Quantitation of Vaporized γ-Aminobutyric Acid in Cigarette Smoke Extract From e-Cigarettes by the Combination of HPLC-Fluorescence Detection and Derivatization With DBD-F.

Gamma-aminobutyric acid (GABA), which has attracted much attention as a bioactive ingredient, is used in functional foods. Recently, electronic cigarette (e-cigarette) products for inhaling vaporized GABA have become commercially available. In this study, we developed a high-performance liquid chromatography-fluorescence method for detecting GABA derivatized with 4-(N,N-dimethylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole (DBD-F) in cigarette smoke extract (CSE).

Accurate LC-MS/MS Analysis of Diacylglycerols in Human Plasma with Eliminating Matrix Effect by Phospholipids Using Fluorous Biphasic Extraction.

We developed an accurate method for determining diacylglycerols (DAGs) in human plasma using a fluorous biphasic liquid-liquid extraction method, followed by liquid chromatography with tandem mass spectrometry (LC-MS/MS) analysis. The lipid mixture in the plasma was first extracted with chloroform by using the Bligh-Dyer method. The resulting solution was subjected to fluorous biphasic liquid-liquid extraction to remove phospholipids, which are known to cause matrix effects during the LC-MS/MS analysis.

Exploration of the optimal GS-441524 trough concentration for treating COVID-19.

Objectives: Remdesivir (RDV) is the cornerstone for treating coronavirus disease 2019 (COVID-19). The active metabolite of RDV, GS-441524 (a nucleoside analogue), has high interindividual variability in plasma concentrations; however, its concentration-response relationship is still unclear. This study investigated the target GS-441524 trough concentration for symptom improvement in COVID-19 pneumonia.

Liquid Chromatographic Determination of o-Phosphoethanolamine in Human Plasma Using Fluorescent Derivatization.

In this study, an HPLC analysis method using pre-column derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) was developed for the determination of o-phosphoethanolamine (PEA), which is a potential biomarker for the diagnosis of major depressive disorder, in human plasma sample. After PEA was derivatized with AQC under mild conditions, the obtained derivative was subjected to purification with a titanium dioxide-modified monolithic silica spin column (MonoSpin TiO). The eluate from the MonoSpin TiO was directly injected into an amide-type hydrophilic interaction liquid chromatography (HILIC) column-equipped HPLC system, and the resulting derivative could be separated on the column under alkaline mobile phase conditions and subsequently detected fluorometrically at excitation and emission wavelengths of 250 and 395 nm, respectively.

Development of an enzyme-linked immunosorbent assay for the quantification of O-Phosphoethanolamine in human plasma.

O-Phosphoethanolamine (PEA) is an endogenous substance that is attracting interest as a biomarker for depression, and thus there is a need to develop a simple analytical method that specifically measures PEA. Therefore, this study aimed to develop a simple and specific enzyme-linked immunosorbent assay (ELISA) for PEA. Anti-PEA antibody was obtained by immunizing mice with an antigen conjugated with mercaptosuccinyl bovine serum albumin using m-maleimidobenzoyl-N-hydroxysulfosuccinimide ester (MBS).

Discrimination of Malignant Pleural Mesothelioma Cell Lines Using Amino Acid Metabolomics with HPLC.

Malignant pleural mesothelioma (MPM) is a malignancy closely associated with asbestos exposure. Although early diagnosis provides a chance of effective treatment and better prognosis, invasive biopsy and cytological procedure are required for definitive diagnosis. In this study, we developed a method to differentiate between MPM and control cell lines, named "amino acid metabolomics," consisting in the assessment of the balance of their amino acid levels in the cell culture medium.

Quantification of Casein in Baked Food Products by Selective Analysis of Phosphorylated Peptides Using Fluorous Derivatization with Liquid Chromatography-Tandem Mass Spectrometry Method.

Casein is one of the allergen proteins present in milk. Therefore, a quantification method for the selective analysis of casein using fluorous derivatization with LC-tandem mass spectrometry (LC-MS/MS) was developed. After two allergen proteins (α-casein and β-casein) extracted from baked sugar cookies were tryptic digested, the obtained phosphorylated peptides were selectively derivatized by β-elimination with Ba(NO) under basic condition and Michael addition with perfluoroalkylthiol (1H,1H,2H,2H-perfluorooctanethiol, PFOT).

Deep eutectic solvent extraction of cortisol and cortisone from human saliva followed by LC-UV analysis.

A novel extraction method was developed for the determination of cortisol and cortisone. In this study, we prepared a hydrophobic deep eutectic solvent (DES) by mixing trioctylmethylammonium chloride and pentafluorophenol as a hydrogen bond acceptor and a hydrogen bond donor, respectively, for use as the extraction solvent. The extraction of cortisol and cortisone was performed by adding a small volume of the DES to the aqueous sample.

Multiple phosphorylated protein selective analysis via fluorous derivatization and liquid chromatography-electrospray ionization-mass spectrometry analysis.

Post-translational modification of proteins is involved in protein function and higher-order structure. Among such modification, phosphorylation is an important intracellular signal transduction pathway. Many studies on phosphorylated protein analysis using liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) have been developed.

