how to separate gamma-butyrolactone from N-methyl-2-pyrrolidone
Cud [sic] a person wanting to separate these just emerse [sic] them into liquid nitro [sic] or any [sic] to get the desired chemical to freeze then filter off the unfrozen butyrolacton [sic]?


With liquid nitrogen this would not be possible because liquid nitrogen condenses/boils at -195 &deg;C.  It would freeze both the pyrrolidone and the lactone.