Dynamic Focusing: A Cryogen-Free Technique for Determining VVOCs, VOCs, and SVOCs

Cryogen-Free Dynamic Focusing for Thermal Desorption 

In analytical chemistry, achieving accuracy, precision, and efficiency is essential. Cutting-edge technology assists researchers and environmental scientists in accurately identifying very volatile, volatile, and semi-volatile organic compounds (VVOCs, VOCs, and SVOCs). One innovative technique that’s been making waves in this field is Cryogen-Free Dynamic Focusing for Thermal Desorption, a method that eliminates the need for cryogenic cooling while delivering exceptional results.

Determination of Very-Volatile (VVOCs), Volatile (VOCs), and Semi-Volatile Organic Compounds (SVOCs) by TD without the need for Cryogenic Cooling 

Dynamic Focusing is a novel cryogen-free technique, integral to the GERSTEL TD Core System, developed for use in thermal desorption analysis to focus and trap VVOCs, VOCs, and SVOCs before releasing them to the gas chromatography (GC) column in a sharp band for analysis. It’s important to highlight that this

technique has successfully undergone rigorous testing, including compliance with methods like U.S. EPA TO-17 and ISO 16000-6, and it has even excelled in inter-laboratory proficiency tests.

Understanding Dynamic Focusing:

Dynamic Focusing diverges from traditional thermal desorption methods in a few key ways. In this technique, a single, relatively weak sorbent is packed into the trap liner, and the trap temperature is set to +10 °C. Instead of trapping and desorbing in two separate stages, these stages are overlapped. Medium to high boilers are trapped by the sorbent and desorbed upon heating, while very volatile organic compounds (VVOCs) are slowed down just enough by the sorbent to be focused into a sharp band, resulting in remarkably sharp peaks. The graphic below illustrates the dynamic and static focusing processes for comparison. 

Precise timing of temperature and flow provides optimum separation

The Advantages of Dynamic Focusing:

  1. Streamlined System Design: The TD tube and trap are directly connected to the GC column, minimizing void volume and eliminating the need for valves or transfer lines. This design reduces active surfaces that can impact analyte recovery and cause carry-over.
  2.  PFAS-Free Pathway: The absence of Teflon™ material in the sample pathway eliminates the potential introduction of PFAS-related compounds or the loss of these compounds into the PTFE, which is crucial for today’s environmental analysis methods.
  3.  Cryogen-Free Cooling: Achieves cryogen-free Peltier cooling at +10 °C, focusing compounds as volatile as propylene (C3) and covering the full range of analytes for standard air analysis methods.
  4. User-Friendly-Low Maintenance: Easy to use, maintain, and troubleshoot, resulting in improved system uptime.
  5. PFAS-Free: A PTFE-free sample flow path ensures no degradation products or loss of PFAS,
  6.  Wide Range of Application: Dynamic Focusing is suitable for a range of standards and methods, including TO-17, ISO 16000-6, and ASTM D6196.

Chromatogram of a TO-17 gas standard (numerically labeled) and spiked gas internal standards (alphabetically labeled). Full spectrum MS detection.

Cryogen-Free Dynamic Focusing for Thermal Desorption, but also without valves or transfer lines, is a game-changer in the world of analytical chemistry. This innovative technique offers researchers and environmental scientists a powerful tool to determine very volatile to semi-volatile organic compounds with unmatched accuracy, precision, and efficiency. By eliminating both the need for cryogenic cooling and valves & transfer lines in the sample pathway, Dynamic Focusing streamlines the entire workflow for targeted VVOC, VOC, and SVOC determination, improving not only data quality but also reducing maintenance costs and system downtime.


TD Core 

Dynamic Focusing 

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