Determination and study on degradation dynamics of fungicide validamycin a residue in soil using pre-column derivatization and capillary gas chromatography

A method for determining validamycin A residue in soil utilizing pre-column derivatization and gas chromatography was developed. Validamycin A was extracted from soil samples by 10% ammonia solution without additional clean-up step and then was derivatized with N,O-bis(trimethylsilyl)acetamide. Derivative of validamycin A was analyzed by gas chromatography on a capillary column. The method showed good linearity in the range of 4.4–142.0 mg/L ( r 2 = 0.9997). The average recoveries were 98.82 and 98.61% with relative standard deviations 1.95 and 2.87% at spiking levels 0.2 and 2.0 mg/kg, respectively. The limit of detection of validamycin A in soil was 0.2 mg/kg. The degradation dynamics of validamycin A in soil was studied. The result shows that validamycin A degradation in soil in the open field in Beijing suburb can be described by the equation c = 6.6109 e −0.0196 t ; the half-life is 35.4 h.