Supramolecular solvent dispersive liquid–liquid microextraction based on solidification of floating drop and graphite furnace atomic absorption spectrometry for the determination of trace lead in food and water samples

Abstract

A novel, sensitive and environmentally friendly supramolecular solvent dispersive liquid-liquid microextraction method based on the solidification of a floating drop was developed for the preconcentration of trace lead (Pb) prior to its determination by graphite furnace atomic absorption spectrometry. In this method, a supramolecular solvent, a coacervate of reverse micelles formed by decanoic acid (DeA) dispersed in tetrahydrofuran (THF)-water mixture, was used to extract the metal chelate produced from the reaction of Pb(II) with diethyldithiocarbamate. After centrifugation, the coacervate phase floated on the surface of the solution, and was then solidified in an ice bath to favor phase separation. Several parameters that affect the extraction efficiency, such as the amount of DeA, the volume of THF, the pH of the sample solution, the concentration of the chelating agent, the extraction time and coexisting ions were systematically investigated. Under the optimized conditions, the linearity of the calibration curve was in the Pb concentration range of 0.1-30 ng mL À1 with a correlation coefficient (R 2 ) of 0.9995. The detection limit of this method for Pb was 27 ng L À1 with an enhancement factor of 52, and the relative standard deviations for 1.0 ng mL À1 and 20 ng mL À1 of Pb were 3.2% and 2.5%, respectively. The method was successfully applied in the determination of trace amounts of Pb in food and water samples.

Development of preconcentration strategies for the simultaneous ultratrace determination of As, Cd and Pb in foods by ICP-OES: knotted-reactor vs. dispersive liquid–liquid microextraction

“…Supramolecular solvents based on the use of THF with either alcohols [28][29][30] or organic acids 31 have been employed in the literature for metal extraction by means of DLLME and atomic absorption spectrometry detection. To date, however, no previous attempt to apply these solvents in ICP-based techniques has been reported.…”

“…In this work, supramolecular solvents were prepared by combining THF with different surfactants, namely: (i) 1-decanol; 28,29 (ii) 1-undecanol; 30 and (iii) decanoic acid. 31 Initially, supramolecular solvents were directly introduced into the ICP-OES instrument using a FIA manifold, but emission signals from As, Cd and Pb were highly irreproducible. These results are the expected, taking into account that supramolecular solvents are highly viscous substances 31 and, consequently, analytical figures of merit in ICP-OES can be compromised due to the negative influence of this physical property on aerosol generation.…”

“…31 Initially, supramolecular solvents were directly introduced into the ICP-OES instrument using a FIA manifold, but emission signals from As, Cd and Pb were highly irreproducible. These results are the expected, taking into account that supramolecular solvents are highly viscous substances 31 and, consequently, analytical figures of merit in ICP-OES can be compromised due to the negative influence of this physical property on aerosol generation. 15,16 To solve this problem, supramolecular solvents were diluted with methanol (1:1 proportion).…”

Trace determination of heavy metals in farmed trout fish using dispersive liquid–liquid microextraction based on solidification of floating organic drop and graphite furnace atomic absorption spectrometry

“…To study the effect of the extraction solvent volume on the extraction recovery in the DLLME-SFO method, different volumes of 1-undecanol (20,30,40, 50 and 60 mL) containing 1.0 mL of methanol were tested to select the optimum volume of the extraction solvent to be applied in subsequent experiments. The results are shown in Fig.…”

“…24 In DLLME-SFO, the extraction solvent aer DLLME was collected on the top of a test tube and was then cooled by inserting it into an ice bath for few minutes. [28][29][30] Also, several reviews have been written on this issue. However, conventional DLLME as well as DLLME-SFO are usually applied to analysis of aqueous samples and only to a lesser extent to analysis of solid biological and food samples.…”