Electrospray Research Articles

Development and Validation of a UHPLC-MS/MS Method for the Simultaneous Quantification of Candesartan and Bisoprolol Together with Other 16 Antihypertensive Drugs in Plasma Samples.

Antihypertensive pharmacological therapy is often characterized by a coadministration of different classes of drugs. Therefore, analytical methods allowing the simultaneous quantification of many drugs are needed for therapeutic drug monitoring (TDM) purposes in this context. In particular, TDM represents a useful tool to discriminate poor adherence from real cases of resistant hypertension. For this reason, the aim of this study is to validate, following the Food and Drug Administration (FDA) and the European Medicines Agency (EMA) guidelines, an ultrahigh-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS) method for the simultaneous quantification of 18 antihypertensive drugs in human plasma. A LX-50 coupled with a QSight 220 UHPLC-MS/MS system with electrospray ionization and multiple reaction monitoring mode was used, after a binary gradient separation (13 min) on a reverse-phase Acquity UPLC HSS T3 [1.8 μm, 2.1 mm × 150 mm] column. Method validation showed a stable and acceptable matrix effect, recovery, high accuracy, and precision, assessing the eligibility of this method for routine use in the clinical context.

Identification and quantification of potential genotoxic impurity N-nitroso isoproterenol in bradycardia drug isoproterenol hydrochloride by LC-MS/MS technique

A highly sensitive and robust LC-MS/MS method was developed and validated for the quantification of N-Nitroso Isoproterenol (NNIP) impurity in Isoproterenol Hydrochloride. The method employed a Heated Electrospray Ionization (HESI) source, with selective reaction monitoring (SRM) mode and with 3600 Voltage negative ion, to detect NNIP with a precursor ion of 238.967 m/z and product ions of 136.883 m/z and 190.967 m/z. Chromatographic separation was achieved using a Kinetex-Biphenyl 100Å (250 mm x 4.6 mm, 5 µm) column with a gradient program consisting of 0.1% Formic acid in Water (Mobile Phase A) and 0.1% Formic acid in Methanol (Mobile Phase B). The method demonstrated excellent linearity (R2 = 0.9982) across concentrations from LOQ to 150% of the target level, with a limit of detection (LOD) of 1.14 ppm and a limit of quantification (LOQ) of 3.46 ppm. Precision, indicated by a %RSD of 3.1%, and accuracy, with recoveries ranging from 91.3% to 103.6%, confirmed the method’s reliability. The NNIP peak was consistently observed at 8.56 minutes, supporting the method’s applicability for routine analysis of NNIP impurity in Isoproterenol Hydrochloride formulations.

Creation of Gas-Phase Organo-Uranium Species by Removal of "yl" Oxo Ligands From UO2 2+ Carboxylate Precursor Ions.

These experiments were conducted to measure the diversity of organo-U (IV) and U (III) ions created using multiple-stage tandem MS and collision-induced dissociation of halogen-substituted UVIO2-phenide complexes [UO2(C6H3FX)]+, X = Cl, Br, or I. Samples of UO2(O2C-C6H3FX)2 were prepared by digesting UO3 with appropriate halogen-substituted carboxylic acids in deionized water. Solutions for ESI were created by diluting the digested sample in 50:50 H2O/CH3OH. Precursor ions for multiple-stage tandem MS were generated by electrospray ionization (ESI). Multiple-stage collision-induced dissociation (He collision gas) in a linear quadrupole ion trap mass spectrometer was used to prepare species such as [UIVFX(C≡CH)]+ and UIIIF(C≡CH)]+ for subsequent study of ion-molecule reactions with adventitious neutrals in the ion trap. Multiple-stage CID of the [UO2(C6H3FX)]+, X = Cl, Br, or I, complexes caused removal of both "yl" oxo ligands from of the UO2 2+ moiety to create ions such as [UIVFX(C≡CH)]+ and [UIIIFX]+. For [UIVFXC≡CH]+ and [UIIIFC≡CH]+ products, hydrolysis to generate [UIVFX (OH)]+ and [UIIIF (OH)]+, with concomitant loss of HC≡CH, was observed. CID of [UO2(C6H3FBr)]+ and [UO2(C6H3FI)]+ caused reductive elimination of the respective halogen radicals to generate interesting organo-U (III) species such as [UIIIF(C≡CH)]+ and [UIIIC2]+. The use of "preparative" tandem mass spectrometry and a suite of halogen substituted benzoic acid ligands can be used to remove both oxo ligands of UO2 2+ and generate a group of homologous organo-U (IV) and organo-U (III) ions for studies of intrinsic reactivity.

