detecting hydrazide groups

[PaulG at cbme.unsw.edu.au]

Hi
	I am trying to attach hydrazide groups to nylon membrane so that 
I can eventually attach antibody to the Hz and make an affinity membrane. I
have got a protocol for attaching the Hz, but I want to detect the presence of Hz
before adding antibody.
	Normally, adding Tri-nitrobenzenesulphonic acid in borate buffer
works like a dream. Hz goes bright red or rusty colour. I have done
this for sephadex and cuprophan.
	But I get nothing for nylon. Either the assay works, and there is
no nylon, or the assay doesn't work and the nylon is there...
	Has anybody got any ideas about this ?