Firstly thanks for the answers .I have read about Berthelot reaction that can be successfully used for determining quantity of omega amino acids spectrophotometerically
https://www.ncbi.nlm.nih.gov/pubmed/5821840
Actually I have also read about PITC,dansyl,orthophthalaldehyde derivative but have already bought 2-hydroxynapthaldehyde and have faced several problems.Now I can't afford any more costly chemicals and need something simple