Ultrasound-Assisted Dispersive Microsolid-Phase Extraction for Preconcentration of Trace Cobalt and Nickel in Environmental Samples Prior to their Determination by Flame Atomic Absorption Spectrometry

A new, green, simple, and validated ultrasound-assisted dispersive microsolid-phase extraction method applying unprecedented adsorbent-modified multiwalled carbon nanotubes was achieved for preconcentration and separation of trace cobalt (Co(II)) and nickel (Ni(II)) ions in diverse ecological samples before determination by flame atomic absorption spectrometry. The suggested approach uses a novel chelating agent named 3-(2,4-dihydroxyphen-1-ylazo)-1,2,4-triazole, which is chelated with Co(II) or Ni(II) ions as efficient and selective sorbent at pH 8.0. The impact of many parameters has been studied and optimized. Under ideal conditions, the calibration curves were linear within 1.0-200 and 2.0-300 mu g/L ranges, with limits of detection equaling 0.30 and 0.60 mu g/L for Co(II) and Ni(II) ions, respectively. The preconcentration factor attained 200, while the highest sorption capacities of Co(II) and Ni(II) are around 300 and 380 mg/g, respectively. The relative standard deviation (%RSD) regarding repeatability for Co(II) and Ni(II) upon calculation was 1.30 and 1.70% for intraday, and 1.750 and 1.95% for interday. To ensure the correctness of the suggested preconcentration approach, certified reference materials (SRM 1570A spinach leaves and TMDA-52.3 enriched water) were employed. The proposed approach was applied to determine the concentration of Co(II) and Ni(II) ions in a range of genuine water, juice, and food samples, and the findings were excellent.

Automated summary

A new ultrasound-assisted dispersive microsolid-phase extraction method using modified multiwalled carbon nanotubes has been developed for preconcentration and separation of trace cobalt and nickel ions in environmental samples. The method shows high selectivity, good repeatability, and has been successfully applied to the analysis of water, juice, and food samples.