It is possible to calculate the encapsulation efficiency using this equation from the indirect method. As total arsenic you can use the total amount that you used in your nanoparticles formulation and as you said the free arsenic would be that one that is not inside your nanoparticle.

If arsenic was added as a salt I can assure you that your encapsulation efficiency will be close to zero. The equation you want to use relies on the fact that a significant amount (with respect to what was initially added) of arsenic is encapsulated. You need to wash the particles, dissolve the polymer, and quantify arsenic using a sensitive method.

I have taken arsenic trioxide aqaous solution + same amount of plga in methylene chloride + PVA then sonicate for 10 min filter it then dry centrifuge n dry pellete in oven and after that crushed it to make powder.

The total amount is the amount present in your suspension (encapdulated + free) so you have to dissolve your sample to make sure all the arsenic is free and then determine the total concentration.

Dear Rana,

It is necessary to understand that encapsulation efficiency and loading capacity are different from each other;

Encapsulation efficiency (EE%) is calculated by (total drug added – free non-entrapped drug) divided by the total drug added. Loading capacity is the amount of drug loaded per unit weight of the nanoparticle, indicating the percentage of mass of the nanoparticle that is due to the encapsulated drug.

However, loading capacity (LC%) can be calculated by the amount of total entrapped drug divided by the total nanoparticle weight. In drug delivery, yield, given as a percent, is a reflection of the amount of drug delivered per amount encapsulated.

So, now you can calculate what you want.

Best regard

My doubt is that... As i have added .2 gm of arsenic and. 2gm of PLGA, to make nano particles so it is possible to not loss any arsenic during whole process??? N one more confusion..I mixed .2gm arsenic in 10 ml distil water +.2 gm PLGA in 4ml dcm + 2.25% PVA (25ml). Now drug added =200mg /35ml or 200mg/10 ml?????

Total drug added as mass not as a concentration (which you will have to multiply by 10 mL if you want), you added 200 mg of arsenic. Look to hear from your results, I anticipate 1% of encapsulation efficiency. You are using way to much water that will contribute towards zero encapsulation.