ASIAN JOURNAL OF CHEMISTRY ASIAN JOURNAL OF CHEMISTRY http://dx.doi.org/10.14233/ajchem.2017.20149 INTRODUCTION Besides direct pollution of the environment, industrial agriculture has placed an extremely heavy burden on world water resources. One of the main causes of pollution of the Earth’s surface water with pesticides and herbicides is washing by rain which transfers the substances from treated fields to large water-supply basins and thus into surface water (lakes, rivers, streams and drinking water) [1]. Clopyralid (3,6-dichloropicolinic acid) is a selective, auxins type herbicide of pyridine carboxylic acid group used to control broad leaf weeds of the family polygonaceae, compo- sitae, legmuminosae and umbelliferae in sugarbeet, fodder beet, oilseed rape, brassicas, onions, strawberries, flax and grassland (lawn and turf also) [2]. Clopyralid is highly water- soluble and degradation is entirely through microbial meta- bolism in aquatic sediments. The half-life of clopyralid in water ranges from 8 to 40 days [3]. Clopyralid is not registered for use in aquatic systems. According to Leitch and Fagg [4] 12 g of clopyralid (0.01 % of that applied) leached into the water stream during the first significant rainfall after the application that occurred 3 days later. Bergstrom et al. [5] found clopyralid is not susceptible to hydrolysis or other types of chemical degradation and a maximum of 0.02 % of applied clopyralid was lost to runoff from clay soils in Sweden. A 3 year study carried out to assess the effects on the downstream water quality showed that clopyralid was 0.31 % of the amounts applied showing its persistence in water [6]. Field study on water quality showed that clopyralid, declined to below detection Dissipation Kinetics Study of Clopyralid in Water ANAND SINGH, SHISHIR TANDON * and N.K. SAND Department of Chemistry (Division of Agricultural Chemicals) College of Basic Sciences and Humanities, G.B. Pant University of Agriculture & Technology, Pantnagar-263 145, India *Corresponding author: E-mail: shishir_tandon2000@yahoo.co.in Received: 21 June 2016; Accepted: 21 October 2016; Published online: 30 November 2016; AJC-18142 The study was undertaken to study the dissipation kinetics of clopyralid in water under laboratory conditions. Water was fortified with clopyralid at 150 μg a.i. per liter and sampling was done at different time interval after application. Residue was estimated by reversed phase HPLC with UV detector at 229 nm. Dissipation study showed that clopyralid degraded with decay rate (λ = 0.06 ± 0.02/days) in water and no detectable residue was found on 30 th day of application. Dissipation in water followed monophasic first order kinetics. The half life of clopyralid in the water was found to be 11.55 days. The limit of detection was 5 ng/mL of water and the RSD was 1.87 %. Keywords: Clopyralid, Dissipation, Water, HPLC, First order kinetics. Asian Journal of Chemistry; Vol. 29, No. 2 (2017), 271-273 limits before monitoring was concluded and not detoriating the quality of water [7]. At different pH range (1.0 to 9.0) clopyralid solutions was found to stable for at least a period of two months [8]. Donald et al. [9] estimated the annual calcu- lated concentration of different herbicides including clopyralid in drinking water and found concentrations of the individual chemicals were well below their respective tolerance limits. The clopyralid herbicide is not registered in India for use commercially but likely to be used in near future. Thus, viewing the above facts of high leachability of this compound study was conducted to look into the dissipation of clopyralid in water under Indian environmental conditions. EXPERIMENTAL Technical grade clopyralid of 95 % pure and its formula- tion (clopyralid 10 % SL) were obtained from M/s Willowood, Hong Kong. The technical compound was re-crystallized prior to use. All the solvents used were of analytical (AR) or HPLC grade. Triple distilled water was prepared in the laboratory by double distillation of single metal distilled water in all quartz double distillation assembly. Ground water was taken for dissipation study and characterized for its physicochemical properties Beckman HPLC, Systronics UV-visible spectrophoto- meter, Buchii flash evaporator. Recovery: For recovery experiment 200 mL water was taken and fortified with 10 mL of 0.5-2.0 ppm solution of technical grade of clopyralid.