Acetonitrile Research Articles

Long-Lived Charge-Separated State in Naphthalimide-Phenothiazine Compact Electron Donor-Acceptor Dyads: Effect of Molecular Conformation Restriction and Solvent Polarity.

To study the charge separation (CS) and long-lived CS state, we prepared a series of dyads based on naphthalimide (NI, electron acceptor) and phenothiazine (PTZ, electron donor), with an intervening phenyl linker attached on the N-position of both moieties. The purpose is to exploit the electron spin control effect to prolong the CS-state lifetime by formation of the 3CS state, instead of the ordinary 1CS state, the spin-correlated radical pair (SCRP), or the free ion pairs. The electronic coupling magnitude is tuned by conformational restriction exerted by the methyl groups on the phenyl linker. Differently from the previously reported NI-PTZ analogues containing long and flexible linkers, we observed a significant CS emission band centered at ca. 600 nm and thermally activated delayed fluorescence (TADF) with a lifetime of 13.8 ns (population ratio: 42%)/321.6 μs (56%). Nanosecond transient absorption spectroscopy indicates that in cyclohexane (CHX), only the 3NI* state was observed (lifetime τ = 274.7 μs), in acetonitrile (ACN), only the CS state was observed (τ = 1.4 μs), whereas in a solvent with intermediate polarity, such as toluene (TOL), both the 3NI* (shorter-lived) and the CS states were observed. Observation of the long-lived CS state in ACN, yet lack of TADF, confirms the spin-vibronic coupling theoretical model of TADF. Femtosecond transient absorption spectroscopy indicates that charge separation occurs in both nonpolar and polar solvents, with time constants ranging from less than 1 ps in ACN to ca. 60 ps in CHX. Time-resolved electron paramagnetic resonance (TREPR) spectra indicate the existence of the 3NI* and CS states for the dyads upon photoexcitation. The electron spin-spin dipole interaction magnitude of the radical anion and cation of the CS state is intermediate between that of a typical SCRP and a 3CS state, suggesting that the long CS-state lifetime is partially due to the electron spin control effect.

Solvent engineering of SnO2 electron transport layer for high-performance perovskite solar cells

Perovskite solar cells (PSCs) show great potential as industrial photovoltaic devices due to their low fabrication cost and high power conversion efficiency. Owing to high electron conductivity and good energy level matching with perovskites, SnO2 is widely used as electron transport layers (ETLs) for PSCs. However, the agglomeration of SnO2 nanoparticles makes them have poor contact with the glass substrate and it is easy to produce defects on the film surface. Herein, acetonitrile (ACN) is used to optimize the conventional solvent of commercial SnO2 colloid to solve these problems. The addition of ACN in solvent resulted in better-performing SnO2 ETLs, thus eliminating the need for long-time ultraviolet ozone (UV-ozone) treatment of the glass substrate, which undoubtedly greatly simplified the fabrication process. The subsequent vacuum treatment of SnO2 films before annealing further improves morphology of the ETLs film and performance of the overall device. Finally, the best devices after the above solvent engineering treatment achieved an efficiency of 22.28%, increased by 16% with respect to the control device fabricated by conventional method. In addition, the long-term stability of devices was also apparently improved. This solvent engineering strategy provides a simple route to prepare high-quality SnO2 ETL for high-performance PSCs.

DETERMINATION OF RESIDUAL SOLVENTS IN PSMA 11 - AN ACTIVE PHARMACEUTICAL SUBSTANCE IN PSMA-11 KIT FOR Ga-68 LABELLING

A selective, sensitive and low sample consumption GC method for determination of residual solvents in PSMA samples was developed. Selectivity with respect to solvents such as ethanol, diethyl ether, 2-propanole, acetonitrile, dichloromethane, used in manufacturing of PSMA-11, was obtained on two different GC systems and columns. In all these cases, good separation and other system suitability parameters were obtained. The values of detection limit (LOD) and limit of quantitation (LOQ) were estimated and verified experimentally for ethanol, diethyl ether, 2-propanol (IPA), acetonitrile (ACN) and dichloromethane. Full validation parameters i.e.: selectivity, limit of detection (LOD), limit of quantitation (LOQ), linearity, precision, accuracy, robustness and system suitability parameters are presented with respect to ACN and IPA. Accuracy and precision were measured on two GC systems. Statistical tests exhibit, that there are no significant differences in accuracy and precision between two GC systems

Tailored Properties of Carbon for Supercapacitors by Blending Lignin and Cellulose to Mimic Biomass as Carbonaceous Precursor.

