title: Simple laccase-based biosensor for formetanate hydrochloride quantification in fruits.
abstract: This work describes the development of an electrochemical enzymatic biosensor for quantification of the pesticide formetanate hydrochloride (FMT). It is based on a gold electrode modified with electrodeposited gold nanoparticles and laccase. The principle behind its development relies on FMT's capacity to inhibit the laccase catalytic reaction that occurs in the presence of phenolic substrates. The optimum values for the relevant experimental variables such as gold nanoparticles electrochemical deposition (at -0.2V for 100s), laccase immobilization (via glutaraldehyde cross-linking), laccase concentration (12.4mg/mL), substrate selection and concentration (5.83×10(-5)M of aminophenol), pH (5.0), buffer (Britton-Robinson), and square-wave voltammetric parameters were determined. The developed biosensor was successfully applied to FMT determination in mango and grapes. The attained limit of detection was 9.5×10(-8)±9.5×10(-10)M (0.02±2.6×10(-4)mg/kg on a fresh fruit weight basis). Recoveries for the five tested spiking levels ranged from 95.5±2.9 (grapes) to 108.6±2.5% (mango). The results indicated that the proposed device presents suitable characteristics in terms of sensitivity (20.58±0.49A/μM), linearity (9.43×10(-7) to 1.13×10(-5)M), accuracy, repeatability (RSD of 1.4%), reproducibility (RSD of 1.8%) and stability (19days) for testing of compliance with established maximum residue limits of FMT in fruits and vegetables.
authors.affiliation: REQUIMTE, Instituto Superior de Engenharia do Porto, Instituto Politécnico do Porto, Rua Dr. António Bernardino de Almeida 431, 4200-072 Porto, Portugal; GELCORR, Departamento de Química Analítica e Físico-Química, Centro de Ciências, Universidade Federal do Ceará, Bloco 940 Campus do Pici, 60455-970, Fortaleza, CE, Brazil.
authors.forename: Francisco Wirley Paulino
authors.initials: FW
authors.lastname: Ribeiro
authors.forename: Maria Fátima
authors.initials: MF
authors.lastname: Barroso
authors.forename: Simone
authors.initials: S
authors.lastname: Morais
authors.forename: Subramanian
authors.initials: S
authors.lastname: Viswanathan
authors.forename: Pedro
authors.initials: P
authors.lastname: de Lima-Neto
authors.forename: Adriana N
authors.initials: AN
authors.lastname: Correia
authors.forename: Maria Beatriz Prior Pinto
authors.initials: MB
authors.lastname: Oliveira
authors.forename: Cristina
authors.initials: C
authors.lastname: Delerue-Matos
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D002219:Carbamates / Q000032:analysis* / Q000737:chemistry; D004563:Electrochemistry; D004566:Electrodes; D004800:Enzymes, Immobilized / Q000737:chemistry / Q000378:metabolism; D005506:Food Contamination; D005638:Fruit / Q000737:chemistry*; D006046:Gold / Q000737:chemistry; D042845:Laccase / Q000737:chemistry* / Q000378:metabolism*; D053768:Metal Nanoparticles / Q000737:chemistry; D010573:Pesticide Residues / Q000032:analysis* / Q000737:chemistry; D013997:Time Factors; D055454:Trametes / Q000201:enzymology
chemical_list: D002219:Carbamates; D004800:Enzymes, Immobilized; D010573:Pesticide Residues; C100163:formetanate; D006046:Gold; D042845:Laccase
keywords: Enzymatic biosensor; Formetanate hydrochloride; Fruits; Gold nanoparticles; Laccase