A Good Time for Down Time?
“Time is money” and an instrument costs money even when it is not being used. Your customers pay for accurate and speedy results but if your instrument is not generating them, then revenue is lost. There’s also the fact that power supplies, environmental controls, gas supplies, and lab space are all costs that carry on accumulating when the instrument is offline. This means that keeping an instrument in good working order is critical for any analytical lab and preventative maintenance is always preferable to unplanned maintenance.
Preventative maintenance will keep chromatography instrumentation in optimal condition and reduce unplanned shutdowns which always take more time to perform. So, what are the fundamental ways to keep your instrument happy?
Get to know your system!
How many times has a user shown a “problem” chromatogram and the piece of the puzzle is to figure out what the actual problem is? How can you tell if there’s definitely an issue that needs to be resolved?!
Look, listen and feel your system. You can see buffer crystallising from leak sites, cracks in the tubing, damage to unions. You can hear when your degasser is struggling or when a turbopump is labouring. You can feel when your rough pump is not switching on or when a column is not connected properly.
By far the best method of proving that there is an issue is to have a known sample run on a known method that will give you a baseline chromatogram to compare against. You can use the chromatogram that was taken when you know the instrument is performing correctly and see what differences there are in the same sample/method that has just been run. Have retention times shifted globally or just for a single peak? Is the noise louder? Are the peak shapes correct? Are the tune parameters reading back at similar levels?
Many labs do this routinely by adding control samples and system suitability test (SST) samples that check if the system is working and optimised during analytical runs so that the data generated is valid. Taking the time to see if any maintenance is required before shutting down or narrowing down the focus of the investigation will keep the lab running.
Figure 1 - An example of overlapping SST, showing global retention time shift.
Keep Good Records!
Everyone has a “Bob” in their lab — the person who has been with the company the longest and does all the maintenance on the instruments. Everyone goes to Bob when there is a problem. But what happens to the “Bob Jobs” when Bob isn’t around?
Keeping good records of any maintenance that has been carried out and sample types that have been analysed on the system will allow anyone to get started with troubleshooting and/or maintenance. Record keeping can also be used to see if there are trends appearing in the maintenance that is being carried out — such as filters being blocked more often than they should, indicating unsuitable sample/mobile phase preparation. Whatever the issue, proactive steps can be taken. Complete records can also flag up potential future needs — such as detector voltages starting to rise rapidly.
Figure 2 - example of HPLC service record.
Rubbish in, Rubbish out
Think of your analysis as a recipe for a meal. Fresh, clean ingredients (samples and mobile phase) are always a much better basis to build from and a little seasoning (buffers, pH) will dramatically improve the taste (quality of data). Of course, if you are in a rush then you can always use yesterday’s leftovers if you check them first to make sure they won’t cause damage. Just don’t expect it to taste as nice!
Clean pots and pans will ensure that the previous meal’s flavours (sample carryover) are removed and washing them afterwards will make sure they stay in the right condition for the next chef to use.
All this is to say that the quality of the material you put into the system, and the system itself, will dictate the quality of the end data. The more time you put into preparation, the less time you will spend on instrument and chromatogram clean up. There are many ways this can be achieved including techniques such as SPE, split injections and solvent purification.
Figure 3 - Example of an aqueous mobile phase that has not been prepared correctly.
It is said that, in general, adults take in about 20% of what they read/hear but 80% of what they personally experience. So there’s no substitute for getting your hands a little dirty and taking apart an instrument (when it is called for!). Instruments are designed to be routinely maintained by the user, not just a highly trained engineer, so if you are careful, you are unlikely to cause damage, meaning that you are not dependant on annual PMs to keep an instrument in good condition. Schematics and written instructions are good for preparation but lack the realism of hands-on experience.
Having a fundamental understanding of the theory will also prove invaluable for keeping an instrument in perfect order. For example, if you understand how important band broadening is to the quality of the chromatography, then you will be aware of the choice of and condition of the sample loop, connective tubing, and injection volumes.
Many users see instruments as big grey boxes and can be intimidated by their operation and, therefore, their maintenance needs. A few basic changes to your approach can demystify the process and improve the output of your lab, not only saving time and money but also the stress of the analysts!