GNP/Al-MOF nanocomposite as an efficient fiber coating of headspace solid-phase micro-extraction for the determination of organophosphorus pesticides in food samples.

The synthesis and utilization of a high porous nanocomposite comprising MIL-53(Al) metal-organic framework (Al-MOF) and graphene nanopowder (GNP) is reported as a fiber coating for headspace solid-phase micro-extraction (HS-SPME) of selected organophosphorus pesticides (OPPs) from apple, potato, grape juice, tomato, and river water. The adsorbed OPPs on the coated fiber were subsequently determined using GC-MS. Several parameters affecting the efficiency of extraction including time and temperature of extraction, desorption condition of extracted analytes, pH and agitation of sample solution, and salt concentration were investigated. The optimum extraction condition was achieved at 70 °C with an extraction time of 40 min, pH = 4-8, and NaCl concentration of 6.0% (w/v). The best condition of desorption were observed at 280 °C for 2.0 min under a flow of helium gas in the GC inlet. Under optimal conditions, the detection limits ranged from 0.2 to 1.5 ng g-1 and the linear ranges between 0.8 and 600 ng g-1. The proposed method showed very good repeatability with RSD values ranging from 4.5 to 7.3% (n = 5). The relative recoveries were between 88% and 109% at the spiked level of 25.0 ng g-1 for the tomato sample. The fabricated fiber exhibited good enrichment factor (62-195) at optimum condition of HS-SPME. The applied HS-SPME technique is facile, fast, and inexpensive. The thermally stable GNP/Al-MOF exhibited a high sensitivity toward OPPs. So, this nanocomposite can be considered as a sorbent for the micro-extraction of other pesticides in food.