Three drug product cartridges were analysed for each study condition (5 ◦C, 25 ◦C 60%RH and 40 ◦C 75%RH) Fig. 1.and for different analysis times (T0, T0+3, 6, 9, 12 and 18 months): Table 1. Three cut-outs on the inside and outside of the polypropylene cartridge (around 1mm2 surface by 0.5mm thickness) were studied. These cut-outs – 1–10 g plastic container were placed in the mass spectrometer source using a direct probe.