Graphitic carbon nitride as sorbent for the emulsification-enhanced disposable pipette extraction of eight organochlorine pesticides prior to GC-MS analysis.

Graphitic carbon nitride (g-CN) was explored as a sorbent for the emulsification-enhanced (EE) disposable pipette extraction (DPX) of eight organochlorine pesticides (OCPs) from environmental waters. The OCPs, including α-hexachlorocyclohexane, Aldrin, α-Chlordane, Dieldrin, 4,4'-dichlorodiphenyldichloroethylene, 4,4'-dichlorodiphenyldichloroethane, Heptachlor and Heptachlor epoxide (Isomer A), were analyzed by gas chromatography-mass spectrometry. The sorbent g-CN was characterized by elemental analysis, X-ray diffraction, scanning electron microscopy, Fourier-transform infrared and Raman spectroscopy. As a C-N analogue of graphite, g-CN exhibits good water dispersibility and allows easy analyte recovery - a characteristic not commonly observed in carbon-based materials. When applied to DPX, g-CN rapidly establishes strong interactions with the OCPs. Consequently, g-CN displays superior extraction capability in comparison to six other commercial sorbents. An emulsification step prior to DPX was found to enhance the overall extraction efficiency by pre-concentrating the OCPs into the microdroplets of an organic solvent. The microdroplets were then adsorbed onto g-CN. Under the most favorable conditions, wide linear responses spanning over two to four orders of magnitudes are established. The limits of detection range between 2.4 ng·L and 46.2 ng·L. The method is reproducible (relative standard deviations ≤ 7.4%) and enrichment factors are between 42 and 57. When applied to the analysis of lake and river water samples, EE-DPX-gas chromatography-mass spectrometry exhibits good resilience against matrix interferences. The relative recoveries range between 77.7% and 106.3%. In comparison to other sorbent-based extraction techniques reported for the analysis of OCPs in aqueous samples, EE-DPX utilizes the minimal amount of sample and solvent, and requires the shortest sample preparation time. Graphical abstractSchematic representation of the emulsification-enhanced disposable pipette extraction (DPX) of organochlorine pesticides (OCPs) using graphitic carbon nitride (g-CN) as sorbent. Emulsification and DPX work synergistically, thus allowing rapid dissolution of analytes into microdroplets of organic solvent, before being extracted by g-CN.