Zinc/Aluminum layered double hydroxide–titanium dioxide composite nanosheet film as novel solid phase microextraction fiber for the gas chromatographic determination of valproic acid

A nanosheet thin film based on Zn/Al layered double hydroxide (LDH) and TiO2 composite was prepared via sol–gel process on capillary glass rod. Characterization of the fiber coating using X-ray diffraction (XRD) pattern and scanning electron microscopy (SEM) images showed that it consists of a large number of intercrossed and curved nanosheets with hexagonal architecture. The thickness of these plates is about few nanometers, and the lateral dimension is varying from 400 to 1000 nm. Application of the proposed coating as a solid phase microextraction fiber was investigated. As a model analyte, valproic acid (VPA, antiepileptic drug) was selected and its extraction from biological (human serum) and pharmaceutical (tablet and syrup) samples were performed without any considerable matrix effect. Analytical merits of the method, under optimum conditions (extraction temperature: 50±1 °C, extraction time: 15 min, desorption temperature: 250 °C, desorption time: 2 min, solution pH: 1.5, salt concentration: 5 mol L−1), are 70 μg L−1 and 0.20–100 mg L−1 for LOD and LDR, respectively.