Ligandless-ultrasound-assisted emulsification microextraction followed by inductively coupled plasma-optical emission spectrometry for simultaneous determination of heavy metals in water samples

Abstract

In this study, a simple and efficient method of ligandless-ultrasound-assisted emulsification microextraction (LL-USAEME) followed by inductively coupled plasma-optical emission spectrometry (ICP-OES) has been developed for simultaneous extraction, preconcentration and determination of manganese, cadmium, cobalt and nickel in water samples. In the proposed approach, tetrachloroethylene was selected as extraction solvent. The effect of important experimental factors such as volume of extraction solvent, pH, sonication time, salt concentration, and temperature was investigated by using a fractional factorial design (2⁵⁻¹) to identify important factors and their interactions. In the next step, a Box-Behnken design (BBD) was applied for optimisation of significant factors. The obtained optimal conditions were: 30 µL for extraction solvent, 12 for pH, 5 min for sonication time, and 5% w/v for salt concentration. The limits of detections (LODs) for Cd(II), Co(II), Mn(II) and Ni(II) were 0.20, 0.13, 0.21 and 0.28 µg L⁻¹, respectively. Relative standard deviations (RSD, C = 200.0 µg L⁻¹, n = 9) were between 3.4–7.5% and the calibration graphs were linear in the range of 0.25 to 1000.0 µg L⁻¹ for Mn, 0.5–1000.0 µg L⁻¹ for Co and Ni and 1.0–250.0 µg L⁻¹ for Cd. The determination coefficients (R ²) of the calibration curves for the analytes were in the range of 0.993 to 0.999. The proposed method was validated by using two certified reference materials, and also the method was applied successfully for the determination of heavy metals in different real water samples.

Keywords:

• ligandless
• ultrasound-assisted emulsification microextraction
• inductively coupled plasma-optical emission spectrometry
• Box-Behnken design
• heavy metals