Speciation of Fe(II) and Fe(III) in Chinese Yellow Rice Wine Using Direct Immersion Dual-Drop Microextraction Coupled with Graphite Furnace Atomic Absorption Spectrometry (GFAAS)

Abstract

A new direct immersion dual-drop microextraction (DIDDME) procedure is described for Fe(III) and Fe(II) speciation followed by detection with graphite furnace atomic absorption spectrometry. This method is based upon the selective reaction of 1-(2-pyridylazo)-2-naphthol (PAN) and N-benzoyl-N-phenylhydroxylamine (BPHA) with Fe(II) and Fe(III) to form complexes at pH 1.5. Two solvent drops that contain PAN and BPHA were concurrently immersed in a sample solution for simultaneous separation of Fe(III) and Fe(II), respectively. This method eliminated time-consuming and labor-intensive oxidation of Fe(II) or reduction of Fe(III), which may provide incomplete conversion and contamination. Using the optimal conditions, the detection limits were 0.067 ng mL⁻¹ and 0.054 ng mL⁻¹ for Fe(II) and Fe(III) with relative standard deviations of 6.0% and 5.1%, respectively. Enrichment factors of 300-fold were obtained. The procedure was successfully utilized for the determination of Fe(II) and Fe(III) in Chinese yellow wine. To evaluate accuracy of this method, a rice certified reference material was analyzed and the result was in good agreement with the certified value.

Keywords:

• Fe speciation
• direct immersion dual-drop microextraction (DIDDME)
• graphite furnace atomic absorption spectrometry (GFAAS)
• Chinese yellow rice wine samples

Conflict of interest

The authors declare that they have no conflicts of interest.

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Funding

This work was financially supported by the Key Research and Development Project of Hubei Province (No.2020BBB068), Central Committee Guides Local Science and Technology Development Special Project of Hubei Province (No. 2019ZYYD059) and Nature Science Foundation of Hubei Province (No.2020CFB400).