Voltammetric and flow amperometric determination of drug guaifenesin in pharmaceutical and biological samples using screen-printed sensor with boron doped diamond electrode

New voltammetric and flow amperometric methods for the determination of guaifenesin (GFE) using a perspective screen-printed sensor (SPE) with boron-doped diamond electrode (BDDE) were developed. The electrochemical oxidation of GFE was studied on the surface of the oxygen-terminated BDDE of the sensor. The GFE provided two irreversible anodic signals at a potential of 1.0 and 1.1 V (vs. Ag|AgCl|KCl sat.) in Britton-Robinson buffer (pH 2), which was chosen as the supporting electrolyte for all measurements. First, a voltammetric method based on differential pulse voltammetry was developed and a low detection limit (LOD = 41 nmol L-1), a wide linear dynamic range (LDR = 0.1-155 μmol L-1), and a good recovery in the analysis of model and pharmaceutical samples (RSD <3.0 %) were obtained. In addition, this sensor demonstrated excellent sensitivity and reproducibility in the analysis of biological samples (RSD <3.2 %), where the analysis took place in a drop of serum (50 μL) without pretreatment and additional electrolyte. Subsequently, SP/BDDE was incorporated into a flow-through 3D printed electrochemical cell and a flow injection analysis method with electrochemical detection (FIA-ED) was developed, resulting in excellent analytical parameters (LOD = 86 nmol L-1, LDR = 0.1-50 μmol L-1). Moreover, the mechanism of electrochemical oxidation of GFE was proposed based on calculations of HOMO spatial distribution and spectroelectrochemical measurements focused on IR identification of intermediates and products.

Green highly sensitive and selective spectroscopic detection of guaifenesin in multiple dosage forms and spiked human plasma

Guaifenesin (GUA) is determined in dosage forms and plasma using two methods. The spectrofluorimetric technique relies on the measurement of native fluorescence intensity at 302 nm upon excitation wavelength "223 nm". The method was validated according to ICH and FDA guidelines. A concentration range of 0.1-1.1 μg/mL was used, with limit of detection (LOD) and quantification (LOQ) values 0.03 and 0.08 µg/mL, respectively. This method was used to measure GUA in tablets and plasma, with %recovery of 100.44% ± 0.037 and 101.03% ± 0.751. Furthermore, multivariate chemometric-assisted spectrophotometric methods are used for the determination of GUA, paracetamol (PARA), oxomemazine (OXO), and sodium benzoate (SB) in their lab mixtures. The concentration ranges of 2.0-10.0, 4.0-16.0, 2.0-10.0, and 3.0-10.0 µg/mL for OXO, GUA, PARA, and SB; respectively, were used. LOD and LOQ were 0.33, 0.68, 0.28, and 0.29 µg/mL, and 1.00, 2.06, 0.84, and 0.87 µg/mL for PARA, GUA, OXO, and SB. For the suppository application, the partial least square (PLS) model was used with %recovery 98.49% ± 0.5, 98.51% ± 0.64, 100.21% ± 0.36 & 98.13% ± 0.51, although the multivariate curve resolution alternating least-squares (MCR-ALS) model was used with %recovery 101.39 ± 0.45, 99.19 ± 0.2, 100.24 ± 0.12, and 98.61 ± 0.32 for OXO, GUA, PARA, and SB. Analytical Eco-scale and Analytical Greenness Assessment were used to assess the greenness level of our techniques.

Adsorption of terbutaline β-agonists from wastewater by mechano-synthesized iron oxide nanoparticles modified copper (II) isonicotinate metal-organic framework

Frequent detection of terbutaline in wastewater highlights its potential risks to human health associated in the environment. Exposure to terbutaline through contaminated water sources or food chain have adverse effects to human health. This work emphasized on the removal of terbutaline from wastewater using adsorption technology. Mechanochemically synthesized [Cu(INA)2] metal-organic frameworks (MOFs) and its magnetic composite ([Cu(INA)2]-MOF@Fe3O4) are designed with higher specific surface areas and tailored features to accommodate the molecular size and structure of terbutaline. Thus, batch experiment has been conducted using the [Cu(INA)2]-MOF and [Cu(INA)2]-MOF@Fe3O4 for the terbutaline adsorption. The adsorption efficiency achieved by the MOFs was 91.8% and 99.3% for the Cu(INA)2]-MOF and [Cu(INA)2]-MOF@Fe3O4 respectively. The optimum for the adsorption study included terbutaline concentration of 40 mg/L, adsorbent dose of 5 mg/L, pH of 11, temperature of 25 °C and equilibrium time of 40 minutes. The kinetics and isotherms have been described by pseudo-second order and Langmuir models, while the thermodynamics revealed the exothermic and spontaneous nature of the process. The promising performance of the MOFs is manifested on the ease of regeneration and reusability, achieving adsorption efficiency of 85.0% and 94.7% by the Cu(INA)2]-MOF and [Cu(INA)2]-MOF@Fe3O4, respectively at five consecutive cycles. The higher performance of the MOFs demonstrates their excellent potentialities for the terbutaline adsorption from the aqueous solution.

