Influence of Long Term Application of Butachlor on its Dissipation and Harvest Residues in Soil and Rice.

The study delineates the effect of repeated application of butachlor to rice crop from 1997 onwards. Additionally, in 2014 and 2015, dissipation kinetics of butachlor in soil was studied under field and laboratory conditions. The average recovery of butachlor for soil, rice grain and rice straw ranged between 80.3%-93.2% and 82.8%-96.5% with quantification limit of 0.01 and 0.003 µg g-1 for HPLC and GC-MS/MS, respectively. The dissipation of butachlor followed first order kinetics and half-life under long term field trials in rice soil varied from 15.2 to 19.29 days and 25.94 to 29.79 days under field and laboratory conditions, respectively. The residue of butachlor in soil, rice grain and straw samples at harvest over the years was below the quantification limit and no quantifiable amount of metabolites were present in soil at harvest suggestive of its safe application.

Persistence behaviour of pretilachlor in puddled paddy fields under subtropical humid climate.

The paper delineates the field trials conducted to investigate the persistence behaviour and dissipation kinetics of pretilachlor in puddled paddy fields under subtropical humid climatic region. Matrix solid phase dispersion (MSPD) method was used for extraction of the pretilachlor from paddy grain and paddy soil samples collected from the experimental field. Pretilachlor residues were quantified using high-performance liquid chromatography (HPLC) with UV/Vis detector at 210 nm. The average recoveries of pretilachlor extracted from matrix ranged from 80.3 to 103.3% with standard deviation less than 10% and sensitivity of 0.01 µg g(-1). The dissipation rate of pretilachlor in paddy field soil and paddy field water followed first-order kinetics with decrease in pretilachlor residues as a function of time. Faster dissipation of pretilachlor was observed in paddy field water than in paddy field soil with half life of 1.89-2.97 days and 7.52-9.58 days, respectively. At harvest, the residues of pretilachlor in the paddy soil and paddy crop samples were below the detection limit.

Quantification of penoxsulam in soil and rice samples by matrix solid phase extraction and liquid-liquid extraction followed by HPLC-UV method.

The paper exploits the development of novel, simple and sensitive methodology involving matrix solid phase dispersion (MSPD) and the comparison of MSPD with liquid-liquid extraction (LLE) for the evaluation of residual penoxsulam in soil and rice samples. Extracted samples were analyzed by high-performance liquid chromatography (HPLC) with ultraviolet detector at 230 nm. Both methods were optimized, considering different parameters, and under optimum conditions, the mean recoveries obtained were in the range of 85-104 % for MSPD and 78.8-90.7 % for LLE. Precision values expressed as relative standard deviation (RSD) were ≤10 for MSPD and ≤15 for LLE. Linearity for penoxsulam was in the range of 0.01-20 µg mL(-1) with limits of detection and limits of quantification of 0.01 and 0.03 mg kg(-1), respectively.