Abstract
A simple and highly sensitive method is developed for the simultaneous determination of Ni2+, Cr2O72−, Co2+, and Hg2+ by using in syringe low density solvent-dispersive liquid liquid microextraction (ISLD-DLLME), followed by high performance liquid chromatography with a UV detector. The four metal ions were derivatized with pyrrolidine dithiocarbamate (PDC) based on complexation before their enrichment by ISLD-DLLME in which 1-octanol and methanol were used as the extraction solvent and the dispersive solvent, respectively. The extraction was performed in a commercially available syringe under vortex agitation. Phase separation was achieved without centrifugation, and the extraction phase was easily collected by moving the syringe plunger. Parameters affecting the extraction efficiency were studied and optimized. Under the optimum conditions, the four metal-PDC complexes were detected within 18 min, and ISLD-DLLME could increase the detection sensitivity in the range of 64–230 times compared to the direct HPLC analysis. The obtained limits of detection (LODs) were found to be in the range of 0.011–2.0 µg L−1. The applicability of the method is demonstrated for freshwater fish, shrimp, and shellfish samples. In addition, the results are in good agreement with those obtained by inductively-coupled plasma-optical emission spectrometry (ICP-OES).
Highlights
The determination of metal ions is still an importance issue in many fields such as the environment and food sectors. [1]
There are a number of reports on the determination of metal ions based on pyrrolidine dithiocarbamate (PDC)-complexes by using various instrumental methods such as UV-Vis spectrophotometry [37], flame atomic absorption spectrometry (FAAS) [2], electrothermal atomic absorption spectrometry (ETAAS) [3], inductively-coupled plasma-optical emission spectrometry (ICP-OES) [4], inductively-coupled plasma-mass spectrometry (ICP-MS) [5] and high performance liquid chromatography (HPLC) [38,39]
The anion of pyrrolidine dithiocarbamate forms neutral complexes with most metal ions, and it has been documented that the analysis of metal–PDC complexes can be achieved by extracting the complexes into organic solvents before their instrumental analysis [35,39,41,42]
Summary
The determination of metal ions is still an importance issue in many fields such as the environment and food sectors. [1]. The instrumental methods that are widely used for the determination of metal ions are based on atomic spectrophotometry like as atomic absorption spectrometry (AAS) [2,3], inductively-coupled plasma-optical emission spectrometry (ICP-OES) [4], and inductively-coupled plasma-mass spectrometry (ICP-MS) [5]. Optical sensors have been employed for the detection of metal ions [6,7]. Though these methods are sensitive, highly precise and accurate, they are recognized as a “single-element” analytical technique. Multi-elemental analysis can be achieved with either ICP-OES or ICP-MS, but the instrument and operating costs are expensive. Another instrumental technique for the simultaneous analysis of metals is high performance liquid chromatography (HPLC). Various modes of HPLC have been successfully employed for Molecules 2020, 25, 552; doi:10.3390/molecules25030552 www.mdpi.com/journal/molecules
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