LC-MS/MS method for the simultaneous determination of six phenolic acids in rat plasma and hypoglycemic effects in normal and T2DM rats after oral administration of Eleutherococcus senticosus fruits extract

AbstractEleutherococcus senticosus (Rupr. & Maxim.) Maxim. fruits (ESF) is a natural health food that has been widely used in traditional medicine. This study aimed to establish and validate a rapid and sensitive method for determining of six phenolic acids in plasma of normal and T2DM rats by ultra-performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS). Separation and quantification were performed on a Waters HSS T3 column (100 × 2.1 mm, 1.8 μm) with water (A) and methanol (B). The electrospray ionization (ESI) source was operated in negative ionization mode. Multiple reaction monitoring (MRM) was used to quantitatively analyzed hyperoside m/z 463.2→301.1, caffeic acid m/z 179.1→135.1, chlorogenic acid m/z 353.2→190.9, gallic acid m/z 169.0→125.1, protocatechuic acid m/z 153.1→109.1, and isofraxidin m/z 221.1→191.0, respectively. The hypoglycemic effect of ESF was verified by determining blood glucose and lipid levels in a type 2 diabetes model. This study laid the foundation for exploring ESF clinical guidelines in the future.

Mass Spectrometry Imaging Reveals Spatial Metabolic Alterations and Salidroside’s Effects in Diabetic Encephalopathy

Background: Diabetic encephalopathy (DE) is a neurological complication of diabetes marked by cognitive decline and complex metabolic disturbances. Salidroside (SAL), a natural compound with antioxidant and neuroprotective properties, has shown promise in alleviating diabetic complications. Exploring the spatial metabolic reprogramming in DE and elucidating SAL’s metabolic effects are critical for deepening our understanding of its pathogenesis and developing effective therapeutic strategies. Methods: Air-flow-assisted desorption electrospray ionization–mass spectrometry imaging (AFADESI-MSI) was employed to investigate spatial metabolic alterations in the brains of db/db mice, a spontaneous DE model. The mice were treated with SAL (30 and 150 mg/kg, orally) for 12 weeks. Differential metabolites were identified and characterized using high-resolution mass spectrometry and validated against public databases. Results: Our AFADESI-MSI analysis revealed significant changes in 26 metabolites in the brains of DE mice compared to the controls. These metabolic changes indicated disruptions in glucose, glutamate-glutamine, nucleotide, lipid, choline, aspartate, and L-carnitine metabolism. Notably, glucose 6-phosphate (G6P), glutamine, adenosine, L-carnitine, and choline exhibited similar trends in both db/db mice and STZ-induced rat models of DE, suggesting their potential as reliable biomarkers. Twelve weeks of SAL treatment demonstrated a positive regulatory effect on glucose metabolism, the glutamate–glutamine cycle, and lipid metabolism. Conclusions: This study identifies key metabolic alterations in DE and demonstrates the therapeutic potential of SAL in modulating these disturbances, offering valuable insights for targeted interventions in diabetic complications.

Desorption Electrospray Ionization-Mass Spectrometry Imaging-Based Spatial Metabolomics for Visualizing and Comparing Ginsenosides and Lipids among Multiple Parts and Positions of the Panax ginseng Root.

Ginsenosides and lipids are both bioactive ingredients for ginseng. Targeting these two categories of components, this study was designed to develop desorption electrospray ionization-mass spectrometry imaging approaches and spatial metabolomics strategies, achieving the visualization and differentiation among different parts of Panax ginseng root (e.g., rhizome, main root, lateral root, fibrous root, and adventitious root). Potential chemical markers were identified by searching an in-house ginsenoside library and online Lipid Maps database, together with high-resolution MS2 data analysis. Six ginsenosides and 11 lipids were diagnostic to differentiate five different parts of the P. ginseng root. Additionally, three ginsenosides and 20 lipids were identified as differential markers among the six positions of the main root of P. ginseng. High-abundance malonyl- and oleanolic acid-ginsenosides were observed in the rhizome. These results assist in understanding the accumulation of bioactive molecules all through the root of P. ginseng, which can benefit its quality control and rational use.

