FLUOROMETRIC-DETERMINATION OF MERCURY-(II) BASED ON THE INHIBITION OF THE ENZYMATIC-ACTIVITY OF UREASE

An automated method for the determination of traces of Hg(II) based on the inhibition of enzyme activities is proposed. The approach used is a flow-injection (FI) configuration where the enzyme urease is immobilized on controlled pore glass. The mercury inhibits the dissociation of urea into carbonate and ammonia by binding with sulphydryl groups of the urease. The inhibited and non-inhibited (blank) enzymatic reactions are monitored fluorimetrically (lambda(ex) = 340 nm, lambda(em) = 458 nm), after reaction with o-phthalaldehyde and N-acetyl-L-cysteine. The immobilized enzyme reactor is regenerated by L-cysteine injected between samples. The linear determination range is between 0.5 and 100 ng/mL (r2=0.998, rsd < 6.5%) and the sampling frequency is 6 h-1.