Principles, devices and theoretical aspects of SPME

A solid-phase microextraction process involves two steps, namely partitioning of the analytes between the coating and the sample, and desorption of the concentrated species into an analytical instrument. In the first step, the coated fibre is exposed and the target analytes are extracted from the sample matrix into the coating. In the second step, the fibre with the concentrated analytes is transferred to an instrument for desorption. A third, clean-up step can also be incorporated by using selective solvents, as in SPE. 

Solid sample treatments involving the removal of volatile species 

Desorption from the fibre can also be accomplished by using an appropriate solvent, a condensed medium such as compressed CO, or even an aqueous solution. For example, the selective extraction of bismuth from a fibre coated with an ion-exchange polymer can be accomplished by using an acidic potassium iodide solution as a complexing reagent [206]. 

The most important analytical parameters (viz. throughput, sensitivity, accuracy and precision) of SPME are largely determined during the extraction step. Desorption, which strongly influences the efficiency of the chromatographic separation and the precision of the quantitation, largely dictates the quality of the results and the scope of SPME. 

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