2.4. Analytical determinations
Concentrations of simazine and diuron in aqueous solutions
were measured against external standards in methanol using a
Shimadzu HPLC equipped with a Shimadzu UV diode array detector
and an RP-18 column (5 lm, Lichrospher 100; the Lichrocart
250–4 cartridge). The mobile phase was a 70:30 (v v1) acetonitrile:
water mixture with a flow rate of 1 mL min1. The detection
wavelengths were 222 and 252 nm for simazine and diuron,
respectively. No difference was found when comparing the standards
prepared in methanol with the standards on the basis of
aqueous compound solutions containing CaCl2 and NaN3 (as in
the analyzed soil samples).