HPLC with parallel ESI-MS and ICP-AES detection as a tool for the speciation studies of phosphovanadotungstates

The presence of different equilibrated chemical species in aqueous solutions of polyoxometalates represents a challenge for their identification, requiring the use of both separation and detection techniques. The use of reversed-phase ion-pair high-performance liquid chromatography (HPLC) in gradient elution mode resulted in optimal separation conditions. The detection was accomplished by parallel hyphenation of the inductively coupled plasma atomic emission spectrometry (ICP-AES) and electrospray ionization mass spectrometry (ESI-MS), which combined the advantages of element and molecule specific detectors. This hyphenation resulted in an unambiguous identification of the products of the synthesis of mixed-addendum Keggin-type phosphovanadotungstates of [PVxW12-xO40](3+x)- (x = 1 – 3) general formula without the isolation of the individual species.

Four luminous cyclen-protected Silver-Alkynyl clusters

For investigating the coordination ability and the reactivity of Cyclen, four luminous cyclen-protected Silver-Alkynyl clusters, named [Ag5(CCtBu)2(Cyclen)3(OTf)·(OTf)2] (1), [Ag4(CCPh)(Cyclen)3(H2O)·(OTf)3] (2), [Ag4(CCPh)(Cyclen)3(H2O)·(BF4)3·(CH3OH)2] (3), and [Ag12(CCPh)6(Cyclen)6(BF4)2·(BF4)4] (4), where OTf = Trifluoromethanesulfonate, have been prepared by adding Cyclen into the different silver-alkynyl systems. Their composition and charge state, have been confirmed by X-ray single-crystal structural analysis, Electrospray Ionization Mass Spectrometry (ESI-MS), and other methods. The thermogravimetric analysis (TGA) reveals the decomposition temperature of all four clusters was over 150 °C, showing excellent thermal stability. Contrastively studies of their emission properties by the photoluminescence (PL) spectra indicate the variation of the cluster cores have a great impact on their emission color in the solid state at 77 K. This study introduces a new way to prepare new structures of silver-alkynyl clusters, and will enlighten further explorations of the structure control of silver clusters with excellent emission.

Oxidative pathways of apo, partially, and fully Zn(II)‐ and Cd(II)‐metalated human metallothionein‐3 are dominated by disulfide bond formation

Oxidative stress is a key component of many diseases, including neurodegenerative diseases such as Alzheimer's disease. Reactive oxygen species (ROS) such as hydrogen peroxide and nitric oxide lead to disease progression by binding to proteins and causing their dysregulation. Metallothionein‐3 (MT3), a cysteine‐rich brain‐located metalloprotein, has been proposed to be a key player in controlling oxidative stress in the central nervous system. We report data from a combination of electrospray ionization mass spectrometry (ESI‐MS), ultraviolet (UV)‐visible absorption spectroscopy, and circular dichroism spectroscopy that identify the oxidation pathway of MT3 fully bound to endogenous Zn(II) or exogenous Cd(II) together with the partially metalated species. We characterize the intermediate species formed during the oxidation of MT3, which is dominated by disulfide bond formation. We report the rates of oxidation. For both fully and partially metalated MT3, MT3 is oxidized at 5 to 10 times the rate of MT1, a similar but kidney‐expressed isoform of MT. As oxidation progresses, MT3 follows a domain‐specific demetallation pathway when it is fully metalated, and a domain‐independent pathway when partially metalated. This suggests the presence of a significant susceptibility toward oxidation when MT3 is partially metalated, and, therefore, a possible protective role of Zn(II) when fully metalated. With the evidence for the rapid oxidation rate, our data support the proposals of MT3 as a key antioxidant in physiology.

