GC/MS Analysis of Cerebrospinal Fluid

Compounds in CSFAb were analyzed and identified by GC/MS at the National Instrumentation Center for Environmental Management (NICEM, Seoul National University, Republic of Korea). GC/MS data were acquired using a TRACE 1310 GC unit attached to an ISQ LT single quadrupole mass spectrometer (Thermo Scientific, Waltham, MA, USA) as previously described [59 (link)]. Briefly, derivatized CSFAb was separated on a DB-5MS column (60 m × 0.25 mm, 0.25 μm; Agilent Technologies, Santa Clara, CA, USA) at a flow rate of 1 mL/min. The GC oven temperature was programmed as follows; 50 °C for 5 min, 50 to 65 °C at 10 °C/min, 65 to 210 °C at 5 °C/min, 210 to 310 °C at 20 °C/min, and held at 310 °C for 10 min. The scanned mass range was 35–550 m/z, and the data acquisition rate was 0.2 scans/s in the MS setting. The transfer line and ion source temperatures were 300 °C and 270 °C, respectively. Metabolites were identified by comparing their MS spectra and retention indices (RI) with reference standards obtained from the NIST/NIH/EPA mass spectral library (NIST 11, version 2.0 g). A standard mixture of n-alkanes (C₇–C₃₀) was used to determine compound RIs. Final identification was performed by comparing retention times and spectra with those of commercially available standards.