High-performance Liquid Chromatography Coupled With Electrospray Ionization Mass Spectrometry Research Articles

Exploring Negative Chemical Ionization of Per- and Polyfluoroalkyl Substances via a Liquid Electron Ionization LC-MS Interface.

Per- and polyfluoroalkyl substances (PFASs) are a class of aliphatic manufactured compounds comprising fluoro-chemicals with varied functional groups and stable carbon-fluorine bonds. They are defined as "forever chemicals" due to their persistent and bioaccumulative character. These substances have been detected in various environmental samples, including water, air, soil, and human blood, posing significant health hazards. High-performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC-ESI-MS) is typically employed for the analysis of PFASs. Negative chemical ionization (NCI) is generally coupled to gas chromatography (GC) and offers high selectivity and sensitivity for compounds containing electronegative atoms, such as PFASs. The liquid electron ionization (LEI) interface is an efficient mechanism developed to robustly couple a liquid flow rate from an LC system to an EI or a CI source. This interface has been successfully utilized for pesticide determination in UHPLC-LEI-CI in negative ion mode (NCI). This work aims to evaluate different parameters involved in the ionization of PFASs analyzed in LC-LEI-NCI and subsequently develop a method for their detection in real samples. The parameters considered for this study include (i) a comparison of different CI reagent gases (methane, isobutane, and argon); (ii) the use of acetonitrile as both the chromatographic solvent and CI reagent gas; (iii) the presence of water and formic acid as chromatographic mobile phase components; and (iv) the mobile phase flow rate. The optimal combination of these parameters led to promising results. Tentative fragmentation pathways of PFASs in NCI mode are proposed based on the dissociative electron capture mechanism.

Probing Downstream Olive Biophenol Secoiridoids.

Numerous bioactive biophenol secoiridoids (BPsecos) are found in the fruit, leaves, and oil of olives. These BPsecos play important roles in both the taste of food and human health. The main BPseco bioactive from green olive fruits, leaves, and table olives is oleuropein, while olive oil is rich in oleuropein downstream pathway molecules. The aim of this study was to probe olive BPseco downstream molecular pathways that are alike in biological and olive processing systems at different pHs and reaction times. The downstream molecular pathway were analyzed by high performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC-ESI/MS) and typed neglected of different overlap (TNDO) computational methods. Our study showed oleuropein highest occupied molecular orbital (HOMO) and HOMO-1 triggered the free radical processes, while HOMO-2 and lowest unoccupied molecular orbital (LUMO) were polar reactions of glucoside and ester groups. Olive BPsecos were found to be stable under acid and base catalylic experiments. Oleuropein aglycone opened to diales and rearranged to hydroxytyrosil-elenolate under strong reaction conditions. The results suggest that competition among olive BPseco HOMOs could induce glucoside hydrolysis during olive milling due to native olive β-glucosidases. The underlined olive BPsecos downstream molecular mechanism herein could provide new insights into the olive milling process to improve BPseco bioactives in olive oil and table olives, which would enhance both the functional food and the nutraceuticals that are produced from olives.

Effect of overcharge on Li(Ni0.5Mn0.3Co0.2)O2 cathodes: NMP-soluble binder. II — Chemical changes in the anode

Cells based on nickel manganese cobalt oxide (NMC)/graphite electrodes, which contained polyvinylidene difluoride (PVDF) binders in the electrodes, were systematically charged to 100, 120, 140, 160, 180, and 250% state of charge (SOC). Characterization of the anodes by inductively-coupled-plasma mass spectrometry (ICP-MS), X-ray photoelectron spectroscopy (XPS), and high-performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC-ESI-MS) showed several extent-of-overcharge-dependent trends. The concentrations (by wt) of nickel, manganese, and cobalt in the negative electrode increased with SOC, but the metals remained in the same ratio as that of the positive. Electrolyte reaction products, such as LiF:LiPO3, increased with overcharge, as expected. Three organic products were found by HPLC-ESI-MS. From an analysis of the mass spectra, two of these compounds seem to be organophosphates, which were formed by the reaction of polymerized electrolyte decomposition products and PF3 or O=PF3. Their concentration tended to reach a constant ratio. The third was seen at 250% SOC only.

Investigation of α-dicarbonyl compounds in baby foods by high-performance liquid chromatography coupled with electrospray ionization mass spectrometry.

