Please, evaluate some advices in attachment.

Dear Jaywant Pawar, dissolution studies may be performed for various applications including comparison of previously available formulation of a drug with newer formulation. For example, you may compare one diclofenac tablet with a modified diclofenac tablet or you may compare diclofenac tablet with diclofenac microparticles. Comparison of your drug delivery system with standard brand of the same drug gives evidence that you have improved certain characteristics.

The major thing that you should keep in your mind during dissolution studies is to maintain sink condition i.e. amount of dissolution medium should be more than the amount required to dissolve the drug (3 to 5 times more dissolution medium). This is challenging, because the drugs that have low solubility will require a large amount of dissolution medium which is either practically impossible, or the first samples of dissolution studies are so diluted that they cannot be quantified. This is my personal experience. In this scenario, scientist add surfactants in dissolution medium to enhance drug solubility in water. This method is becoming more acceptable now. Please see following literature.

http://www.dissolutiontech.com/DTresour/201308Articles/DT201308_A01.pdf

http://www.sciencedirect.com/science/article/pii/S0939641111000580

http://pjpps.com/HTML/Previous%20Issue/Volume-2-1/Journal-3/10-THE%20EFFECT%20OF%20SURFACTANT%20ON%20213-216.pdf

For the sake of comparison, you should perform dissolution studies of both new and standard drug product in the same medium. 

Thank you Vladimir and Mubashar Rehman Sir for the detailed information.