was applied at high temperature (310◦C) to effectively remove lateeluting sample components. The developed program (see Table 2and Fig. 1) provided separation of all analyte peaks within 30 min.The total per sample analysis time was shorter than 38 min (includ-ing the 8 min in back-flush for system cleanup). This time is almosttwo times shorter that those reported in the literature (for instance75 min [1]).Initially, GC-MS analysis was performed in full scan mode(scan range from 60 to 320 amu) and total ion current (TIC)chromatograms were studied to identify the peaks of the TMSderivatives of the organic acids. Retention times and mass spectrawere recorded for each derivative. The NIST library of mass spectrawas used for peak identity verification. A primary fragment (Q-ion)was selected for quantitation of each organic acid and two con-firmatory (C-ions) were also monitored, except for methylmalonicacid, ethylmalonic acid, 3-hydroxy-propionic acid and the IS. Forthe lastly mentioned organic acids, only one C-ion was monitored.Table 1 provides the m/z values for Q- and C-ions for all analyzedorganic acids. Selection of these ions was in agreement with lit-erature data and relevant mass spectra libraries available in ourlaboratories (NIST, Agilent Fiehn Metabolomics Library). Yet, it isnoteworthy that literature generally reports only one ion or in bestcase one Q- and one C-ion).For quantitation purposes, SIM mode was applied and analyticaltime was fragmented into 11 separate time slots corresponding tothe 10 organic acids and the internal standard PDA. In each slotthe detector was set to collect the Q-ion and the C-ion(s) for adetermined time window. Dwell time was adjusted to 60 ms foreach analyte to retain 4.95 cycles/s. Fig. 1A shows a chromatogramobtained from the GC-MS analysis of a standard mixture of organicacids in SIM mode. Fig. 1B shows a full scan ion chromatogram of aurine sample. Table 1 gives the linear dynamic range for the studiedorganic acids.