamic ranges of propranolol were found to be in the range of 1.0–500 ng mL−1 with an excellent correlation coefficient (R2 > 0.999). This method also showed good precision (5.2–18.5%, n = 5) and acceptable recovery (70.0–81.5%, n = 5). Furthermore, clinical DBS collected from volunteer patients before and after oral doses of propranolol were successfully analyzed. This study demonstrated that heating PSMS is a promising method for rapid detection of propranolol in DBS for point-of-care diagnostics.