Chromatography Forum

There is a difference in the peak shape between the Kinetex and a regular porous column. It doesn't show any difference in plate count and asymmetry, but the Kinetex peaks are not gaussian shaped. They are sharper close to the Apex and broader at the bottom (if you understand what I mean...). The difference is tiny, but visible.

Finally I had to call the manager at the QC lab and get the information. They had 50% MeOH in the weak needle wash bottle.... I don't know how many times I have told them to put 10% acetonitrile in this flask.

So problem is solved. Formulation not soluble in 50% MeOH = precipitation = column crash. Even if there is no precipitation, the MeOH destroys the separation.

Then I wonder what is the reason for this Waters design? Why is the needle wash injected with the sample? And how could a Waters technician spend two full days without looking at these bottles (knowing that the problem was peak splitting and band broadening)????

It seems as not even Waters knows how their instruments work.

Unfortunately service engineers at most major instrument manufacurers simply test the performance of each component individually, i.e. pump delivers correct flow rate, etc. When purchasing a new instrument I have requested inclusion of a chromatographic test (test their column using their QC conditions) of the system. One manufacturer finally agreed although it took ~1month to get this "unusual request" processed and I had to pay extra for this service. The manufacturer would not agree to a performance specification even though they were using their column, their QC conditions with their new instrument.

It seems instrument manufacturers dont believe they need to perform a functional test of the system or are afraid of what such tests would show.

There is a difference in the peak shape between the Kinetex and a regular porous column. It doesn't show any difference in plate count and asymmetry, but the Kinetex peaks are not gaussian shaped. They are sharper close to the Apex and broader at the bottom (if you understand what I mean...). The difference is tiny, but visible.

I have not observed such unusual peak shapes (triangular?) when using many Kinetex columns. This visual observation would easily be quantified by comparing peak widths and tailing factors at 5% height of a Kinetex column and any competitor.

Is this shape observed in isocratic, gradient or both elution modes?