A simple, efficient and green analytical procedure for monitoring sub ppb amounts of chlorpyrifos (CP) and chlorpyrifos-oxon (CPO) in urine samples was reported. The methodology is based on the solidified floating organic drop microextraction of the analytes with a free microdrop of 2-dodecanol. The parameters those can affect the microextraction efficiency, such as solvent type, extraction solvent volume, extraction time and temperature, salt effect, pH and stirring rate on extraction were optimized. The analytes were extracted from the urine samples by using 10 mu L of 2-dodecanol for 40 min at 70 degrees C and then, the extracts were injected to GC-MS column by applying 100 kPa injection pressure. The regression coefficients relating to linearity were at least 0.99. The accuracy of the developed method was tested upon recovery studies for CP and CPO calculated as 100 +/- 7% and 110 +/- 9% (at 0.1 ng mL(-1) level), respectively. LOD value for CP was found 4.8 ng L-1 and for CPO it was found 3.8 ng L-1. This method can easily be adopted by clinical laboratories for the contribution to policies aiming to reduce exposure of pesticides. (C) 2014 Elsevier B.V. All rights reserved.