Determination of Phenylethanoid Glycosides in Lagotis brevituba Maxim. by High-Performance Liquid Chromatography–Electrospray Ionization Tandem Mass Spectrometry

High performance liquid chromatography coupled with electrospray ionization quadrupole-time-of-flight tandem mass spectrometry was used to profile the phenylethanoid glycosides in Lagotis brevituba. A total of twenty-three phenylethanoid glycosides were characterized by comparing the retention time and fragmentation with standards, accurate mass measurements, and fragmentation at low and high collision energies. Most phenylethanoid glycosides were reported in L. brevituba for the first time. This established method may be employed for comprehensive quality control of L. brevituba.     

Preliminary Characterization of the Composition and Phenolic Fragmentation of Olive Byproducts by Gas Chromatography–Mass Spectrometry and High-Performance Liquid Chromatography–Tandem Mass Spectrometry

Olive waste is a potential resource due to its rich variety of biologically active compounds. To investigate chemical components of olive waste, the selected samples were extracted using ultrasound assisted enzyme hydrolysis and petroleum ether, ethyl acetate and n-butyl alcohol were used to obtain a series of solvent extracts. Gas chromatography–mass spectrometry analysis showed hydrocarbons, esters, acids, alcohols, and ketones present in the extracts. Some fatty acids were considered to be predominant; it is noteworthy that phenolic compounds were detected in the ethyl acetate extract fraction. Furthermore, the primary phenolic compounds were also determined by high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry. The possible fragmentation patterns have been proposed in positive and negative ion modes; the main fragment ions were observed from the loss of methyl, hydroxyl, or carboxyl groups. The compounds showed different fragmentation ions types in both positive and negative ionization modes and gave structural information on the main phenolic compounds in olive waste. The results of this study may be used to identify valuable active compounds and guide commercial applications of olive waste.     

Determination of Flavonoids in Stellaria by High-Performance Liquid Chromatography–Tandem Mass Spectrometry

The genus Stellaria (Caryophyllaceae) presents widely distributed plants often used in traditional medicine. Flavonoids are highly active plant secondary metabolites that may be involved in some of the effects of Stellaria plants. In this study, two new high-performance liquid chromatography–electrospray ionization tandem mass spectrometry (HPLC–ESI-MS-MS) methods were developed for the determination of flavonoids and isoflavonoids in plant material. The separations were performed on a reverse-phase C₁₈ column with gradient elution using methanol and water with 0.5% acetic acid as the mobile phase. Multiple reaction monitoring was used for the tandem mass spectrometry detection and the two most intensive transitions were chosen for the identification of each analyte. The limits of detection and the limits of quantification were between 0.2 and 15.0 ng/mL and 0.6 and 50.0 ng/mL. The developed methods were successfully used for the analyses of four representatives of the genus Stellaria. All the studied herbs contained luteolin and its 7-O-glycosides, naringenin, kaempferol, quercetin, its glycoside rutin, apigenin, and its 7-O-glycoside. One coumarin, scopoletin, was also found. Isoflavones were primarily represented by genistein, genistin, and ononin. Some of the analytes were detected for the first time in Stellaria sp. The findings support that these methods are suitable for analyses of plant material.     

Determination of Eupatilin in Human Plasma by High-Performance Liquid Chromatography–Tandem Mass Spectrometry

A rapid, sensitive and selective liquid chromatography-tandem mass spectrometric method (LC-MS-MS) for the determination of eupatilin in human plasma has been developed. Eupatilin and an internal standard; (S)-N-(3-{3-fluoro-4-[6-(1-methyl-1H-tetrazol-5-yl)-pyridine-3-yl]-phenyl}-2-oxo-oxazolidin-5-ylmethyl)-acetamide (DA-7867) were extracted from human plasma by liquid-liquid extractionand analyzed on a phenyl-hexyl column using the mobile phase: acetonitrile-ammonium formate (10 mM, pH 3.0) (60:40, /). Analytes were detected using electrospray ionization-tandem mass spectrometry in multiple-reaction monitoring mode. The calibration curve was linear (r = 0.999) over the concentration range: 1.00–500 ng mL^–1 with a lower limit of quantification of 1.0 ng mL^–1 using a 100 L plasma sample. The precision (CV%) of this assay ranged: 2.4–7.0%, relative error: –7.0 to +2.0%. Recoveries of eupatilin ranged: 64.3–65.0%, with that of DA-7867 (internal standard) being 87.0 ± 5.3%.     

