The preparation of a certified reference material of polar pesticides in freeze-dried water (CRM 606)

The preparation of a certified reference material of polar pesticides in freeze-dried water is described. The pesticides selected were atrazine, simazine, calbaryl. propanil, linuron, fenamiphos and permethrin which were added to 6000 litres of tap water at 50-80 mu g.L-1 (200-320 mu g.L-1 for prrmethrin) level in presence of NaCl (3.5 g.L-1) prior lyophilization. After the freeze-drying process the residue was rehomogenized, filled into amber glass bottles end stored at -20 degrees C, +4 degrees C and +20 degrees C. All pesticides were determined by HPLC/diode array detector, except permethrin which was determined by GC/ECD. The results obtained for atrazine, simazine, carbaryl. propanil, linuron and fenamiphos showed no within- or between-bottle inhomogeneity, however the material was non-homogeneous for permethrin and therefore this was withdrawn from further studies. With respect to the stability for over one year, all pesticides were stable at -20 degrees C. At +4 degrees C all pesticides were stable for at least 9 months and at +20 degrees C the stability was demonstrated only during the first month of storage. The content (mass fractions) of atrazine, simazine, carbaryl, propanil and linuron in freeze-dried water (CRM 606) was certified by an interlaboratory testing and a certification campaign.