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By Anonymous on Wednesday, May 26, 2004 - 06:00 pm:
I need suggestion for desloratadine analytical method development. I prefer not to use ion-pair method for desloratadine. Here is the data:
Compound: Desloratadine
Important functional groups:
- pyridine (pKa 4.3)
- piperidine (pKa 9.7)
Solubility:
- very sol in MeOH, EtOH
- sol in 0.1 N HCl
- slight sol in water, 0.1 N NaOH
solubility is increased by reducing pH
These days I try HILIC system.
Any suggestions will be appreciated.
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By Zelechonok on Thursday, May 27, 2004 - 04:59 am:
All basic compounds (amines) if they not retain well by reverse phase columns can be retained and separated by mixed-mode chromatography without ion-pairing reagents. You will find multiple examples on our web: http://allsep.com/Applications_By_ApplicationName.php (check this link for example http://allsep.com/makeChr.php?chr=Chr_044 )
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By Uwe Neue on Thursday, May 27, 2004 - 04:02 pm:
If indeed you do not get much retention at acidic pH, you can switch to alkaline pH on an XTerra column. The retention for basic compounds typically increases by a factor of 30 at alkaline pH compared to acidic pH.
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By Anonymous on Thursday, May 27, 2004 - 05:48 pm:
If we see the pKa value of desloratadine, the pH of mobile phase must be set at least 10.7. The suitable basic compounds for this mobile phase are Pyrrolidine (pKa 11.3), TEA (pKa 10.7), 1-Methylpiperidine (pKa 10.3), and Glycine (pKa 9.
. If I decide to choose TEA:
- How much is max conc of TEA?
- If I need to adjust the pH, what compound should be used? May I use acid, like acetic acid or formic acid?
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By Uwe Neue on Friday, May 28, 2004 - 02:38 pm:
For most applications, we are using successfully pH 10 with the MS compatible ammoniumbicarbonate buffer. I would start with this. We have also used TEA and pyrrolidine. As counterions, you can choose something that is compatible with your detection system, for example formate or acetate for MS.
You may not need to go as far as using the basic amines. After all, the pK values of bases shift to more acidic values due to the organic solvent in the mobile phase. On the other hand, the pH of an ammoniumbicarbonate buffer remains practically constant with the addition of an organic solvent.
I need suggestion for desloratadine analytical method development. I prefer not to use ion-pair method for desloratadine. Here is the data:
Compound: Desloratadine
Important functional groups:
- pyridine (pKa 4.3)
- piperidine (pKa 9.7)
Solubility:
- very sol in MeOH, EtOH
- sol in 0.1 N HCl
- slight sol in water, 0.1 N NaOH
solubility is increased by reducing pH
These days I try HILIC system.
Any suggestions will be appreciated.
-------------------------------------------------------------------------------------------------------
By Zelechonok on Thursday, May 27, 2004 - 04:59 am:
All basic compounds (amines) if they not retain well by reverse phase columns can be retained and separated by mixed-mode chromatography without ion-pairing reagents. You will find multiple examples on our web: http://allsep.com/Applications_By_ApplicationName.php (check this link for example http://allsep.com/makeChr.php?chr=Chr_044 )
-------------------------------------------------------------------------------------------------------
By Uwe Neue on Thursday, May 27, 2004 - 04:02 pm:
If indeed you do not get much retention at acidic pH, you can switch to alkaline pH on an XTerra column. The retention for basic compounds typically increases by a factor of 30 at alkaline pH compared to acidic pH.
-------------------------------------------------------------------------------------------------------
By Anonymous on Thursday, May 27, 2004 - 05:48 pm:
If we see the pKa value of desloratadine, the pH of mobile phase must be set at least 10.7. The suitable basic compounds for this mobile phase are Pyrrolidine (pKa 11.3), TEA (pKa 10.7), 1-Methylpiperidine (pKa 10.3), and Glycine (pKa 9.
. If I decide to choose TEA:
- How much is max conc of TEA?
- If I need to adjust the pH, what compound should be used? May I use acid, like acetic acid or formic acid?
-------------------------------------------------------------------------------------------------------
By Uwe Neue on Friday, May 28, 2004 - 02:38 pm:
For most applications, we are using successfully pH 10 with the MS compatible ammoniumbicarbonate buffer. I would start with this. We have also used TEA and pyrrolidine. As counterions, you can choose something that is compatible with your detection system, for example formate or acetate for MS.
You may not need to go as far as using the basic amines. After all, the pK values of bases shift to more acidic values due to the organic solvent in the mobile phase. On the other hand, the pH of an ammoniumbicarbonate buffer remains practically constant with the addition of an organic solvent.