Portable and on-site electrochemical sensor based on surface molecularly imprinted magnetic covalent organic framework for the rapid detection of tetracycline in food

In this study, for the first time, surface molecularly imprinted magnetic covalent organic frameworks (Fe₃O₄@COFs@MIPs) were combined with disposable screen-printed electrode (SPE) to construct a portable and on-site electrochemical sensor for the rapid detection of tetracycline (TC). The Fe₃O₄@COFs@MIPs, which was prepared by layer-by-layer modification method, had good magnetism and excellent adsorption ability. With the help of disposable SPE, equipped with a magnet, the electrode modification process was simplified and the detection efficiency was improved. Under optimal conditions, the fabricated electrochemical sensor exhibited linearity ranging from 1 × 10^-10 to 1 × 10^-4 g mL^-1. It had good selectivity, excellent reproducibility, desirable stability and remarkable applicability. The fabricated sensor was successfully applied to detect TC in real samples with satisfactory recoveries (96.15-106.20%). The detection strategy separated the recognition and adsorption process from the electrochemical detection process, providing a design idea for the application of COFs in the construction of high-efficiency molecularly imprinted electrochemical sensors.

Electrospun nanofibers modified with zeolitic imidazolate framework-8 for electrochemiluminescent determination of terbutaline

For the first time it is demonstrated that zeolitic imidazolate framework-8 electrospun nanofibers (ZIF-8 NF) could serve as electrochemiluminescence (ECL) accelerator for the facile detection of terbutaline residual. A novel ECL sensor for the determination of terbutaline was fabricated based on ZIF-8 NF. The ZIF-8 NF were successfully prepared according to electrospinning and in-situ growth method. First, chitosan was modified on the surface of the electrode, and then the ZIF-8 NF was modified onto the upper layer of the chitosan. Taking advantages of chitosan and ZIF-8 NF in conductivity and electrocatalysis, the modified electrode presents obvious ECL phenomenon in 0.2 M PBS solution (pH 10.0) containing 0.025 M luminol. After the addition of terbutaline, ECL intensity decreased significantly, and the decreasing value showed a linear relationship with the logarithm of terbutaline concentration. The linear range was from 2.0 × 10^-10 to 2.0 × 10^-5 M, and the detection limit was 1.41 × 10^-11 M (3σ/m). The method had high sensitivity, good stability, and good applicability to actual pork samples.

Electrochemical sensor to detect terbutaline in biological samples by a green agent

In this research, reduced graphene oxide (RGO) which is a form of graphene oxide (GO) was formed through a reduction process using a "green agent" called Ascorbic acid (AA). RGO was then modified on the surface of the glassy carbon electrode (GCE) to generate RGO/GCE (an advanced electrode). The RGO/GCE was then used to detect Terbutaline (TB) in urine samples of volunteer athletes (n = 5) using well-known spectrophotometric analyses including X-ray diffraction analysis (XRD), Fourier-transform infrared spectroscopy (FT-IR), ultraviolet-visible Spectroscopy (UV-Vis), and Raman and electrochemical methods using voltammetric analyses such as differential pulse anodic stripping voltammetry (DP-ASV) and cyclic voltammetry (CV). Comparing various analysis methods using RGO/GCE to detect TB in human urine samples, voltammetric analysis specifically DP-ASV demonstrated higher sensitivity and selectivity in detecting TB than spectrophotometric analyses. Thus, in this study, several factors that would affect the voltammetric signals such as pH and interferents were evaluated and the electroactive surface area was also calculated. Our findings indicated that the RGO/GCE showed excellent repeatability, reproducibility, and long-term stability suggesting that TB could be detected more effectively using RGO/GCE than bare GCE. The detection limit of 0.0052 μM achieved in this study indicated that RGO/GCE can effectively detect TB in human urine while demonstrating reasonable selectivity and sensitivity.