Improve Your Preventative GC Maintenance

by | Gas Chromatography

Boost your confidence in making gas chromatography maintenance decisions through a self-paced video course 


Gas chromatography (GC) is a versatile tool for separating and analyzing volatile chemicals in a sample. To make the most of these detection capabilities, GC instruments need regular preventative maintenance. But in the face of practical lab realities—multiple users, 300-page service manuals, demanding workloads—the exact details of instrument upkeep can sometimes become unclear.

“Lots of customers ask how often they should complete routine maintenance,” says Rachael Ciotti, a GC-MS Application Chemist at Agilent. “Unfortunately, there’s not an easy answer to that question.”

To help researchers respond to this problem and other challenging GC maintenance issues, Ciotti and her Agilent colleague Angie Smith-Henry have developed Starting good GC habits: Tips & tricks to improve your analyses. This video tutorial empowers users with information about tools, including decision-making trees, troubleshooting flow charts, and software that helps automate maintenance processes. Real-world quality control and environmental case studies demonstrate that continuous learning about best practices is critical to having a healthy GC.

How often should routine GC maintenance occur?

In the tutorial, Ciotti explains that each lab has to decide on a routine maintenance schedule based on two factors:

  • How often is the instrument used?
  • How ‘dirty’ or concentrated are typical samples?

By ‘dirty’, Ciotti refers to samples that contain non-volatile materials, sediments, or solids that build up in injection inlets and the head of the column. She suggests that the best way to prevent excessive maintenance is for labs to take a hard look at clean-up procedures: using syringe filters or removing high-boiling point materials could reduce instrument downtime in the long run.

“The samples don't always have to look dirty—they can be completely clear but still contain difficult matrix components,” she notes. “If you're running those types of samples, expect to change your liner and trim your column more frequently.”

The tutorial suggests dividing GC maintenance tasks into three categories: often, sometimes, and when needed.



When Needed

Replace wash solvents

Clean inlet body

Replace the column

Replace inlet septum and liner

Replace gold seal

Clean detector

Trim column

Change split-vent trap

Change gas filters

Next, the Agilent team recommends following a decision tree based on a fundamental question: do you know the last time maintenance occurred? If not, get prepared to tackle a full suite of cleaning chores.

How can I automate GC maintenance?

Instead of relying on fixed calendar dates to perform GC maintenance, Smith-Henry advocates for a software-based approach that tracks the actual instrument usage. She explains how Agilent’s Early Maintenance Feedback software can count injection numbers, log service histories, and provide age limits and statuses of all serviceable parts.

“And if there’s a counter that you want but it doesn’t exist yet, it’s easy to add a user-defined counter with the click of a button,” says Smith-Henry.

The Early Maintenance Feedback software uses color-coded alerts to warn users when service thresholds approach—the instrument status panel lights up with increasing numbers of red bars as due dates come closer.

“It's a nice way to remind you that you have service due, but make sure to look at the instrument status box every so often to check what your thresholds are,” she advises.

What is a split vent trap? Do I need to change it?

Most analytical researchers are aware of split injection techniques that direct only a small portion of a gas sample to the GC column for separation to prevent overloading the column and detector. However, notes Ciotti, many users are unaware that both split and splitless GC instruments have a split vent trap—a small plastic reservoir that sits where gasses exit the GC.

“If you have any kind of purge time, the sample that’s hanging out in the liner can be swept right out to that split vent trap, even in splitless analysis,” says Ciotti. “You definitely need to worry about changing your split vent trap.”

According to the tutorial, common symptoms of clogged or contaminated split vent traps include:

  • GC stuck in standby or ‘not ready’ mode
  • Elevated baseline signals
  • Ghost peaks, bonus peaks, contamination signals

The Agilent team recommends changing the split vent trap every six months, or more frequently if samples are particularly dirty. The installation is straightforward and is available on Agilent’s GC troubleshooting YouTube channel.

“We had a customer that called in for their Agilent field service engineer because there was all kinds of goop stuck in their split vent line,” says Ciotti. “You want to make sure this doesn't happen to you—this lab was down for a couple of days waiting for service.”

How do quality control labs make GC maintenance decisions?