KOH-activated carbon materials prepared from biomass-derived carbon source, cellulose and lignin, were compared. Mixtures of different ratios of cellulose and lignin were used to partially mimic biomass as carbon source. This allows tailoring and optimizing of the KOH activated carbon materials by getting rid of the restriction of the intrinsic proportion of cellulose and lignin in specific biomass. The results indicate that cellulose use results in a more porous structure, whereas lignin use leads to more partially activated graphite structure. The activated carbon material (CL1) prepared from blend of cellulose with lignin in mass ratio of 1 : 1 exhibits a high specific surface area of 2000.39 m2 g-1 , and in TEABF4 /ACN (tetraethylammonium tetrafluoroborate dissolved in acetonitrile) electrolyte it showed a maximum specific capacitance of 136.10 F g-1 , a maximum energy density of 18.11 Wh kg-1 , and a capacitance retention of 85.04 % under current density as high as 15 A g-1 .

Application of Principal Component Analysis and DoE-Driven Green Analytical Chemistry Concept to Liquid Chromatographic Method for Estimation of Co-formulated Anti-Hypertensive Drugs.

The fixed-dose combination (FDC) of metoprolol succinate (MTS), cilnidipine (CDN), and telmisartan (TST) is used for the management of hypertension. Numerous reversed phase (RP)-HPLC methods have been reported in the literature for chromatographic analysis of MTS, CDN, and TST. According to the concept of green analytical chemistry (GAC), toxic organic solvents should be avoided or minimized during chromatographic method development for the safety of analysts and the protection of the environment. The reported RP-HPLC methods have been developed using acetonitrile (ACN) or methanol as an organic component of the mobile phase and diluent for sample preparation. These organic solvents are considered toxic solvents as per the International Council for Harmonization (ICH) Q3C (R6) guideline and Pfizer medicinal chemistry solvent selection (PMCSS) guide. We aimed to develop an environment-friendly and economical RP-HPLC-photo-diode array (PDA) method for the analysis of MTS, CDN, and TST using less toxic organic solvents to support the concept of GAC. The method development was carried out by the implementation of chemometrics and design of experiments (DoE) to avoid wastage of organic solvent. Principal component analysis (PCA) was applied as a chemometric tool for the identification of critical method risk variables (MRVs) and method performance attributes (MPAs). The identified critical MRVs and MPAs were further studied by DoE-based response surface modelling for optimization of the method. The chromatographic analysis of MTS, CDN, and TST was carried out using a Shim-pack ODS column as a stationary phase and ethanol as an organic modifier in the mobile phase. The developed method was applied to the assay of FDCs and results were found to be in compliance with the label claim. The greenness profiles of reported and present RP-HPLC methods were evaluated by national environmental method index (NEMI) and analytical greenness (AGREE) methods. The developed method was found to be green, robust, and economical as compared to published methods for the analysis. Development and validation of an RP-HPLC method for simultaneous estimation of MTS, CDN, and TST using safe organic solvents. Implementation of a analytical quality by design (AQbD) approach in method development using PCA and DoE. Application of the method for assay of FDCs of MTS, CDN, and TST.

One-pot sample preparation procedure for the determination of protein N-linked homocysteine by HPLC-FLD based method

