Figure 7. Absence of clusters at high temperature.

Mass spectra (500 averages) of 100-μM mixtures of the amino acids serine (Ser), threonine (Thr), phenylalanine (Phe), tyrosine (Tyr), and tryptophan (Try) at 250 °C (a) or 100 °C (b) and 6.8 mmol m⁻³ (2.5×10² ppmv) of 2-butanol (2B) in the buffer gas. No clusters were present at high temperature; in contrast, at low temperature, there is an extensive formation of clusters. The clusters of serine (m/z 180.2 and 254) may be overlapped with the broad protonated molecule peak of tyrosine (m/z 182) and its cluster at (m/z 256 ). The cluster of threonine with two molecules of 2-butanol appears as a small peak at m/z 264.3.