Determination of Floridoside and Isofloridoside in Red Algae by High-Performance Liquid Chromatography–Tandem Mass Spectrometry

A facile method based on liquid chromatography coupled with triple quadrupole mass spectrometry was established to determine floridoside and isofloridoside in red algae. Correlation coefficients of the calibration curves were larger than 0.9989, indicated good linearity. Detection limits of floridoside and isofloridoside were 0.05 and 0.20 ng/mL, respectively, and the limits of quantification were 0.1 and 0.4 ng/mL. The recoveries varied from 75.7% to 76.8%, and relative standard deviations of inter-day and intra-day precision were lower than 8.5% (n = 5). The effects of sea level variations in the intertidal zone on the osmotic role of floridoside and isofloridoside concentrations in seven red algae were investigated. It was shown that algae that inhabit higher levels in the intertidal zone contained higher concentrations of floridoside and isofloridoside. The results suggest that the presence of direct sun, exposure time, and temperature influenced to the concentrations of floridoside and isofloridoside due to the osmotic pressure adjustments.     

Selective Determination of Fourteen Nitroimidazoles in Honey by High-Performance Liquid Chromatography–Tandem Mass Spectrometry

A selective method for the determination of fourteen nitroimidazoles and their hydroxy-metabolites in honey was developed based on improved molecularly imprinted solid-phase extraction followed by liquid chromatography–tandem mass spectrometry. The separation of analytes was performed on a C₁₈ column using a mobile phase of 0.1% formic acid in acetonitrile and 0.1% formic acid in water with gradient elution. The method was suitable for metronidazole, hydroxymetronidazole, dimetridazole, ronidazole, hydroxydimetridazole, ipronidazole, hydroxyipronidazole, carnidazole, menidazole, nimorazole, ornidazole, secnidazole, ternidazole, and tinidazole. The procedure was evaluated according to EU Commission Decision 2002/657/EC requirements by determining linearity, specificity, recovery, repeatability, within-laboratory reproducibility, decision limit, detection capability, matrix effects, and stability. The method determined nitroimidazoles and their hydroxy-metabolites below the recommended concentration level of 3 µg kg^?1. The decision limits and detection capabilities ranged from 0.110 µg kg^?1 to 0.387 µg kg^?1 and from 0.179 µg kg^?1 to 0.508 µg kg^?1, respectively. The results from stability tests indicated that all analyzed nitroimidazoles were stable in honey stored at 4°C for at least 28 weeks and that elevated temperature and exposure to light exposure accelerated their degradation. The method was successfully applied to the analysis of a wide variety of honey samples.     

Determination of Polyphenols in Lycium barbarum Leaves by High-Performance Liquid Chromatography–Tandem Mass Spectrometry

High-performance liquid chromatography coupled with high-resolution mass spectrometry was used for the determination of polyphenols in Lycium barbarum leaves. Twenty compounds extracted by methanol–water were tentatively identified that included chlorogenic acids, flavonoids, and phenolic acids. Neochlorogenic acid, chlorogenic acid, cryptochlorogenic acid, isochlorogenic acid B, isochlorogenic acid A, and isochlorogenic acid C were identified in Chinese cultivated L. barbarum leaves for the first time. Caffeic acid and isoquercitrin were also present. The concentrations of these compounds in L. barbarum leaves were determined. The results showed that all analytes had linear calibration relationships with limits of detection from 0.318 to 3.35?ng mL^?1. The polyphenols and flavonoids in L. barbarum leaves provided strong 2,2-diphenyl-1-picrylhydrazyl radical-scavenging capacity (IC₅₀ of 23.1?±?0.4 to 26.0?±?0.4?µg mL^?1). This method is suitable for the determination of polyphenols in L. barbarum leaves, which provide polyphenols with suitable antioxidant activity.     

Elucidation of O-Phosphoryl and N-Phosphoryl Amino Acids by Electrospray Ionization Tandem Mass Spectrometry

Mass spectroscopic characteristics of phosphoryl amino acids were studied in detail by positive and negative electrospray ionization mass spectrometry (ESI-MS) in conjunction with tandem mass spectrometry (MS/MS). Besides N-diisopropyloxyphosphoryl amino acids (N-DIPP-AA), O-phospho- and O-diisopropyloxyphosphoryl amino acids (O-DIPP-AA) were studied and compared to N-DIPP-AA. The fragmentation pathways of [M H]^ ,[M Na]^ and [M-H]^- ions of phosphoryl amino acids were summarized. In addition to several similar patterns, each of them showed its characteristic fragmention.     