Molecular insight into algae-derived dissolved organic matters via Fourier-transform ion cyclotron resonance mass spectrometry: Effects of pretreatment methods and electrospray ionization modes

The release of algae-derived dissolved organic matter (ADOM) significantly increased in serious eutrophication waters, posing great threats to drinking water safety. Thus, the molecular composition decipherment is urgently in need. However, due to unsatisfactory pretreatment and ionization effects, the application of Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) on ADOM was limited. Therefore, the effects of pretreatment methods (cartridge type and loading) during solid-phase extraction (SPE) and electrospray ionization (ESI) modes with FT-ICR-MS on the molecular composition of ADOM were evaluated. The results showed compared with silica-based octadecyl (C18) cartridge, styrene-divinylbenzene polymer (PPL) cartridge exhibited higher recovery efficiency and retained more saturated and oxygenated compounds, such as carbohydrate-like and tannin-like. Furthermore, the recovery efficiency decreased with increasing loading, and hydrophilic and high-oxygenated carbohydrate-like and tannin-like were continuously replaced by hydrophobic and low-oxygenated aliphatic and aromatic compounds. Moreover, compared to negative ESI mode, the addition of positive ESI mode increased the molecular chemodiversity, especially more lipid-like and protein-like compounds. Thus, we proposed < 1:500 DOC/PPL mass ratio during SPE and dual ESI modes coupled with FT-ICR-MS could identify ADOM molecules more comprehensively. This work contributes to more comprehensive understanding of the molecular composition of ADOM and provides more references for pretreatment and characterization strategies of severely eutrophic waters.

In-situ reaction monitoring and kinetics study of photochemical reactions by optical focusing inductive electrospray mass spectrometry

In-situ reaction monitoring and kinetics study of photochemical reactions by optical focusing inductive electrospray mass spectrometry

Preparation and characterization of ferulic oligosaccharides from different sources by cell-free GH10 and GH11 xylanases

The feruloyl oligosaccharides (FOs) produced by the decomposition of plant hemicellulose have broad potential applications in the food and biomedical areas. FOs were prepared through the specific enzymatic degradation of insoluble dietary fiber from different sources by cell-free GH10 and GH11 xylanases. The cell-free GH10 and GH11 xylanases were obtained by the heterologous expression in Escherichia coli. The enzymatic hydrolysis conditions were optimized as follows: temperature 50 °C, pH 5.5, hydrolysis time 12 h, GH10 xylanase addition 101.74 U, and GH11 xylanase addition 121.60 U. The compositions and structural characterization of wheat bran FOs (WB-FOs), corncob FOs (CC-FOs), and buckwheat straw FOs (BS-FOs) were identified by fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), high-performance liquid chromatography (HPLC), and electrospray ionization tandem mass spectrometry (ESI-MS). Degrees of polymerization (DP) of WB-FOs, CC-FOs, and BS-FOs were 3–11, 3–7, and 3–6, respectively. Ultraviolet (UV) radiation was investigated in vitro. The results demonstrated that BS-FOs possessed excellent UV resistance and photostability, followed by effectiveness in WB-FOs and CC-FOs. These results have improved our understanding of the relationship between FOs with different structural types and their UV radiation.

Synchronization of extraction and chromatographic conditions of diverse physicochemical behavior of pseudoephedrine, loratadine and desloratadine for their simultaneous determination in human plasma: Application to pharmacokinetic study

