Tuesday 13 December 2011

Ireland HPLC Training Schedule for 2012

The dates for the next MTS open enrolment training courses in Ireland in 2012 are now available:

Tuesday 5th June
How to Run HPLC Methods

Wednesday 6th June
How to Troubleshoot HPLC

Thursday 7th June
How to Develop HPLC Methods

Friday 8th June
How to Develop HPLC Methods for Challenging Separations

We also plan to run the course 'Validation of Analytical Methods for Pharmaceutical Analysis' on Tuesday 23rd & Wednesday 24th October.

The location is Dublin; full details will be on the website early next year. Contact us for more information.

Monday 12 December 2011

MTS Recommends... Measuring pKa using UV/Vis

When delivering HPLC method development training, I usually advise that the pKa of an analyte is taken into consideration, if appropriate, when selecting a suitable buffer pH. The problem with this approach is that the pKa value is not always known. A resource which may prove helpful is provided in the Chemistry Resources section of the Chemagination website where there are directions on ‘How to measure pKa by UV-vis spectrophotometry’.

Friday 9 December 2011

Help on: Acceptable Variation for HPLC Retention Time

Do you have any problems relating to analytical chemistry for pharmaceuticals or training? Send your questions to the MTS helpdesk using our contact form.

“I assess assay results for imported pharmaceutical products performed by a third party lab. The methods we use do not always specify an "allowed" retention time range. What would a reasonable guide be when assessing this – plus or minus 10%? Basically, what I should like to know is when should we ask the laboratory to investigate/explain a retention time shift from one assay to the next? Put another way, when should the laboratory make system adjustments like the temperature of the column, flow rate etc. in order for the retention time to conform? Often the method will say the active elutes at say 10 minutes. Does this mean that 9 to 11 minutes is also OK, or are there justifiable limits that we can impose?”

“The reasons for variation of retention time from analysis to analysis includes small differences in the following: the composition of the mobile phase (in terms of the aqueous and organic solvent portions); the pH of the mobile phase (particularly important for ionisable molecules like acids and bases); HPLC columns (column to column variation), and HPLC systems (particularly the system volume). As a result of these variables it is expected that the retention time will vary and usually small variations do not cause any problems. The potential problems associated with retention time variation from run to run (not injection to injection in the same run, that is a more serious problem which may indicate a problem) includes:
  • The change in runtime means that a peak is not fully collected by the end of the run and thus the analysis has to be repeated.
  • For analysis of mixtures, such as impurity analysis, peaks may be difficult to assign if the retention time varies.
  • Automatic integration events may have problems relating to identifying peaks correctly, thus requiring extra time for reprocessing.
To answer your question, it is difficult to set an allowable retention time range without a good understanding of the individual method. Ideally the person who develops the method should investigate its robustness and thus gain information on the range of retention times which might be expected due to normal variation and where the method still performs as required. Of course, it is not an ideal world and often you will be presented with data from methods where this has not been done, or if it has, it is not written into the method. From experience I would say that about 10 to 20% of the time quoted in the method is a reasonable guide but be careful not to apply it too restrictively. If you have an analysis where the retention time is on the limits, the best way to assess if there is a problem is to look at the chromatograms for the analysis and compare to a previous satisfactory analysis (preferably an example chromatogram should be included in the method). If there aren’t any differences except for retention time, and the system suitability testing is all fine, then the results should be satisfactory to use. If the retention time is very different to that expected and well outside of this approximate range then I would suspect that something has been changed in the way the method was applied and would want the analyst to investigate further.

Although pharmacopoeia sometimes include adjustments to temperature, flow rate etc. to make sure that a peak is at a particular retention time these changes are actually deviations to the method and unless you are following a pharmacopoeia method or have validated your method to show that these alterations are valid then it is not a good idea to change the method parameters.”

Monday 5 December 2011

New Associate @ NSF DBA

I am delighted to announce that I am now an associate of NSF DBA. You will probably be familiar with NSF DBA, formerly David Begg Associates, if you work in the pharmaceutical industry since they are Europe’s largest provider of pharmaceutical training, both in-house and external, and also provide pharmaceutical auditing and consulting services. I will be contributing my expertise in the area of analytical chemistry, and in particular the analysis and testing section of Qualified Person (QP) training.

Friday 2 December 2011

HPLC Training in Helsinki

I will be delivering 3 HPLC training courses from the ‘How to...’ series in Helsinki at the end of January 2012 in collaboration with Phenomenex. The courses are:

Tuesday 31st January
How to Troubleshoot HPLC
Wednesday 1st February
How to Develop HPLC Methods
Thursday 2nd February
How to Develop HPLC Methods for Challenging Separations

Contact the Nordic Phenomenex office for more details: nordicinfo@phenomenex.com