Baby foods are exposed to elevated temperatures during processing treatments such as sterilization or spray drying. These treatments decompose sugars leading to the formation of α-dicarbonyl compounds that are of importance since they have been associated with several metabolic disorders. In this study, an analytical method based on high-performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC-ESI-MS) was used to determine α-dicarbonyl compounds in baby foods. The method entailed aqueous extraction of α-dicarbonyl compounds from the samples and derivatization with o-phenylenediamine prior to chromatographic analysis. The results indicated that major degradation product was 3-deoxyglucosone in the samples including cereal-based infant formula, canned fruit and vegetable puree. Its concentration ranged between 3.9 and 827.1 mg/kg in infant formula and between 26.7 and 92.3 mg/kg in fruit puree samples. The concentrations of glucosone, 1-deoxyglucosone, 5-hydroxymethyl-2-furfural, furfural, glyoxal, methylglyoxal, and dimethylglyoxal levels were rather low.

Analysis of Peptides in Plasma by High Performance Liquid Chromatography Coupled with Electrospray Ionization Mass Spectrometry

In this study, a high performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC-ESI-MS) method for the determination of eight endogenous peptides, which included angiotensin-II, neurotensin, 5-met-enkephalin, 5-leu-enkephalin, somatostatin, bradykinin, dynorphin A and oxidized glutathione, was developed. MS parameters were optimized in order to obtain the best signal intensity. The optimum MS parameters were: fragmentor: 100 V; nebulizer gas (N2) pressure: 40 psi; drying gas (N2) flow rate: 10 L/min; drying gas temperature: 350 °C; capillary voltage: 2000 V. Validation of the method showed positive results. The correlation coefficients (R2) between the peak areas and the corresponding concentrations of peptides were greater than 0.9903. The limits of detection (LODs) (S/N = 3) of the eight peptides were 3.88 ng/mL ~ 17.5 ng/mL. The developed method had been successfully applied to analyzing the human plasma fortified with the eight peptides, which indicated the potential of the methodology for the analysis of biological sample.

ANALYSIS OF URINARY PORPHYRINS BY HIGH PERFORMANCE LIQUID CHROMATOGRAPHY-ELECTROSPRAY IONIZATION MASS SPECTROMETRY

A high-performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC-ESI-MS) method was developed for the simultaneous separation and detection of six porphyrins, namely uroporphyrin (UP), heptacarboxylic acid porphyrin (HEPTAP), hexacarboxylic acid porphyrin (HEXAP), pentacarboxylic acid porphyrin (PENTAP), coproporphyrin (CP), and mesoporphyrin (MP), in human urine samples. The recoveries of the porphyrins in urine ranged from 84 to 108%. The intra- and inter-day precisions at spiked porphyrin concentrations were 4.0–9.7% and 5.5–15%, respectively. The limits of detection (LOD) ranged from 0.2 to 3 nM. The developed method was successfully applied to the determination of endogenous porphyrins in human urine. UP, HEPTAP, and PENTAP were detected at levels of 42.4, 21.3, and 18.0 nM, respectively. CP was detected as the predominant species at 135.6 nM, wheres MP and HEXAP were not detected in the urine samples from healthy females. Significant increases of CP excretion in urine from liver disease patients were observed. This method proved potentially applicable for the routine diagnosis and treatment of porphyrin-related diseases.

Determination of exemestane and 17-hydroxyexemestane by high-performance liquid chromatography coupled with tandem mass spectrometry and high-resolution mass spectrometry

An approach was developed for determining and confirming the presence of exemestane and its metabolite 17-hydroxyexemestane in urine. It is based on the application of high-performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC-MS/MS) and atmospheric pressure chemical ionization high-resolution mass spectrometry (HPLC-HRMS). To detect hydroxyexemestane, the analysis of the hydrolyzed fraction of urine is preferable. The recovery rates of exemestane and 17-hydroxyexemestane were 83 and 91%, respectively. The detection limits were 1 ng/mL for HPLC-MS/MS and 2.5 ng/mL for HPLC-HRMS. In spite of a considerable effect of ionization suppression, the sensitivity and selectivity of the determination are affected by the selection of the optimal detection conditions in HPLC-MS/MS and by the high accuracy of mass determination in mass spectrometry with orbitrap detection, enabling resolution at a level of 5 ppm. The procedures can be used for screening and confirmatory analysis.

Determination of Warfarin and Coumatetralyl in Serum by HPLC Coupled with Electrospray Ionization Mass Spectrometry

A sensitive, fast, and accurate method to determine warfarin and coumatetralyl in serum by high performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC‐ESI‐MS) was developed. After warfarin and coumatetralyl in serum was extracted by ethyl acetate, a satisfactory separation was achieved on a XDB C18 column, 150 mm×2.1 mm×5 µm, by using the mobile phase consisting of acetic acid‐ammonium acetate (10 mmol/L, pH=4.5) (20%) and methanol (80%) in isocratic eluent at a constant flow rate of 0.30 mL/min. The molecular ions m/z [M‐H]− 307 and 291 were selected for the quantification in the selected ion monitoring (SIM) mode for warfarin and coumatetralyl, respectively. The linear range was 0.5∼100.0 µg/L for warfarin and coumatetralyl. The limit of quantification in serum was found to be 0.5 µg/L for each. The recoveries were between 91.9∼94.9% for warfarin and 90.9∼104.0% for coumatetralyl, the intra‐ and inter‐day RSDs for each were less than 10.1%. This method can determine trace warfarin and coumatetralyl in serum and it can be used to diagnose poisoned humans and other animals.

