SecureTD-Q™: quantitative sample re-collection for thermal desorption
The quality of analytical data is fundamentally dependent on effective validation of the method used and is especially critical whenever potentially toxic organic emissions are being measured from complex, real-world samples.
Thermal desorption has historically been a single shot process and this presents a unique challenge for validation. For this reason, many international thermal desorption methods specify key sample and data protection features, particularly for automated instrumentation. These include:
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Stringent leak testing of each sample tube prior to desorption (without flow or heat applied)
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Effective sealing of sample tubes, both before and after analysis, to prevent loss of analytes and/or ingress of contaminants from lab air
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Pre-purge of air to vent before desorption to eliminate oxidation
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Internal standard addition capabilities
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Inert flow path
As well as all these standard method/data validation tools, Markes TD systems uniquely feature:
SecureTD-Q - Quantitative re-collection of the split flow for repeat analysis and method or data validation
Markes systems are explicitly designed for SecureTD-Q. Any aliquot of sample which is directed to split may be quantitatively re-collected onto a clean sorbent tube for repeat analysis and method/data validation. If the chromatographic profile obtained from the SecureTD-Q tube matches that of the original sample, taking into account the split ratio, quantitative recovery is confirmed.
SecureTD-Q - validation of routine method performance
Desorption of a re-collected sample should produce an exact match to the original chromatogram, but at a lower peak area - proportional to the split ratio used. By producing a replicate chromatogram or series of chromatograms from re-collected samples, SecureTD-Q can be used to demonstrate lack of bias & quantitative performance. It is thus a convenient tool for validation of routine methods.
SecureTD-Q - validation of challenging methods
SecureTD-Q is also an ideal tool for the validation of challenging applications such as:
- Thermally labile compounds - for example phosphorous pesticides and odorous sulphur compounds
- Chemical agents such as VX are particularly challenging samples due to their low volatility, extreme reactivity and ultra-low concentration in the environment. SecureTD-Q was used to validate the quantitative analysis of sub-ng masses of free-VX and to demonstrate >90% recovery through the system.
SecureTD-Q - for repeat analysis and third party confirmation
As well as method validation, quantitative repeat analysis gives numerous other benefits to the TD user:
- Back-up for situations when the primary analysis fails, for example due to the GC run finishing prematurely or the GC detector failing
- Sample archiving for future analysis or for third party confirmation - particularly useful for forensic applications such as monitoring drugs of abuse and arson debris analysis
- Data confirmation - because SecureTD-Q overcomes the one-shot limitation of thermal desorption it allows critical samples (which may be hard to collect in duplicate) to be re-analysed if necessary
- Repeat analysis by alternative technology e.g. selective detection such as FPD, process mass spectrometry
The ULTRA 50:50 offers automated thermal desorption for up to 100 tubes plus re-collection of up to 50 samples into a corresponding number of re-collection tubes. Alternatively, up to 100 TD samples can be automatically re-collected back into the original sorbent tube if required. The ULTRA 50:50 system comprises an ULTRA-UNITY configured with a 50:50 module accessory.
An ULTRA 50:50 system can be further enhanced by the addition of a second ULTRA configured for SecureTD-Q re-collection of both inlet and outlet split for every sample in a sequence. The second ULTRA may be easily reconfigured to sampling mode for maximum operational flexibility. DiffLok caps are fitted to both desorption and re-collection tubes ensuring the integrity of primary and re-collected samples. Trays on the autosampler are colour coded for clear identification of sample and re-collection tubes.
For part numbers and pricing please contact your local Markes distributor or visit our online shop.
Relevant technical support publications from Markes International can be automatically downloaded from this web site (registration required). Examples include: