Utilizing a nano-sorbent for the selective solid-phase extraction of vanillic acid prior to its determination by photoluminescence spectroscopy.

Vanillic acid (VA) is a phenolic acid, and acts as a natural antioxidant in fruits, vegetables and plants. The extraction and determination of trace levels of VA in plants is important, because stimulation of protein synthesis and activation of antioxidant enzymes occur in the presence of phenolic acids at trace levels. In this research, a photoluminescence spectroscopic method was developed for the quantification of VA in plant samples after separation and pre-concentration. Selective extraction of VA from aqueous solution was performed using a solid-phase extraction column packed with nickel-aluminum layered double hydroxide as a nano-sorbent. After elution of extracted analyte from the column using 3 mL of a 3 mol/L NaOH solution, its concentration was determined spectrofluorometrically at λ(em) = 357 nm with excitation at λ(ex) = 280 nm. The spectrofluorometry method gave a linear response for VA within the range 20.0-900.0 µg/L, with a correlation coefficient of 0.9982. The limit of detection and sorption capacity were 7.6 µg/L and 66.2 mg/g, respectively. The method was validated by comparing the obtained results with gas chromatographic data. This method was used to determine VA in Chenopodium album and Prangos asperula plants.