Thanx for the reply..
i had already referred to wikipedia ; my conclusion after wiki - still no chemically precise definition for "tar" , but it seems to contain a lot of PAH(Polycyclic aromatic hydrocarbon) {but what else ? }. if PAHs are the (only) major constituents - how to separate it from other gaseous components of cigarette smoke - CO, NOx, NH3, HCN,hydrazine - one simple way seems to be pass the gas+suspension through some kind of oil (PAH being lipophilic would be dissolved and nicotine will pass through)..however which oil ?? ,
and what are the better measures to do this filtering ??