Electrospray Ionization Source Research Articles

Determination of eugenitin in mouse blood by ultra-performance liquid chromatography-tandem mass spectrometry and its application to a pharmacokinetic study

Abstract Eugenitin is a non-volatile chromone derivative which is always found in dried flower buds of Syzygium aromaticum L. (Merr.) & L.M. Perry. Until now, there were no reports about the pharmacokinetics of eugenitin in biological fluids. A UPLC-MS/MS method developed to determine eugenitin in mouse blood. The blood samples were prepared by protein precipitation with acetonitrile. Chrysin (internal standard, IS) and eugenitin were gradient eluted by mobile phase of acetonitrile and water (0.1% formic acid) in a BEH C18 column. The multiple reaction monitoring (MRM) of m/z 221.1→206.0 for eugenitin and m/z 255.1→152.9 for IS with an electrospray ionization (ESI) source was used for quantitative detection. The calibration curve ranged from 0.5 to 500 ng/mL (r > 0.995). The accuracy ranged from 98 to 113%, the precision was less than 12%, and the matrix effect was between 86 and 94%, the recovery was better than 81%. The developed method was successfully used for pharmacokinetics of eugenitin in mice after intravenous (5 mg/kg) and oral (20 mg/kg) administration, and the absolute availability of eugenitin was 12%.

Hybrid solid-phase extraction to overcome interference due to phospholipids for determination of neratinib in human plasma using UPLC-MS/MS.

A reliable and robust bioanalytical method was developed to quantify neratinib, a tyrosine kinase inhibitor in human plasma, using UPLC-MS/MS. The extraction of neratinib and its deuterated internal standard, neratinib-d6, was successfully performed on hybrid solid-phase extraction ultra-cartridges to remove the interference of phospholipids and proteins. Chromatographic analysis was performed on a UPLC BEH C18 (50× 2.1 mm, 1.7 μm) column using 0.1% formic acid and acetonitrile under gradient conditions. The total analysis time was 1.5min. Neratinib was quantified using electrospray ionization source operated in the positive-ion multiple reaction monitoring mode. The mass transitions of neratinib and neratinib-d6 were m/z 557.3/112.1 and m/z 563.1/118.2, respectively. The linear concentration range for neratinib was 0.5-500 ng/mL, which adequately covers concentration levels expected in real subject samples. The assay was extensively validated for various validation parameters following standard guidelines for a bioanalytical assay. The intra- and inter-batch precision was ≤4.6%, and neratinib was found to be stable under various stability conditions. The mean internal standard-normalized matrix factor and recovery were 0.997 and 95.4%, respectively. The validated method was successfully applied to a pharmacokinetic study in healthy subjects with different doses.

LC–MS/MS Assay of Fluoropezil and Its Two Major Metabolites in Human Plasma: An Application to Pharmacokinetic Studies

Background: LC-MS/MS methods were developed for pharmacokinetic analysis and verified to measure fluoropezil, a new AchE inhibitor for Alzheimer's disease treatment, and its two primary metabolites (N-debenzyl fluoride fluoropezil [M1] and N-oxidized fluoropezil [M11]) in human plasma. Methods & results: Analytes were extracted from 50μl plasma using protein precipitation and separated by HPLC using a bridged ethyl hybrid column and gradient elution procedure. Analytical detection was performed with a triple quadrupole mass spectrometer and electrospray ionization source in multiple reaction monitoring mode. The LC-MS/MS method was fully validated. The quantification linear ranges were 0.100-50.0ng/ml (fluoropezil), 0.0500-25.0ng/ml (M1) and 0.0500-25.0ng/ml (M11). Conclusion: A sensitive, reliable LC-MS/MS method was established and used successfully to explore the pharmacokinetics of fluoropezil.

