Synthesis of PANI/hematite/PB hybrid nanocomposites and fabrication as screen printed paper based sensors for cholesterol detection

In this work, the composites of polyaniline/nano-hematite (α-Fe2O3)/Prussian Blue (PB) were successfully synthesized via a sonochemical method. This nanocomposite (PB/CPANI) has been used for the modification of paper-based sensors for cholesterol detection. The electrochemical studies of this nanocomposite showed a well-defined cyclic voltammogram for hydrogen peroxide (H2O2) with a remarkable electrochemical sensitivity. This nanocomposite modified paper-based electrode also showed excellent electrocatalytic activity towards H2O2 in the interference-free cathodic region. In addition, cholesterol oxidase was immobilized on the PB/CPANI-modified paper-based electrode for selective detection of cholesterol. Under optimum conditions, a linear range of 0.6–6.0 mM with a very low detection limit of 0.52 mM for cholesterol and a good sensitivity of 411.7 μA mM−1 cm−2 were obtained which indicated that the method presented is outstandingly appropriate to determine cholesterol in bovine serum albumin. This work might be an alternative, interference-free, and cost-effective approach for biomonitoring of cholesterol both in methodological studies and in clinical laboratories

Development of Extraction and Analytical Methods of Nitrite Ion from Food Samples: Microchip Electrophoresis with a Modified Electrode

Two simple and fast methods for the extraction of the nitrite ion (NO2 -) from food samples have been developed. The methods were characterized by UV-visible spectroscopic and electrochemical measurements, and their performance for NO2 - extraction was compared with a standard method. The extraction methods yielded relative recoveries between 100 and 120% with good reproducibility of 3.9% (RSD, n = 4) in UV-visible experiments. Microchip electrophoresis with electrochemical detection (MCE-ED) coupled with a copper (3-mercaptopropyl)trimethoxysilane [Cu(II)-MPS] complex- modified carbon paste electrode (CPE) has been employed to detect NO2 - in extracted samples. The Cu(II)-MPS complex was synthesized and characterized by voltammetry, XPS, and FT-IR analyses. Experimental parameters affecting the separation and detection performances of the MCE-ED method were assessed and optimized. The potential for the electrocatalytic reduction of NO2 - for MCE-ED was found to be -190 mV (vs Ag/AgCl). When extracted food samples were analyzed by the MCE-ED method, a reproducible response for the NO2 - reduction (RSD of 4.3%) at the modified-CPE reflected the negligible electrode fouling. A wide dynamic range of 1.0-160 ppm was observed for analyzing standard NO2 - with a sensitivity of 0.05106 ( 0.00141, and the detection limit, based on S/N = 3, was found to be 0.35 ( 0.05 ppm. No apparent interference from NO3 -, other inorganic ions, and biological compounds was observed under the optimal experimental conditions. A standard addition method for real samples showed wide concentration ranges of 1.10-155 and 1.2-150 ppm for analyzing NO2 - in ham and sausage samples, respectively