FIGURE 3.

a and b) Extracted time traces of the most significant mass/charge ratio (151.0247) and c and d) total ion chromatography (TIC) recorded in negative ionisation mode from a and c) a 13-year-old and b and d) a 4.5-year-old patient with cystic fibrosis. The recorded signal exhibits good reproducibility for both age groups across several consecutive exhalations. As expected, the time of exhalation, which is clearly visible in the time trace of the TIC, was longer in older children. cps: counts per second.