Ultrasound-assisted dispersive microsolid-phase extraction approach for preconcentration of trace cobalt and nickel and sensitive determination in water, food and tobacco samples by flame atomic absorption spectrometry

Abstract

ABSTRACT Simpleand validated ultrasound-assisted dispersive microsolid-phase extraction (UA-DMSPE) approach for separation, and preconcentration of trace cobalt (Co(II)) and nickel (Ni(II)) ions in various water, juice, food and tobacco samples prior to their flame atomic absorption spectrometry determination (FAAS) was developed. The proposed method based on using oxidized multiwalled carbon nanotubes (ox-MWCNTs) as adsorbent and 3-(2-hydroxy-5-acetylphen-1-ylazo)-1,2,4-triazole (HAPAT) as complexing agent at pH 7.0. The effect of different parameters has been investigated and optimised. The calibration curves were linear in the ranges of 1.0–300 and 2.0–400 μg L−1 and the limits of detection were 0.30 and 0.60 μg L−1 for Co(II) and Ni(II) ions, respectively, under the optimum conditions.The preconcentration factor was 200. Co(II) and Ni(II) havemaximum sorption capacities of around 300 and 370 mg g–1, respectively. The recovery rates of the analytes ranged from 96.0 to 101%. Furthermore, relative standard deviation (RSD%) for intra-day (1.40 and 1.90%) and inter-day (1.70 and 2.10%) as repeatability for Co(II) and Ni(II), respectively. Certified reference materials (SRM 1570A spinach leaves and TMDA-52.3 fortified water) were used to verify the accuracy of the proposed preconcentration protocol. The proposed method was successfully used to determine the content of Co(II) and Ni(II) ions in a variety of real water, juice, food and tobacco samples yielding satisfactory results.