institute with Atomic absorption spectrometer facility for analysis of heavy metal like Cu, Cd, Zn, Mn, Ni, Fe,Co, Pb and Hg in plant samples with minimal charges or free for research students preferably in and around chennai.
You first have to digest the plant sample and have the resultant digest filtered with Watman 42. There are many labs that has AAS. Most IIT environmental Sc department have it. But the charges would be sample basis and I don't think same is cheap though. Still talking in person can resolve the issue. Some faculties may have the same analyzed free of charge for their name in authorship in the resultant paper. So you should talk in person to the faculties.