A method is developed for the determination of sixteen polar pesticides (i.e. sulfonylurea, phenoxy acid herbicides) in surface water at the low ng/l level for most of compounds. Acidification of the sample and off-line solid phase extraction is combined with HPLC-ESI-MS/MS. The aim of this work is 1) to optimize the extraction parameters using design of experiments (DOE) and 2) to compare the benefits of two different types of chromatographic columns: classic reverse phase which is widely used for pesticides separation, and hydrophilic interaction liquid chromatography (HILIC) which is an emerging technic for polar compound separation.