Can I calculate Total Impurities based from known and unknown having different test method? Let say, I have unknown impurity via UV and known via HPLC, and then the percent of each will be summed for total impurities? Thanks.
From the information you have provided I do not think you can. As you are not able to quantify the unknown impurity using UV, if you know nothing about its properties. Do you have any other information such as whether the impurity is due to degradation or is a process impurity? Why are you not able to measure the unknown impurity by HPLC?
Please feel free to PM me if I can be of further assistance.
David
[quote=David1]From the information you have provided I do not think you can. As you are not able to quantify the unknown impurity using UV, if you know nothing about its properties. Do you have any other information such as whether the impurity is due to degradation or is a process impurity? Why are you not able to measure the unknown impurity by HPLC?
Please feel free to PM me if I can be of further assistance.
David
[/quote]
sorry for my previous question. Mean to say, both impurity (known and unknown) test via HPLC but they have different Mobile phase let say.
This should be no problem, you could estimate the amount of the impurity using a relative response factor of 1 as you do not know any thing about the properties of the unknown impurity. However, I would recommend obtaining as much information about the unknown as possible such as obtaining and interpreting HPLC/DAD and HPLC/MS information. Try also to identify to source of the impurity. Is it from degradation? Is it a process impurity?
Hope this helps but please feel free to contact me if I can be of further assistance