2.2.1. Reference materials, reagents and solutions Pesticide reference standards, all >95% purity, were obtained
fromDr. Ehrenstorfer GmbHand Chemservice. Stocks were prepared in a concentration around 500 mgmL
1
, using methanol as solvent, and were stored in amber glassware under appropriate conditions such as 20
C and exclusion of moisture and light. All the solvents were HPLC grade supplied by J.T. Baker (Phillisburg, NJ, USA).