monitoring number of injections

[The Chemist]

I wonder how many LC users monitor number of injections on a column dedicated to a particular method and change the column routinely when certain number of injections is used.

Alternatively how many LC users rely on system suitability and change the column only when system suit fails for column related reasons

many thanks

[Rndirk]

Food/environmental lab here. We monitor the number of injections on each column, but we don't dispose it right away after reaching a certain number. There are system suitability tests for each method.

[James_Ball]

Environmental here also. Most of our methods don't have a system suitability test, just calibration and continuing calibration checks. As long as the checks pass you keep going, if it fails you can recalibrate then keep going again. Once I lose baseline resolution or pressure is excessive I consider a column dead.

I ran HPLC for probably 15 years before I even head the term System Suitability, which was when we started working for a company that produced pharmaceutical excipients. The only thing close to that was the Performance Check standard for EPA531 carbamates which had one resolution check and one breakdown check and another compound that looked for tailing factor. It was a single injection test at the beginning of the run.

[mattmullaney]

Good Evening,

Monitoring injections in Pharma QC was a matter of routine with two of my previous firms...and will also be a matter of routine in my current post. Some pharma methods are just Really Antagonistic to the stationary phase of the column, necessitating such measures. The methods employing alkaline eluents of pH >/= 8 were particular offenders. Columns often did not last 60 injections in some of these isocratic methods with basic (pH) mobile phases...I've had amino acid columns last more than 2,000 injections...and those methods were gradient separations. Shameful waste of money, guess that the money made by the drug products well outweighed the loss of money in columns...

[tkubowicz]

Hello

No matter what method/column I'm using I always monitor number of injections on column. It helps to keep column in good condition and saves time to diagnose problems (especially with expensive chiral columns)
I also plot pressure at the beginning of the run vs. number of injections - it is good indicator of column condition (it is easier to decide to throw or clean column).

Regards

Tomasz Kubowicz

[lmh]

platform service in a research institute; we try to use a combination, but it's a bit messy. Very few people have formal system suitability tests, but obviously most will be running standards regularly. I encourage users to check their standard against a "good" run, rather than against the previous set of data (which is always a tempting option), because if a method deteriorates gradually, it never looks much worse than last time, but after a few months, looks dreadful. Most users look at back-pressure and reject columns when the back-pressure becomes excessive or there are obvious problems (peak-splitting, contamination).
I do monitor injections, but because most of my columns are shared with other users, the accuracy of the injection count depends on other users' recording properly. When I was using largely Luna columns, I automatically threw away guard columns at 500 injections because they only cost the equivalent of 20 vials with caps and inserts. UHPLC guards are more expensive, so I'm less inclined to throw them away without evidence of deterioration.

[DR]

Pharma user here -
Always used columns until suitability issues or excessive pressure cropped up, but we also tracked injections, always noted pressure at run start.
The only benefit to tracking injections was to spot if a column died really early.

Record: nearly 10,000 injections on a certain column for assay of a stimulant.

[The Chemist]

Thank you all for responding!