Simultaneous determination of 11 neurotransmitters in brain microdialysis samples from rats by UPLC-MS/MS

This study established a method for simultaneous determination of 11 neurotransmitters, such as acetylcholine, glutamic acid, glycine, and norepinephrine from rat brain microdialysis samples using UPLC-MS/MS. A total of 20 μL of rat brain dialysate was diluted with 60 μL of acetonitrile-water(4∶1) and centrifuged for 10 min at 10 000 r·min~(-1),and 5 μL was injected into UPLC-MS/MS system for assay. Chromatographic separation was performed on a Waters ACQUITY BEH amide column(2.1 mm×100 mm, 1.7 μm) with gradient elution using acetonitrile/0.2% formic acid-water as mobile phases with a flow rate of 0.35 mL·min~(-1) and column temperature of 35 ℃. The eluate was detected by multiple-reaction monitoring(MRM) scanning with an electrospray ionization source operating in the positive ionization mode with an analysis duration of 3.5 min. The relationship between the recovery rate of 11 neurotransmitters and the perfusion rate or the concentration of neurotransmitters was investigated. Furthermore, the effects of puerarin alone or combined with borneol on the content of 11 neurotransmitters in the striatum of rats were investigated. The results showed the calibration curves displayed good linear regression with coefficients all greater than 0.99 and the lower limit of quantification(LLOQ) less than 12.5 nmol·L~(-1) for each analyte. The within-run and between-run precision(RSD) of the 11 neurotransmitters at low, medium, and high levels was less than 9.3%, and the relative error of the accuracy ranged from-8.4% to 9.5%. The stability, recovery, and matrix effects were in line with the biological sample analysis requirements. As revealed by experimental results, the levels of most neurotransmitters in the brain striatum changed significantly after rats were treated with puerarin as compared with the conditions in the blank group. Except for dopamine and norepinephrine, the degree of changes of other neurotransmitters in the combination group(borneol and puerarin) was less than that of the puerarin group. The established UPLC-MS/MS method could be applied to the quantitative determination of 11 neurotransmitters in microdialysis samples, providing an efficient and useful tool to study neurotransmitter changes in animal models of health and diseases.

Determination of meloxicam in human plasma by ultra-high-performance liquid chromatography-tandem mass spectrometry and its application in a pharmacokinetic study.

A rapid, selective and sensitive ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was developed to detect meloxicam in human plasma. A triple quadrupole tandem mass spectrometer equipped with an electrospray ionization source was used in positive ion mode. Protein precipitation with acetonitrile was used for sample preparation. Meloxicam and 13 C6 -meloxicam internal standard were analyzed on an Acquity CSH C18 column with a mobile phase of acetonitrile and water in 0.1% formic acid using a gradient program for separation. The retention time of meloxicam was 1.1min and the total run time was only 2.0min. Detection was performed in multiple reaction monitoring mode using an electrospray ionization source with optimized mass spectrometry parameters. The calibration curves were linear in the range 10.0-3.00 × 103 ng/ml (r ≥ 0.99). The within-run and between-run RSDs were ≤14.8%. The within-run and between-run REs ranged from -4.6 to 10.7%. There was no significant matrix effect, and the recovery rate was high. This method was fully validated, including reinjection reproducibility in human plasma. The method was applied to the pharmacokinetic study. All of the incurred sample reanalysis methods met the criteria.

Simultaneous Characterization and Determination of Warfarin and Its Hydroxylation Metabolites in Rat Plasma by Chiral Liquid Chromatography-Tandem Mass Spectrometry.

Warfarin is extensively used for venous thromboembolism and other coagulopathies. In clinical settings, warfarin is administered as a mixture of S- and R-warfarin, and both enantiomers are metabolized by multiple cytochrome P450 enzymes into many hydroxylation metabolites. Due to the high degree of structural similarity of hydroxylation metabolites, their profile possesses significant challenges. The previous methods generally suffer from lacking baseline resolution and/or involving complex analysis processes. To overcome this limitation, a sensitive and specific chiral liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to simultaneously identify warfarin and hydroxywarfarins enantiomers. Chromatographic separation was achieved on a HYPERSIL CHIRAL-OT column. The mass spectrometric detection was carried out in negative ion MRM mode with electrospray ionization source. The optimized method exhibited satisfactory within-run and between-run accuracy and precision with lower limit of quantification (LLOQ) of 10.0 ng/mL and 1.0 ng/mL for warfarin and 7-, 10(R)-OH-warfarin enantiomers, respectively. Linear responses of warfarin enantiomers and 7-, and 10(R)-OH-warfarin enantiomers in rat plasma were observed over the range of 10.0–8000 ng/mL, and 1.00–800 ng/mL, respectively. The analytes were shown to be stable in various experimental conditions in rat plasma. Protein precipitation was used in sample preparation without a matrix effect. This method was successfully applied to pharmacokinetic study for quantitating the concentrations of S/R-warfarin, S/R-7-OH-warfarin, and S/R-10(R)-OH-warfarin and relatively quantitating 3′-, 4-, 6-, and 8-OH warfarin enantiomers in rat plasma.

