Dissipation, half-lives, and mass spectrometric identification of endosulfan isomers and the sulfate metabolite on three field-grown vegetables

Abstract

Endosulfan 3 EC, a mixture of α- and β-stereo isomers, was sprayed on field-grown pepper, melon, and sweet potato plants at the recommended rate of 0.44 kg A.I. acre⁻¹. Plant tissue samples (leaves, fruits, or edible roots) were collected 1 h to 30 days following spraying and analyzed for endosulfan isomers (α- and β-isomers). Analysis of samples was accomplished using a gas chromatograph (GC) equipped with a mass detector in total ion mode. The results indicated the formation of endosulfan sulfate as the major metabolite of endosulfan sulfite and the relatively higher persistence of the β-isomers as compared to the α-isomer. The initial total residues (α- and β-isomers plus endosulfan sulfate) were higher on leaves than on fruits. On pepper and melon fruits, the α-isomer, which is the more toxic to mammals, dissipated faster (T_1/2 = 1.22 and 0.95 d, respectively) than the less toxic β-isomer (T_1/2 = 3.0 and 2.5 d, respectively). These results confirm the greater loss of the α-isomer compared to the β-isomer, which can ultimately impact endosulfan dissipation in the environment. Additionally, the higher initial residues of endosulfan on pepper and sweet potato leaves should be considered of great importance for timing field operations and the safe entry of harvesters due to the high mammalian toxicity of endosulfan.

Keywords:

• α-Endosulfan
• β-endosulfan
• endosulfan sulfate
• pepper
• melons
• sweet potato

Acknowledgments

The authors acknowledge Darrell Slone, Eric Turley, and Janet Pfeiffer for their kind assistance in planting peppers and melons at KSU research farm. This investigation was supported by two grants from USDA/CSREES to Kentucky State University under agreements No.KYX-10–08-43P & No.KYX-2006–1587.

Notes

^†Log K_OW = Logarithms of the octanol/water partition coefficient; N/A = Data not available.