Electrochemical and Quantum Chemical Investigations of the Insecticide Fipronil

Okumura, Fabiano; Amaral, Raquel B.; Orestes, Ednilsom; Silva, Albérico B. F.; Mazo, Luiz Henrique

doi:10.5935/0103-5053.20150347

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Articles • J. Braz. Chem. Soc. 27 (5) • May 2016 • https://doi.org/10.5935/0103-5053.20150347 copy

Electrochemical and Quantum Chemical Investigations of the Insecticide Fipronil

Authorship SCIMAGO INSTITUTIONS RANKINGS

This work describes an electrochemical and quantum chemical investigation of the fipronil insecticide. Cyclic voltammetry (CV) and square wave voltammetry (SWV) experiments were performed over a graphite-polyurethane (GPU) composite electrode. The fipronil molecule presents an one-electron irreversible oxidation reaction. Profiting the SWV signal a square wave stripping voltammetry (SWSV) procedure to determine the fipronil molecule in a 0.10 mol L^-1 Britton-Robinson buffer solution, pH 8.0 was developed with accumulation potential and time of 0.50 V and 120 s, respectively. The limits of detection and quantification were 0.80 and 2.67 μg L^-1, respectively. Recovery tests were performed in three natural waters samples with values ranging from 99.67 to 101.37%. Quantum chemical studies showed that the nitrogen atom of the pyrazole group is the most probable oxidation site of the fipronil molecule.

Keywords:
fipronil; graphite-polyurethane; square wave voltammetry; density-functional theory

Parameter	Value
b^a a b: slope of calibration curve; / (A Lmol L^-1)	3.95
Relative standard deviation / %	0.01
Regression coefficient	0.999
s_B^b b sB: mean of ten blank measurements. / μA	2.41 × 10^-3
Limit of detection / (μg L^-1)	0.80
Limit of quantification / (μg L^-1)	2.67
Recovery sample 1 / %	101.37 ± 1.05
Recovery sample 2 / %	99.67 ± 2.32
Recovery sample 3 / %	100.33 ± 1.18

Atom	Ground state / a.u.		Cationic state / a.u.				Δ(gas, vertical) / a.u.	Δ(gas, adiabatic) / a.u.	Δ(water, vertical) / a.u.	Δ(water, adiabatic) / a.u.
	Gas	Water	Gas		Water
	Gas	Water	Vertical	Adiabatic	Vertical	Adiabatic
C1	−0.02	−0.07	0.00	−0.04	−0.03	−0.01	0.02	−0.02	0.04	0.06
C2	−0.06	−0.01	−0.06	−0.04	−0.02	−0.03	0.00	0.02	−0.01	−0.02
C3	0.37	0.31	0.31	0.24	0.26	0.25	−0.06	−0.12	−0.05	−0.05
C4	−0.09	−0.03	−0.08	−0.04	−0.04	−0.04	0.00	0.05	−0.01	−0.02
C5	−0.02	−0.05	0.01	−0.03	−0.03	0.00	0.02	−0.01	0.02	0.05
C6	−0.14	−0.09	−0.12	−0.08	−0.08	−0.10	0.03	0.07	0.01	−0.01
H7	0.12	0.16	0.14	0.15	0.16	0.14	0.02	0.03	0.00	−0.02
H8	0.12	0.15	0.13	0.14	0.15	0.13	0.02	0.02	0.00	−0.01
Cl9	−0.02	−0.05	0.03	0.01	0.00	−0.01	0.05	0.03	0.04	0.04
Cl10	−0.05	−0.07	−0.01	0.00	−0.04	−0.03	0.04	0.05	0.03	0.04
N11	0.13	0.16	0.03	0.12	0.09	0.17	−0.10	−0.01	−0.06	0.02
C12	0.24	0.29	0.25	0.28	0.25	0.32	0.01	0.04	−0.04	0.03
C13	−0.07	−0.12	−0.06	−0.09	−0.04	−0.05	0.01	−0.02	0.08	0.06
C14	0.20	0.21	0.27	0.32	0.29	0.30	0.07	0.12	0.09	0.10
N15	−0.50	−0.58	−0.28	−0.32	−0.33	−0.38	0.22	0.18	0.25	0.20
N16	−0.71	−0.77	−0.48	−0.58	−0.38	−0.49	0.23	0.13	0.39	0.27
H17	0.29	0.38	0.29	0.33	0.36	0.38	0.00	0.04	−0.02	0.01
H18	0.35	0.41	0.36	0.43	0.38	0.43	0.01	0.07	−0.03	0.02
S19	0.28	0.43	0.42	0.33	0.54	0.45	0.14	0.05	0.11	0.02
O20	−0.41	−0.56	−0.30	−0.31	−0.46	−0.45	0.11	0.11	0.10	0.11
C21	0.42	0.41	0.34	0.47	0.30	0.44	−0.08	0.04	−0.11	0.02
C22	0.73	0.73	0.68	0.67	0.70	0.68	−0.05	−0.06	−0.03	−0.05
F23	−0.23	−0.26	−0.20	−0.19	−0.24	−0.23	0.03	0.04	0.02	0.02
F24	−0.23	−0.24	−0.20	−0.20	−0.22	−0.22	0.03	0.03	0.01	0.02
F25	−0.24	−0.24	−0.22	−0.22	−0.23	−0.23	0.02	0.02	0.01	0.02
F26	−0.20	−0.17	−0.15	−0.18	−0.13	−0.14	0.05	0.02	0.04	0.03
F27	−0.13	−0.15	−0.08	−0.13	−0.11	−0.15	0.05	0.00	0.04	0.01
F28	−0.11	−0.13	−0.04	−0.07	−0.06	−0.10	0.07	0.05	0.06	0.02
C29	0.43	0.51	0.32	0.31	0.41	0.41	−0.11	−0.12	−0.10	−0.10
N30	−0.45	−0.56	−0.30	−0.30	−0.45	−0.44	0.14	0.15	0.11	0.12

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[1] *e-mail: fabiano.okumura@embrapa.br