Navigate Flying Molecular Elephants Safely to the Ground: Mass-Selective Soft Landing up to the Mega-Dalton Range by Electrospray Controlled Ion-Beam Deposition.

The prototype of a highly versatile and efficient preparative mass spectrometry system used for the deposition of molecules in ultrahigh vacuum (UHV) is presented, along with encouraging performance data obtained using four model species that are thermolabile or not sublimable. The test panel comprises two small organic compounds, a small and very large protein, and a large DNA species covering a 4-log mass range up to 1.7 MDa as part of a broad spectrum of analyte species evaluated to date. Three designs of innovative ion guides, a novel digital mass-selective quadrupole (dQMF), and a standard electrospray ionization (ESI) source are combined to an integrated device, abbreviated electrospray controlled ion-beam deposition (ES-CIBD). Full control is achieved by (i) the square-wave-driven radiofrequency (RF) ion guides with steadily tunable frequencies, including a dQMF allowing for investigation, purification, and deposition of a virtually unlimited m/z range, (ii) the adjustable landing energy of ions down to ∼2 eV/z enabling integrity-preserving soft landing, (iii) the deposition in UHV with high ion beam intensity (up to 3 nA) limiting contaminations and deposition time, and (iv) direct coverage control via the deposited charge. The maximum resolution of R = 650 and overall efficiency up to Ttotal = 4.4% calculated from the solution to UHV deposition are advantageous, whereby the latter can be further enhanced by optimizing ionization performance. In the setup presented, a scanning tunneling microscope (STM) is attached for in situ UHV investigations of deposited species, demonstrating a selective, structure-preserving process and atomically clean layers.

Simultaneous determination of five cytotoxic drugs in surface wiped samples using liquid chromatography and tandem mass spectrometry for the control of environmental contamination in a comprehensive cancer centre

ABSTRACT The most common strategy to assess the occupational exposure risk to hazardous drugs in cancer healthcare settings is by monitoring environmental contamination of work surfaces with cytotoxic drugs. Healthcare workers, especially pharmacy technicians and nursing, handle multiple hazardous drugs, so they really may be exposed to different cytotoxic drugs simultaneously. Therefore, simultaneous determination of several cytotoxic drugs provides a more accurate assessment of the real occupational exposure risk in healthcare settings. Our objective was to develop a method for surface wipe sampling and a quantification method for five cytotoxic drugs commonly used in chemotherapy treatments preparation: cyclophosphamide, 5-fluorouracil, epirubicin, gemcitabine and paclitaxel. Wiping procedure was performed using cellulose swabs moistened in a mixture solution containing acetonitrile, water, 2-propanol and methanol with 0.1% formic acid. The obtained extracts were simultaneously quantified by an LC-MS/MS method. Chromatographic separation was achieved using an Acquity UPLC® BEH C18 column by a gradient elution, and detection was carried out in multiple reaction monitoring mode with electrospray source operating in positive and negative ion mode. Wipe and extraction procedures developed were simple and easy to implement, being able to recover the cytotoxic target drugs from two type surfaces sampling, stainless steel surfaces and polyethylene bags surfaces. The analytical method was linear over the calibration range and the limits of quantification were 1 ng/mL for cyclophosphamide, gemcitabine and paclitaxel, 1.5 ng/mL for epirubicin and 5 ng/mL for 5-fluorouracil. Intra- and inter-day precision and accuracy for all drugs were always inferior to 15%. This work provides a suitable procedure to identify cytotoxic contamination on work surfaces, being a useful tool to monitor occupational exposure risk to hazardous drugs, as well as to evaluate the effectiveness of decontamination protocols applied and hazardous drug handling protocols in cancer healthcare settings.

