Comparison of GC-MS Calibration Properties of Volatile Organic Compounds and Relative Quantification Without Calibration Standards

In this study, the calibration properties of volatile organic compounds (VOCs) were evaluated using two different types of sample transfer approaches for gas chromatography with mass spectrometry (GC-MS), [i.e., direct injection (DI) and solid-phase microextraction (SPME)]. The calibration of liquid-phase VOCs conducted by both approaches showed that the sensitivity of the SPME method is two to three times lower than that of DI. If such a comparison was extended further to gas phase standards, the relative dominance of DI was more prominent by approximately a single order of magnitude than SPME. The basic response characteristics of GC-MS, when assessed for a given compound (X) against a reference compound of toluene (T), showed an increase in the response factor ratio [R(X/T)] as a function of the carbon number [C(X/T)], regardless of injection method. This relationship was useful to roughly predict the concentrations of certain compounds in the absence of a standard for their calibration.