Getting more out of thermal desorption
Monday, 21 October 2019 at 12:50:PM
range of applications for thermal desorption continues to grow, with analysts
around the world using this technique to sample vapour phase organic compounds in
applications as diverse as monitoring of ambient air, sampling of volatiles
found in whale breath, and analysis of ‘new car smell’. To achieve this,
laboratories invest in systems, supplies, training and maintenance at every stage
– from sample collection and preparation through to analysis by TD–GC–MS. The quality
of data ultimately generated is where the value can be seen – and the return on
that investment. Factors impacting the quality of that data should therefore be
quality is underpinned by several well-established aspects of sampling and
analysis. Key factors include tube desorption efficiency, tube cleanliness and sample integrity
transport & storage – not forgetting best practice instrument set up and
maintenance. Even after decades in use misperceptions about thermal desorption persist.
Common areas for misunderstanding include topics such as untargeted analysis,
quantitation, re-collection, compatibility with semi-volatile or reactive
compounds, and the assumption that liquid cryogenic cooling is required.
One of the more common misunderstandings relates
to calibration and validation and use of the appropriate accessories. Calibration
is fundamental to using your system to its full potential, supporting quantitative
analysis, reproducibility and confidence in results. When calibrating any analytical equipment, it
is important that the loading and analysis of standards closely represents the
samples, which may contain only trace amounts of the compounds of interest. For
this reason, tube-based thermal desorption (TD–GC) systems should be calibrated
by loading standards onto conditioned sorbent tubes using precision equipment
such as the Calibration Solution Loading Rig. Equally important are the processes
for validation and quality assurance.
In order to
maintain the quality of results from the entire analytical system you should
- Frequency of
calibration. Calibrate when
starting a new application, after any major system maintenance or if the
instrument response drifts outside of pre-defined criteria (refer to EPA Method
TO-17 for example). It is also advisable to run a reference standard from the
mid-point of the calibration more regularly (e.g. every 10 samples) as a check
on system performance.
- Ongoing quality
control (QC). Monitor the
day-to-day consistency of the analytical system using reference samples or
check standard tubes.
- Use of internal
standard. Identify any
anomalies in the analytical data, or variation in system performance.
To learn more about these topics, join us for a Separation
Science webinar, The insider’s guide to thermal desorption: a walk-through sorbent tube sampling and analysis, taking you through:
practices for sampling and analysing samples and for calibration
tips for method development and validation by thermal desorption
the latest technology enhancements in thermal desorption could streamline your
The webinar is presented by Dr Diane Turner, Senior
Consultant & Director, Anthias Consulting Limited and President-Elect of
the Royal Society of Chemistry Analytical Division, and Dr Helen Martin, Thermal
Desorption Product Marketing Manager, Markes International.
Download the infographic "10 Questions asked about thermal desorption".
Nick van Noorden
Nick van Noorden joined Markes
International in 2018 as Marketing Manager – Supplies. He started his career in scientific
publishing and has a background in marketing communications & strategy for organisations
in the business, consumer and not-for-profit sectors.