A purge and trap autosampler is a vital laboratory instrument used in environmental analysis to detect volatile organic compounds (VOCs). However, like any instrument, it can occasionally encounter issues that hinder its performance.
This article aims to highlight some common problems users face with these autosamplers and explore tips for troubleshooting and resolving these concerns. We will also discuss the Purge and Trap essentials in the process.
1. Insufficient Sample Volume
Insufficient sample volume is one of the most prevalent issues faced by purge and trap autosampler users. This issue typically arises when the provided sample volume does not meet the instrument’s requirements. It can lead to inaccurate results and compromise the effectiveness of chromatographic analysis.
To address this problem, users should carefully review the instrument specifications regarding minimum sample volumes. If their sample volume falls below this threshold, they should consider diluting it or using a different vial size that allows a higher sample volume.
2. Contamination
Contamination is another recurring problem encountered by purge and trap autosampler users. Contaminants can interfere with accurately detecting and quantifying VOCs in samples, compromising data integrity. Familiar sources of contamination include dirty liners, contaminated carrier gas lines, or inadequately cleaned glassware.
To mitigate contamination issues, it is essential to adopt stringent cleaning protocols for all elements involved in the analysis process. To remove potential contaminants safely, liners, tubing, septa, needles, and glassware should be regularly cleaned using appropriate solvents or cleaning agents.
3. Carryover Effects
Carryover effects occur when trace amounts of previous samples persistently contaminate subsequent samples during analysis runs on purge and trap autosamplers. These effects can lead to inaccuracies in data interpretation if not addressed promptly.
Users can reduce carryover effects by implementing thorough flushing protocols between samples using solvents compatible with their instrument’s setup. To optimize flushing conditions and reduce carryover, it is advisable to consult the instrument and contract manufacturer’s guidelines or seek assistance from technical support.
4. Drift in Retention Times
Retention time drift can significantly impact the reproducibility and reliability of data acquired from purge and trap autosamplers. This issue could arise due to column aging, stationary phase degradation, or fluctuating carrier gas flow rates.
Users should regularly train their autosampler instrumentation to counteract retention time drift on a stable reference compound such as naphthalene. Tracking any deviations in retention times of this reference compound over time makes it easier to calibrate and correct for any observed drift.
Additionally, it is essential to routinely maintain and replace consumables in the autosampler to prevent unexpected fluctuations.
5. Degradation of Analytes
Analyte degradation during analysis is another concern that may be encountered when utilizing purge and trap autosamplers. Certain VOCs are more prone to thermal degradation or hydrolysis than others, leading to inaccurate quantification.
Successful troubleshooting involves addressing this concern through instrument optimization during sample introduction and optimizing temperature programming parameters in the chromatographic method. Likewise, optimizing purge flow rates can help minimize contact time between analytes and potentially reactive system parts, ultimately reducing degradation.
6. Loss of Sensitivity
Users sometimes face loss of sensitivity with purge and trap autosamplers. This problem can result in lower signal intensities and difficulties detecting and quantifying low-level VOCs in samples.
To address this concern, users should verify that they use the appropriate sampling parameters and settings for their specific analysis. Optimal conditions for sample desorption, trap purging, heating ramps, and other factors may need to be adjusted to maximize sensitivity. Regularly checking and replacing consumables such as trap sorbents and inlet liners can help maintain sensitivity over time.
Conclusion
While purge and trap autosamplers are sophisticated instruments crucial for analysis in environmental laboratories, issues are bound to arise at times. By understanding common problems such as insufficient sample volume, contamination, carryover effects, retention time drift, and analyte degradation, users can better troubleshoot these problems when they occur.
Employing best practices like adhering to instrument specifications, implementing rigorous cleaning protocols, and optimizing instrumentation settings stress-tested against reference compounds are fundamental to reliable analytical results using purge and trap autosamplers.
Hence, they maintain seamless operations, ensuring the utmost analytical success whenever a problem arises.
Article and permission to publish here provided by Ethan William. Originally written for Supply Chain Game Changer and published on May 21, 2024.
Cover image by Alana Jordan from Pixabay.