Electrospray ionisation is the most commonly used method for mass spectrometry analysis in the department. It is quick and easy to run, and usually results in the molecule of interest being ionised as a protonated (M+H⁺), sodiated (M+Na⁺) or potassiated (M+K⁺) species. Peaks in the resulting spectrum therefore correspond to the molecular mass plus 1 for H, 23 for Na or 39 for K.