A novel monolithic Zn/Cr-LDH composite for in-tube solid-phase microextraction of acidic herbicides from water samples

A monolithic composite based on Zn/Cr-layer double hydroxide (Zn/Cr-LDH) was introduced for in-tube solidphase microextraction (IT-SPME) of chlorophenoxy acetic acid (CPAs) herbicides. A polymeric monolith composed of methacrylic acid (MAA) and Zn/Cr-LDH was simply prepared in a polypropylene tube by in situ polymerization method. 2,4-Dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA) were identified and measured using gas chromatography coupled to mass spectrometry (GC-MS). The fabricated composite was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and Fourier transform infrared spectroscopy (FT-IR). The extraction efficiency was enhanced by optimizing crucial factors, such as salt concentration, sample solution pH, extraction, and desorption conditions. Under the optimum conditions, low detection limits (LODs) were obtained in the range of 0.01-0.05 ng mL-1 with good linearity in the range of 0.1-500 ng mL-1 and coefficient of determinations (R2) better than 0.9975. The inter and intra-assay precisions (RSD%, for n = 3) were achieved in the range of 7.1-8.2% and 6.8-7.9%, respectively. The monolithic composite displayed satisfying extraction performance and effective clean-up of CPAs from water samples.