An electrochemical molecularly imprinted sensor based on chitosan capped with gold nanoparticles and its application for highly sensitive butylated hydroxyanisole analysis in foodstuff products.

One of the most widely used synthetic antioxidants in food, butylated hydroxyanisole (BHA) has raised serious concerns due to its potential toxic effects on human health. Hence, elaboration of simple, effective and sensitive methods for BHA detection is pressing. In this regards, the present research work highlights a facile, simple, and fast synthesis approach for the development of an electrochemical sensor for the analysis of BHA in foodstuffs. In this study, the chitosan (CS) capped with gold nanoparticles (AuNPs) were self-assembled on a screen-printed carbon electrode (SPCE) and complete the elaboration of the molecularly imprinted polymer (MIP) sensor in the presence of BHA as templates. The electrochemical behaviour of the MIP sensor was investigated by using electrochemical impedance spectroscopy (EIS), differential pulse voltammetry (DPV), and cyclic voltammetry (CV). Similarly, the morphology of the electrodes surface of the different elaboration steps was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and atomic force microscopy (AFM). In addition, the obtained results demonstrate satisfactory sensitivity and selectivity to BHA compared to interfering species, including ascorbic acid and citric acid. Under optimal experimental conditions, the MIP sensor exhibits responses proportional to concentrations over a range of 0.01-20 µg mL-1, with a low detection limit (LOD) of 0.001 µg mL-1 (signal-to-noise ratio S/N = 3). Besides, the reproducibility, stability, and repeatability of the MIP sensor were proven. Taking into account all these outcomes, the MIP sensor well demonstrates its ability towards the determination of BHA in food samples with a relative standard deviation (RSD ≤ 8%). Spectrophotometry was utilized as a validation method. Partial least squares (PLS) prediction models were constructed from the MIP sensor and spectrophotometer data with a regression coefficient (R = 0.99). According to the achieved outcomes, the MIP sensor could be a viable tool for food control.

Characterization and Analysis of Okoume and Aiele Essential Oils from Gabon by GC-MS, Electronic Nose, and Their Antibacterial Activity Assessment.

Essential oil resins of Aucoumea klaineana (Okoume) and Canarium schweinfurthii (Aiele) species, of the Burseraceae family, were studied to investigate their bioactive constituents and their antibacterial activities. Aiele resin had a higher yield (6.86%) of essential oil than Okoume (3.62%). Twenty-one compounds for Okoume and eighteen for Aiele essential oil were identified using a gas chromatography-mass spectrometry (Gp-C-MS) technique. The main compounds identified in Okoume essential oil were benzenemethanol, α, α,4-trimethyl (28.85%), (+)-3-carene (3,7,7-trimethyl bicyclo[4.1.0]hept-3-ene) (17.93%), D-Limonene ((4R)-1-methyl-4-prop-1-en-2-ylcyclohexene) (19.36%). With regard to the Aiele essential oil, we identified (1R,4S)-1-methyl-4-propan-2-ylcyclohex-2-en-1-ol (26.64%), and 1-methyl-4-propan-2-ylcyclohex-2-en-1-ol (26.83%). Two strains of bacteria, Escherichia coli and Staphylococcus aureus, were used in antibacterial tests. S. aureus was found to be more sensitive to Okoume and Aiele essential oils, with a high inhibition zone ranging from 20 to 16 mm. In comparison, the inhibition zone ranged from 6 to 12 mm for E. coli. An electronic nose (e-nose) combined with pattern analysis methods such as principal component analysis (PCA), discriminant function analysis (DFA), and hierarchical cluster analysis (HCA) were used to discriminate the essential oil samples. In summary, the e-nose and GC-MS allowed the identification of bioactive compounds in the essential oil samples, which have a strong antimicrobial activity, with satisfactory results.

Synthesis and characterization of a highly sensitive and selective electrochemical sensor based on molecularly imprinted polymer with gold nanoparticles modified screen-printed electrode for glycerol determination in wastewater.

Glycerol is widely used as humectant in cosmetics to improve skin's smoothness and moisture. However, its level must be controlled in cosmetics at the risk of causing irritation or allergy. Therefore, determining glycerol concentration in environmental waters with more advanced, inexpensive and accurate sensing systems is of great importance. In this work, a fast, simple, portable and cheap molecular imprinted polymer (MIP) approach is used to develop an electrochemical sensor for glycerol determination. The MIP based screen-printed gold electrode (Au-SPE) is prepared by electro-polymerizing Acrylamide/Bisacrylamide (AAM/NNMBA) and gold nanoparticles (AuNPs) in the presence of glycerol as a template. Techniques, such as cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) are used for electrochemical measurements. Energy-dispersive X-ray spectroscopy (EDS) is utilized to characterize the chemical composition analysis. In contrast to its high response towards glycerol, the electrochemical sensor exhibits negligible responses when exposed to interfering species, such as glycolic acid, glycerol monostearate, tartaric acid, sodium citrate, ammonium sulfate, decyl-glucoside, caprylyl glucoside and glutamic acid. Under optimal experimental conditions, a detection limit (LOD) as low as 0.001 µg/mL (signal-to-noise ratio S/N = 3) is calculated over a linear concentration range (20.00-227.81 µg/mL). Interestingly, the sensor was successfully applied to wastewater samples relating to glycerol determination with a relative standard deviation (RSD) less than 4%. Besides, the reproducibility, the working and storage stabilities of the sensor were proven. According to these outcomes, the electrochemical MIP sensor could be viable enough to detect the presence and levels of pollutants in real water samples.

Electrochemical sensor based on molecularly imprinted polymer for sensitive triclosan detection in wastewater and mineral water.

Triclosan (TCS) is a topical antiseptic widely used in different cosmetic products. It is also a common additive in many antimicrobial household consumables. Over a certain concentration, it becomes risky for human and environmental health. This work describes the development of an electrochemical sensor based on molecularly imprinted polymer (MIP), assembled on screen-printed gold electrode (Au-SPE), dedicated to the TCS detection in environmental water sources. To achieve this goal, an acrylamide/bisacrylamide solution was polymerized after linking TCS with the carboxylic polyvinyl chloride (PVC-COOH) layer onto the Au-SPE. The sensor device fabrication and its retention capabilities were characterized through cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS), atomic force microscopy (AFM) and Fourier transform infrared (FTIR) spectroscopy. As control experiment, negligible responses were obtained during the non-imprinted polymer (NIP) test. The sensor could effectively detect TCS avoiding interferences of structural similar substances like 2,4,6-trichlorophenol and catechol. Under optimal conditions, the sensor responses were found logarithmic in the concentration range from 0.1 to 1000 pg mL-1. Indeed, compared with reported works, this sensor exhibits lower detection limit (LOD) and quantification limit (LOQ) of 0.23 and 0.78 pg mL-1, respectively. The developed sensor was effectively applied to wastewater samples for TCS detection and displayed satisfactory performances. Moreover, the different wastewater samples, regarding their TCS contents, were correctly classified by using principal component analysis (PCA) technique. Correspondingly, this work has demonstrated a cheap, simple and effective sensing platform for TCS detection thus making it a promising tool for future evolution of accurate and reliable environmental analysis.