Direct coupling of dispersive micro-solid phase extraction and thermal desorption for sensitive gas chromatographic analysis

In this paper, the coupling between dispersive micro-solid phase extraction and thermal desorption is evaluated for the sensitivity enhancement of gas chromatographic/mass spectrometric determinations. A novel interface that enables the extraction of the analytes and their subsequent thermal desorption is presented, optimized and practically evaluated. All the variables affecting the extraction of the analytes have been studied using the determination of polycyclic aromatic hydrocarbons in water as model analytical problem. Thus, the target compounds can be extracted from 12.5 mL of sample using 5 mg of RP-C-18. After phase separation in the dedicated interface, a thermal desorption step (300 degrees C, 2 min) was carried out in the same interface. The method was characterized on the basis of its linearity, precision and limits of detection. The proposed combination resulted to be sensitive for the determination of the target analytes in the very low microgram per litre range. In fact, limits of detection ranged from 0.1 mu g L-1 to 0.2 mu g L-1, with relative standard deviations lower than 8.4%.