Both ESI and atmospheric pressure ionisation (APCI) interfaces were investigated, working in the positive and in the negative mode of ionisation. ESI in the positive mode gave higher sensitivity and was therefore selected for further optimisation. Full MS scan for the epimers revealed a signal at m/z corresponding to [M−H2O+H]+ higher than that of the protonated molecules. Therefore, further optimisation of the MS signal was carried out on the ion at m/z corresponding to [M−H2O+H]+ for the epimers except ergometrinine.