Tuesday, 25 August 2009

Help on: GPV testing


Do you have any problems relating to analytical chemistry for pharmaceuticals or training? Send your questions to the MTS helpdesk using our contact form.
"can we use ipa(isopropyl alcohol) in gpv test if yes then why."
"To answer your question about using IPA for a GPV test I am going to make a few assumptions about what you are trying to achieve. I take it that you want to perform a gradient proportioning valve test for a low pressure mixing HPLC system, the intent being to test if the proportions of each solvent that you programme during your HPLC analysis are actually being performed accurately by the system. The normal method to perform this test is use two solvents: The first is water, and the second is water containing a small amount of acetone (approximately 0.1%v/v). You can also use methanol in place of water. It is best to use just one solvent since you want to test the proportioning of the valve only, and don’t want the effects of differing compression of solvents included in the results.

Some manufacturers sell GPV test solvents, e.g. Waters provide propyl paraben in methanol for their test. The purpose of the acetone (or propyl paraben) is to introduce a component into one of the solvents which will have a corresponding UV response, so obviously this approach is used for systems which have a UV detector installed. The response for the solvent containing the UV absorbing compound will change as the proportion of this solvent is introduced by the GPV and therefore it allows you to measure how well the GPV is mixing the solvent lines.

Since your question was about the solvents and not actually how to do the test I will assume that you already know about how to do it. If you want to use IPA for your GPV test then it would only make sense if you regularly use IPA as a mobile phase component. You want to test how well the GPV works in its typical use. The UV cutoff for IPA is at about 210nm so it will work fine with a UV absorbing component added to one portion of IPA and just IPA in the other solvent. However if you routinely use aqueous solvents then water may be a better choice."
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