Ligandless, deep eutectic solvent‐based ultrasound‐assisted dispersive liquid‐liquid microextraction with solidification of the aqueous phase for preconcentration of lead, cadmium, cobalt and nickel in water samples

Abstract

A green and efficient sample preparation method using a deep eutectic solvent-based ultrasounds-assisted dispersive liquid-liquid microextraction with solidification of the aqueous phase followed by high performance liquid chromatography analysis was developed for preconcentration and determination of heavy metals in environmental samples. In the proposed method, a novel, low density deep eutectic solvent was prepared by mixing trihexyl(tetradecyl)phosphonium chloride and thiosalicylic acid at a molar ratio of 1:2 and used both as an extractant and complexing agent. Ultrasound was used to disperse the extractant in the aqueous phase of the sample. Then, the phases were separated by centrifugation, after which the aqueous phase was frozen and the surface extractant phase was dissolved in a small volume of acetonitrile and subjected to liquid chromatographic analysis. The proposed method provided precisions (relative standard deviation, n = 5) in the range of 2.6-4.7%. The limit of detection were 0.05, 0.13, 0.06, and 0.11 μg/L for Pb(II), Cd(II), Co(II), Ni(II), respectively. The enhancement factors were equal to 154, 159, 162, and 158 for lead(II), cadmium(II), cobalt(II), and nickel(II), respectively. The accuracy of the proposed method was evaluated using certified reference materials (CA011b -hard drinking water, NIST 1643e -trace elements in water, TMRAIN-04 -simulated rain sample). K E Y W O R D Sdeep eutectic solvents, dispersive liquid-liquid microextraction, heavy metals, solidification of aqueous phase, ultrasound

Recent Applications of Deep Eutectic Solvents in Environmental Analysis

“…Although most applications of DESs in environmental samples analysis have mainly been focused on the evaluation of organic contaminants, the study of inorganic species has also been carried out (see Table 2 [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41]). In this regard, heavy metals such as copper [29,35], lead [27,29,35,40], tungsten [28], arsenic [28,31,37,38], cadmium [27,35,40], cobalt [27], nickel [27,33,35], palladium [34,35], antimony [31,37], mercury [30], and chromium [37,41] represent the main applications of DESs to the analysis of inorganic species, but also trace elements like molybdenum [37], selenium [37,39], and vanadium [37], and compounds including ammonia [36], metal oxides …”

“…In this regard, heavy metals such as copper [29,35], lead [27,29,35,40], tungsten [28], arsenic [28,31,37,38], cadmium [27,35,40], cobalt [27], nickel [27,33,35], palladium [34,35], antimony [31,37], mercury [30], and chromium [37,41] represent the main applications of DESs to the analysis of inorganic species, but also trace elements like molybdenum [37], selenium [37,39], and vanadium [37], and compounds including ammonia [36], metal oxides [32], chlorides [32], acetates [32], phosphates [32], sulphates [32], and carbonates [32] have been studied. Regarding the matrices evaluated, the analysis of environmental waters stands out and different types of waters have been analysed [27,[29][30][31][33][34][35][36][38]…”

“…-The method was applied to the analysis of real samples. [41] With this aim, both NaDESs [29][30][31][32]37,40] or non-NaDESs [27,28,[32][33][34][35][36]38,39,41] have been used for the analysis of inorganic species in environmental samples. Regarding their aqueous compatibility, most cases imply the use of hydrophilic DESs [28][29][30][31][32][34][35][36][37][38][39][40][41] even though some examples of quasi-HDESs [33] and HDESs [27] can be found in the literature.…”

“…[41] With this aim, both NaDESs [29][30][31][32]37,40] or non-NaDESs [27,28,[32][33][34][35][36]38,39,41] have been used for the analysis of inorganic species in environmental samples. Regarding their aqueous compatibility, most cases imply the use of hydrophilic DESs [28][29][30][31][32][34][35][36][37][38][39][40][41] even though some examples of quasi-HDESs [33] and HDESs [27] can be found in the literature. As it is shown in Table 2, ChCl constitutes the most used HBA [28,29,31,32,[34][35][36][37][38][39][40][41], although other quaternary salts such as trihexyl(tetradecyl)phosphonium chloride (THT-DPC) [27] or TBAC [33], a...…”

Microextraction Techniques with Deep Eutectic Solvents

“…The limits of detection were 0.05 µg/L, 0.13 µg/L, 0.06 µg/L, and 0.11 µg/L for lead(II), cadmium(II), cobalt(II), and nickel(II), respectively. Additionally, the method was evaluated by testing spiked certified reference materials, where the recoveries were in the range 91.4-101.6% [111].…”