The determination of organic compounds in food, environmental, and biosamples at low concentrations is always a challenge. In recent years, great advances in analytical instrumentation have occurred, eventually allowing the determination of any compound in such samples. Typically, target analytes are determined by chromatographic or electrophoretic techniques coupled to a convenient detector such as ultraviolet (UV), uorescence or, more recently, mass spectrometry (MS), or tandem MS detectors. However, even when using the powerful and selective MS detection, direct injections of crude sample extracts are not recommended since matrix components can inhibit or enhance analyte ionization, hampering accurate determination. Thus, a clean sample is generally convenient to improve separation and detection, whereas a poorly treated sample may invalidate the whole analysis. Another additional and valuable aspect of the use of cleaned samples is the reduction of time to maintain instruments, thereby reducing associated costs. Besides, new objectives in sample preparation have recently appeared, such as using smaller initial sample sizes, improvement of selectivity in extraction, facilitating automation, and minimizing the amount of glassware and organic solvents to be used. Consequently, the last decade has led to the development of new microextraction techniques, mostly based on miniaturization of traditional sample preparation methods.