Analysis of pharmaceutical formulations using atmospheric pressure ion mobility spectrometry combined with liquid chromatography and nano-electrospray ionisation

The hyphenation of liquid chromatography with atmospheric pressure ion mobility spectrometry is reported using a custom-made dynamic nano-electrospray ionisation (nano-ESI) interface. The analysis of pharmaceutical actives is described, including beta blocker (timolol), antidepressant (paroxetine), analgesic (paracetamol) and opiate (codeine) preparations. On-line ultraviolet diode array (UV) spectroscopic detection was used prior to sample ionisation, to evaluate chromatographic and nano-ESI interface performance. Active drug responses were characterised by chromatographic retention time and electrophoretic ion mobility drift time, and selected ion mobility responses were used to evaluate method performance. Limits of detection for active drugs were in the low-nmol to pmol range. Quantitative responses were investigated using a series of standard solutions of caffeine, showing good linearity (R-2 = 0.9982, n = 6) and reproducibility (RSD = 2.3%, n = 6). The analysis of an over the counter pharmaceutical formulation demonstrates the potential of ion mobility spectrometry combined with liquid chromatography and nano-electrospray ionisation for the rapid determination of active drugs, as a result of the electrophoretic separation and selectivity afforded by IMS.