Determination of trace cobalt in Gastrodia elata Bl. by effervescent tablet-assisted hydrophobic deep eutectic solvent microextraction combined with micro spectrophotometry

A novel hydrophobic deep eutectic solvent (HDES)-based effervescent tablet was first synthesized as an extractant of effervescent tablet-assisted liquid phase microextraction (ETA-LPME) and combined with micro UV–Vis spectrophotometry for the determination of trace cobalt (Co) in Gastrodia elata Bl. The novel effervescent tablets were prepared by mixing the extractants (HDES) and effervescent precursors (sodium bicarbonate (NaHCO3) and malonic acid (MA)). The effective and rapid extraction of Co was accomplished in one step when NaHCO3 and MA in the effervescent tablet react to produce CO2, and HDES are uniformly dispersed into the sample solution. After the Box-Behnken design (BBD) was used to optimize the ETA-LPME process, it was found that the enhancement factor (EF), the limit of detection (LOD), and the limit of quantitation (LOQ) of the method were 38, 0.05 μg/L, and 0.18 μg/L, respectively. The method has the advantages of highly efficient, rapid, and environmentally friendly and has been used in the determination of trace Co in Gastrodia elata Bl.