An effervescence-assisted switchable hydrophobicity solvent microextraction before microsampling flame atomic absorption spectrometry for copper ions in vegetables

Abstract

ABSTRACT A novel method of an effervescence-assisted switchable hydrophilicity-solvent based liquid-phase microextraction (EA-SHS-LPME) was developed to preconcentration of copper traces in organic and conventional growth vegetable samples prior to determination by flame atomic absorption spectrometry with micro-sampling (µS-FAAS) system. The methodology is based on the change of decanoic acid’s hydrophobicity with changing pH. Decanoic acid is solid under room conditions, so phase separation is effortless and highly efficient. In the proposed study, 8-Hydroxyquinoline (8-HQ) was used as a chelating agent, Na2CO3 was used as a CO2 source, and H2SO4 was used as a proton donor. Several factors affecting the microextraction efficiency, such as pH, 8-HQ amount, decanoic acid amount, Na2CO3 and H2SO4 amount and concentration, and extraction temperature, were investigated and optimised. Optimal conditions were determined as pH:6, 100 μL of 0.1% (w/v) 8-HQ, 75 μL decanoic acid, each 500 μL of 0.1 M Na2CO3 and H2SO4, and 40°C. Under the optimal conditions, the enhancement factor (EF) was 52, the limit of detection (LOD) was 0.75 µg L−1, the limit of quantification (LOQ) was 2.52 µg L−1, and relative standard deviation for 25 μg L−1 (n = 10) was 0.94, respectively. The matrix effect was investigated by comparing the solvent-based calibration curve with the matrix-matched calibration curve. The developed method was successfully applied to the extraction and determination of copper in certified reference material and organic and conventional grown vegetable samples. The results were compared with a statistical evaluation method, which is ANOVA. The development EA-SHS-LPME method is a sensitive, repeatable, economical, environmentally friendly, fast, and easy-to-apply to enhance and determine Cu(II) contents in vegetable samples. The LOD values obtained with the proposed method make FAAS compatible with the instruments, which are relatively more expensive and more difficult to use.