Rapid determination of three anticoagulant rodenticides in whole blood by liquid chromatography coupled with electrospray ionization mass spectrometry

A rapid, sensitive and selective method for the simultaneous determination of bromadiolone, flocoumafen and brodifacoum in whole blood using warfarin as internal standard (IS) by high-performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC/ESI-MS) has been developed and validated. The target compounds were extracted from the whole blood with ethyl acetate and separated on an XDB C18 column (150 mm x 2.1 mm i.d. x 5 microm) by using a mobile phase consisting of 0.2% acetic acid/methanol (12/88, v/v) at a constant flow rate of 0.50 mL/min. The analytes were detected using negative ESI-MS in the selected ion monitoring (SIM) mode. The molecular ions [M-H]- of m/z 527, 541,523 and 307 were selected for the quantification for bromadiolone, flocoumafen, brodifacoum and the IS, respectively. The calibration curves were linear (r2 > 0.995) in the concentration range of 0.50-100.00 ng/mL. The method showed a satisfactory sensitivity (0.05-0.5 ng/mL using 200 microL blood), precision (RSD < 11.9%), accuracy (recovery: 82.0-96.1%) and selectivity. This method was successfully applied to the determination of the analytes for the diagnoses of poisoned human beings and animals.

Characterization of impurities in semi-synthetic vinorelbine bitartrate by HPLC-MS with mass spectrometric shift technique

A simple and sensitive method of high-performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC/ESI-MS) was developed to separate and identify impurities in semi-synthetic vinorelbine bitartrate sample. The analytical HPLC was carried out on a reversed-phase C8 column using 0.02 M ammonium formicate buffer (pH 4.2) and methanol (46:54, v/v) as mobile phase at a flow rate of 0.8 ml/min at room temperature and a UV detection at 267 nm. The on-line HPLC/ESI-MS/MS was performed using ion trap analyzer in positive ion mode. Applying mass spectrometric shift technique to HPLC/ESI-MS/MS analysis, four impurities were identified as 18′- O-demethylvinorelbine (impurity-1), 6′- N-methylvinorelbine (impurity-2), 23- O-demethylvinoreline (impurity-3) and 17-bromovinorelbine (impurity-4), respectively, in investigated vinorelbine bitartrate sample. The four impurities, in which the impurity-1 was not reported as the semi-synthetic process impurity for vinorelbine bitartrate elsewhere, were isolated by preparative high-performance liquid chromatography. Their structures were further confirmed by means of 1D and 2D NMR spectra. Structural elucidation by spectral data was discussed.

Site-specific detection and structural characterization of the glycosylation of human plasma proteins lecithin:cholesterol acyltransferase and apolipoprotein D using HPLC/electrospray mass spectrometry and sequential glycosidase digestion.

Site-specific structural characterization of the glycosylation of human lecithin:cholesterol acyltransferase (LCAT) was carried out using microbore reversed-phase high performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC/ESIMS). A recently described mass spectrometric technique involving monitoring of carbohydrate-specific fragment ions during HPLC/ESIMS was employed to locate eight different groups of glycopeptides in a digest of a human LCAT protein preparation. In addition to the four expected N-linked glycopeptides of LCAT, a di-O-linked glycopeptide was detected, as well as three additional glycopeptides. Structural information on the oligosaccharides from all eight glycopeptides was obtained by sequential glycosidase digestion of the glycopeptides followed by HPLC/ESIMS. All four potential N-linked glycosylation sites (Asn20, Asn84, Asn272, and Asn384) of LCAT were determined to contain sialylated triantennary and/or biantennary complex structures. Two unanticipated O-linked glycosylation sites were identified at Thr407 and Ser409 of the LCAT O-linked glycopeptide, each of which contain sialylated galactose beta 1-->3N-acetylgalactosamine structures. The three additional glycopeptides were determined to be from a copurifying protein, apolipoprotein D, which contains potential N-linked glycosylation sites at Asn45 and Asn78. These glycopeptides were determined to bear sialylated triantennary oligosaccharides or fucosylated sialylated biantennary oligosaccharides. Previous studies of LCAT indicated that removal of the glycosylation site at Asn272 converts this protein to a phospholipase (Francone OL, Evangelista L, Fielding CJ, 1993, Biochim Biophys Acta 1166:301-304). Our results indicate that the carbohydrate structures themselves are not the source of this functional discrimination; rather, it must be mediated by the structural environment around Asn272.