Hello there guys-
Hope all is well with you
Had a question - It's not a quantitative Analysis question- But it's related to that..
Wondering what could have happening here- And it has become a mysterious problem.
Thought I could have your feedback
I'm running a drug that has to have Salicylic Acid content of 2.8% - The range is between 2.50 - 3.08%-
My mobile phase is 90% Methanol and 10% (0.1% TFA)- This is what SOP has recommended
My column is Supelco LC18 ( 30cm x 4mm x 5 um)
Retention time is 3.5 minutes- Flow Rate is about 1.0 ml/min and Detection is at 280 nm@ 25 degrees
The sequences that I have run are showing high end results and low end result. In one sequence run, it shows numbers ranging about 2.5 % ( which is low end) and on the other two sequence runs, they show a range of 3.15to 3.3%- ( the high end) Nothing in between, where I am looking for.( about 2.8%)
I'm wondering where could I have made a mistake?
The calibration curves look fine- R square values are ok-R square value =0.9999.
Two of the sequence runs are using 4 point calibration and one uses 5 point.
I calculated propagation error results and I'm within +/- 2%. , So, I think I'm not totally off.
Anyway- I thought you could help me out with the problem
I'm thinking somewhere in the software I may have entered a wrong entry-I'm using Chromeleon 6.4
We have sent the samples out and we got 2.8% results, where it exactly should be.
I'm making my stock standard Weight/Weight,, and then do series of dilutions of working standards.
I also have to mention that I don't have the best peak shape- The peak is tailing on the right-
Any word of wisdom will be appreciated
I'll check in later