Preconcentration of Nickel by Magnetic Solid-Phase Extraction (MSPE) as the 2-(5-Bromo-2-Pyridylazo)-5-Diethylamino-Phenol (PADAP) Chelate upon Multiwalled Carbon Nanotubes (MWCNTs) with Determination by Flame Atomic Absorption Spectrometry (FAAS)

Abstract

A magnetic solid phase extraction (MSPE) method for nickel as the 2-(5-bromo-2-pyridylazo)-5-diethylamino-phenol (PADAP) chelate was established prior to flame atomic absorption spectrometric (FAAS) determination. Magnetic multiwalled carbon nanotubes were used as the adsorbent. Analytical parameters affecting the extraction efficiency of nickel such as pH of the medium (8.0), mass of adsorbent (8.0 mg), eluent concentration and volume (4.0 mL of 1 M HNO3), extraction time (6.0 min), and model solution volume (20 mL) were optimized. In addition, matrix effects were investigated. The preconcentration factor was 5. The relative standard deviation was less than 5%. A standard addition recovery study was performed on water samples to evaluate the accuracy of the method and certified reference materials were used for validation. The limits of detection (LOD) and quantitation (LOQ) were 7.1 µg L−1 and 24.4 µg L−1, respectively. The proposed method was applied to determine nickel in tobacco samples.