The report presents robust and high throughput method, based on liquid chromatography coupled with fluorescence detection (HPLC-FLD), for the determination of total protein N-linked homocysteine (Hcy) in human plasma. The assay involves simultaneous proteins precipitation with perchloric acid and removal of any other form of Hcy, except protein N-linked Hcy, via disulfides reduction with tris(2-carboxyethyl)phosphine (TCEP) and plasma protein pellet wash with perchloric acid followed by liberation of N-linked Hcy from proteins by hydrochloric acid hydrolysis, drying under vacuum and residue reconstitution in diluted hydrochloric acid. The chromatographic separation of resulting in this way Hcy-thiolactone (HTL) is achieved within 3 min at room temperature on PolymerX RP-1 (150 × 4.6 mm, 5.0 µm) column using isocratic elution with eluent, consisted of o-phthaldialdehyde (OPA) in sodium hydroxide and acetonitrile (ACN), delivered at a flow rate 1 mL/min. The analyte is quantified by monitoring fluorescence at 480 nm using excitation at 370 nm, in a linear range from 0.25 to 10 µmol/L in plasma, while the limit of quantification (LOQ) equals 0.25 µmol/L. The method was successfully applied to plasma samples delivered by fifteen apparently healthy donors showing that the HPLC-FLD assay is suitable for screening of human plasma.

BIOANALYTICAL METHOD DEVELOPMENT AND VALIDATION OF MARALIXIBAT IN RAT PLASMA BY LC-MS/MS DETECTION AND ITS APPLICATION TO A PHARMACOKINETIC STUDY

Objective: To quantify maralixibat in rat plasma utilizing liquid-liquid extraction (LLE) approach, a practical, efficient, and accurate LC-MS/MS approach was devised. Methods: As an internal standard (IS), Elobixibat was adopted. Utilizing an Agilent eclipse C18, 150 mm x 4.6 mm, 3.5 µm column, the drug separation was accomplished using an isocratic mobile phase entailing acetonitrile (ACN) and buffer (1 ml Tri fluoro acetic acid into 1liter water and stir well. Filtered through 0.22µ membrane filter paper) composition of 70:30 (v/v), dispensed at 1.0 ml/min. Results: Multiple reaction monitoring (MRM) positive mode allowed for the simultaneous detection of maralixibat and elobixibat exhibiting proton adducts around m/z 676.0278-290.3625 and m/z 696.8541-480.6328, correspondingly. The correlation coefficient (r2) of the approach was ≥0.99977 across a linearity concentration spanning between 5.00–100.00 ng/ml. This technique achieved intra-day accuracy and precision between 99.31-100.93% and 0.22-6.55%, correspondingly. Across 3 freeze-thaw sessions, bench top testings, and postoperative stability investigations, maralixibat was shown to be stable. Conclusion: Through intravenous injection, this approach was effectively utilized in rats for studying the drug's pharmacokinetics.

Controllable synthesis of diazocine - investigation on electroreduction mechanism for intramolecular cyclization of 2,2′- dinitrodibenzyl in the presence of CO2

11,12-dihydrodibenzo[c,g][1,2]diazocine (Diazocine, 12), a molecular switch capable of reversible interconversion between (at least) two states by light, has been widely used in pharmacology and biochemistry. However, most of the synthetic methods so far have been limited by tedious steps, complicated derivatives, and long reaction times, resulting in poor synthetic yields of 12. Here, we propose a green, effective, and controllable strategy for synthesizing 12. The intramolecular cyclization (8-membered ring) of 2,2′-dinitrodibenzyl (1) was achieved by electrochemical reduction in the presence of CO2, and 12 and its derivatives 11,12-dihydrodibenzo[c,g][1,2]diazocine-N-oxide (DDCG-N, 11) were synthesized. The electrochemical reduction mechanism of 1 in the presence of CO2 was investigated by cyclic voltammetry (CV) and in situ FT-IR spectroelectrochemistry. The molecular structures of the electrolytic product (12) and intermediate (11) were confirmed by single-crystal X-ray diffraction, NMR, and MS. The results show that the electrochemical behavior of 1 in acetonitrile (AN) changes from a reversible two-step 1-electron transfer process (in the absence of CO2) to an irreversible 8-electron transfer process (in the presence of CO2). The 12 and 11 can be obtained by controlling the electrolytic potential and time. Under the optimum conditions, the yields of 12 and 11 were 84% and 71%, respectively.