Determination of Nitrofurans in Chicken Feed by High-Performance Liquid Chromatography–Tandem Mass Spectrometry

Liquid chromatography with tandem mass spectrometry was used for the determination of nitrofurantoin, nitrofurazone, furazolidone, and furaltadone in chicken feed. The nitrofurans were extracted with phosphate buffer (pH 7) and sodium chloride. Proteins and lipids were removed with acetonitrile and hexane before purification with ethyl acetate, dilution in 1:1 acetonitrile-5 millimolar ammonium acetate at pH 7.3, and filtration prior to analysis. The limits of detection were 1.69, 1.74, 2.01, and 1.45 microgram per kilogram for nitrofurantoin, nitrofurazone, furazolidone, and furaltadone, respectively. The mean recoveries were between 84.6 and 110.6 percent. The method was employed to determine nitrofurans in chicken feed.     

Preconcentration and Determination of 2,6-Dichlorobenzamide in Water by Stir Bar Extraction and High-Performance Liquid Chromatography–Tandem Mass Spectrometry

Polyacrylate stir bar sorptive extraction (SBSE) of 2,6-dichlorobenzamide followed by liquid desorption and analysis by liquid chromatography–tandem mass spectrometry using electrospray ionization is presented. The parameters influencing the methods were optimized and included a stirring speed of 500 revolutions per minute, an extraction time of two hours, a sample volume of 15 milliliters, 30 percent NaCl, and liquid desorption using acetonitrile under ultrasonication for fifteen minutes. A reverse phase C₁₈ column was used with isocratic elution (50 percent acetonitrile and 50 percent 5 millimoles per liter aqueous ammonium acetate buffer at pH 2.4), a flow rate of 0.4 milliliter per minute, and an injection volume of 10 microliters. Quantitative analysis was carried out by multiple reaction monitoring using positive polarity. The developed method required low sample volume (15 milliliters) and provided satisfactory figures of merit with a limit of detection of 0.002 microgram per liter, a limit of quantification of 0.006 microgram per liter, and good precision (inter-day relative standard deviation below 10 percent). The polyacrylate Twister was employed for up to twenty-five extraction and liquid desorption cycles. The applicability of the method was assessed by analyzing ground water collected at five sites in North Italy. The concentrations of 2,6-dichlorobenzamide were between 0.070 and 0.282 microgram per liter. Preliminary results on the use of polar stir bars for the determination of other polar pesticides in water are also provided.     

Rapid Determination of Coumatetralyl in Human Serum by High‐Performance Liquid Chromatography Coupled with Electrospray Ionization Tandem Mass Spectrometry

Abstract

A rapid, sensitive, and selective high‐performance liquid chromatography‐tandem mass spectrometric method (HPLC‐MS‐MS) for the determination of coumatetralyl in human serum using warfarin as an internal standard has been developed and validated. Coumatetralyl and the internal standard were extracted from the human serum samples by liquid‐liquid extraction with ethyl acetate, followed by separation on a XDB C₁₈ reversed‐phase column (150 mm×2.1 mm i.d., 5 µm) using a mobile phase consisting of acetic acid‐ammonium acetate (5 mmol/L, pH=4.5)/methanol (20:80, v/v) at a constant flow rate of 0.40 mL/min. Coumatetralyl and the internal standard were ionized by negative ion pneumatically assisted electrospray and detected in the multiple‐reaction monitoring mode using precursor→product ion combinations at m/z 291→247 and 307→161, respectively. The calibration curve was linear (r²=0.9945) in the concentration range of 0.5～100.0 ng/mL, with a lower limit of quantification of 0.5 ng/mL in human serum. Intra‐ and inter‐day relative standard deviations were less than 6.3 and 11.0%, respectively. The mean extraction recovery was 87.9% for coumatetralyl and 90.1% for the internal standard. This method is found to be able to determine trace coumatetralyl in human serum and can be used for the diagnosis of poisoned human beings.     

