Development of magnetic dispersive microsolid-phase extraction using lanthanum phosphate nanoparticles doped on magnetic graphene oxide as a highly selective adsorbent for pesticide residues analysis in water and fruit samples

Magnetic graphene oxide/lanthanum phosphate nanocomposite (MGO@LaP) was synthesized and used as an efficient adsorbent for magnetic dispersive microsolid-phase extraction (MD-mu-SPE) of pesticides before gas chromatography-electron capture detector (GC-ECD) analysis. The adsorbent was thoroughly characterized with scanning electron microscopy, vibrating sample magnetometer, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. Optimized extraction conditions were investigated concerning extraction time, adsorbent amount, sample pH, and salt amount as well as desorption conditions (type and volume of desorption solvent and desorption time). Under the optimal conditions, the method demonstrated good linearity (3-1500 mu g L-1) with satisfactory determination coefficients of > 0.997 and low detection limits for both chlorpyrifos (0.67 mu g L-1) and hexaconazole (0.89 mu g L-1). Finally, the method showed high analyte relative recoveries in the range of 78-120% for the determination of the selected pesticides in water and fruit juice samples.