Ultra-trace cadmium determination in eucalyptus and rosemary tea samples using a novel method: deep eutectic solvent based magnetic nanofluid liquid phase microextraction-slotted quartz tube-flame atomic absorption spectrometry

Abstract

In this study, a deep eutectic solvent-based magnetic nanofluid liquid phase microextraction method (DES-MNF-LPME) was developed for the preconcentration of cadmium prior to its determination using the slotted quartz tube flame atomic absorption spectrophotometry (SQT-FAAS) system. A MNF consists of magnetic metal oxide nanoparticles (MNPs) and a deep eutectic solvent. To achieve a high extraction efficiency, the choline chloride-phenol ratio for DES formation, mixing period for MNF formation, MNP amount in DES, MNF volume, mixing type, vortex period, eluent concentration and sonication period were optimized before instrumental measurements. The limit of detection (LOD) and the limit of quantification (LOQ) values of the method developed under the optimum conditions were calculated to be 0.25 ng mL⁻¹ and 0.84 ng mL⁻¹, respectively. A linear calibration plot was constructed between 1.0 and 30 ng mL⁻¹, and relative standard deviation (n = 6) was calculated to be 5.0%. The developed DES-MNF-LPME-SQT-FAAS method achieved 330 times improvement in detection power compared to the traditional FAAS system based on LOD comparison. In order to test the accuracy and applicability of the method, the method was applied to eucalyptus and rosemary tea samples. The recovery values obtained were very close to 100% with low standard deviation.