Biocompatible magnetite nanoparticles coated with ionic liquid-based surfactantas a hydrophilic sorbent for dispersive solid phase microextraction of cephalosporins prior to their quantitation by HPTLC

Extraction of highly hydrophilic compounds from biological fluids including urine or plasma samples is a dilemma due to high hydrophilicity of the matrix itself. The main aim of the current work is to explore the competence of ionic liquid (IL)-based surfactant-coated mineral oxide nanoparticles (NPs) in dispersive solid-phase microextraction (d-SPME) of highly hydrophilic analytes taking cefoperazone (CPZ) as a model analyte for the study. The IL-based surfactant coated Fe₃O₄ NPs is utilized as an innovative adsorbent for the separation and pre-concentration of CPZ after intramuscular injection (I.M) in rabbits. The utilized magnetite NPs were synthesized via simple and reliable co-precipitation procedure, which doesn't require any air-free environment and depends on a single iron (III) salt. Characterization of the as-synthesized NPs was achieved by X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) and energy dispersive X-ray (EDX). Surface area measurements show that Fe₃O₄ NPs have large surface area of 75 m² g^-1. The developed approach utilizes the unique properties of the IL-based surfactant including multiple polar interaction types provided by the polar head in addition to merits of Fe₃O₄ nanoparticles, which include large adsorptive capacity and magnetic properties, to improve separation, save time, and achieve satisfactory recovery. Comprehensive study was developed for the factors, that affect the adsorption capacity such as pH, NPs amount, IL-based surfactant concentration, ionic strength, adsorption time, and desorption conditions. Moreover, the adsorption data was fitted to Langmuir and second-order kinetic models as reflected by the reasonable determination coefficients of 0.9319 and 0.9726, respectively. Under the optimized conditions, the developed approach achieves good correlation coefficient of 0.9975, and 0.9981 over linearity range of 0.7-12.0 and 4.0-50.0 µg mL^-1 for both CPZ standard solutions and spiked rabbit plasma, respectively. It also provides good sensitivity expressed by the low values of limit of detection (LOD) of 0.2 and 1.2 µg mL^-1 and limit of quantitation (LOQ) of 0.7 and 4.0 µg mL^-1 for both the standard solutions and spiked plasma, respectively. The developed approach was also applied successfully for monitoring CPZ in rabbit plasma samples with satisfactory recovery % (83-110). In addition, a detailed pharmacokinetic study is performed where pharmacokinetic parameters of CPZ in rabbit plasma samples were calculated.

Vortex-assisted dispersive solid phase microextraction using Fe3O4/FeOOH magnetic nanocomposites for high-performance thin-layer chromatographic determination of zolmitriptan in rabbit plasma samples

In this work, a fast, versatile, and convenient dispersive solid-phase micro-extraction (DSPME) method is combined with a spectro-densitometric technique for the analysis of zolmitriptan (ZOLM) in biological fluids. Fe₃O₄/FeOOH magnetic nanocomposites (MNCs) were prepared by a co-precipitation method in aqueous solutions and utilized subsequently as a sorbent in DSPME. By coupling DSPME with high-performance thin-layer chromatography (HPTLC) with fluorescence detection, the preconcentration and determination of (ZOLM) in presence of metoclopramide (MET) and paracetamol (PARA), which are prescribed as an adjuvant therapy with ZOLM, was accomplished. Adsorption capability was assessed using both Langmuir and Freundlich adsorption isotherm models. The adsorption data was fitted to Langmuir adsorption isotherm model as reflected by high determination coefficient (R² = 0.9944). Moreover, adsorption kinetics was assessed by pseudo-first and pseudo-second order kinetic models. The data was fitted to pseudo-second order kinetics, which proves that ZOLM interaction with the adsorbent is a chemisorption process. Surface complexation with MNCs was suggested to explain the pH dependence of ZOLM sorption. The key parameters of extraction and desorption steps (including pH, extraction time, sample volume, magnetic adsorbent amount, and desorption circumstances) were evaluated. Optimized conditions for solid phase microextraction of ZOLM were pH 2.9, 5.0 mg Fe₃O₄/FeOOH MNCs, 15 min vortex-assisted extraction time and 3 × 200 μL of methanol: 33% ammonia; 4:1 as eluent. The analysis was achieved using ACN: dichloromethane: 33% ammonia (22.5: 6.0: 1.5, v/v/v) as a mobile phase and the fluorescence detection was carried out at 223 nm. The proposed DSPME method was successfully applied for trace quantification of ZOLM in rabbits' plasma (n = 6) after oral administration with a linearity range of 50.0 - 400.0 ng mL^-1 (R² = 0.9931), a detection limit of 12.0 ng mL^-1 and extraction recovery of 97.27-99.89% with an RSD < 2% (n = 9). Moreover, the selectivity of the proposed approach for analysis of ZOLM in the presence of MET and PARA is demonstrated.

