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about analysis of the isomer,
Posted: Thu Apr 06, 2006 5:12 am
by ahvivian
I am analysing a product by reversed phase chromatography but the only analytical standard I can find is a mixture of two isomers.
so two peaks can be easlily seen in the chromatography.
But one thing make me surprised that when i using the proper composision of the mobile phase, there is only one single peak in the chromatography, so i wonder whether i can draw a conclusion that the resolution of two isomers is nearly zero, or may be explained as the retention times are equal?
the single peak is more fit for quantitative analysis?
so can I developing a chromatography method to quantitative analysis this product using their mixture of two isomers as the analytical standard?
it puzzled me for a long time, please give me some advise,ok? if u will.
thax a lot!
u can also send ur good advise to my mailbox: ahvivian2@gamil.com
waiting for u help!!!!!!!
Posted: Thu Apr 06, 2006 8:51 am
by Rafael Chust
Well, 2 isomers are 2 different substances!
Therefore, you must develop a method that separates both and then, run your sample.
Posted: Thu Apr 06, 2006 2:22 pm
by yangz00g
It depends on what information you want to obtain from the analysis.
Let's say if one of the isomer is an active ingredient in a drug formular, and the other is a toxic or has no theraputic activity at all. You have to separate them and quantify the active one or both. If their bio-activities are exchangeable or the concentration of the mixures instead of one of them has been widely accepted as a bio-marker, I don't see the problem to use the mixture concentration.
thaks!
Posted: Fri Apr 07, 2006 5:41 am
by ahvivian
thaks for yangz00g and Rafael Chust!
I am not study the bio-medicine,
I am only trying to Develope of a new HPLC Method for the determination of a metal using A as a precolumn derivatizing reagent,
But the chelate,metal-A, which has two two geometrical isomers, now I am trying to make the resolutions of the two isomers equal so as to only a single peak in the chromatography.
then any suggestions?
waiting u reply, thaks !
Posted: Fri Apr 07, 2006 6:40 am
by Peter Apps
As long as the two isomers give the same detector response per unit of metal it does not matter at all whether the isomers resolve completely partially or not at all - all you have to measure is the total peak area for both of them.
Peter
Posted: Fri Apr 07, 2006 9:10 am
by Rafael Chust
Wow! That changes the whole view of the subject!
I would follow Peter suggestion and calculate both areas, no matter you have or not baseline resolution.
Posted: Fri Apr 07, 2006 1:41 pm
by yangz00g
Peter's suggestion is great.
If you can use a metal specific detector, say ICP-MS, you won't have the problem, and you don't need any derivation.
to yangz00g
Posted: Sun Apr 09, 2006 3:44 am
by ahvivian
yeah,u r right!
ICP-MS is a sensitive method to determine the concentration of metals,but simply it can only give the total concentration, as far as the speciation of the metals,it cannot simply to use ICP-MS.
while using the precolumn derivation HPLCmethod, different species of metal will be known.
I think one single peak is more suit for quantitative analysis, so I try to find a proper composition of the mobile phase, and i got the single peak later.
Posted: Sun Apr 09, 2006 4:22 am
by yangz00g
ICP-MS detector means using ICP-MS as an online LC detector termed as LC-ICP-MS.