... CNCS (dipo- tassium salt) and Cnitrocatechol (4NC) were purchased from Sigma Chemical Co. ... Analytical Chemistry, Vol. ... Aliquots of 10-500 pL of 1 x M CNCS solutions were diluted to a final volume of 4.95 mLwith 0.1 M acetate buffer (PH 5.6) to give solutions with substrate ...