Fast identification of counterfeit medicines - a comparison of two MS systems

Comparison of a heated atmospheric pressure ionisation (APCI) MS with a vacuum solids probe MS method for the identification of the active pharmaceutical ingredients (API) in powdered fully formulated tablet samples was carried out. Thermal volatilisation allowed direct identification of the APIs at therapeutic levels, in a matter of minutes, in many tablet formulations.

Reference spectra were recorded for pure APIs using the Advion ASAP (APCI) probe and the Bruker vacuum insertion probe. Powder samples in the probe cup were transferred to the MS systems and heated in flowing nitrogen at 300C (ASAP) and 40-250C (Bruker). Crushed globally sourced tablet samples were analysed as above. Comparison of the results with tablet labels identified some suspect tablets.

Thermal vaporization is needed for the analysis of these samples. In APCI the vaporized API is ionised by corona discharge to give M+H+ ions with little fragmentation. Observed signals were: acetaminophen m/z 152,110; caffeine m/z 195, 138; chloroquine phosphate m/z 320, 247 and atenolol m/z 267, 225. Aspirin was detected as a -ve ion at m/z 179, 137. The simplicity of these spectra meant that tablets containing several APIs could be readily identified: acetaminophen/caffeine/aspirin or artemether and lumifantrine in antimalarial tablets. Electron impact is more energetic giving some fragmentation. EI observed signals were: acetaminophen m/z 151,110; caffeine m/z 194, 109; chloroquine phosphate m/z 320, 247 and atenolol m/z 251, 223. Aspirin was detected as a +ve ion at m/z 138, 120. Tablet and reference data was directly comparable. Analysis time was only minutes per sample.

Direct MS analysis of APIs in fully formulated tablet medicines to identify counterfeit or substandard products is novel.