Laboratories today are always looking to improve their productivity, to increase sample throughput, and reduce costs. Analytical chemists are taught a lot about how the gas flow can affect the speed of the workflow, or how the inlet temperature can influence peaks. But often, the effect of the smaller parts of the GC system, such as the consumables, or the output, is forgotten. Installing parts in the right way can save hours of troubleshooting.
Septa – do you know best practice?
The septum is the first element of the GC system the injected sample comes into contact with. It acts as a barrier to prevent contamination, and its effectiveness can determine the success of your chromatography results. Choosing the right one is essential, but so is installing it according to best practice. To make sure that you get it right every time, follow our simple steps:
- Step 1: put on gloves – otherwise you could unwittingly contaminate your own instrument,
- Step 2: turn off the gas flow,
- Step 3: remove the septum nut,
- Step 4: replace septum,
- Step 5: replace septum nut – be careful not to over tighten,
- Step 6: turn on gas flow,
- Step 7: if necessary tighten nut one-quarter of a turn more, or just enough to hold pressure.
A common misconception is that the inlet temperature needs to be turned off while changing the septum, however, that’s not the case. If the nut is tightened at room temperature, it may not be enough to hold your temperature setpoint once turned back on.
Picking the right liner
Similarly to septa, chemists also default to using the same liner when developing a new method, but different types make a big impact. Liners are the centerpiece of the inlet system in which the sample is evaporated and brought into the gas phase. When choosing a liner, there are some simple questions you should ask yourself to find the best one for optimizing GC systems:
- What are you injecting?
- What solvent are you using?
- What is your matrix like?
- How much sample clean-up are you going to do?
The liner should be changed regularly. For dirty samples, such as soil, in high throughput labs, it may be as frequent as once per day. For clean samples, with no visible residue and few injections, it can be once per month.
When selecting the liner, an important consideration is that the more complex a liner is, the more expensive and difficult to de-activate it will be. Find out more about Agilent’s extensive liner range here.
Troubleshooting made easy with a flow meter
Determining the location of a problem can be a tricky task that many GC labs face daily. Shifting peaks, unreproducible retention times, and rising baselines, indicate that there may be a blockage in the system. The blockages can be caused by incorrect liner or septum use.
Optimizing GC systems can be made much simpler with the addition of a flow meter. It gives you the ability to find and fix problems quickly, minimizing any downtime. Agilent’s ADM Flow Meter is a great new option to measure volumetric flow of gases and mixed gases. Find out more here.
Avoid common pitfalls in split vent traps
The split vent trap captures the contaminants released by the injection system. This trap ensures that the split vent line does not clog, as it can create system errors or expensive repairs. Therefore, with incorrect liner use, dirt can build up in the trap, which may lead to rising baselines and ghost peaks. However, due to its location at the back of the instrument, it is often not replaced regularly on GC systems. This cartridge should be replaced every six months, and is easily changed without tools.
Gold standard gold seals
During inlet maintenance, replacing the gold seal is just as important as changing the clogged liner or split vent trap. Gold seals are best suited to this job, as the soft surface allows proper sealing without getting stuck in the inlet. Agilent’s Ultra Inert chemistry blocks active sites, as gold is naturally not inert. The deactivation chemistry makes it perfect for hot inlets. When selecting a gold seal, it is best to opt for one produced with metal injection molding to ensure completely smooth surfaces. A machined seal may have an uneven surface, causing difficulty sealing, and unreproducible results. Reliability in GC counts – choose Agilent Ultra Inert gold seals, when optimizing GC systems.
Making small changes to your GC system can have a big impact on your overall workflow, stopping countless hours being spent on revalidating your methods. To learn more about how Agilent can help you to get more from your GC, click here.