Detection of chlorantraniliprole residues in tomato using field-deployable MIP photonic sensors.

A photonic sensor based on inversed opal molecular imprinted polymer (MIP) film to detect the presence of chlorantraniliprole (CHL) residue in tomatoes was developed. Acrylic acid was polymerized in the presence of CHL inside the structure of a colloidal crystal, followed by etching of the colloids and CHL elution. Colloidal crystals and MIP films were characterized by scanning electron microscopy and FT-IR, confirming the inner structure and chemical structure of the material. MIP films supported on polymethylmethacrylate (PMMA) slides were incubated in aqueous solutions of the pesticide and in blended tomato samples. The MIP sensor displayed shifts of the peak wavelength of the reflection spectra in the visible range when incubated in CHL concentrations between 0.5 and 10 µg L-1, while almost no peak displacement was observed for non-imprinted (NIP) films. Whole tomatoes were blended into a liquid and spiked with CHL; the sensor was able to detect CHL residues down to 0.5 µg kg-1, significantly below the tolerance level established by the US Environmental Protection Agency of 1.4 mg kg-1. Stable values were reached after about 30-min incubation in test samples. Control samples (unspiked processed tomatoes) produced peak shifts both in MIP and NIP films; however, this matrix effect did not affect the detection of CHL in the spiked samples. These promising results support the application of photonic MIP sensors as an economical and field-deployable screening tool for the detection of CHL in crops.

Abatement of 2,4-D by H2O2 solar photolysis and solar photo-Fenton-like process with minute Fe(III) concentrations.

The Photo-Fenton-like (PF-like) process with minute Fe(III) concentrations and the Hydrogen Peroxide Photolysis (HPP), using Xe-lamp or solar light as sources of irradiation, were efficiently applied to eliminate the herbicide 2,4-D from water. PF-like experiments concerning ferric and H2O2 concentrations of 0.6 mg L-1 and 20 mg L-1 respectively, using Xenon lamps (Xe-lamps) as a source of irradiation and 2,4-D concentrations of 10 mg L-1 at pH 3.6, exhibited complete 2,4-D degradation and 77% dissolved organic carbon (DOC) removal after 30 min and 6 h of irradiation respectively whereas HPP (in absence of ferric ions) experiments showed a 2,4-D reduction and DOC removal of 90% and 7% respectively after 6 h of irradiation. At pH 7.0, HPP process achieved a 2,4-D abatement of approximately 75% and a DOC removal of 4% after 6 h. PF-like exhibited slightly improved 2,4-D and DOC removals (80% and 12% respectively) after the same irradiation time probably due to the low pH reduction (from 7.0 to 5.6). Several chlorinated-aromatic intermediates were identified by HPLC-MS. These by-products were efficiently removed by PF at pH 3.6, whereas at neutral PF-like and acid or neutral HPP, they were not efficiently degraded. With natural solar light irradiation, 10 and 1 mg L-1 of 2,4-D were abated using minor H2O2 concentrations (3, 6, 10 and 20 mg L-1) and iron at 0.6 mg L-1 in Milli-Q water. Similar results to Xe-lamp experiments were obtained, where solar UV-B + A light H2O2 photolysis (HPSP) and solar photo-Fenton-like (SPF-like) played an important role and even at low H2O2 and ferric concentrations of 3 and 0.6 mg L-1 respectively, 2,4-D was efficiently removed at pH 3.6. Simulated surface water at pH 3.6 containing 1 mg L-1 2,4-D, 20 mg L-1 H2O2 and 0.6 mg L-1 Fe(III) under natural sunlight irradiation efficiently removed the herbicide and its main metabolite 2,4-DCP after 30 min of treatment while at neutral pH, 40% of herbicide degradation was achieved. In the case of very low iron concentrations (0.05 mg L-1) at acid pH, 150 min of solar treatment was required to remove 2,4-D.