Persistence Of Propaquizafop

Abstract:
The persistence of Propaquizafop was studied in two different soils (Canning-saline soil and Jhargram-red & lateritic soil) under controlled laboratory simulated conditions. Propaquizafop was fortified at 2 and 4 µg g-1 and samples were drawn, extracted and analyzed upto 90 days at regular intervals. Dissipation of Propaquizafop was followed first order kinetics irrespective of any treatment and soil type. Calculated half-life values were found to be in the range of 25.29-27.63 days irrespective of dosage of application. Higher dissipation rate had been observed in Canning soil.
Keywords: Propaquizafop, residue, persistence, dissipation, fortification
1. Introduction:
Perfect soil-applied herbicides should control weeds for the necessary
Materials and Methods:
2.1. Chemicals and Reagents
Technical grade Propaquizafop (97.9%) was obtained from M/S Indofil Chemical Company, Mumbai and stored at –10°C in a deep freezer. All solvents and other chemicals used were of analytical reagent grade. All common solvents were redistilled in all glass apparatus before use. The suitability of the solvents and other chemicals were ensured by running reagent blanks before actual analysis.

2.2. Preparation of Soil Sample
During 2004-05, laboratory simulation study on persistence behavior of Propaquizafop was under taken in soils of various physic-chemical properties (Table 1). Soils samples were collected from i) Jhargram-Red & Lateritic soil (Alfisol), Regional Research Station, Bidhan Chandra Krishi Viswavidyalaya, Midnapore, West Bengal ii) Canning-Saline soil (Entosol), Regional Research Station, Bidhan Chandra Krishi Viswavidyalaya, 24 Parganas (South), West Bengal, India, following standard methodology of soil sampling.
Table1: Physico-Chemical Properties of Saline and Red & Lateritic Soils
Physico-Chemical Properties Canning-Saline Soil Jhargram-Red & Lateritic Soil pH 7.6 5.1
Organic Matter (%) 3.4 5.1
CEC (meqv./100 g) 14.86
Identification and Quantification
Pesticide residue is identified if the retention time matched that of the standard and the relative abundance is within 10% of that of the standard (Ogah et. al. 2012). Identified graminicide was quantified using the external standard method of comparing sample peak area with that of the pesticide standard under the same conditions. Each sample was analyzed three times and the mean values obtained. The pesticide content of each sample was calculated as:

Residue in ppm (µg/g) = --------------------- x Rf
Where,
A1 = Area of the compound in sample.
A2 = Area of the compound in standard.
V1 = Total volume of sample in ml
W1= Concentration of standard injected in µgml-1
V2 = Injected volume of the sample in µl
C = Total weight of the soil sample in gm.
Rf = Recovery factor Fig. 4: HPLC Chromatogram of Control Canning Soil Sample Fig 5: HPLC Chromatogram of Canning Soil Sample Fortified at 0.5 µg