coulmn life

[denial]

Hi All

After how many injection the column (C-18) life is diminished. I Think that after 200 injection the separation will be affected. is this Right?

Thanks

Denial

[Bruce Hamilton]

Maybe, if you're unlucky.

Column life depends on lots of factors, the shortest column life I've had is 1 injection of a fermentation secondary metabolite extract into a C8 column, and the longest is well over 5000 for a C18 column doing trace HCHO in exhaust gases = very clean samples.

The main determinants of column life are the quality of the column, use of a guard column, cleanliness of the samples, reagents, mobile phases, and general care ensuring that rubbish is flushed off the column.

To get reasonable value from investment, I would target at least 1000 injections of samples without significant reduction of column performance.

200 injections would cause me to look at the method, especially sample preparation.

Bruce Hamilton

[tom jupille]

Column life is affected by degradation of the packing by the mobile phase. That is essentially independent of the number of injections, but depends on the time in contact with the mobile phase. The lifetime can vary from months to hours depending on the pH of the mobile phase (among many other things). Short-chain packings (e.g., C1) generally have a shorter lifetime than longer-chain packings (e.g., C18).

Column life is also affected by contamination of the packing by garbage in the sample. This is strongly dependent on the number of injections. As Bruce indicated, the lifetime can vary from 1 injection to several thousand, depending on how much (and what kind) of garbage is in your sample. Packing chain length is less important in this case.

I'll take a wild guess that the lifetime for 95% of columns is between 200 and 2000 injections. Some of the other Forum members who currently work for column manufacturers may be able to give you a more accurate and/or precise estimate.

[LCGUY]

Bruce and Tom has already explained major things.

Besides different other factors bonding also palys role in column life. Polymeric bonded column are inherently have longer life when compared to monomeric columns as polymeric columns gives some shielding effect to the undelying silica surface. But this may not be the thumb rule.

But P-bonded columns will cost you dearer also as compred to M-bonded ones.

[k66]

here are a number of factors that control the number of injections any modern HPLC column can withstand. Some of the factors are based upon the mode: reversed phase, ion exchange, size exclusion, normal phase, chiral, hydrophilic interation and so forth. Some of these factors are based upon the type of packing in the column — silica gel-, hybrid-, zirconia-, or polymeric-based packings or a soft gel or degree of crosslinking of resin. Some factors are based upon the phase itself: coverage, type of bond, polymeric, monolayer, or coated phase. Other factors are based upon the operating conditions: pH, temperature, mobile phase constituents, buffer composition, flow-rate, pressure and so on. Still other factors are based upon the sample that is injected: standards only, sample cleanliness, sample pH, sample volume, sample impurities present, solute molecules themselves and so on.

If a column is abused such as by using it outside of its recommended pH limits or flow-rate range, it might only yield 50 injections or even less. If the sample is simple with no highly retained impurities, then the column might withstand 5000 injections or more. If the column is not continuously operated at its upper limit, it will live longer. If the column is subjected to a variety of samples and never flushed to remove strongly retained impurities, then its life will be shortened.

In the author's experience of visiting many pharmaceutical companies, most of them expect at least 1000 injections out of a 5 μm reversed-phase column when it is used for analysing formulations, simple drug mixtures and standards. If the column is used for "dirty samples" such as biological fluid extracts or environmental extracts that have not been exhaustively cleaned up, then one should not expect 1000 injections.

So, the number of injections expected is not cut and dry but is highly dependent upon the type of column, operating conditions, sample cleanliness and degree of abuse. Of course, with guard columns and, perhaps, in-line filters, column life should be longer. In informal polling of audiences during numerous seminars by the author, a small percentage (less than 15%) of the users actually track the number of injections for a given column. So, many chromatographers don't really know how many injections that they get per column lifetime. Some modern HPLC instruments have built-in column modules and software that permits one to monitor the injection number.

From : Top 10 HPLC Column Myths