Separation of betulin and its derivatives by high-performance liquid chromatography and their determination in extracts of some plants and chaga mushroom

The influence of conditions on the separation of betulin (BT), betulinic (BIA), and betulonic (BOA) acids by reversed-phase high-performance liquid chromatography (RP-HPLC) with isocratic elution was studied. It was shown that the order of peaks in chromatograms changed with varying the acetonitrile (ACN) content in the mobile phase, and a poor separation under certain conditions was observed. The highest peak resolution with minimal retention times was at a column temperature of 20 °C, flow rate of 0.25 ml/min, and 92.5% ACN in the mobile phase. The extracts from jujube (Ziziphus jujuba) dried fruit, chaga mushroom (Inonotus obliquus), and white birch bark (Betula pendula) were studied using the obtained conditions. For extracts from the first two sources, it was found that peaks of the compound studied interfered with unknown peaks. By varying the ACN content in the mobile phase with a small step from run to run and tracking the peaks, a baseline separation was achieved. The optimal % ACN in the mobile phase was 87 and 89 for the extracts from jujube and chaga mushroom, respectively. Jujube dried fruit was found to contain, in terms of dry weight of the jujube, 0.223 ± 0.008 mg/g of BIA and 0.044 ± 0.006 mg/g of BOA. Chaga mushroom studied contains 0.022 ± 0.004 mg/g of BT and 0.062 ± 0.009 mg/g of BIA. White birch bark contains 50.9 ± 0.7 mg/g of BT, 11.2 ± 0.3 mg/g of BIA, and 2.5 ± 0.3 mg/g of BOA.

Antiproliferative and pro-apoptotic effects on cancer cell line HCT116 using marine sponge Tedania species collected from Kalangahan, Lugait, Misamis Oriental, Philippines

Cancer is a major cause of mortality worldwide, and marine sponges have emerged as potential sources of anticancer agents. In this study, we investigated the antiproliferative and pro-apoptotic effects of a marine sponge extract from Tedania sp. against the human colorectal carcinoma cell line (HCT116) using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and Caspase-Glo® 3/7 assays. The extract was prepared using a polar solvent mixture of ethanol:water, and was subjected to reversed-phase flash chromatography consisiting of water(W), acetonitrile(ACN), and ethyl acetate(EA) gradient eluent, yielding 16 Fraction. Treatment of HCT116 cells with Fractions 1-16 showed that only Fraction 16, consisting of 100�, exhibited significant (p<0.05) cytotoxic activity with the lowest viability of 90.9% compared to the negative control. Furthermore, Fraction 9, consisting of 20:80 W and ACN, showed a significantly (p<0.05) highest fold change (FC) value of 2.89 indicating an almost threefold increase in caspase-3/7 activity. These results demonstrate that the Tedania sp. extract has promising antiproliferative and pro-apoptotic effects against HCT116 cell lines, indicating its potential as an anticancer agent.

A Quantitative Analysis of Electrochemical CO2 Reduction on Copper in Organic Amide and Nitrile-Based Electrolytes.

Aqueous electrolytes used in CO2 electroreduction typically have a CO2 solubility of around 34 mM under ambient conditions, contributing to mass transfer limitations in the system. Non-aqueous electrolytes exhibit higher CO2 solubility (by 5-8-fold) and also provide possibilities to suppress the undesired hydrogen evolution reaction (HER). On the other hand, a proton donor is needed to produce many of the products commonly obtained with aqueous electrolytes. This work investigates the electrochemical CO2 reduction performance of copper in non-aqueous electrolytes based on dimethylformamide (DMF), n-methyl-2-pyrrolidone (NMP), and acetonitrile (ACN). The main objective is to analyze whether non-aqueous electrolytes are a viable alternative to aqueous electrolytes for hydrocarbon production. Additionally, the effects of aqueous/non-aqueous anolytes, membrane, and the selection of a potential window on the electrochemical CO2 reduction performance are addressed in this study. Experiments with pure DMF and NMP mainly produced oxalate with a faradaic efficiency (FE) reaching >80%; however, pure ACN mainly produced hydrogen and formate due to the presence of more residual water in the system. Addition of 5% (v/v) water to the non-aqueous electrolytes resulted in increased HER and formate production with negligible hydrocarbon production. Hence, we conclude that aqueous electrolytes remain a better choice for the production of hydrocarbons and alcohols on a copper electrode, while organic electrolytes based on DMF and NMP can be used to obtain a high selectivity toward oxalate and formate.

