Optimization of Gradient Reversed Phase High Performance Liquid Chromatography Analysis of Acetaminophen Oxidation Metabolites using Linear and Non-linear Retention Model

Cysteine conjugates of acetaminophen and p-aminophenol are potent inducers of cellular impairment in human proximal tubular kidney HK-2 cells

Acetaminophen (APAP) belong among the most used analgesics and antipyretics. It is structurally derived from p-aminophenol (PAP), a potent inducer of kidney toxicity. Both compounds can be metabolized to oxidation products and conjugated with glutathione. The glutathione-conjugates can be cleaved to provide cysteine conjugates considered as generally nontoxic. The aim of the present report was to synthesize and to purify both APAP- and PAP-cysteine conjugates and, as the first study at all, to evaluate their biological effects in human kidney HK-2 cells in comparison to parent compounds. HK-2 cells were treated with tested compounds (0-1000 µM) for up to 24 h. Cell viability, glutathione levels, ROS production and mitochondrial function were determined. After 24 h, we found that both APAP- and PAP-cysteine conjugates (1 mM) were capable to induce harmful cellular damage observed as a decrease of glutathione levels to 10% and 0%, respectively, compared to control cells. In addition, we detected the disappearance of mitochondrial membrane potential in these cells. In the case of PAP-cysteine, the extent of cellular impairment was comparable to that induced by PAP at similar doses. On the other hand, 1 mM APAP-cysteine induced even larger damage of HK-2 cells compared to 1 mM APAP after 6 or 24 h. We conclude that cysteine conjugates with aminophenol are potent inducers of oxidative stress causing significant injury in kidney cells. Thus, the harmful effects cysteine-aminophenolic conjugates ought to be considered in the description of APAP or PAP toxicity.

Polyamidoamine with a hyper-branched structure grafted on modified magnetic graphene oxide for the trace separation of diclofenac and acetaminophen followed by high-performance liquid chromatography determination

Different generations of polyamidoamine dendrimers were synthesized on a focal core of magnetic graphene oxide modified with 3-aminopropyltriethoxysilane. After the characterization of synthesized dendrimers, its second generation was employed as a suitable sorbent for simultaneous separation/preconcentration of diclofenac and acetaminophen by a dispersive magnetic solid phase microextraction. The extracted analytes were then quantified by high-performance liquid chromatography with ultraviolet detection. Under optimized conditions, the limits of detection were 0.3 µg/L for diclofenac and 0.1 µg/L for acetaminophen. The intra-day relative standard deviations at 50 μg L-1 levels were 1.8% for diclofenac and 2.1% for acetaminophen, while the inter-day relative standard deviations were 3.6% and 4.5% for diclofenac and acetaminophen, respectively. The calibration graphs were linear in ranges of 1.0-500.0 µg/L and 0.5-600.0 µg/L for diclofenac and acetaminophen, respectively, with good coefficients of determination (r2 > 0.998). The method was successfully applied to the determination of diclofenac and acetaminophen in water, milk, and biological samples.

Construction of functionalized carbon nanotube@metal oxide nanocomposite for high-performance electrochemical measurement of antipyretic drug in water samples

Acetaminophen (AP) acts as supportive clinical therapy for fever and dysmenorrhea. An overdose of AP may result in severe adverse diseases, such as liver dysfunction. In addition, AP is a key-listed environmental pollutant, which is difficult to degrade in the environment and has serious effects on living bodies. Therefore, the simple and quantitative determination of AP is highly relevant today. In this work, tin dioxide (SnO2) nanoparticles with functionalized multi-walled carbon nanotube (f-MWCNT) as a hybrid composite were prepared by hydrothermal-assisted synthesis. The composite material was characterized by various spectral, morphological, and electrochemical tests. Electrochemical investigations were conducted using a SnO2@f-MWCNT-reinforced electrode for the detection of AP. The composite electrode exhibited better functional properties, which facilitated electron transfer and enhanced electrical conductivity. The calculated low detection limit (LOD) of 0.36 nM is with a wide linear range of concentration from 0.001 to 673 µM. Additionally, the SnO2@f-MWCNT-modified electrode exhibited good anti-interference capability, repeatability, reproducibility, storage, and operational stability. The developed SnO2@f-MWCNT-modified electrode was applied to practical analysis in diverse water matrices (river, drinking, and pond) with acceptable recovery percentages. A synthesized nanoscale metal oxide electrocatalyst is of great interest and an active research area that serves as a foundation for the development of new, cost-effective electrochemical antibiotic drug sensors.

