6 - Calibration

Abstract

Solid-phase microextraction (SPME) is a solvent-free sample preparation technique that integrates sampling, isolation, and concentration. Its simplicity of use, relatively short sample processing time, and fiber reusability have made SPME an attractive choice for many analytical applications. SPME has been widely applied to the sampling and analysis of environmental, food, aromatic, metallic, forensic, and pharmaceutical samples. Calibration is a process relating the measured analytical signal to the concentration of analyte in the sample matrix. Several methods have been used for the calibration of SPME. In addition to traditional calibration methods (i.e., external standard, internal standard, and standard addition), the existing SPME calibration methods include equilibrium extraction, exhaustive extraction, and diffusion-based calibration. In this chapter, details and characteristics of these calibration methods will be discussed. SPME calibration technique suitability depends on the application, the number of samples to be analyzed, and the availability of a mass spectrometry instrument in the laboratory. The development of SPME calibration methods is based on an understanding of fundamental principles governing the mass transfer of analytes in multiphase systems. Theories have been developed to understand the principal processes involved in SPME by applying the basic fundamentals of thermodynamics and mass transfer kinetics. Quantification using calibration curves does not require extensive sample preparation, but the sampling procedure and chromatographic conditions must remain constant for both the sample and the standard solutions, and if there are matrix effects, a blank sample matrix is necessary.