FIGURE 8.

Reproducibility of LC-MS with variable sample handling. A: An overlay of the total ion chromatogram of acetonitirile (ACN)-precipitated serum thawed just prior to analysis (blue) with the total ion chromatogram of serum left at room temperature overnight (red) is shown. B: An overlay of the averaged mass spectrum for cLC elution time of 26–27 min of the ACN-precipitated fresh serum (blue) with the averaged mass spectrum (same retention time) of the room temperature incubated serum (red) is provided. The inset in B shows an expanded mass spectrum (1000–1100 m/z). Even with delayed handling of the serum, the mass spectra of the samples matched closely with only slight variation.