Solid-phase extraction (SPE) apparatus consists of a 12-port SPE vacuum manifold with large volume samplers connected through PTFE tubes (Supelco, Bellefonte, PA, USA) and a diaphragm vacuum pump (KNF Laboport, Freiburg, Germany). SPE extracts are evaporated in an N-EVAP nitrogen evaporation system (Organomation Associates Inc., Berlin, MA, USA) with thermostatic water bath.

SPE apparatus is used for sample preparation and chemical compounds pre-concentration prior to instrumental analysis (e.g. LC-MS/MS) enabling the removal of matrix interferences and the trace level detection of the compounds.