Ionic liquids dispersive liquid–liquid microextraction and HPLC‐atomic fluorescence spectrometric determination of mercury species in environmental waters

Abstract

An ionic liquid (IL) based dispersive liquid-liquid microextraction combined with HPLC hydride generation atomic fluorescence spectrometry method for the preconcentration and determination of mercury species in environmental water samples is described. Four mercury species (MeHg(+), EtHg(+), PhHg(+), and Hg(2+)) were complexed with dithionate and the neutral chelates were extracted into IL drops using dispersive liquid-liquid microextraction. Variables affecting the formation and extraction of mercury dithizonates were optimized. The optimum conditions found were as follows: IL-type and amount, 0.05 g of 1-octyl-3-methylimidazolium hexafluorophosphate; dispersive solvents type and amount, 500 μL of acetone; pH, 6; extraction time, 2 min; centrifugation time, 12 min; and no sodium chloride addition. Under the optimized conditions, the detection limits of the analytes were 0.031 μg/L for Hg(2+), 0.016 μg/L for MeHg(+), 0.024 μg/L for EtHg(+), and 0.092 μg/L for PhHg(+), respectively. The repeatability of the method, expressed as RSD, was between 1.4 and 5.2% (n = 10), and the average recoveries for spiked test were 96.9% for Hg(2+), 90.9% for MeHg(+), 90.5% for EtHg(+), 92.3% for PhHg(+), respectively. The developed method was successfully applied for the speciation of mercury in environmental water samples.

Methods and recent advances in speciation analysis of mercury chemical species in environmental samples: a review

“…The technique has been widely applied as a pre-concentration purpose in speciation analysis of Hg in environmental samples. [12,14,44,56] In DLLME, application of dispersive solvent, usually which dissolve in both sample and extraction solvent, have been practiced for complete transfer of the target analytes between the two phases which can be stated as one of its drawbacks since solvent consumption should be minimized in analysis from environmental point of view and it also decreases the distribution ratio from analytical perspective. [57] To avoid this, other processes like ultrasonication [58,59] and vortexing [15,16,59] can be used for effective agitation of the mixtures.…”

“…The appropriate sample storage place and temperature has been reported to be in dark and 4 °C, respectively. [5,12,14,17,21,39,[44][45][46] In recent, SPME [30,47] and DGT [48][49][50] methods have shown to be the promising approach for the storage of Hg species in the analysis of environmental samples. In these techniques, the analytes are adsorbed and stabilized on the solid materials in the field which is easy to transport and store rather than in a liquid phase, and it also minimize the analyte loss.…”

“…[57] To avoid this, other processes like ultrasonication [58,59] and vortexing [15,16,59] can be used for effective agitation of the mixtures. For high enrichment of the analytes, chelating agents like sodium diethyldithiocarbamate, [12] APDC, [16] dithizone, [44,56] 1-(2-pyridylazo)-2-naphthol and L-cysteine [14] have LPME • DLLME • SDME • VA-LLME • HF-LPME SPE/SPME…”

“…[55] The apparatuses employed in the analysis process (sample collection and storage containers, glassware, and filtration devices) should be pre-treated before use, usually soaked in 10% (v/v) HNO 3 bath for 24 h and rinsed with purified water several times before use. [5,17,36,39,44] In general, the use of appropriate sampling procedure, transportation, and storage materials, pretreatment of the apparatuses, and sample pretreatment strategies should be known in speciation analysis of Hg in environmental samples. In situ preconcentration techniques like SPME and DGT seem promising as much of the processes are simplified and hence we recommend researchers to emphasis on their development and applications.…”

“…Water sample is usually filtered with 0.22 μm [12,26,[37][38][39][40] or 0.45 μm [5,9,14,17,36,[41][42][43][44] pore size membrane filters to avoid particulate materials and treated with acidic solutions of HNO 3 [9,36,45] or HCl [17,21,35,38,46] to preserve the analytes and also to prevent the formation of microbes. The appropriate sample storage place and temperature has been reported to be in dark and 4 °C, respectively.…”