Metabolite Profiling in CSF Samples

TargetLynx application manager for MassLynx 4.1 software (Waters Corp. Milford, MA, USA) was used for data processing. A set of parameters associated to metabolites included in the analysis (Rt m/z, mass-to-charge ratio pairs, retention time) were incorporated into the program. Using a mass tolerance window of 0.05 Da and after peak detection and noise reduction (at LC and MS levels), only true metabolite related features were processed by the software. For each sample injection, a list of chromatographic peak areas was generated. Data normalization was performed following the procedure described by Barr et al. [23 (link)], where the ion intensity corresponding to each peak present in each CSF sample was normalized in respect to the sum of peak intensities in each CSF sample. There were no significant differences (t-test = 0.1031) between the total intensities used for normalization of the sample groups compared in the study.