As a case study, the tutorial reviews how a quality control (QC) lab auto-schedules a weekly GC analysis of 4 different analytes:

  • A long-chain alkane (n-decane) to measure column efficiency
  • A long-chain alcohol (1-octanol) to probe for contamination near the column head
  • An acid-base pair of aromatic compounds (2,6-dimethyl phenol and 2,6-dimethyl aniline) to test for contamination along the column surface

The QC lab uses laboratory information management system (LIMS) software to monitor changes to three major aspects of the chromatograms:

  • Retention times
  • Area counts
  • Peak symmetry

Because retention time shifts could cause operators to miss critical sample peaks, it’s essential for users to flag changes due to column trims or other physical adjustments. Changes in area counts, on the other hand, could indicate mis-installed columns or mistaken syringe volumes.

“And if your peaks are tailing, there’s obviously a problem with active sites around the inlet,” adds Ciotti. “It's going to be time to change the inlet liner, maybe the gold seal or trim the column.”

How do environmental labs make GC maintenance decisions?

Endrin and DDT are historic pesticides now regulated or banned due to health and environmental risks. Over time, these compounds can degrade into various metabolites or products that may still pose environmental concerns.

Regular monitoring of endrin/DDT breakdown reactions can help environmental labs spot potential GC problems, explains Smith-Henry. Because pesticide degradation increases as surface sites in the column become deactivated, using breakdown thresholds is an effective way to decide to intervene with maintenance tasks.

“Breakdown reactions can be further aggravated by additional active sites, such as metal particles getting into your inlet liner and then sitting on top of your glass wool,” she cautions. “Check the vial caps and look at where the syringe puncture holes are—you may be impacting the septum and knocking metal particles inside. Also, remember that syringe guides are consumables and should be replaced with age.”

What are some GC troubleshooting strategies?

In the face of GC instrument problems, the Agilent team suggests looking for quick fixes first. Do the GC hardware parameters—such as column or syringe sizes—match the listed values in the software? Are wash vials full and clean? Are the syringes and other components of autosamplers in good working order?

“Next, I’d ask have you done recent maintenance—because if you have, there may be some leaks going on,” says Smith-Henry. “If you're not sure there's been recent maintenance, then change the liner, the septum, the syringe, and maybe trim the column to see if that'll help.”

If the user has a mass spectrometer (MS) coupled to their GC, Smith-Henry recommends trying a GC-MS quick tune report to verify how well the instrument is operating. Finally, she suggests measuring chromatograms of known samples, such as in the QC lab case study, to pinpoint lingering problems.

Ready to become a better chromatographer?

Intrigued by the practical tips available in this video tutorial? In the GC Learning Hub, a collaborative education effort between Separation Science and Agilent, users can access this tutorial and seven other courses aimed at skill development for the modern chromatographer.

Learn about:

  • Troubleshooting like a pro: Develop fundamental insights into problems with peaks, baselines, and detectors
  • Restoring columns: Strategies, optimizations, and practical insights with petrochemicals
  • Improving column performance though smart choices in consumables
  • Agilent’s Intelligent GC system: Learn ten ways that smart technology can improve your workflow
  • Remote operations: Get an action plan for connecting, integrating, and maintaining remote GC systems
  • Maximize high-throughput productivity: Liners, columns, and maintenance schedules for demanding data collection instruments
  • Ask the Agilent experts: Find answers for the toughest questions about liners, columns, contamination, peaks, and more!


The Presenters

Angie Smith-Henry
(Applications Chemist for GC and MS Supplies, Agilent
Angie is is an applications chemist for GC and MS Supplies at Agilent in Wilmington, Delaware, USA. Previously, she was an applications chemist for the MSD Solutions and Applications group with a focus on developing analysers and applications for energy, chemical and environmental markets. Angie holds a PhD in Physical Chemistry from Lehigh University and BS in Chemistry from Juniata College.

Rachael Ciotti
(Product Manager, Agilent Technologies, Wilmington, Delaware, USA)
Rachael Ciotti is a GCMS Application Chemist at Agilent in Wilmington, Delaware. Previously, she was a field service engineer specializing in installing, maintaining, and repairing Agilent GC and GC/MS systems. Prior to joining Agilent, Rachael worked at DuPont as an analytical chemist responsible for GC and GC/MS method development and transfer to manufacturing labs. She holds a Bachelor of Arts in Mathematics from Rutgers University.

Looking to develop your GC skills and become the go-to source of practical GC knowledge in your lab? Explore our full self-paced GC learning hub, produced in conjunction with Agilent.


Published  Jul 26, 2023

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