A selective, sensitive, and rapid LC-MS/MS method has been developed, optimized, and validated for the simultaneous determination of pseudoephedrine (PSE), loratadine (LOR), and LOR active metabolite, desloratadine (DES) in K3EDTA human plasma. A simple liquid–liquid extraction method was adopted for extraction of the 3 analytes and their internal standards; chlorpheniramine (CLP), loratadine D4 (LOR-D4), and desloratadine D4 (DES-D4), respectively, giving consistent recovery results (78.38––88.23 %) using diethyl ether: dichloromethane (80:20, v/v) as the extraction solvent. The chromatographic separation was challenging due to the polarity differences between PES, which is more polar, and LOR and DES, which are less polar that affected their physicochemical properties including the retention of the drugs on C18 column. The separation was achieved using of isocratic elution of 20 mM ammonium formate and 2 mM trifluoracetic acid ammonium salt: acetonitrile containing 0.15 % formic acid (12:88, v/v) as a mobile phase pumped onto a Supelco Discovery® C18 (4.6 mm x 100 mm, 5 µm) at 35 °C with a flow rate of 0.8 mL/min. The use of trifluoracetic acid ammonium salt as an ion pair reagent in the selected mobile phase allowed good retention of the polar PSE on the used C18 column with a reasonable retention time. Positive Electrospray ionization was employed followed by detection using a tandem mass spectrometer in multiple reactions monitoring (MRM) mode. The sample analysis of this study was conducted in compliance with ICH guideline M10 on bioanalytical method validation and study sample analysis. The method was linear over the concentration range of (4–1200) ng/mL for PSE, (50–15000) pg/mL for both LOR, and DES. The developed method was accurate (91.14–110.30 %), precise (0.53–7.86 %), and was applied to study the pharmacokinetic profile of the cited drugs in the plasma of healthy human volunteers after single oral administration of the fixed-dose combination Claritin D® tablet, (240/10 mg) of PSE, and LOR, respectively.

Development and Validation of a Sensitive LC-MS/MS Method for Determination of Lenvatinib and Its Major Metabolites in Human Plasma and Its Application in Hepatocellular Carcinoma Patients.

Lenvatinib has been demonstrated effective in advanced hepatocellular carcinoma (HCC), but the pharmacokinetic-pharmacodynamics behavior of lenvatinib and its metabolites remains unclear. To investigate the pharmacokinetic-pharmacodynamics behavior of lenvatinib and its active metabolites in advanced HCC patients, it is important to develop a simple and rapid method to analyze the exposures of lenvatinib and its metabolites in human samples. Here, we established and validated a simple and rapid method for determining lenvatinib and its three major metabolites, descyclopropyl lenvatinib (M1), O-demethyl lenvatinib hydrochloride (M2), and lenvatinib N-Oxide (M3) by liquid chromatography-tandem mass spectrometry method. Lenvatinib and its main metabolites were separated on an X-Terra RP18 column (50 × 2.1mm, 3.5 µm) at 35°C within 3min, and the analytes were isocratically eluted with the mobile phase of methanol-water (10:90, v/v) containing 0.1% of formic acid at a flow rate of 0.15mL/min. The calibration range was 1-1000ng/mL for lenvatinib, while 0.1-100ng/mL for M1-M3 under positive electrospray ionization mode. The inter- and intra-batch precisions and accuracy were acceptable for lenvatinib and its metabolites. This method was successfully applied to measure lenvatinib and its metabolites in plasma samples from HCC patients, which provides a robust tool for pharmacokinetic-pharmacodynamics studies of lenvatinib.

Highly selective separation of 99TcO4−/ReO4− with rapid liquid-liquid two-phase disengagement by amine-diamide ligands

Efficient and selective extraction of pertechnetate (TcO4−) from nitric acid medium has become a significant challenge, especially in the presence of a large excess of interfering anions. By employing a combined strategy involving H-bonding and electrostatic interaction, a highly selective extraction of TcO4− can be achieved. The present work reports three homologous amine-diamide ligands with different alkyl chain lengths on the amine N atom of 2,2′‐(metylimino)bis(N,N‐dioctylacetamide) (MIDOA), 2,2′‐(butylimino)bis(N,N‐dioctylacetamide) (BIDOA) and 2,2′‐(octylimino)bis(N,N‐dioctylacetamide) (OIDOA), and their extraction behaviors for TcO4−/ReO4− in HNO3 solution are also investigated by using n-dodecane as a diluent. It has been shown that all of them exhibit excellent extractability and high selectivity to TcO4−/ReO4−. Their extractability and phase disengagement follow the order of OIDOA > BIDOA > MIDOA, revealing a greater extractability and rapider phase disengagement for the amine-diamide ligand with longer chain substituents on the amine N atom. Both slope analysis and loading capacity test indicate the formation of 1:1 metal/ligand extracted complex, which is also confirmed by the analyses of single-crystal X-ray diffraction (SC-XRD), electrospray ionization mass (ESI-MS), Fourier transform infrared (FT-IR), and X-ray photoelectron spectroscopy (XPS). The extraction of TcO4−/ReO4− by the amine-diamide ligand follows the anion exchange extraction model and is a spontaneous and endothermic process. Furthermore, a competing extraction test was also conducted and demonstrates excellent extractability and high selectivity to TcO4−/ReO4−.

