Abstarct: In the first section, a fast, sensitive, and convenient technique named mictroextraction in packed syringe (MEPS) coupled with GC-MS was developed for the preconcentration and determination of five organochlorine pesticides in natural water samples. Carboxyl purified multi-walled carbon nanotubes were used as a sorbent. baxsed on this technique, ۶.۰ mg of sorbent was used. The analytes was eluted using organic solvents. The influence of important parameters such as pH, type and volume of the organic desorption solvent, and amount of the sorbent on the extraction efficiency were investigated. The proposed method showed linearity and detection limits in the range of ۰.۳-۳۰.۰ µg L‒۱ and ۰.۰۸-۰.۲ µg L‒۱ respectivilly. Reproducibility of the method was in the range of ۱.۹- ۸.۵% for the studied pesticides. In order to evaluate the matrix effect, the developed method was applied to the preconcentration and determination of the selected pesticides in different water samples. Recovery was in the range of ۹۲%- ۱۱۰%. In the second part, MEPS method was applied for preconcentration and of three organochlorine pesticides. For the first time, the natural nano diatomite was used as sorbent. ۶.۰ mg of the sorbent was used. The analytes would be adsorbed on the solid phase, and would subsequently be eluted using organic solvents. The MEPS method showed good linearity and limits of detection in the range of ۰.۶- ۴۰.۰ µg L‒۱, ۰.۰۸-۰.۲۵ µg L‒۱. The reproducibility of this method was in the range of ۳.۵-۱۲.۱%. In the third part, the MEPS method was applied for the preconcentration some organophosphorous pesticides. The natural nanoperlite was used as sorbent. The proposed method showed a good linearity in the range of ۰.۶-۳۰.۰ µg L‒۱ for ethion and ۰.۶-۳۰.۰ µg L‒۱ for both diazinon and malathion. The limits of detection in the range of ۰.۰۷-۰.۳۸ µg L‒۱ were obtained. The reproducibility of the method was found to be in the range of ۱.۹-۳.۵%. Finally in the last section nano diatomite was applied for the preconcentration of organophosphorous pesticides including diazinon and ethion in aqueous samples.. The proposed method showed a good linearity and limits of detection in the range of ۰.۶-۳۰.۰ µg L‒۱ and ۰.۰۷-۰.۱۳ µg L‒۱. The reproducibility of the method was found to be in the range of ۴.۳% -۶.۱%.