Dear Yuvaraj we here use a much more effective method that uses pre-weighted freeze-dried samples and extraction with 100% acetone overnight in the dark. After the samples are run in a spectrophotometer from 350-700 nm in steps on 1nm providing this way a step. After that we apply an algorithm that can extract chl a, chl b, pheophytin a and b, b-carotene, lutein, antheraxanthin, zeaxanthin and its isomers, neoxanthin and violaxanthin. It is very simmilar to the method you want to employ but gives much more information so I think it is more worth to use that a simple extraction for chl a. If you need help please see my papers and tell me your doubts and I can help you.

Best regards