Sensitivity Enhancement of FAAS for Trace Cobalt Determination in Horsetail (Equisetum Arvense) Tea Samples Using Supramolecular Solvent-Based Liquid Phase Microextraction

This study presents the development of a sensitive analytical approach for the determination of trace-level cobalt in horsetail (Equisetum arvense) tea samples. A supramolecular solvent-based liquid phase microextraction (SUPRAS-LPME) method was applied as a preconcentration step to improve analyte detectability. In addition, both complex formation and preconcentration were achieved simultaneously by incorporating the complexation agent directly into the prepared SUPRAS. After completion of the complexation and preconcentration stages, cobalt was quantified using flame atomic absorption spectrometry (FAAS). Under optimum microextraction conditions, the limits of detection (LOD) and quantitation (LOQ) were calculated as 4.04 and 13.47 µg/kg, respectively. Compared with conventional FAAS measurements, the developed method provided a 24-fold enhancement in detection power and a 23.4-fold increase in calibration sensitivity which shows a substantial improvement in analytical performance. The accuracy and practical applicability of the SUPRAS-LPME-FAAS method were assessed by analyzing spiked horsetail tea samples using matrix–matching calibration strategy. Recovery values ranged between 84.5% and 116.4%, confirming the method's accuracy and suitability for cobalt determination in real samples.