Thursday, 27 July 2017

HPLC: Should I use a Column Log?

When I deliver my HPLC troubleshooting course, one of the questions that I ask delegates is whether they use a column log. The answer is usually 'yes' from most of the class. Then I ask again do they use the column log (as in reading and reviewing the information in it) and the answer goes down to just a few in each class. The column log can be a great source of useful information if used properly but it can be difficult to get a column log system working effectively.

The benefits of keeping a log for the use of your HPLC columns is that you have a record of what was used on a particular column. This may be used in a number of ways:
  • It could help to predict when a column is coming near the end of its life. This is much easier if the column has only been used for a particular method, or perhaps type of method.
  • It could help to provide information on how this particular column behaves as it nears the end of its life (again easier if it is dedicated to a particular method or type of method). The signs of column degradation are not always the same. Sometimes you might observe that the pressure is increasing and even with the use of guards and filters it is still the criteria that indicates that the column may not be useful for much longer. More often it is chromatography symptoms that will indicate that the lifetime of the column is approaching, such as loss of efficiency and resolution, or peak tailing.
  • You will be able to tell if this individual column is behaving as expected if you have previous ones to compare it to when you are troubleshooting.
  • You will know if you are getting value for money from your column based on how long it lasts.
One of the reasons that it can be difficult to make a column log system work effectively is that it is not always easy to remember to fill them in, or to persuade others to remember to fill them in! Additionally they may be seen as something that is required and done for that reason rather than something which is considered genuinely useful. Thus they may end up filled in but nobody ever looks at them!

I usually advise that it is best to choose carefully when deciding what to record in the log, too many required entries will reduce the likelihood of it being completed. The list below includes many of the useful entries that you could choose from. Probably one of the most important is a running tally of the number of injections that have been performed on the column since this is how we measure lifetime. After that, be pragmatic and choose those that would be most useful for a particular column/method combination. This won't be possible for the first column you use for a particular method but after that it is worth updating the log fields based on experience to make your life easier. 

Typical Column Log Entries Include:
  • Date used
  • Samples injected
  • Method used (if used for more than one method)
  • Number of injections
  • Efficiency, N (not useful for gradient methods)
  • Resolution (may need to specify which peaks)
  • Tailing/fronting (often major peak is used, if applicable)
  • Pressure
  • Retention times (some variation is normal from run to run)
  • HPLC system used
  • etc.


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