Glyphosate herbicide residue determination in samples of environmental importance using spectrophotometric method.

A simple selective spectrophotometric method has been developed for the determination of glyphosate herbicide in environmental and biological samples. Glyphosate was reacted with carbon disulphide to form dithiocarbamic acid which was further followed for complex formation with copper in the presence of ammonia. The absorbance of the resulting yellow coloured copper dithiocarbamate complex was measured at 435 nm with molar absorptivity of 1.864 x 10(3) L mol(-1)cm(-1).The analytical parameters were optimized and Beer's law was obeyed in the range of 1.0-70 microg mL(-1). The composition ratio of the complex was glyphosate: copper (2:1) as established by Job's method with a formation constant of 1.06 x 10(5). Glyphosate was satisfactorily determined with limit of detection and quantification of 1.1 and 3.7 microg mL(-1), respectively. The investigated method was applied successfully to the environmental samples. Recovery values in soil, wheat grains and water samples were found to be 80.0+/-0.46 to 87.0+/-0.28%, 95.0+/-0.88 to 102.0+/-0.98% and 85.0+/-0.68 to 92.0+/-0.37%, respectively.