In-tube Stir Bar Sorptive Extraction Based on 3-Aminopropyl Triethoxysilane Surface-Modified Ce-doped ZnAl Layered Double Hydroxide Thin Film for Determination of Nonsteroidal Anti-Inflammatory Drugs in Saliva Samples

A thin-film based on 3-aminopropyl triethoxysilane surface-modified Ce-doped zinc–aluminum layered double hydroxide was synthesized on the inner surface of an aluminum tube. It has been applied to in-tube stir bar sorptive extraction of nonsteroidal anti-inflammatory drugs in saliva samples followed by high-performance liquid chromatography. The sorbent was characterized by scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and elemental mapping. The extraction parameters including sample pH (4.2), extraction time (10 min), stirring speed (800 rpm), type of eluent (acidified tetrahydrofuran), eluent volume (100 μL), and desorption time (6 min) were thoroughly optimized. Under the optimum conditions, limits of detection were found to be less than 5.0 ng mL−1. Calibration plots were linear within the range 10–1000 ng mL−1 (R2 > 0.9982). Absolute recoveries were calculated in the range 63.5 to 72.4%. The repeatability (intra- and inter-day precision) and reproducibility (tube-to-tube precision) at concentrations of 50, 250, and 500 ng mL−1 were less than 7.6% and 9.4%, respectively. The method accuracy based on the relative error was calculated at these concentrations and ranged from − 4.9 to − 9.3% for intra-day relative error (%) and − 6.8 to − 11% for inter-day relative error (%). Finally, the method applicability was examined for the determination of nonsteroidal anti-inflammatory drugs in saliva samples, and good relative recoveries were obtained within the range 86.5 to 95.2%. As a result, the introduced method can be applied as a suitable alternative to measuring nonsteroidal anti-inflammatory drugs in biological fluids.