Preparation and characterization of chemically and electrochemically synthesized 3,4-ethylenedioxy pyrrole/pyrrole (EDOP/Py) copolymers

Abstract In this study, 3,4-ethylenedioxypyrrole (EDOP) and pyrrole (Py) copolymers were prepared by chemical and electrochemical polymerization methods. The properties of the polymers obtained by both methods were compared. Chemical synthesis of copolymers was carried out with ferric chloride (FeCl3) in the acetonitrile (ACN) environment. The electrochemical synthesis was carried out with lithium perchlorate (LiClO4) electrolyte and suitable oxidation potential range in ACN solution. The properties of polypyrrole (PPy) copolymers were performed with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and conductivity measurements. Depending on the polymerization method and pyrrole amount in copolymer, thermal stability, conductivity and surface morphology were varied.

Ion transport in non-aqueous electrolyte mixtures of zinc chloride deep eutectic solvent (DES) and molecular solvents

The ion dynamics of null solvents 1ZnCl2:4EtG and 1ChCl:1ZnCl2:6EtG incorporating 1M water, propylene carbonate (PC) or acetonitrile (AcN) were investigated using 1H NMR spectra and spin-lattice relaxation time (T1) measurements combined with ionic conductivity, density, and viscosity, all as a function of temperature. Results show that the inclusion of all co-solvents increased the available free volume of the mixtures and followed the trend H2O ≤ PC < AcN. 1H NMR spectra and T1 inferred the presence of multiple ionic species with varying rates of mobilities. These dynamic heterogeneities were displayed by the broad T1 minima – especially for the 1ZnCl2:4EtG mixtures – and asymmetrically broadened linewidths. T1 results also revealed selective interaction sites between the hydrogen bond donors and acceptors, as well as with the co-solvents.

Long-Lived Charge Separated States in Anthraquinone-Phenothiazine Dyads: Synthesis and Study of the Photophysical Property by Using Transient Optical and Magnetic Resonance Spectroscopies.

In order to obtain long-lived charge separated (CS) states in electron donor-acceptor dyads, herein we prepared a series of anthraquinone (AQ)-phenothiazine (PTZ) dyads, with adamantane as the linker. UV-vis absorption spectra show negligible electronic interaction between the AQ and PTZ units at ground state, yet charge transfer (CT) emission bands were observed. Nanosecond transient absorption shows that the 3 AQ state is populated upon photoexcitation for AQ-PTZ in cyclohexane (CHX), but in acetonitrile (ACN) a 3 CS state is formed. Similar results were observed for AQ-PTZ-M. The 3 CS state lifetimes were determined as 0.52 μs and 0.49 μs, respectively. Upon oxidation of the PTZ unit, the 3 AQ state was observed in both polar and non-polar solvents. For AQ-PTZ, femtosecond transient absorption spectra show fast formation of the 3 AQ state in all solvents, with no charge separation in CHX, while formation of the 3 CS state takes 106 ps in ACN. For AQ-PTZ-M, a 3 CS state is formed in CHX within 241 ps. Time-resolved electron paramagnetic resonance (TREPR) spectra show that a radical ion pair with electron exchange energy of |2 J|≥5.68 mT was observed for AQ-PTZ and AQ-PTZ-M, whereas in the dyads with the PTZ unit oxidized, only the 3 AQ state was observed.

Successful LC-MS/MS assay development and validation for determination of valproic acid and its metabolites supporting proactive pharmacovigilance

Valproic acid (VPA) is a well-documented contributor to liver injury, which is likely caused by the formation of its toxic metabolites. Monitoring VPA and its metabolites is very meaningful for the pharmacovigilance, but the availability of a powerful assay is a prerequisite. In this study, for the first time, a sensitive and specific LC-MS/MS method was developed and validated to simultaneously quantify the concentrations of VPA and its six pestering isomer metabolites (3-OH-VPA, 4-OH-VPA, 5-OH-VPA, 2-PGA, VPA-G, and 2-ene-VPA) in human plasma, using 5-OH-VPA-d7 and VPA-d6 as the internal standards (ISs). We also figured out another tricky problem that the concentrations of the parent drug and the metabolites vary widely. Of note, after protein precipitation and dilution with acetonitrile (ACN) and 50% ACN successively, the analytes and the ISs were successfully separated on a Kinetex C18 column. Intriguingly, sacrificing its signal intensity by elevated collision energy of VPA finally achieved the simultaneous determination. As expected, the method showed great linearity (r > 0.998) over the concentration ranges for all analytes. The inter-day and intra-day accuracy and precision were both acceptable. The method was successfully applied in 127 children with epilepsy. This novel assay will support the VPA-associated pharmacovigilance in the future.