A non-target evaluation of drinking water contaminants in pilot scale activated carbon and anion exchange resin treatments

This study evaluates the effectiveness of five types of Granular Activated Carbon (GAC) and one anion exchange resin in a pilot plant for treating groundwater for drinking water production, specifically targeting the removal of persistent compounds like PFAS. Using liquid chromatography and supercritical fluid chromatography coupled with high-resolution mass spectrometry, hundreds of features (i.e. peak at specific mass and retention time) were detected in the groundwater by non-target analysis. Initially, after treating <3200 bed volumes (BV), the GAC filter materials showed < 6 % breakthrough for all features from the groundwater, with decreasing efficiency down to 79 % breakthrough after seven month (69,000 treated BV for µGAC). Using resin as a lag filter after GAC did not improve the removal of compounds detected in positive electrospray ionization mode. However, it enhanced removal by up to 35% for compounds detected in negative electrospray ionization mode, indicating higher selectivity of resin for acidic compounds like PFAS. The shortest detected PFAS (PFBA and PFPeA) broke through completely for all GAC and the resin material except the proprietary blended GAC (at 15,700 treated BV), which had only 19% breakthrough for PFPeA. The so far rarely detected perfluoro(4-ethylcyclohexane)sulfonic acid (PFECHS) was well adsorbed by GAC coupled to resin and by the proprietary blended GAC. Pesticides were effectively removed by GACs, but not by the resin filter. Contaminants not previously detected in groundwater, 2,4,5-trichlorobenzenesulfonic acid (TCBS) and 2-amino-4-chloro-5-methylbenzenesulfonic acid (ACMBS), were effectively removed (>92 %), but high ACMBS concentrations (360 ng/L) in groundwater are of concern. The drinking water after the resin filter revealed 20 new contaminants, such as tributylamine derivatives and monobutyl phthalate, indicating resin filters contribution to drinking water contamination. Accelerated migration experiments of the resin revealed additional contaminants, such as NDBA and further phthalates, highlighting the need for continued monitoring and evaluation of resin materials in water treatment systems.

Existing Forms of Notoginsenoside R1 in Rats and Their Potential Bioactivities.

Notoginsenoside R1 (NG-R1) is a primary active constituent in Panax notoginseng, a medicinal and edible plant. It is a saponin with protopanaxatriol (PPT) as its aglycone. UHPLC-ESI-Q-TOF-MS/MS was used to clarify the existing forms of NG-R1 and their distributions in rats. The nomenclature of the ESI MS fragmentation pathway and ions of PPT was proposed for the first time. Totally, 105 metabolites with 89 new metabolites were identified. In terms of their LC-MS data, 7 were accurately identified by comparison with reference compounds, and 41 were clearly identified. Polyhydroxylation, pentosylation, acetylation, glucuronidation, and amino acid conjugation are new metabolic reactions of NG-R1. In total, 69, 48, 47, 43, 24, 15, and 7 metabolites were detected in the large intestine, stomach, small intestine, liver, lungs, kidneys, and heart, respectively. Then, 48 metabolites were predicted to be effective by PharmMapper, and their mechanisms of action on three diseases were predicted by network pharmacology. Finally, the antitumor effects on cell proliferation and the anti-inflammatory effects of the eight compounds were verified by cellular experiments. These results help further elucidate the in vivo existing forms of dammarane-type triterpenoids and form the basis for discovering their effective forms in the future.

Tandem Deacetalization-Knoevenagel Condensation Reactions for the Synthesis of Benzylidene Malononitrile Using Ruthenium(II) Cymene Complexes.

