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By mmm on Friday, July 23, 2004 - 11:05 am:
I work in HPLC analytical support for polymer R&D.
In many cases I fear I have a solubility problem when the analyte enters the gradient of high percentage non-organic solvent.For example water/acetonitrile.We test this by running the pure analyte in 100% acetonitrile and compare the area to the gradient run which starts at 15% acetonitrile.We always notice loss of area and in normal phase as well where we have a non-polar/polar gradient.
Is this a valid concern, or do we assume the same loss in the standard as the sample? If it is a problem, is this a good way to test?
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By Uwe Neue on Friday, July 23, 2004 - 03:11 pm:
It is possible, but it is also possible that the detector response might change with the solvent composition. I would run a blank gradient and see if there is a signal from the previous injection. This has been done in protein chromatography.
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By mmm on Monday, July 26, 2004 - 08:47 am:
I will give that a try.
Thanks!
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By PETER on Thursday, August 12, 2004 - 06:01 am:
I also suppose it's the detector.It seems you are working with ELSD (polymer/gradient).Gradient runs or 100% modifier give different retention times,obviously.Different eluent composition means different spraying conditions like surface tension.Different retention times mean different areas with that detector.
I work in HPLC analytical support for polymer R&D.
In many cases I fear I have a solubility problem when the analyte enters the gradient of high percentage non-organic solvent.For example water/acetonitrile.We test this by running the pure analyte in 100% acetonitrile and compare the area to the gradient run which starts at 15% acetonitrile.We always notice loss of area and in normal phase as well where we have a non-polar/polar gradient.
Is this a valid concern, or do we assume the same loss in the standard as the sample? If it is a problem, is this a good way to test?
-------------------------------------------------------------------------------------------------------
By Uwe Neue on Friday, July 23, 2004 - 03:11 pm:
It is possible, but it is also possible that the detector response might change with the solvent composition. I would run a blank gradient and see if there is a signal from the previous injection. This has been done in protein chromatography.
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By mmm on Monday, July 26, 2004 - 08:47 am:
I will give that a try.
Thanks!
-------------------------------------------------------------------------------------------------------
By PETER on Thursday, August 12, 2004 - 06:01 am:
I also suppose it's the detector.It seems you are working with ELSD (polymer/gradient).Gradient runs or 100% modifier give different retention times,obviously.Different eluent composition means different spraying conditions like surface tension.Different retention times mean different areas with that detector.
