Off-line in-tube solid-phase microextraction of some herbicides based on poly(styrene-divinylbenzene) coated Fe3O4 nanoparticles

Triazines are a class of persistent micropollutants in environmental areas with high toxicity. Because of their general usage and poisonous and stability of their deteriorated products, extraction and determination trace amounts of triazines are important. Off-line in-tube solid phase microextraction efficiently used for extraction of trace amounts of analytes. In addition, magnetic field was used to keep the nanoparticles in the tube and also to enhance preconcentration of the analytes. Magnetic nanoparticles can be utilized as a reusable sorbent with high surface area, strong interaction, chemical stability and high selectivity.

A novel approach was introduced using a magnetic nanocomposite of cross-linked poly(styrene-divinylbenzene) for the in-tube solid-phase microextraction of triazine herbicides. The prepared material was characterized using various techniques. High performance liquid chromatography-ultraviolet detection was used to separate and determine the analytes. The effects of pH (6), extraction time (20 min), type and volume of elution solvent (500 µL methanol) and extraction flow rate (2 mL min^-1), desorption flow rate (50 µL min^-1) and salt addition (15%) and applying magnetic field on the extraction efficiency of the triazines were investigated. Under optimum conditions, calibration curves were found to be linear in the range of 0.3-500 µg L⁻¹ for cyanazine, simazine, and propazine with a coefficient of determination (R²) of 0.9951, 0.9984, and 0.9984, respectively. The LODs were 0.1 µg L⁻¹ for all of the analytes. The method was successfully used for the extraction and determination of triazine herbicides in fruit juice samples.

Magnetic nano particles illustrate minimum back pressure in tube due to elimination of filters, high surface-to-volume ratio and lot of active sites favorable for the adsorption of the analytes. Despite the limitations imposed by the chemical conditions of extraction on the application of nanoparticles and polymeric sorbents, variables such as pH, concentration, and surface charges do not influence the magnetic interactions of MNPs. By applying magnetic field, the magnetic nature of the analytes is effective on the preconcentration of them.