Cold vapor ionic liquid-assisted headspace single-drop microextraction: A novel preconcentration technique for mercury species determination in complex matrix samples

Abstract

A novel technique named cold vapor ionic liquid-assisted headspace single drop microextraction (CV-ILAHS-SDME) was developed for Hg species determination at trace levels. Inorganic (InHg) and organomercury (OrgHg) species separation, preconcentration and determination were performed by in situ cold vapor generation (CV) followed by headspace extraction with a suspended microdrop of a low cost RTIL, i.e. tetradecyl(trihexyl)phosphonium chloride (CYPHOS^® IL 101), and direct injection in electrothermal atomic absorption spectrometry (ETAAS). Stannous chloride (SnCl₂) was used to reduce Hg²⁺ to volatile Hg⁰, while oxidation of OrHg species permitted the determination of total Hg. OrHg species concentration was evaluated based on the difference between total Hg and InHg concentration. Different variables of CV-ILAHS-SDME technique, such as cold vapor generation conditions, temperature, sample and solvent volume, extraction time, and stirring rate were carefully studied. The analytical sensitivity was enhanced by a factor of 75. A low detection limit (10 ng L⁻¹) and good precision (relative standard deviation of 4.6% at 0.25 μg L⁻¹ Hg and n = 10) were achieved. Experimental results demonstrated that CV-ILAHS-SDME using CYPHOS^® IL 101 is a rapid, cost-effective and green microextraction technique for Hg determination in samples with a complex matrix, such as sea water, fish tissues, hair and wine.