Determination and Characterization of the Uptake of Voriconazole in Human Lung Epithelial Cells by High-Performance Liquid Chromatography–Tandem Mass Spectrometry

Voriconazole is used to prevent invasive pulmonary aspergillosis. However, little is known about the concentrations of voriconazole in human lung epithelial cells (A549), which is the target for preventing invasive pulmonary aspergillosis. The goal of this study was to develop a high-performance liquid chromatography–tandem mass spectrometry method to quantify voriconazole in A549 cells. A triple-quadrupole mass spectrometer in selected reaction monitoring mode was used with positive electrospray ionization. The total duration of each run was 5?min. The calibration curves fit a least squares model for the voriconazole concentration ranging from 0.625 to 160?ng/mL. Intraday and interday coefficients of variation were less than 10%. Recoveries at the concentrations of the quality control samples where greater than 85%, and the matrix effects showed that the ratios of the peak response exhibited a 15% suppression of the signal in the matrix compared to water. Voriconazole may penetrate A549 cells. However, the voriconazole uptake was slow in A549 cells, reaching a plateau at 2?h, where the dose-dependent intracellular voriconazole concentrations were 1.98?±?0.38, 4.43?±?0.54, and 8.14?±?0.52?ng/mg protein for extracellular voriconazole concentrations of 5, 10, and 20?µg/mL, respectively. The uptake of voriconazole by A549 cells was linear at extracellular concentrations from 0 to 20?µg/mL. This study established a rapid and sensitive method suitable for determining voriconazole in A549 cells and described the kinetic properties of the absorption of voriconazole by A549 cells.     

Determination of Methylphosphonic Acid in Human Blood Plasma by High-Performance Liquid Chromatography–Tandem Mass Spectrometry

Using high-performance liquid chromatography combined with tandem mass spectrometric detection, an approach has been developed for the determination of the most stable nerve agent biomarker, methylphosphonic acid, in human blood plasma. The proposed method is based on the derivatization of methylphosphonic acid with p-bromophenacyl bromide. The optimization of conditions for human plasma sample preparation, mass spectrometric detection conditions, and gradient elution program has been performed. The proposed approach has demonstrated satisfactory reproducibility and selectivity of the determination; the limit of detection for methylphosphonic acid in human plasma was 3 ng mL^–1.     

Analysis of the Heterocyclic Aromatic Amines in Cigarette Smoke by Liquid Chromatography–Tandem Mass Spectrometry

In this paper, a sensitive accurate method for the determination of heterocyclic aromatic amines (HAAs) in cigarette smoke has been developed and validated using solid-phase extraction coupled with liquid chromatography–tandem mass spectrometry. A calibration curve was obtained with representative cigarette smoke using the standard addition method to compensate for matrix effects because the smoke of different cigarettes shows similar matrix effects. With this method, the accuracy of the method can be improved using a common analog of HAAs, which will greatly reduce the expense of using an isotope-labeled internal standard. Validation results showed that the method has high sensitivity (quantification limits of 0.08–0.56 ng cig⁻¹), good reproducibility (RSD 6.37–9.31 %) and satisfactory recoveries (81.0–111 %). With this method, the emissions of HAAs in 30 commercial cigarette samples were analyzed and compared.

     

Characterization of the Retro-[3+2] Reaction of Protonated 2,3′-Bisindolylmethanes by Electrospray Ionization–Tandem Mass Spectrometry

Twelve 2,3′-bisindolylmethanes with various substituents were investigated using electrospray ionization quadrupole time-of-flight tandem mass spectrometry in positive ion mode. A retro-[3+2] reaction was observed in the collision-induced dissociation spectra of protonated 2,3′-bisindolylmethanes for the first time. The mechanism of retro-[3+2] reaction was concerted or stepwise. For the concerted pathway, carbon–carbon bonds of a protonated compound simultaneously cracked and the m/z 208 ion ([C₁₅H₁₀D₂N]⁺) was observed with hydrogen–deuterium exchange labeling. The stepwise pathway goes through 1,3-hydrogen migration twice and the m/z 208 ion ([C₁₅H₁₀D₂N]⁺) and m/z 207 ion ([C₁₅H₁₁DN]⁺) were detected with deuterium labeling. In the deuterium-labeled tandem mass spectrum for one compound, only the peak at m/z 208 was present at high abundance, suggesting that the concerted pathway is more likely. In addition, the substituents have no obvious trends on the ratios of the product intensity to the base intensity, further supporting the concerted pathway.     