Fluorous and Fluorogenic Derivatization for Selective Liquid Chromatographic Analysis of Cyanide in Human Plasma.

A liquid chromatographic (LC) method with fluorous derivatization for the determination of cyanide in human plasma is described. In this method, the cyanide was transformed to a fluorous and fluorogenic compound by derivatizing with 2,3-naphthalenedialdehyde and perfluoroalkylamine reagent under mild reaction conditions (a reaction time of 5 min at room temperature). The obtained derivative was successfully retained on the perfluoroalkyl-modified LC column with the use of a high concentration of organic solvent in the mobile phase, whereas non-fluorous derivative was hardly retained, followed by fluorometric detection at excitation and emission wavelengths of 420 and 490 nm, respectively.

Application of a fluorous derivatization method for characterization of glutathione-trapped reactive metabolites with liquid chromatography-tandem mass spectrometry analysis.

The glutathione (GSH) trapping assay is commonly utilized for the screening and characterization of reactive metabolites produced by drug metabolism. This study describes a fluorous derivatization method for a more sensitive and selective analysis of reactive metabolites trapped by GSH using liquid chromatography-tandem mass spectrometry (LC-MS/MS). In this study, the GSH-trapped reactive metabolites, which were obtained after incubation of the test compounds with human liver microsome (HLM) in the presence of GSH and NADPH, were derivatized using the perfluoroalkylamine reagent through oxazolone chemistry.

Determination of Gemcitabine in Plasma of Bladder Cancer Patients by Hydrophilic Interaction Chromatography with Ultraviolet Detection.

Gemcitabine is a deoxycytidine analog that has been used for a broad spectrum of tumor, such as nonsmall-cell lung cancer, bladder cancer and pancreatic cancer. Because gemcitabine is hydrophilic, hydrophilic interaction liquid chromatography (HILIC), where analytes are retained on a polar column according to their hydrophilicity, should be adequate for separation analysis of gemcitabine. In the present study, we proposed a hydrophilic interaction chromatography with ultraviolet (HILIC-UV) method with liquid-liquid extraction and adding tetrahydrouridine to plasma samples for gemcitabine analysis of clinical samples with respect to daily and wide usage.

Recent development and trends in sample extraction and preparation for mass spectrometric analysis of nucleotides, nucleosides, and proteins.

This review describes the recent developments in sample extraction and preparation techniques for mass spectrometric analysis of nucleotides, nucleosides, and proteins. Unique materials and techniques have been developed for highly selective extraction of nucleotides and nucleosides by solid-phase extraction strategies using various affinities. However, for proteins, the analysis of small-scale sections of diseased tissues (formalin-fixed, paraffin-embedded tissues) and the direct analysis of an exact lesion on the surface of diseased tissues (liquid extraction surface analysis) have become important advances in this field.

Assessment of Anticancer Drug Effects on Pancreatic Cancer Cells under Glucose-Depleted Conditions Using Intracellular and Extracellular Amino Acid Metabolomics.

Previously, we developed a method to evaluate states of cells treated with anticancer drugs via the comprehensive analysis of amino acids, termed amino acid metabolomics. In the present study, we evaluated the effects of the anticancer drugs, gemcitabine hydrochloride and pyrvinium pamoate, on the proliferation of a pancreatic cancer cell line (PANC-1) under hypoglycemic conditions using amino acid metabolomics. Intracellular and extracellular amino acid profiles of PANC-1 were determined by hydrophilic interaction chromatography-tandem mass spectrometry with simple pretreatment.

Fluorous-assisted metal chelate affinity extraction for nucleotides followed by HILIC-MS/MS analysis.

We herein developed a selective method for the determination of nucleotides by fluorous-assisted metal chelate affinity extraction followed by hydrophilic interaction liquid chromatography (HILIC) combined with tandem mass spectrometric (MS/MS) analysis. In this study, the nucleotides were selectively chelated by Fe(III)-immobilized perfluoroalkyliminodiacetic acid, and the resulting chelates were subsequently extracted into a fluorous solvent. The nucleotides present in the fluorous solvent were then back-extracted into a non-fluorous solution, such as a solution of ammonia in aqueous acetonitrile.

Fluorous-assisted metal chelate affinity extraction technique for analysis of protein kinase activity.

We have developed a fluorous affinity-based extraction method for measurement of protein kinase activity. In this method, a fluorescent peptide substrate was phosphorylated by a protein kinase, and the obtained phosphopeptide was selectively captured with Fe(III)-immobilized perfluoroalkyliminodiacetic acid reagent via a metal chelate affinity technique. Next, the captured phosphopeptide was selectively extracted into a fluorous solvent mixture, tetradecafluorohexane and 1H,1H,2H,2H-tridecafluoro-1-n-octanol (3:1, v/v), using the specificity of fluorous affinity (fluorophilicity).

[Development of Selective LC Analysis Method for Biogenic and Related Compounds Based on a Fluorous Affinity Technique].