Polymers of micro(nano) plastic in household tap water of the Barcelona Metropolitan Area

Microplastics (MPLs) are emerging persistent pollutants affecting drinking water systems, and different studies have reported their presence in tap water. However, most of the work has a focus on particles in the 100–5 µm range.Here, a workflow to identify and quantify polymers of micro and nanoplastics (MNPLs), with sizes from 0.7 to 20 µm in tap water, is presented. The analytical method consisted of water fractionated filtration followed by toluene ultrasonic-assisted extraction and size-exclusion chromatography, using an advanced polymer chromatography column coupled to high-resolution mass spectrometry with atmospheric pressure photoionization source with negative and positive ionization conditions (HPLC(APC)-APPI(±)-HRMS) and normal phase chromatography HILIC LUNA® column and electrospray ionisation source in positive and negative mode (HPLC(HILIC)-ESI(±)-HRMS). The acquisition was performed in full scan mode, and the subsequent tentative identification of MNPLs polymers has been based on increasing the confirmation level, including the characterisation of monomers by using Kendrick Mass Defect (KMD) analysis, and confirmation and quantification using standards. This approach was applied to assess MNPLs in tap water samples of the Barcelona Metropolitan Area (BMA), that were collected from August to October 2020 from home taps of volunteers distributed in the 42 postal codes of the BMA.Polyethylene (PE), polypropylene (PP), polyisoprene (PI), polybutadiene (PBD), polystyrene (PS), polyamide (PA), and polydimethylsiloxanes (PDMS) were identified. PE, PP, and PA were the most highly detected polymers, and PI and PBD were found at the highest concentrations (9,143 and 1,897 ng/L, respectively).A principal component analysis (PCA) was conducted to assess differences in MNPLs occurrence in drinking water, that was provided from the two drinking water treatment plants (DWTPs) suppliers. Results showed that no significant differences (at 95% confidence level) were established between the drinking water supplies to the different areas of the BMA.

A novel sensitive analytical method for the simultaneous analysis of vancomycin and teicoplanin in human urine via single high‐performance liquid chromatography coupled with photodiode array and mass spectrometry in series

Analysis of vancomycin and teicoplanin in biological fluids is vital since they are used in the treatment of hospital infections. For the determination of both glycopeptides in urine, a sensitive and accurate analytical method using high‐performance liquid chromatography coupled with photodiode array and mass spectrometry was developed and validated. This research work is the first attempt to develop a chromatographic method for the determination of two glycopeptides with structural similarities. Moreover, the used non‐invasive sampling method is an advantage of this research effort, especially when the blood sampling is difficult. Urine was treated with acetonitrile and 5% trichloroacetic acid, followed by solid‐phase extraction. The chromatographic separation was established at a C18 column (4.6 × 150 mm, 5 μm), using a gradient method and an electrospray ionization source in a positive mode. The linearity of the method was R 2≥ 0.9900. The precision was estimated with a maximum coefficient of variation below 15%, while the accuracy ranged from 64 to 121%. The limit of detection and quantification of both glycopeptides ranged from 0.076 up to 0.33 mg/L and 0.33 up to 2.1 mg/L, respectively, showing the same sensitivity as the triple quadrupole mass spectrometry, which is the most frequently used method.

Multiscale modeling of electrospray ion emission

A multi-scale approach to electrospray ion source modeling has been developed. The evolution of a single-emitter electrospray plume in a pure ionic regime is simulated with a combination of electrohydrodynamic fluids and n-body particle modeling. Simulations are performed for the ionic liquid, EMI-BF4, firing in a positive pure-ion mode. The metastable nature of ion clusters is captured using an ion fragmentation model informed by molecular dynamics simulations and experimental data. Results are generated for three operating points (120, 324, and 440 nA) and are used to predict performance relevant properties, such as the divergence angle and the extractor surface impingement rate. Comparisons to experimental data recorded at similar operating points are provided.

