Preventive maintenance is key to maintaining your GC and GC/MS systems. Annual maintenance is often covered by your service package, but several smaller tasks should be carried out throughout the year to ensure that your machine preserves its peak GC performance.
These tasks vary, depending on your gas supply and type of samples. It’s important to know the initial signs so that you can take action before these consumables affect your GC performance. When troubleshooting, many analysts focus on the columns, yet the gas flowpath, EM horn, and vacuum pump can have a big impact on your GC results.
Protect your gas flowpath
The gas supply is essential in the GC system, pushing the sample through to the detectors. A consistent supply is critical, along with selecting a gas that’s inert, and won’t react to your samples. In LC, the mobile phase participates in the separation but in GC, the mobile phase is just there to keep the compounds moving. The gas selected must also be clean as any impurities can greatly affect your results, causing column degradation.
Leaks in the GC system can be the bane of any analytical chemist’s life, letting moisture and air into the lines, which, over time, shortens the life of your column liner. Having a filter in the system is necessary to prevent any of these contaminants reaching your GC, especially moisture, which can quickly corrode the metal of the detectors.
Wavy, higher, or inconsistent baselines are a clue your system may have a leak and be contaminated. The leaks can become obvious when processing data as you see a significant drop in sensitivity, showing you that it’s time to change your filter. New gas filters have color changing properties to indicate that maintenance is needed. The changing color makes it easy to know if your filter is saturated. Replacing the filter takes less than five minutes, with no tools needed, and can save you from rerunning samples or wasting time troubleshooting a rising baseline.
Multiple heating and cooling cycles, which cause the ferrule to expand and contract, can trigger leaks when using traditional nuts. Usually, the fix is easy, just tighten the nut. However, to prevent this problem, Agilent has self-tightening nuts, resulting in leak-free seals.
Preserving the EM horn
Autotune reports are often overlooked but can uncover a wealth of information, including air leaks. Looking at this report helps you foresee problems and look for solutions before they cause unnecessary downtime.
Autotune can also show you the EM volts, which indicates the voltage that is being applied to the electron multiplier horn (EM horn). When the number rises, it indicates that the source is starting to get dirty or the horn is saturated. The EM horn ranges from 0 to 3000 electron volts, with most new systems in the range of 900 to 1100. If the system reaches between 1600 and 1800, the ion source may need cleaning. Above 2500, the EM horn may have become saturated, and it’s time to replace it.
In a new system, there are fresh surfaces for electrons to bounce off, so the voltage required to push the electrons through is low. After a long period of use, the electrons saturate the surfaces and voltage increases.
Best practice pump maintenance
The vacuum pump is an important part of the GC system, but also comes with a list of preventive maintenance measures. Many users experience multiple pain points with traditional oil vacuum pumps, such as oil leaks, which cause slipping hazards in the lab. Semi-annual preventive maintenance costs can also add up. Consider, too, the costs of oil and mist filter changes and the cost of disposing of the old oil. The maintenance can add up to approximately $387 per maintenance or $774 a year, as it should be completed every six months.
The new IDP3-Scroll pump is an alternative oil-free option to avoid these woes. You can find out more about the new model in this article.