A separation-oriented derivatization method combined with LC has been developed for the selective analysis of biogenic and related compounds. In this method, we utilized a specific affinity between perfluoroalkyl-containing compounds, i.e.

Direct tandem mass spectrometric analysis of amino acids in plasma using fluorous derivatization and monolithic solid-phase purification.

In this study, we developed a novel direct tandem mass spectrometric method for rapid and accurate analysis of amino acids utilizing a fluorous derivatization and purification technique. Amino acids were perfluoroalkylated with 2H,2H,3H,3H-perfluoroundecan-1-al in the presence of 2-picoline borane via reductive amination. The derivatives were purified by perfluoroalkyl-modified silica-based monolithic solid-phase extraction (monolithic F-SPE), and directly analyzed by tandem mass spectrometry using electrospray ionization without liquid chromatographic separation.

Selective and sensitive liquid chromatographic determination method of 5-hydroxyindoles with fluorous and fluorogenic derivatization.

A liquid chromatographic (LC) method with improved selectivity for the simultaneous determination of 5-hydroxyindoles (5-HIs; 5-hydroxytryptophan, 5-hydroxytryptamine, N-acetyl-5-hydroxytryptamine, 5-hydroxyindole-3-acetic acid, and 5-hydroxytryptophol) is described. This method involves precolumn derivatization with 4-(3',3',4',4',5',5',6',6',7',7',8',8',9',9',10',10',10'-heptadecafluorodecyl)benzylamine (HFBA) and separation of the derivatives using a fluorous LC column. In this study, stable benzoxazole derivatives of 5-HIs with HFBA have been obtained by a simple derivatization procedure; their fluorescent properties enabled highly sensitive detection.

[Highly selective analysis of biogenic-related compounds utilizing fluorous chemistry].

Perfluoroalkyl-containing compounds are highly fluorous, meaning that they have a remarkable affinity for one another and effectively exclude non-fluorous species. Utilizing this unique property, we have developed a fluorous derivatization with a liquid chromatographic analysis method for highly selective analysis of target analytes. Although most previous methods focused on extremely sensitive detection-oriented derivatization, the fluorous derivatization method involves highly specific separation for analytes.

Liquid chromatography/tandem mass spectrometry with fluorous derivatization method for selective analysis of sialyl oligosaccharides.

Rationale: A separation-oriented derivatization method using a specific fluorous affinity between perfluoroalkyl-containing compounds was applied to selective liquid chromatography/tandem mass spectrometric (LC/MS/MS) analysis of sialyl oligosaccharides. The perfluoroalkyl-labeled sialyl oligosaccharides could be selectively retained on an LC column with the perfluoroalkyl-modified stationary phase and effectively distinguished from non-derivatized species.

Methods: Sialyl oligosaccharides (3'-sialyllactose, 6'-sialyllactose, sialyllacto-N-tetraose a, sialyllacto-N-tetraose b, sialyllacto-N-tetraose c, and disialyllacto-N-tetraose) were derivatized with 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecafluoroundecylamine via amidation in the presence of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (condensation reagent).

Fluorous affinity-based separation techniques for the analysis of biogenic and related molecules.

Perfluoroalkyl-containing compounds have a unique 'fluorous' property that refers to the remarkably specific affinity they share. Fluorous compounds can be easily isolated from non-fluorous species on the perfluoroalkyl-functionalized stationary phases used in fluorous solid-phase extraction and fluorous liquid chromatography by means of fluorous-fluorous interactions (fluorophilicity). Recently, this unique specificity has been applied to the highly selective enrichment and analysis of different classes of biogenic and related compounds in complex samples.

Concerted derivatization and concentration method with dispersive liquid-liquid microextraction for liquid chromatographic analysis of 5-hydroxyindoles in human serum.

We developed a concerted derivatization and concentration method based on dispersive liquid-liquid microextraction (DLLME) for the liquid chromatography (LC) determination of 5-hydroxyindoles (5-HIs; serotonin, 5-hydroxyindole-3-acetic acid, N-acetylserotonin, and 5-hydroxytryptohol). Concerted derivatization and concentration could be affected by adding a mixture of an ionic liquid (1-hexyl-3-methylimidazolium hexafluorophosphate, extraction solvent), methanol (disperser), and water containing fluorescence derivatization reagents [benzylamine and potassium hexacyanoferrate(III)] into the sample. The resulting sedimented phase was injected into a reversed-phase LC column using a mixture of acetonitrile and 250 mM acetate buffer (pH 4.

Fully automated reagent peak-free liquid chromatography fluorescence analysis of highly polar carboxylic acids using a column-switching system and fluorous scavenging derivatization.

In this study, we combined a column-switching system with a fluorous scavenging derivatization method to develop a fully automated reagent peak-free LC fluorescence detection protocol for the analysis of highly polar carboxylic acids. In this method, highly polar carboxylic acids were derivatized with fluorescent 1-pyrenemethylamine in the presence of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and 1-hydroxy-1H-benzotriazole. Residual excess of the unreacted reagent was tagged with 2-(perfluorooctyl)ethyl isocyanate and then removed selectively using a fluorous column-switching system placed in front of an analytical reversed-phase column.