Shorter-chained trialkylsulfonium cations are preferable as admixtures to lithium-ion and sodium-ion electrolytes in acetonitrile

The development and improvement of electrolytes is a persisting research agenda in the context of electrochemical energy sources. The sodium-ion is a possible and partial substitute for Li-ion in alkali ion batteries of the future. Many large-scale applications urge electrolytes featuring a competitive interplay of ionic conductivity, shear viscosity, and cohesion energy. The general applicability of sulfonium ionic liquids (ILs) reinforced with Li-ions to energy storage was experimentally exemplified in recent years. Herein, we employed potential energy surface exploration bundled with electronic-structure simulations to shed light on the ion-ionic and ion-molecular interactions in perspective electrolyte systems involving trialkylsulfonium cation, Li/Na salts, and acetonitrile (ACN). By analyzing a wealth of supramolecular conformations and characterizing them via thermodynamics, structure, charge density distributions, electrostatic potential surfaces, atom–atom couplings, and reactivity descriptors, we outline the most promising sulfonium-based electrolytes. We provide a critical discussion of the future of sodium-ion batteries and compare them to lithium-ion batteries directly. The oxygen atoms of bis(trifluoromethanesulfonyl)imide anion [TFSI] coordinate Li+ and Na+ to remarkably various extents. Surprisingly, the size of the chosen trialkylsulfonium-based cation impacts the ion-ionic interactions weakly, contrary to expectations. Whereas the difference between the behavior of the Li-ion and Na-ion is paramount irrespective of all other components and their stationary points. [TFSI] was confirmed to be a highly flexible chemical structure although its conformations (one cis and two trans) were unraveled to differ only within an amount of thermal energy at room conditions. The reported discussion drives ongoing trials of the alkali-ion electrolytes based on sulfonium ILs and ACN.

Separation of liquid crystalline racemic mixtures obtained on the basis of (R,S)-2-hexanol on amylose tris(3-chloro-5-methylphenylcarbamate) covalently immobilised on silica in high-performance liquid chromatography

ABSTRACT The separation on the enantiomers of thirteen newly synthesised liquid crystalline racemic mixtures obtained on the basis of (R,S)-2-hexanol was studied in HPLC on a chiral column prepared by covalent immobilisation of the chiral selector, namely amylose tris(3-chloro-5-methylphenylcarbamate) on silica. The mobile phases (MPs) consisting of n-heptane/isopropanol (IPA) or acetonitrile (ACN)/water (H2O) at different volume ratios were used. All measurements were made at room temperature. The order of the elution was also determined. The chromatographic parameters such as: resolution - (R), selectivity - (α) and number of theoretical plates - (N) were determined. On the basis of the obtained results, optimal conditions were indicated for the best separation of the tested racemic mixtures.

Multiplexing Iduronate-2-Sulphatase (MPS-II) into a 7-Plex Lysosomal Storage Disorder MS/MS Assay Using Cold-Induced Phase Separation.

Mucopolysaccharidosis type II (MPS-II, Hunter syndrome, OMIM:30990) is a lysosomal storage disorder (LSD) that results in iduronate 2-sulphatase (I2S) enzyme deficiency. MPS-II was added to the Recommended Uniform Screening Panel (RUSP) in August 2022; thus, there is an increased demand for multiplexing I2S into existing LSD screening assays. After incubation with LSD synthetic substrates, extracts are cleaned using liquid-liquid extraction with ethyl acetate or protein precipitation using acetonitrile (ACN). We investigated cold-induced water ACN phase separation (CIPS) to improve the combination of 6-plex and I2S extracts to create a 7-plex assay, and compared it to room temperature ACN and ethyl acetate liquid-liquid extraction. The extracts were dried and resuspended in the mobile phase, and then analyzed using an optimized 1.9 min injection-to-injection liquid chromatography method coupled with tandem mass spectrometry (LC-MS/MS). The combination of ACN and CIPS improved the detection for I2S products without significant detriment to other analytes, which is attributable to a more complete coagulation and separation of heme, proteins, and extracted residual salts. Using CIPS for sample cleanup in dried blood spots (DBS) appears to represent a promising and straightforward way of achieving cleaner sample extracts in a new 7-plex LSD screening panel.

