You can do it spectrophotometrically with Schiff's reagent http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=5950

Dear Pietrzak,

First of all thank you for the link and good answer.

I have not access to the data as it should be purchased!

So, do you have a copy of this iso and would you please send me a copy if you have?

Bests,

Mohammad Ramezani.

Dear Mohammad,

Here you can find some more info http://www.inchem.org/documents/ehc/ehc/ehc196.htm the procedure is attached.

Regards

Witek

thank you my friend.

bests for you.