Figure 3.

Electrospray ionization mass spectra of a meibum sample using 1 mM ammonium acetate additive at different cone voltages: (a) 15 V, (b) 50 V, and (c) 75 V. The sample contained ∼13 μg/mL (∼17 μM) total lipids and was dissolved in a mixture of chloroform and methanol (2:1, vol/vol). The flow rate was 40 μL/min, the desolvation temperature was 150°C, and the acquisition time was 1 minute. The range m/z 600 to 760 of the spectra is shown and only the WE peaks were labeled. Some of the unlabeled peaks corresponded to CEs. Since these peaks were previously identified by tandem mass spectrometry and high mass accuracy (mass spectrometry analysis with internal calibration), no internal calibrations for mass accuracy were performed in this work.