In this study, we report the synthesis and full characterization of five novel ruthenium(II) cymene complexes with the general formula [Ru(cym)(L')Cl], featuring N,O- and N,N-coordinating pyrazolone-based hydrazone ligands. We have characterized these complexes using single X-ray crystallography, Fourier-transform infrared spectroscopy (FT-IR), Nuclear magnetic resonance (NMR), elemental analysis, and Electrospray Ionization Mass Spectroscopy (ESI-MS). Crystallographic analysis confirmed that all of the complexes have a similar type of half-sandwich, pseudo-octahedral "three-legged piano-stool" geometry where the cymene moiety displays the typical η6-coordination mode and the hydrazone ligands coordinate to the Ru(II) center in a bidentate fashion. These complexes, with multiple catalytic sites, demonstrated high efficiency in catalyzing one-pot cascade deacetalization-Knoevenagel condensation reactions under mild conditions, achieving up to 92% of final product yield at 75 °C after 4 h of reaction time under solvent-free condition. Additionally, DFT calculations provided insight into the catalytic mechanism, suggesting a pathway driven by metal-ligand cooperation, assisted by the basic oxygen site of the pyrazolone ring and by the weakly acidic character of the NNH proton of the hydrazone group.

Flow Rate Determination of the Nanoflow Sheath Liquid CE-MS-Coupling Applying the nanoCEasy Interface.

In recent years, nanoflow sheath liquid (nanoSL) interfaces have been used more commonly for capillary electrophoresis-mass spectrometry (CE-MS) coupling due to their high sensitivity combined with flexibility in CE separation conditions. So far, the exact amount of sheath liquid (SL) and, thus, the dilution effect remain unknown due to the self-supplying type of the nanoSL interfaces. To quantify the SL flow rates, we present here an approach for the determination of the flow rate based on isotopically labeled standards using the nanoCEasy interface. SL and pumped CE flow are spiked with atrazine and d5-atrazine, respectively, enabling the determination of the total flow rate for different electrospray (ES) conditions. Generally, flow rates increase with higher ES voltages. Only at high ES voltages, larger emitter sizes lead to higher flow rates; for low voltages, flow rates are independent of emitter size. Additionally, smaller emitter sizes can generally be operated at lower ES voltages. Visualizing the ES, higher flow rates lead to a larger spray angle. Higher flow rates may decrease the signal intensity by diluting the CE-separated analytes. Indeed, this effect is observed for the flow-injected atrazine analytes and in the CE-MS analysis of an amino acid standard mix under aqueous acidic separation conditions. Therefore, lower flow rates are preferred for low electroosmotic flow (EOF) applications. However, in high EOF applications, higher voltages are required to prevent the accumulation of aqueous background electrolyte (BGE) at the emitter tip, which otherwise leads to peak broadening and inefficient ionization. Overall, the presented data enable the selection of stable and sensitive settings for nanoSL interfaces.

Four-Dimensional Lipidomic Analysis Using Comprehensive Online UHPLC × UHPSFC/Tandem Mass Spectrometry.

Multidimensional chromatography offers enhanced chromatographic resolution and peak capacity, which are crucial for analyzing complex samples. This study presents a novel comprehensive online multidimensional chromatography method for the lipidomic analysis of biological samples, combining lipid class and lipid species separation approaches. The method combines optimized reversed-phase ultrahigh-performance liquid chromatography (RP-UHPLC) in the first dimension, utilizing a 150 mm long C18 column, with ultrahigh-performance supercritical fluid chromatography (UHPSFC) in the second dimension, using a 10 mm long silica column, both with sub-2 μm particles. A key advantage of employing UHPSFC in the second dimension is its ability to perform ultrafast analysis using gradient elution with a sampling time of 0.55 min. This approach offers a significant increase in the peak capacity. Compared to our routinely used 1D methods, the peak capacity of the 4D system is 10 times higher than RP-UHPLC and 18 times higher than UHPSFC. The entire chromatographic system is coupled with a high-resolution quadrupole-time-of-flight (QTOF) mass analyzer using electrospray ionization (ESI) in both full-scan and tandem mass spectrometry (MS/MS) and with positive- and negative-ion polarities, enabling the detailed characterization of the lipidome. The confident identification of lipid species is achieved through characteristic ions in both polarity modes, information from MS elevated energy (MSE) and fast data-dependent analysis scans, and mass accuracy below 5 ppm. This analytical method has been used to characterize the lipidomic profile of the total lipid extract from human plasma, which has led to the identification of 298 lipid species from 16 lipid subclasses.