Dear Beena
If you merely wish to determine Recycled or Virgin the following should help. If you required more detailed analysis you will need access to a lab to give you this information - all major paper suppliers should be able to help.
There is no exact science to differentiating Virgin & Recycled but there are a number of 'tricks' you can use to tell.
1. With a little experience the easiest method is visual. Within recycled paper manufacture there is a process called fractionation. This process is effectively layering different quality of fibres together (similar to ply board).
Recycled pulp/paper is grey in its nature, the brown colour is a die that is added to the outside ply of paper. If you look at a recyled paper the inside ply is greyish (usually particles of coloured waste are visible) and obviously a different colour to the outside Brown outside ply. (WARNING a few poorer quality test papers die all the layers to try to look better).
Kraft papers do not use the fractionation process and are usually a consistent colour inside and out.
2. Iodine Test:
Dilute Iodine in approx 50/50 in a squirty bottle. Spray the iodine onto the inside ply of the paper. Recycled papers are more porous, the paper fibres will stain black, where as the iodine will sit on the surface of the Kraft / Virgin papers.
3. Mullen Burst Test
Kraft Papers have a higher burst resistance than recycled papers. Typically the Burst Index of a Kraft paper will be over 4, where recycled papers will be 2.5 -3.0.
Burst index is the Recorded Burst Value (Kn/m2) divided by the paper grammage (GSM).
4. If all else fails there are organisations such as PIRA that will be happy to charge you a ridiculous amount of money to carry out the above (the better option would be to go on their training days which are still quite expensive but can be very informative)
Hope this helps.
Regards
Richard