-
- Posts: 14
- Joined: Sat Apr 14, 2007 2:11 am
Hi,
I have a question regarding the purity assignment. We have been assigning the purity for non-pharmacopeial compounds for a long time now.
Now I have some tricky molecules where I am not sure what is the correct way to assign the purity. I think people in this forum would help me out to find the correct way of assigning the purity.
The subject compound is in Sodium salt form (Now I have 4 compounds like this)and it is a new drug molecule. It has other metals (Palladium and Arsenic) also in traces.
We have done full characterization of the molecule for Identification and also have the complete evaluation data as given below:
Purity (HPLC area %) : 99.1%
Heavy Metals : < 20 ppm
Sulphated Ash : 14.0%
(Residue on Ignition)
Sodium Content : 4.1%
Arsenic Content : <0.5ppm (0.00005%)
(ICP-MS)
Palladium Content : 1.1ppm (0.00011%)
(ICP-MS)
Thermogravimetric Analysis : <0.1% weight loss at 150°C
Residual Solvents (by GC) : 1427ppm (0.1427%)
Acetic Acid Content : 8179ppm (0.8179%) (total = 0.1427+0.8179 = 0.9606%)
Water Content (KF) : 0.27%
Now my question is that for purity assignment, do we need to take into account the sulphated ash value or use the individual metals content values in purity purity assignment.
The formula we use for purity assignment for a non-pharmacopeial compounds is as shown below:
%Purity = (100 - %chromatographic impurities) x (100 - %water - %residual solvents - %residue on ignition)/100.
I use this formula exactly as it is if the compound is in the form other than in metallic salt form.
My calculation for this compound for purity assignment was as shown below:
%Purity = (100 - %chromatographic impurities) x (100 - %water - %residual solvents - %Sodium - %Palladium - %Arsenic)/100.
%Purity = 99.1 x (100-0.27-0.9606-4.1-0.00005-0.00011)/100
= 99.1 x 94.7/100
= 93.8%
Notes:
1) As I do not have a value for chromatographic impurities, I used the HPLC Area% for the first part.
2) I did not use the Residue on Ignition/Sulphated Ash value in the calculation since I have the exact values for Sodium, Palladium and Arsenic (I assumed these as inorganic impurities). I used these values in the purity assignment.
I would greatly appreciate your help, if you could let me know whatever the formula I used for purity assignment is ok or not.
Thanks for your help.
Regards
Banala
I have a question regarding the purity assignment. We have been assigning the purity for non-pharmacopeial compounds for a long time now.
Now I have some tricky molecules where I am not sure what is the correct way to assign the purity. I think people in this forum would help me out to find the correct way of assigning the purity.
The subject compound is in Sodium salt form (Now I have 4 compounds like this)and it is a new drug molecule. It has other metals (Palladium and Arsenic) also in traces.
We have done full characterization of the molecule for Identification and also have the complete evaluation data as given below:
Purity (HPLC area %) : 99.1%
Heavy Metals : < 20 ppm
Sulphated Ash : 14.0%
(Residue on Ignition)
Sodium Content : 4.1%
Arsenic Content : <0.5ppm (0.00005%)
(ICP-MS)
Palladium Content : 1.1ppm (0.00011%)
(ICP-MS)
Thermogravimetric Analysis : <0.1% weight loss at 150°C
Residual Solvents (by GC) : 1427ppm (0.1427%)
Acetic Acid Content : 8179ppm (0.8179%) (total = 0.1427+0.8179 = 0.9606%)
Water Content (KF) : 0.27%
Now my question is that for purity assignment, do we need to take into account the sulphated ash value or use the individual metals content values in purity purity assignment.
The formula we use for purity assignment for a non-pharmacopeial compounds is as shown below:
%Purity = (100 - %chromatographic impurities) x (100 - %water - %residual solvents - %residue on ignition)/100.
I use this formula exactly as it is if the compound is in the form other than in metallic salt form.
My calculation for this compound for purity assignment was as shown below:
%Purity = (100 - %chromatographic impurities) x (100 - %water - %residual solvents - %Sodium - %Palladium - %Arsenic)/100.
%Purity = 99.1 x (100-0.27-0.9606-4.1-0.00005-0.00011)/100
= 99.1 x 94.7/100
= 93.8%
Notes:
1) As I do not have a value for chromatographic impurities, I used the HPLC Area% for the first part.
2) I did not use the Residue on Ignition/Sulphated Ash value in the calculation since I have the exact values for Sodium, Palladium and Arsenic (I assumed these as inorganic impurities). I used these values in the purity assignment.
I would greatly appreciate your help, if you could let me know whatever the formula I used for purity assignment is ok or not.
Thanks for your help.
Regards
Banala
