Coupling of microextraction and voltammetry techniques for thedetermination of hemin in human serum samples

Extra concentrations of hemin (ferriprotoporphyrin) are toxic since it may intercalate in lipidmembranes and catalyze the formation of hydroxyl radicals and the oxidation of low densitylipoproteins, damage mitochondrial DNA of hepatocytes, inhibit cytochrome P450-catalyzedreactions of human liver microsome, cause the oxidation of membrane components which maypromote cell lysis and death (1, 2). So, determination of hemin concentration is of importance.However, a sample preparation step seems to be inevitable prior to the determination due to thecomplexity of the biological samples. Dispersive liquid–liquid microextraction (DLLME) is avery simple and rapid method for the extraction and separation of various analytes from complexsamples (3). Ionic liquids (ILs) are green solvents comprised of asymmetric organic cation andorganic or inorganic anion, so are liquids which represent a new class of non-aqueous but polarsolvents with high ionic conductivity (4). In the present work, an ammonium-based task-specificionic liquid containing salicylate as anion was synthesized and used for the extraction of heminHemin is extracted into the ionic liquid after interaction with the anion of the ionic liquid.Voltammetric determination followed the extraction process. For this purpose, the IL-rich phaseseparated from the sample was placed on the surface of a glassy carbon electrode with the help ofnafion and ethanol. In this way, the IL was used as both extracting solvent (due to its polarity andwater-immiscibility) and electrode modifying agent (due to its ionic structure). The peak currentobtained from the electrochemical reduction of hemin was used as the analytical signal correlatedto the concentration of hemin. Different experimental parameters affecting both the extractionand electrochemical processes were optimized. Under the optimized conditions, a linearconcentration range of 0.020-2.60 mM with a detection limit of 3.16×10¯³ mM was obtained. The presented methodology was successfully applied to the determination of hemin in human serumsamples indicating its applicability to complex media.

Keywords:

Hemin , Ionic liquids , Microextraction , Voltammetry