Ionic liquids in electrokinetic chromatography

There is an interest in the application of ionic liquids as additives into the separation media to improve achiral and chiral separations in electrokinetic chromatography (EKC). This review will critically discuss the developments on the use of ionic liquids in the different modes of EKC during the last five years (2015-mid 2020). A healthy number of 48 research articles searched through Scopus were categorised into two: ionic liquids as sole pseudophase (micelles, microemulsions, ligand exchange pseudophase or molecular pseudophase) and ionic liquids with pseudophase (achiral or chiral). More than half of the papers dealt with chiral separations that were mostly facilitated by another additive or pseudophase. The role of ionic liquids for improvement of separations were analysed, and we provided some recommendations for further investigations. Finally, the use of ionic liquids in different on-line sample concentration or stacking methods (i.e., field enhancement and sweeping) was briefly discussed.

Urinary Nucleosides and Deoxynucleosides

Urinary nucleosides and deoxynucleosides are mainly known as metabolites of RNA turnover and oxidative damage of DNA. For several decades these metabolites have been examined for their potential use in disease states including cancer and oxidative stress. Subsequent improvements in analytical sensitivity and specificity have provided a reliable means to measure these unique molecules to better assess their relationship to physiologic and pathophysiologic conditions. In fact, some are currently used as antiviral and antitumor agents. In this review we provide insight into their molecular characteristics, highlight current separation techniques and detection methods, and explore potential clinical usefulness.

Hydrophilic interaction chromatography coupled to tandem mass spectrometry in the presence of hydrophilic ion-pairing reagents for the separation of nucleosides and nucleotide mono-, di- and triphosphates

A fast and efficient method for the simultaneous separation of highly polar compounds, in this case nucleosides and nucleotide mono-, di- and triphosphates, using hydrophilic interaction chromatography coupled with tandem mass spectrometry (HILIC-MS/MS) is proposed. This new separation method revealed the possibilities of the formation of hydrophilic ion-pairing compounds. Three stationary phases (HILIC XBridge-Amide, HILIC-CoreShell and ZIC-HILIC) were assayed for the separation of 20 target analytes, and a detailed study of the composition of the mobile phase was made using different salts at different concentrations in a organic-rich mobile phase. We report that in order to prevent the adsorption of nucleotides on the LC-MS setup and to enhance their retention on the HILIC stationary phase, a mobile phase containing hexafluoro-2-propanol and different cations should be used. Four cations were evaluated: ammonium, diethylammonium, triethylammonium and tetrabutylammonium. The results revealed the formation of an ionic-association compound between the phosphorylated analytes and the cationic ion-pairing reagents, whose retention increased with the polarity of the cationic ion-pairing reagent. HILIC XBridge-Amide was found to be the most suitable column for the separation of these analytes, and the optimized mobile phase consisted of an ACN/UHQ water mixture (3min of isocratic elution using 82:18%, v/v and then a fast gradient from 18% to 22% of water) with 100mM hexafluoro-2-propanol and 50mM diethylamine (w(w)pH 9-w(s)pH 10). In a total analysis time of 8min, good results were achieved in terms of resolution. Under these optimum conditions, a further comprehensive study of the retention mechanism was carried out.