Separation and characterization of sulfonates in dissolved organic matter from industrial wastewater by solid phase extraction and high-resolution mass spectrometry.

Electrospray ionization(ESI) source combined with high-resolution mass spectrometry (HRMS) has been successfully used to characterize the molecular composition of dissolved organic matter (DOM) in industrial wastewaters. However, sulfonates are commonly presenting in these wastewaters and showing strong ionization suppression for the ESI analysis, which seriously affects the characterization of other DOM components. In this paper, a novel method based on polymer anion exchange (PAX) solid phase extraction (SPE) was proposed to separate DOMs from petroleum refining and coal coking wastewaters into hydrophobic neutral, hydrophobic acids, and hydrophobic strong acids; the fractions were analyzed by negative-ion ESI Fourier transform ion cyclotron resonance mass spectrometry. The results show that PAX-SPE separated sulfonates from wastewaters and enabled the molecular characterization of oxygen-containing compounds, which are the major component of DOM in the wastewaters. Semi-quantitative analysis of sulfonates in the wastewaters was carried out and the results show that these compounds account for 11% and 2% in total organic carbon for the refinery and coal coking wastewaters, respectively. PAX-SPE with stepwise elution and followed by high-resolution mass spectrometry analysis enables a comprehensive characterization for the molecular composition of industrial wastewater DOM. The method has potential for extensive application and the results are instructive for the understanding of the molecular composition of DOM in industrial wastewaters.

Untargeted Metabolomics Identifies a Novel Panel of Markers for Autologous Blood Transfusion.

Untargeted metabolomics was used to analyze serum and urine samples for biomarkers of autologous blood transfusion (ABT). Red blood cell concentrates from donated blood were stored for 35–36 days prior to reinfusion into the donors. Participants were sampled at different time points post-donation and up to 7 days post-transfusion. Metabolomic profiling was performed using ACQUITY ultra performance liquid chromatography (UPLC), Q-Exactive high resolution/accurate mass spectrometer interfaced with a heated electrospray ionization (HESI-II) source and Orbitrap mass analyzer operated at 35,000 mass resolution. The markers of ABT were determined by principal component analysis and metabolites that had p < 0.05 and met ≥ 2-fold change from baseline were selected. A total of 11 serum and eight urinary metabolites, including two urinary plasticizer metabolites, were altered during the study. By the seventh day post-transfusion, the plasticizers had returned to baseline, while changes in nine other metabolites (seven serum and two urinary) remained. Five of these metabolites (serum inosine, guanosine and sphinganine and urinary isocitrate and erythronate) were upregulated, while serum glycourdeoxycholate, S-allylcysteine, 17-alphahydroxypregnenalone 3 and Glutamine conjugate of C6H10O2 (2)* were downregulated. This is the first study to identify a panel of metabolites, from serum and urine, as markers of ABT. Once independently validated, it could be universally adopted to detect ABT.

Simultaneous determination of abiraterone and its five metabolites in human plasma by LC-MS/MS: Application to pharmacokinetic study in healthy Chinese subjects

In this study, a rapid, simple and sensitive liquid chromatography–tandem mass spectrometry (LC-MS/MS) method was developed and validated to simultaneously quantify abiraterone (ABI), a widely used anti-metastatic castration-resistant prostate cancer drug, and its metabolites comprising Δ4-abiraterone (D4A), 3-keto-5α-abiraterone (5αA), abiraterone N-oxide (A-NO), abiraterone sulfate (A-Sul) and abiraterone N-oxide sulfate (A-NO-Sul) in human plasma. The analytes were extracted by protein precipitation with acetonitrile and ideal chromatographic separation was achieved on ACE-C18 column (2.1 × 50 mm, 5 µm) using a gradient elution. Triple Quad™ 6500+ mass spectrometer equipped with an electrospray ionization (ESI) source was used and the multiple reaction mode (MRM) was performed. In terms of method validation, good linearity was observed in preassigned validated concentration range for each analyte of interest. Both intra- and inter-batch accuracy was within the range of 87.6–113.8% for all analytes, while intra- and inter-batch precision was below 14.0%. Additionally, both low matrix effects and high recovery were obtained. All analytes remained stable in human plasma at room temperature for 4 h, on wet ice for 8 h, at − 80 °C for 42 d, over three freeze-thaw cycles and under auto-sampler temperature (4 °C) for 48 h post sample preparation. Subsequently, the validated LC-MS/MS method was applied for pharmacokinetic study in healthy Chinese volunteers following an oral dose of 250 mg abiraterone acetate tablet under fasted conditions. Our study for the first time reported the pharmacokinetic parameters of the ABI metabolites in Chinese subjects.

