Molecularly imprinted polymer filter modified with natural polyphenols for extraction of levothyroxine from biological samples

In this study, a molecularly imprinted polymer (MIP) filter, modified with natural polyphenols extracted from green tea, was employed for the extraction of levothyroxine, followed by analysis <i>via</i> high-performance liquid chromatography with ultraviolet-visible detection (HPLC-UV). The filter's characteristics were comprehensively assessed using Fourier-transform infrared spectroscopy (FT-IR) to identify functional groups, scanning electron microscopy (SEM) to examine surface morphology, energy-dispersive spectroscopy (EDS) for elemental analysis, and X-ray diffraction (XRD) to elucidate crystalline structure. Following the passage of sample solutions through the filter, which was integrated with a solvent delivery system, and optimization of extraction parameters by response surface methodology (RSM), a linear range of 1 to 1000 μg L^-1 was achieved for levothyroxine, with a coefficient of determination of 0.9999. The limit of detection and limit of quantification were 0.36 μg L^-1 and 1.19 μg L^-1, respectively. The method has an enrichment factor ranging from 245.0 to 250.5. Furthermore, the effect of the matrix on the extraction was insignificant. Applying this method to biological samples of blood serum and urine yielded recoveries exceeding 98.3%, with RSD below 6.1%.