The Malaysian Journal of Analytical Sciences, Vol 14 No 2 (2010): 50 – 55

 

 

 

HYDROLYSIS OF CHLORPYRIFOS IN AQUEOUS SOLUTIONS AT DIFFERENT TEMPERATURES AND pH

 

(Hidrolisis Chlorpyrifos dalam Larutan Akueus pada Suhu dan pH Berbeza) 

 

Tay Joo Hui^1,2, Marinah Mohd Ariffin¹, Norhayati Mohd Tahir^1*

 

¹Environmental Research Group (ERG),

Department of Chemical Sciences, Faculty of Science and Technology,

Universiti Malaysia Terengganu (UMT),Mengabang Telipot,

 21030 Kuala Terengganu, Terengganu, Malaysia.

 

²Faculty of Industrial Sciences and Technology (FIST),

Universiti Malaysia Pahang (UMP), Lebuhraya Tun Razak,

26300 Gambang, Kuantan, Pahang Darul Makmur, Malaysia.

 

*Corresponding author: hayati@umt.edu.my

 

 

Abstract

The hydrolysis of chlorpyrifos (O,O-diethyl-O-3,5,6-trichloro-2-pyridyl phosphorothionate) was investigated in buffered aqueous media at different temperature and pH conditions.  Rate constants and half-life studies revealed that chlorpyrifos was relatively stable in acidic medium.  The rate of degradation increased as the pH increased.  Temperature showed a significant effect on the rate of hydrolysis.  The hydrolysis of chlorpyrifos in water follows first-order kinetics.  The half-life of chlorpyrifos in aqueous solutions was short (half-lives ranged from 4.57 to 14.0 days), depending on the initial concentration of chlorpyrifos and the type of the aqueous solutions.  The rate of degradation was slower in the 0.02M CaCl₂ solution containing higher initial concentration of chlorpyrifos.  Comparison between hydrolysis rate of chlorpyrifos in sterilized and non-sterilized water did not showed significant contribution of biodegradation component.  These results indicate that pH alone cannot be used as a single parameter to predict hydrolysis of chlorpyrifos.          

 

Keywords: Chlorpyrifos, hydrolysis, organophosphorus pesticide.

 

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