Figure 3. Batch reproducibility of magnetic beads used in this study for tear sample purification before MALDI-TOF MS analysis. A: Virtual gels representing profiles from control (CT) tear samples processed with two different magnetic bead batches (1 and 2) from the same company. Tear profiles were obtained after separately processing 1 µl of tear sample from control individuals CT1 and CT2 with both batches. The same number and intensities of peaks were observed in the profiles obtained from the CT1 tear sample treated with sphere batches 1 and 2. With tears from patient CT2, identical results were also obtained using both batches. These profile similarities indicate the reproducibility which can be obtained using the two tested batches. An inherent difference in peak intensities between patient CT1 and CT2 was observed due to inter-individual variability. B: The PCA plot identifies CT1 and CT2 as different individuals, which are spatially separated. However, sample from the same individual processed with bead batches 1 (light spheres) and 2 (dark spheres) from the same manufacturer, are almost coincidental.