Use of 2-Hydrazinobenzothiazole-Modified Copolymer(s) as Potential Chelating Agent for Sensitive and Selective Determination of Low Levels of Mercury in Seafood by Ultrasound-Assisted Cloud-Point Extraction Combined with Spectrophotometry

  • H. B. Zengin
  • R. Gürkan


In this study, a new method was developed for the pre-concentration of trace mercury from seafood samples prior to analysis by spectrophotometry. The method is based on the complexation between 2-hydrazinobenzothiazole (2-HBT)-modified copolymer(s) and Hg(II) in the presence of an ionic surfactant, cetyltrimethylammonium bromide (CTAB), as sensitivity enhancer at pH 4.5 and the extraction of the complex into the surfactant-rich phase of polyethylene glycol tert-octylphenyl ether (Triton X-114) as the extractant. The variables affecting extraction efficiency were evaluated and optimized. Due to the observation that the modified copolymers are 2.5-fold more sensitive and selective to the Hg2+ ions than the CH3Hg+, the amounts of free Hg2+ and total Hg were determined at 325 nm by spectrophotometric detection of free Hg2+ and total Hg in the pre-treated and extracted fish samples using dilute acid mixture containing Triton X-114 and K2Cr2O7, before and after oxidation of CH3Hg+ to Hg2+ with mixture of KBr and KBrO3 in the acidic media. The amount of CH3Hg+ was calculated from the difference between total Hg and free Hg2+ amounts. The accuracy was tested by analysis of two certified samples. The results were statistically in good agreement with the certified values, and the precision was lower than 6.4%. The limits of detection were 1.40 (1.58) and 1.91 (2.11) μg L−1 for Hg2+ from the two calibration solutions spiked before the pre-treatment, respectively. It has been observed that there is no significant matrix effect by comparison of slopes of the calibration curves. The method was applied to seafood samples for speciation analysis of free Hg2+ and CH3Hg+. In terms of speciation, while total Hg is detected in the range of 12.6–143.8 μg kg−1, the distribution of mercury in seafood was in the range of 7.4–53.3 μg kg−1 for CH3Hg+ and in 8.3–90.5 μg kg−1 for free Hg2+.


Hg2+ CH3Hg+ 2-Hydrazinobenzothiazole Copolymer Seafood Spectrophotometry Ultrasound-assisted cloud-point extraction 



The financial support from the Scientific Research Projects of the Commission, CUBAP, University of Cumhuriyet (Sivas, Turkey), is gratefully acknowledged. For the thermal and spectroscopic characterization of the modified copolymers, we would like to thank the technical staff of the Cumhuriyet University and the advanced technological research and application center (CUTAM) for the technical assistance and support.

Compliance with Ethical Standards

The authors have no financial relationship with the organization that sponsored the research.

Conflict of Interest

The authors declare that they have no conflict of interest.

Ethical Approval

This article does not contain any studies with human or animal subjects.

Informed Consent

On behalf of the other author, informed consent was obtained from each participant included in the study.


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© Springer Science+Business Media, LLC, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Department of Chemistry, Faculty of SciencesCumhuriyet UniversitySivasTurkey

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