Purification of Two Taxanes from Taxus cuspidata by Preparative High-Performance Liquid Chromatography

In the present study, an effective method of preparative high-performance liquid chromatography (Prep-HPLC) was established to purify two taxanes in Taxus cuspidata. During the experimental operation, the effects of flow rate, injection volume, and column temperature on the purity of 10-deacetyltaxol (10-DAT) and paclitaxel (PTX) were investigated, and the optimized conditions were as follows: flow rate of 10 mL/min, injection volume of 0.5 mL, and column temperature of 30 °C. Under these conditions, the purity of 10-DAT and PTX reached 95.33% and 99.15%, respectively. The purified products were characterized by scanning electron microscopy (SEM), high-performance liquid chromatography (HPLC), and electrospray ionization-high resolution mass spectrometry (ESI-HRMS). The results demonstrated that preparative HPLC can effectively purify 10-DAT and PTX from Taxus cuspidata with a purity of >95%, which was suitable for the large-scale preparation of 10-DAT and PTX.

Liquid chromatography at the university of pardubice: a tribute to Professor Pavel Jandera

Pavel Jandera was a world-leading analytical chemist who devoted his entire professional life to research in the field of high-performance liquid chromatography. During all his scientific career, he worked at the Department of Analytical Chemistry at the University of Pardubice, Czech Republic. His greatest contribution to the field of liquid chromatography was the introduction of a comprehensive theory of liquid chromatography with programmed elution conditions. He was also involved in the research of gradient elution techniques in preparative chromatography, modeling of retention and selectivity in various phase systems, preparation of organic monolithic microcolumns and, last but not least, in the development of theory and practical applications of two-dimensional liquid chromatography, mainly in the comprehensive form. In this review article, we have tried to capture the highlights of his scientific career and provide the readers with a detailed overview of Pavel Jandera's contribution to the evolution of separation sciences. This article is protected by copyright. All rights reserved.

Effect of phenyl numbers in polyphenyl ligand on retention properties of aromatic stationary phases

Aromatic phase, as one type of reversed-phase stationary phases, shows complementary selectivity to the n-alkyl counterparts especially for certain challenging separation tasks. However, effect of phenyl numbers in aromatic ligands on retention behaviors has rarely been addressed compared with the alkyl stationary phases. To illustrate the issue, a series of polyphenyl stationary phases were facially prepared via the coupling chemistry of isocyanate with amine, including aniline (π¹), 4-aminobiphenyl (π²), 4-amino-p-terphenyl (π³) and [1,1':4',1'':4'',1'''-quaterphenyl]-4-amine (π⁴), respectively. The chromatographic behaviors of the new stationary phases as well as the traditional C18 were systematically compared in terms of retention mode, hydrophobic and aromatic selectivity, shape selectivity and π-π interaction by various analytes, including alkylbenzenes, polycyclic aromatic hydrocarbons congeners and substituted benzenes with electron-withdrawing groups. Due to the homologous structure of four polyphenyl ligands, the hydrophobic selectivity, aromatic selectivity and shape selectivity of stationary phases increase with phenyl numbers in the bonded polyphenyl ligands, whereas the increment becomes insignificant from U-π³ to U-π⁴. This phenomenon is explained by the insertion degree of analytes in the polyphenyl ligand brushes. Compared with the homemade C18, the polyphenyl phases indicate insignificant changes of shape selectivity with temperature. Notably, the new polyphenyl phases demonstrate the great selective separation towards the electron-deficient compounds through the π-π interaction. These findings make up for the understanding of the retention behavior of aromatic stationary phases.