-
- Posts: 85
- Joined: Wed Oct 19, 2011 9:46 am
Hi guys (and girls, of course)
I am trying to develop a new analysis RP-HPLC method on Acetaminophen and Pregabalin tablets, about 1:10. Pregabalin is a gamma amino acid.
Here´s the problem. It is very dificult to separate them, Pregabalin absortion is very poor and at low nm, usually about 210 nm. Paracetamol, well, you know, its like a monster at 210 nm.
There are no papers of this two together, so I have started from a technique from Pregabalin capsules that worked for tablets too. C8 column, 250 x 4.6, 5um, isocratic, phosphate buffer pH 6.9:Acetonitrile (94:6). Pregabalin rt is about 11 min. When attempting with Paracetamol, they didn´t separate enough. So I tryed gradient elution. Initial 98:2 and goes to 92:8 in 20 min. The best I have achieved is Pregabalin about 11 and Paracetamol 13, with good resolution but, when doing specificity, some degradation products of Pregabalin are under Paracetamol peak. I tryed different gradients, flows, columns brands and type (C18 too), etc.
So, tryed a new method found in a paper for Pregabalin alone. A buffer, Methyl alcohol, Acetonitrile 16:3:1 at pH 7. Didn´t worked (I didn´t expected too much, was like the other one). They do not separate.
So tryed a Paracetamol method from a USP phorum. Water:Methanol 1:3, C18, 300 x 3.9 (I do not have so tryed 250 x 4.6, 10 um), 10 um, flow 1.5. Pregabalin didn´t came out. Obviously, pH is crucial. But I started making changes, and arrived at 0.25 mM tetrabutylammonium phosphate in water:aceto 90:10. Pregabalin about 8 and Paracetamol about 11, at 0.5 flow.
Today I´m trying:
5um column
lower organic
try a gradient.
But I´m running out of ideas, so
CAN ANYBODY HELP ME?
Thanks guys.
I am trying to develop a new analysis RP-HPLC method on Acetaminophen and Pregabalin tablets, about 1:10. Pregabalin is a gamma amino acid.
Here´s the problem. It is very dificult to separate them, Pregabalin absortion is very poor and at low nm, usually about 210 nm. Paracetamol, well, you know, its like a monster at 210 nm.
There are no papers of this two together, so I have started from a technique from Pregabalin capsules that worked for tablets too. C8 column, 250 x 4.6, 5um, isocratic, phosphate buffer pH 6.9:Acetonitrile (94:6). Pregabalin rt is about 11 min. When attempting with Paracetamol, they didn´t separate enough. So I tryed gradient elution. Initial 98:2 and goes to 92:8 in 20 min. The best I have achieved is Pregabalin about 11 and Paracetamol 13, with good resolution but, when doing specificity, some degradation products of Pregabalin are under Paracetamol peak. I tryed different gradients, flows, columns brands and type (C18 too), etc.
So, tryed a new method found in a paper for Pregabalin alone. A buffer, Methyl alcohol, Acetonitrile 16:3:1 at pH 7. Didn´t worked (I didn´t expected too much, was like the other one). They do not separate.
So tryed a Paracetamol method from a USP phorum. Water:Methanol 1:3, C18, 300 x 3.9 (I do not have so tryed 250 x 4.6, 10 um), 10 um, flow 1.5. Pregabalin didn´t came out. Obviously, pH is crucial. But I started making changes, and arrived at 0.25 mM tetrabutylammonium phosphate in water:aceto 90:10. Pregabalin about 8 and Paracetamol about 11, at 0.5 flow.
Today I´m trying:
5um column
lower organic
try a gradient.
But I´m running out of ideas, so
CAN ANYBODY HELP ME?
Thanks guys.
Q. F. Ignacio Viera
