The Use of Different PTV Inlet Liner Types for Trapping Alkanes, Aromatics and Oxygenated Compounds During Thermal Desorption

App Note 3/2002

PTV inlets are often used for cryo-focussing and trapping of analytes for large volume, headspace, and thermal desorption applications. Selecting and optimizing trapping conditions for thermal desorption applications can be challenging, since often a wide variety of analytes spanning a broad boiling point range are present in each sample. For efficient, high fl ow thermal desorption systems such as the GERSTEL TDS, a variety of inlet liner configurations with different trapping characteristics are available. This study was conducted to qualify the best type of liner for the determination of alkanes, aromatics and oxygenated compounds by thermal desorption GC. Inlet liners packed with materials of different trapping strengths ranging from glass wool to adsorbents (Carbotrap™ or Tenax TA™) to special purpose multi-bed liners were used to cryo-focus test mixtures of alkanes, aromatics and oxygenates thermally desorbed from air sampling adsorbent tubes. The parameters trapping temperature and desorption fl ow were optimized for the best trapping efficiency. Guidelines are given for choosing appropriate trapping conditions for these analyte classes.