Preparation and application of chlorpyrifos molecularly imprinted solid‐phase microextraction probes for the residual determination of organophosphorous pesticides in fresh and dry foods

Abstract

A solid-phase microextraction probe was prepared on the surface of a stainless-steel wire through molecular sol-gel imprinting technology using chlorpyrifos as a template molecule, tetraethoxysilane as a sol-gel precursor, and acrylamide and β-cyclodextrin as functional monomers. The polymer was characterized by infrared spectrometry and scanning electron microscopy. Moreover, the selectivity and the parameters including the type and volume of the extraction solvents, ionic strength, pH, temperature, extraction time, stirring speed, and desorption time affecting extraction performance were evaluated. Under the optimum solid-phase microextraction and gas chromatography conditions, the linear ranges were 0.25-25.0 μg/L for chlorpyrifos, quinalphos, triazophos, pirimiphos-methyl, and chlorpyrifos-methyl with the correlation coefficient above 0.99. The detection limits (S/N = 3) were in the range of 0.02-0.07 μg/L and the RSDs were <7.3%. The developed method was successfully used to determine the multi-residues of chlorpyrifos, quinalphos, triazophos, pirimiphos-methyl, and chlorpyrifos-methyl in green peppers and cinnamon with satisfactory recoveries.

Simultaneous determination of five organophosphorus pesticide residues in different food samples by solid‐phase microextraction fibers coupled with high‐performance liquid chromatography

“…It can also be seen that the MIP and NIP probes have certain adsorption ability for the quinalphos template and its structural analogs, although the MIP and NIP probes have different capacities to selectively adsorb the template molecules and their analogs. The adsorption capacity of the MIP on the template molecule is higher than that of other structural analogs, indicating that the porous surface formed on the SPME coating is complementary with the template molecule in terms of size, shape and functional groups, leading to the specific adsorption of the template molecules . Although the structural analogs have a certain degree of similarity, the adsorption capacity will be far less than the template molecules.…”

“…The extraction efficiency decreased when the pH continued to increase. This effect could be explained by the fact that electroneutral molecules are the primary molecular form of pesticides, which benefits the extraction through the hydrogen bonding and hydrophobic interactions in a neutral solution . The major molecular form of pesticides would be cations, which hinder the extraction process by reducing the hydrogen‐bonding force and hydrophobic contacts in a relatively weak acidic environment.…”

“…This effect suggests that the binding site formed by the imprinting effect has a specific adsorption effect on the quinalphos template molecules. A certain amount of adsorption on the NIP is mainly a simple physical adsorption, and not the specific adsorption of the hydrogen bond, on the surface of NIP; therefore, its adsorption capacity is low …”

“…The solution was stored at 4 °C in a refrigerator until use. The quinalphos imprinted SPME fiber was prepared as described in our previous study with several modifications . A stainless‐steel wire, the core of the microinjector (100.0 μL), was taken out from the microinjector, immersed in water and acetone for ultrasonic cleaning for 20 min, and air‐dried for the preparation of coating.…”

“…Numerous previous studies have been conducted to extract the OPPs in food and environmental samples using SPME methods . However, to the best of our knowledge, no attempt has yet been made to establish a method for determining the OPPs in different food samples by using the sol–gel molecular imprinting technique combined with HPLC.…”