Indoor air quality

Automated thermal desorber doubles productivity, and increases data precision and accuracy in air studies

When studies of volatile organic compounds take several years to complete, how do analysts ensure the same precision and accuracy in the data for each sample for the duration of a project? Dr Rebecca Cordell from Leicester University in the UK relies on Markes International’s TD100-xr multi-tube thermal desorber, which delivers fast and consistent results time and time again thanks to its automated internal standard addition feature. It also saves further sampling time with its automated dry-purge feature.

Improved accuracy and precision in air quality study

Dr Cordell is studying air quality in hospitals to determine whether healthcare workers are exposed to poor-quality air. For three years, her team has been collecting air samples onto sorbent tubes to analyse their volatile organic compound (VOC) content. So far, the team has collected over 600 samples from two hospitals and analysed each one by thermal desorption–twodimensional gas chromatography with a flame ionisation detector or mass spectrometer (TD–GC×GC–FID/MS).

The challenge for Dr Cordell and her team in this project, which may last up to five years, is maintaining consistency throughout so that the first batch tested is comparable to the very last batch. They do this by running an internal standard through the entire analytical system. Internal standards allow you to account for instrument variability over time, such as changes in detector response, giving improved precision and accuracy. However, Dr Cordell’s team had found in the past that making up standards and injecting them by hand into a manually operated thermal desorber interferred with the accuracy of their results. There was a bias depending on who made up the standards and who injected them. “Making a 10 mL solution should be the same whoever does it, but it’s not,” said Dr Cordell. “We had to statistically merge out batches to get rid of the batch bias.”