Simultaneous determination of 2-(3-hydroxy-5-phosphonooxymethyl-2-methyl-4-pyridyl)-1,3-thiazolidine-4-carboxylic acid and main plasma aminothiols by HPLC–UV based method

The report presents the first method for simultaneous determination of plasma 2-(3-hydroxy-5-phosphonooxymethyl-2-methyl-4-pyridyl)-1,3-thiazolidine-4-carboxylic acid (HPPTCA), an adduct of cysteine (Cys) and active form of vitamin B6 pyridoxal 5′-phosphate (PLP), as well as total low molecular-weight thiols content, including Cys, homocysteine (Hcy), cysteinyl-glycine (Cys-Gly), and glutathione (GSH). The assay is based on high performance liquid chromatography coupled with ultraviolet detection (HPLC–UV) and involves disulfides reduction with tris(2-carboxyethyl)phosphine (TCEP), derivatization with 2-chloro-1-methylquinolinium tetrafluoroborate (CMQT) followed by sample deproteinization with perchloric acid (PCA). The chromatographic separation of obtained stable UV-absorbing derivatives is achieved on ZORBAX SB-C18 (150 × 4.6 mm, 5.0 µm) column using gradient elution with eluent consisted of 0.1 mol/L trichloroacetic acid (TCA), pH 1.7 and acetonitrile (ACN), delivered at a flow rate 1 mL/min. Under these conditions, the analytes are separated within 14 min at room temperature, and quantified by monitoring at 355 nm. Regarding HPPTCA, the assay linearity was demonstrated within a 1–100 µmol/L in plasma and the lowest concentration on the calibration curve was recognized as the limit of quantification (LOQ). The accuracy ranged from 92.74 to 105.57% and 95.43 to 115.73%, while precision varied from 2.48 to 6.99% and 0.84 to 6.98% for intra- and inter-day measurements, respectively. The utility of the assay was proved by application to plasma samples delivered by apparently healthy donors (n = 18) in which the HPPTCA concentration ranged from 19.2 to 65.6 µmol/L. The HPLC–UV assay provides complementary tool for routine clinical analysis, facilitating further studies on the role of aminothiols and HPPTCA in living systems.

Preparation of a novel poly-(di-ionic liquid)/BDD-modified electrode for the detection of tetrachloro-p-benzoquinone

During the COVID-19 pandemic, the release of toxic disinfection by-products (DBPs) has increased due to the intensive, large-scale use of disinfectants. Halogenated benzoquinones (HBQs) are among the most toxic DBPs, but there is no rapid, convenient, and economical detection method. In this study, a novel PDIL/BDD-modified electrode was prepared in a mixed solvent of dimethyl sulfoxide (DMSO) and acetonitrile (ACN) by electrochemical polymerization with a di-ionic ionic liquid containing alkenyl groups as the monomer. The electrochemical behavior of tetra-chloro-p-benzoquinone (TCBQ) on the modified electrode was studied. By studying the cyclic voltammetry behavior of TCBQ on the PDIL/BDD electrode, it was concluded that the electrode reactions of TCBQ included the reduction of TCBQ to TCBQH2 (C1) and the reduction of bis-quinhydrone imidazole π-π type charge transfer complex to TCBQH2 (C2). By studying the SWV responses of TCBQ in the concentration range of 1–100 ng/L on the PDIL/BDD electrode, it was found that the reduction peak current (Ipa) had a linear relationship with the concentration. The electrochemical SWV technique was used to detect the concentration of trace TCBQ in water and is expected to be used for the detection of other HBQs in drinking water and swimming pool water.