Foreword

Sample preparation involving extraction is normally required prior to analysis by chromatography, electrophoresis, or mass spectrometry. The main purposes of the sample preparation are to clean-up the sample, to make it compatible with the analytical instrumentation, and to enrich the analytes of interest. Sample clean-up is intended to remove major matrix components from the sample, which can interfere with the analyte detection or which can reduce the performance of the analytical instrumentation. Enrichment of the analytes is intended to improve the trace level detectability.

Most sample preparation in routine laboratories today is performed with classical extraction techniques, like solid-phase extraction or liquid-liquid extraction. However, in the scientific literature, a large number of research papers have been published on the development of microextraction techniques. The difference between the classical extraction techniques and the microextraction techniques is the mass / volume of the extraction phase, which has been substantially down-scaled in the latter.

The field of microextraction was essentially initiated in 1990 by Professor Janusz Pawliszyn and his co-workers by the introduction of solid-phase microextraction (SPME). In the years after this, a large number of scientific papers related to SPME emerged, SPME became commercially available, and several other microextraction techniques different from SPME were introduced. In general, a main driving force for all the activities in the field of microextraction has been to reduce the consumption of hazardous organic solvents and other materials required for sample preparation (green chemistry). In addition, the development of different microextraction techniques has been motivated by reduced sample volumes, reduced extraction times, improved analyte enrichments, improved sample clean-up, and improved compatibility with analytical instrumentation.

Definitely microextraction techniques will replace traditional methods in the future, but this will take time. Meanwhile, a lot of progress takes place, and microextraction is currently a very active field of research within analytical chemistry. New techniques and methods based on these are continuously being developed. Some of them are based solid-phase extraction principles, and includes solid-phase microextraction, stir bar sorptive extraction, microextraction by packed sorbent, dispersive micro-solid phase extraction, magnetic solid phase extraction, and thin film extraction. Others are based on liquid-liquid extraction principles, like single-drop microextraction, membrane-based microextraction, hollow-fibre microextraction and dispersive liquid-phase microextraction. In addition to all this, new materials are also entering the field of microextraction, like nanoparticles, ionic liquids and novel solid gels. All this you can read about in this e-book, which is a very comprehensive guide to the most important developments of analytical microextraction techniques. Enjoy the reading!