Determination of Traces of Ni, Cu, and Zn in Wastewater and Alloy Samples by Flame-AAS after Ionic Liquid-Based Dispersive Liquid Phase Microextraction

Abstract

A procedure has been developed for simultaneous separation/preconcentration of copper, nickel, and zinc based on in situ ionic liquid-based dispersive liquid-liquid microextraction method as a prior step to their determination by flame atomic absorption spectrometry. The analytes reacted with sodium diethyl dithiocarbamate at pH 7 to form hydrophobic chelates, which were separated and preconcentrated in the ionic liquid phase. The method is fast, simple, accurate, and environmentally friendly. The parameters affecting the extraction efficiency of the proposed method such as the pH of sample solution, centrifugation time, type and volume of the dispersive solvent, and the salt effect were studied. Enrichment factors of 61.8, 61.2, and 40.0 and detection limits of 0.79, 0.93, and 0.71 µg L -1 were obtained for copper, nickel, and zinc, respectively. The relative standard deviations based on six replicate measurements were between 1.0 and 2.7%. The method was successfully applied to the extraction and determination of these metals in wastewater and alloy samples.Keywords: dispersive liquid-liquid microextraction, nickel, zinc, copper, ionic liquid, sodium diethyl dithiocarbamate IntroductionIn the priority list of Agency for Toxic Substances and Disease Registry (ATSDR), Ni is at rank 57, Zn at 75, and Cu at 118.1 Nickel is essential for many biological activities such as activation of some enzymes and enhancement of insulin activity. 2 Copper plays important roles in metabolism, including antioxidant effects, energy generation and incorporation of Fe into hemoglobin.3 Zinc also has an important role in various biological systems, such as gene expression, protein-protein interaction, and neurotransmission. 4 Although nickel, copper, and zinc come into the category of essential trace elements, when they are taken at high levels, they can also produce toxic effects. 5-8Thus, determination and monitoring of these toxic metals in industrial effluent, biological samples and food stuff are of prime concern.The trace elements level in samples to be analyzed are sometimes lower than the detection limit of analytical instruments such as flame atomic absorption spectroscopy (FAAS), inductively coupled plasma optical emission spectrometry (ICP OES) and graphite furnace-atomic absorption spectrometry (GF-AAS).9,10 Therefore, a suitable sample pretreatment step is a required step prior to the analysis. Several techniques including solid phase extraction, 11,12 liquid-liquid extraction, [13][14][15][16] cloud point extraction, 17-19 and co-precipitation 20,21 have been employed to solve this issue. Most of these techniques suffer from limitations that limit their application. Some examples of these limitations include significant chemical additives, solvent losses, large secondary wastes, unsatisfactory enrichment factors, complex equipment, and high time consumption.Dispersive liquid-liquid microextraction (DLLME) overcomes some of the drawbacks of old sample preparation techniques. [22][23][24] It is simple, fast, and does n...

Voltammetric determination of Hg (II) using poly (methane disulfide)/Au nanoparticle/MWCNT modified glassy carbon electrode by differential pulse anodic stripping voltammetry (DPASV) technique

“…It is well known that the maximum environmental tolerable amount of mercury is 0.6 ppm, and therefore, accurate determination of low concentrations of mercury in water and other environmental systems is of crucial importance. Mercury is being determined with several techniques such as colorimetric methods [1,2] atomic absorption spectrometry [3][4][5][6][7][8][9][10][11], inductively coupled plasma [11][12][13], high performance liquid chromatography, ion chromatography, other separation methods [13][14][15][16][17][18][19][20][21] and hyphenated techniques [14,[22][23][24][25][26][27][28]. Some of these techniques are time consuming, expensive, and need proficiency.…”

Evaluation of calcium alginate microparticles for copper preconcentration prior to F AAS measurements in fresh water

“…Notwithstanding, the relatively poor LOD of F AAS, inherent of its characteristic concentration of 0.03 mg L -1 at 324.8 nm absorption line [7], impairs reliable measurements at low Cu concentrations (e.g., < 0.1 mg L -1 ). Therefore, precise and accurate Cu measurements by F AAS at the aforementioned concentration levels can only be achieved after preconcentration procedures, which can be carried out by using different approaches, such as solid phase extraction (SPE), cloud-point extraction [9], ionic liquids [10,11], dispersive liquid-liquid microextraction [12,13], among others. These strategies not only improve analyte detectability, but also are relevant for removing matrix components that may induce inaccurate measurements [14].…”