Dear Sir. Concerning your issue about the estimation of plasma drug concentration using UV spectroscopic methods. I think the following below links may help you in your analysis:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3658075/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3658021/

https://www.sciencedirect.com/science/article/pii/S1815385213000096

https://www.sciencedirect.com/science/article/pii/S1815385213000539

Thanks

Dear Sagar, your question is too general. In order to help you with your problem, I would need to know the compound in question. Alternatively, you can make your literature search yourself, stating probably something like "your compound name" and "pharmacokinetics" a "UV spectroscopy" as search terms. You might try with Google or Google Scholar, PubMed or a search machine according to your wish..

Chose a wavelengths where there is no interference with the matrix. This is drug specific!