Gas Flow Liquid Phase Microextraction

Sample pretreatment before chromatographic analysis is the most time consuming and error prone part in the analytical procedure and it is a key factor in the final success of the analysis. Many kinds of sample pretreatment techniques such as SPE, SPME, LPME, HS and HS-LPME were developed in recent two decades years. Those techniques were mainly focused on integration, fast and high extraction efficiency. Among them, the headspace liquid microextraction was greatly concerned by wide range of scientists for directly GC/MS analysis of trace levels of volatile and semivolatile chemicals. While the technique could not commonly used by workers until now due to limitations of application. In order to overcome limitations of the technique, the extraction mechanism was systematically invested and gas flow microsyringe liquid phase microextraction (GF-MS-LPME) technique was developed based on theory of ideal gases and principle of gas chromatography. The system is designed as an open or semi-close system, where an inert gas containing the target compounds of gasify in high temperature sample cell flows continuously through a special gas outlet channel, and the target compounds are trapped on a extraction solvent. A key point is that the extracting gas phase volume is increased with extraction time using a gas flow, as a result, a high enrichment factor is obtained. Using simple gas flowing system, temperature control system and conventional microsyringe, greatly increased the surface area of the liquid phase micro solvent, and achieved quantitative recoveries for both volatile and semivolatile chemicals within short extraction time (just only 2 min). For model compounds (PAHs, APs and OCPs), the recovery was from 87.47%to 101.88%, reproducibility was between 3.03%and 8.48%, and the method detection limit was varied from 5.20 to 11.86 pg mL"1 for 10 mL water samples spiked with 4 pg mL-1 of eighteen polycyclic aromatic hydrocarbons (PAHs). In particular, the technique demonstrates high sensitivity for semivolatile chemicals which is hardly available in the other sample pretreatment techniques such as headspace liquid phase microextraction technique. In this paper, the effecting parameters on the extraction efficiency such as gas flow rate, extraction time, extracting solvent type, temperature of sample and extracting solvent were investigated. Finally, the technique was evaluated to determine PAHs, alkylphenols (APs) and organic chlorine pesticides (OCPs) from environmental water and sediment samples. The results demonstrated that the technique is inexpensive, not need desorption and cleanup steps, fast, simple to operate and quantitative extraction method.