For encapsulation efficiency you can use SPME headspace analysis.

Hi Robin Joshi,

thanks for answering.

Besides using HPLC and GC, are there any other ways?

Sure there are other ways. You can check which is a good solvent for your compound (ethanol, methanol, usually work well for hydrophobic phenolics, but I don't know the entity of "A"). 

First of all you have to extract A from the encapsulating matrix. You can try to do it directly in the solvent, however maltodextrin can be tough to release its cargo when  it is dispersed in a non polar solvent. One possibility to tackle this is to grind the capsules very well prior to the extraction and to do the extraction for a long period. 

Consider also where would you want A to be released (if you encapsulate it, I guess you want to release at some point). In that case what you can do is to perform release experiments in the medium that your are interested, i.e., water at a certain pH (no matter if it is acqueous phase, aftwerwards it has to be released there) and then measure how much is actually released to that medium. At some point there will be equilibrium, and the maximum amount that is released can be considered for calculating and "Effective Efficiency Ratio". Meaning that even if you have more compound encapsulated inside, it won't be released, so you can consider it "lost".

If you really want to calculate how much is encapsulated, though, the most accurate thing to do is thermogravimetric analysis (TGA). You can read further about it, there is plenty of information online and probably someone in your university has one TGA instrument (Chemistry or Chemical Engineering Departments usually do).

Remember you are encapsulating an antioxidant, so instead of measuring the concentration (for example with chromatography), you can use the classical Folin, DPPH, ABTS or any other simple in-vitro antioxidant capacity test!

Now good luck with your experiments!!