Determination of Phytate in Urine by High-Performance Liquid Chromatography–Mass Spectrometry

An indirect method is described for determination of phytate in human urine. The method is based on hydrolysis of the phytate and determination of myo-inositol, one of the hydrolysis products. Chromatographic separations were performed on an Aminex HPX-87C column with Milli-Q water as mobile phase; 5 mM ammonium acetate was added post-column. The detector counted positive ions by monitoring m/z=198, which corresponds to the adduct of myo-inositol with the ammonium cation. The relative standard deviations obtained for standards containing 0.5, 1, and 1.5 mg L^–1 phytate were 4.1, 3.0, and 2.7% respectively (n=5). The limit of detection was 60 g L^–1. Different urine samples were analyzed both by this method and by an alternative analytical method based on GC–MS. The results from both methods were comparable.     

Analysis of the Heterocyclic Aromatic Amines in Cigarette Smoke by Liquid Chromatography–Tandem Mass Spectrometry

In this paper, a sensitive accurate method for the determination of heterocyclic aromatic amines (HAAs) in cigarette smoke has been developed and validated using solid-phase extraction coupled with liquid chromatography–tandem mass spectrometry. A calibration curve was obtained with representative cigarette smoke using the standard addition method to compensate for matrix effects because the smoke of different cigarettes shows similar matrix effects. With this method, the accuracy of the method can be improved using a common analog of HAAs, which will greatly reduce the expense of using an isotope-labeled internal standard. Validation results showed that the method has high sensitivity (quantification limits of 0.08–0.56 ng cig^?1), good reproducibility (RSD 6.37–9.31 %) and satisfactory recoveries (81.0–111 %). With this method, the emissions of HAAs in 30 commercial cigarette samples were analyzed and compared.     

Determination of Meropenem and Ertapenem in Lagoon Water,Bedding Soil,and Silage by High-Performance Liquid Chromatography–Tandem Mass Spectrometry

A simple and sensitive method was developed and validated by high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) for the determination of meropenem and ertapenem in environmental materials from dairy farms. The limits of quantification were between 1 and 20?ng/mL for the analytes in lagoon water, bedding soil, and silage. The recoveries for meropenem and ertapenem exceeded 80%. The intraday and interday precision values were less than 15% in all samples. The validated method was employed to determine the meropenem and ertapenem in environment samples obtained from dairy farms.     

Simultaneous Determination of Flonicamid and its Metabolites in Tea by Liquid Chromatography–Tandem Mass Spectrometry

An analytical method was established to simultaneously quantify flonicamid and its metabolites 4-trifluoromethylnicotinic acid (TFNA), N-(4-trifluoromethylnicotinoyl) glycine (TFNG), and 4-trifluoromethylnicotinamide (TFNA-AM) in tea using orthogonal experimental design and liquid chromatography–tandem mass spectrometry (LC–MS/MS). Residues were extracted from the samples with acetonitrile containing 1% acetic acid and were purified with graphitized carbon black. The linearity of the method was excellent in the concentration range of 0.01–10?µg/mL, producing correlation coefficients greater than 0.996 for the target compounds. The limits of detection and quantification of all analytes in tea were 0.0013–0.013?mg/kg and 0.004–0.040?mg/kg, respectively. The average recoveries of flonicamid, TFNA, TFNG, and TFNA-AM ranged from 75.14 to 92.72%, with intra- and interday relative standard deviations of 1.07–9.75%. The proposed method was successfully applied to the terminal residue determination of flonicamid and its metabolites in dry tea processed from three field trials’ fresh samples. The determined total terminal residue concentrations of flonicamid 10?days after the last application at all three sites were below the maximum residue limit (MRL) set by the European Union (0.1?mg/kg) and the residues in all samples were lower than the MRL established by the United States Environmental Protection Agency (EPA) (8?mg/kg). This method may be used to meet the requirements for the determination of flonicamid and its metabolites that could provide guidance for establishing a MRL for flonicamid in tea in China.     

Analysis of Norditerpenoid Alkaloids. Extracted from Aconitum sinomantanum Nakai by Electrospray Ionization Tandem Mass Spectrometry

Introduction AconitumsinomantanumNakai(GaowutouinChi nese)isdistributedinthenorthwesternareaofChina,anditsroots(RAS)areexternallyusedasakindof folkmedicineinChina.Themainactiveconstituentsof RASarenorditerpenoidalkaloids.Themajoralkaloid,lappaconitine,was…