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Cloud point extraction combined with flame atomic absorption spectrometry for the determination of copper, iron and zinc using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol-tetraphenylborate ion-pairing agent

Meiyi Xie, Weiting Liu, Xiaotang Hao, Xun Jiang, Yizhou Zhong, Tiantian Liu, and Mei Wang

School of Public Health, Guangdong Pharmaceutical University, Guangzhou, China



Received: 14 December 2020  Accepted: 29 June 2021


A novel cloud point extraction was developed for the pre-concentration and determination of Cu(II), Zn(II) and Fe(III) in bottled mineral water samples by flame atomic absorption spectrometry. The procedure was based on the formation of a charge transfer ion-pairing agent between the 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) and tetraphenylborate (TPB) in the presence of 0.1 mol L−1 HCl, and the selective cloud point extraction was achieved after its complexation with target metals. Under the optimum conditions, good linearity was observed in the concentration ranges of 10–160 μg L−1 for Cu(II), 2–30 μg L−1 for Zn(II) and 20–300 μg L−1 for Fe(III). In a 50 mL of sample, concentration factors of 38.4, 39.0 and 29.9 and limits of detection of 0.44, 0.14 and 0.78 μg L−1 for Cu(II), Zn(II) and Fe(III) were obtained, respectively. Compared with single complexing reagent, the ion pair (5-Br-PADAP-TPB) significantly enhanced the enrichment factor of each analyte and tolerance levels of interference ions and obtained the lower detection limit. The proposed method was validated via the analysis of certified reference materials and successfully used for the determination of Cu(II), Zn(II) and Fe(III) in ten brands of bottled mineral water samples. All samples contained lower levels of Cu(II), Fe(III) and Zn(II) according to the maximum allowable concentration recommended by Chinese legislation. And recoveries for Cu(II), Zn(II) and Fe(III) were found to be between 95.0 and 105%; the relative standard deviation of this method was 0.620−1.67%

Graphic abstract

Keywords: 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol-tetraphenylborate; Cloud point extraction; Metal ions; Flame atomic absorption spectrometry; Bottled mineral water

Full paper is available at

DOI: 10.1007/s11696-021-01765-x


Chemical Papers 75 (11) 5849–5859 (2021)

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