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Sample preparation for the analysis of low-molecular-weight analytes prior to chromatographic analysis

Wolfgang Buchberger, Johannes-Kepler University, Analytical Chemistry, Linz (Austria)

Appropriate sample preparations steps are a key to successful quantitative analysis in real samples. The focus of these steps may include

  • sample clean-up in order to simplify the matrix and to remove interferences
  • Improving the detection limits by proper enrichment steps
  • Improving the reliability of the quantitation
  • making the sample compatible with the chromatographic injection and separation system

Nowadays, various techniques are in use for routine sample preparation, and various kits are commercially available for special applications. However, there is still ongoing progress with respect to enhanced efficiency and broader applicability. Within this workshop the state-of-the-art is presented and modern trends are highlighted for low- and medium-molecular-weight analytes. Approaches that may be specific for high-molecular-weight analytes are not included.

For liquid samples the following strategies will be discussed:

  • liquid-liquid extraction, including variants like liquid phase microextraction (LPME), dispersive liquid-liquid microextraction (DLLME), membrane-assisted liquid-liquid extraction, supported liquid extraction, dialysis
  • liquid-solid extraction, such as solid-phase extraction (SPE), dispersive solid phase extraction, solid-phase microextraction (SPME), stir bar sorptive extraction
  • thermal extraction (head-space analysis)
  • precipitation procedures for sample clean-up

Approaches for solid samples will cover

  • solvent extraction including ultrasound-, microwave-, or pressure-assisted extraction
  • supercritical fluid extraction
  • thermal extraction (thermodesorption techniques)

Special attention will be paid to a critical evaluation of the performance of each technique and to the proper combination of different sample pretreatment step in order to be able to establish robust analytical methods for complex samples from different application fields. In addition, examples from the literature will be used to demonstrate the advantages/disadvantages of different approaches.