Magnetic restricted-access carbon nanotubes for the extraction/pre-concentration of organophosphates from food samples followed by spectrophotometric determination

In this work, magnetic restricted-access carbon nanotubes (M-RACNTs) were synthesized, characterized and used in the dispersive solid-phase extraction (d-SPE) of organophosphate pesticides (OPPs) from food samples (broccoli, eggplant, cauliflower, and soy milk), followed by spectrophotometric determination in a flow injection analysis system. Fe3O4 nanoparticles were incorporated in the multi-walled carbon nanotubes employing dimethylformamide. The dimethylformamide was used as a solvent in the incorporation process, forming the suspension of both particles. The resulting M-CNTs were covered with an external bovine serum albumin (BSA) layer, chemically crosslinked. M-RACNTs were able to efficiently capture OPPs, excluding about 95% of the proteins from food matrices. The analyses were carried out in a flow injection analysis system (FIA), with the spectrophotometric detection (at 560 nm) of the complex formed by the reaction between OPPs, N-bromosuccinimide and rhodamine B. A fractional factorial design method was used to optimize the experimental parameters. The addition/recovery test showed results from 95.5% to 108.9%. Accuracies were checked by comparing the results obtained with the proposed and standard HPLC methods, which were in agreement. The proposed method was linear from 5 to 90 μg L−1 of OPPs, with limits of detection and quantification of 0.74 and 5 μg L−1 and precision of 3.67%, expressed as relative standard deviation. The pre-concentration factor was about 164 times. [Display omitted] •The magnetic restricted-access carbon nanotubes were used for extraction of organophosphates.•The solid material promoted the exclusion of macromolecules and organophosphates preconcentration.•The developed method exhibited suitable validation parameters.•The method is simple, reproducible, quick and reduced the amounts of solvent consumed due to the FIA system.