High-Throughput Screening Using a Synchronized Pulsed Self-aspiration Vacuum Electrospray Ionization Miniature Mass Spectrometer.

With the advantages of rapid analysis, high sensitivity, and multicomponent identification, mass spectrometry (MS) is recognized as an appealing choice for high-throughput screening (HTS) analysis. Aiming at the small size, simple operation, and adequate performance, the development of miniature mass spectrometers has made great progress over the last 2 decades. Besides the essential analytical performance, simple operation and HTS capability are two other crucial features desired in miniature MS instruments. In this paper, an induced self-aspiration vacuum electrospray ionization source (ISA-VESI) was developed and coupled to a miniature ion trap mass spectrometer. A special timing sequence was designed to synchronize all the operation steps in each measurement, including dual-pulse sample injection, multipulse gas injection, MS analysis, and the movement of the homemade HTS platform used as the sampler. Then, the automatic high-throughput analysis of multiple samples can be accomplished with close coordination among the sample delivery, the sample introduction and ionization, and the ion trap operation. The measurement time of each ISA-VESI-MS analysis was about 7 s, with a sample consumption of less than 100 nL.

First report of flavonoids from leaves of Machaerium acutifolium by DI-ESI-MS/MS

The aqueous fraction obtained by the partition of the ethanolic extract from leaves of Machaerium acutifolium (Fabaceae-Papilionoideae) was analyzed by high-performance liquid chromatography with a diode array detector (HPLC-DAD) and direct insertion in a mass spectrometer with an ion trap analyzer equipped with an electrospray ionization source (DI-ESI-MS/MS). The chemical analysis of the extract demonstrated the occurrence of eight flavonols ( 1 – 8 ), two isoflavonoids ( 9 and 10 ) and one biflavonoid ( 11 ). These compounds are being reported for the first time from M. acutifolium . The aqueous fraction showed 28.37 ± 0.94% of AA in assay on DPPH and 151.70 ± 9.44 GAE of the total phenolic content.

Determination of 19 chlorophenols in fish by QuEChERS-gas chromatography-mass spectrometry

大量含氯农药、次氯酸消毒水以及水产品杀虫剂和杀菌剂的广泛使用,使鱼类容易受到氯酚类化合物的污染,因而建立鱼肉中氯酚类化合物的检测方法十分重要。建立了QuEChERS结合气相色谱-质谱法同时检测鱼肉中19种氯酚类化合物的分析方法。19种氯酚类化合物选用DB-5MS毛细管色谱柱(30 m×0.25 mm×0.25 μm),载气流速1 mL/min进行分离,可以得到很好的峰形。前处理采用改良的QuEChERS方法,通过对提取剂的种类和剂量、净化剂的种类和剂量,以及衍生条件中的衍生温度、衍生时间和衍生剂用量等进行优化,确定最优的前处理方法。选择10 mL乙酸乙酯作为提取剂,500 mg的C18作为净化剂,加入3 g氯化钠和5 g无水硫酸镁,过0.22 μm的有机滤膜,加入50 μL的硅烷化衍生剂在45 ℃条件下衍生30 min,用EI源测定,选择离子监测模式,以外标法定量。19种氯酚类化合物在0.4~10 μg/L范围内具有良好的线性关系,相关系数R2大于0.998,方法定量限为0.04~0.16 μg/kg。空白基质不同加标水平的回收率为70.6%~115.0%,相对标准偏差为2.6%~10.5%。将建立的方法应用于实际样品的检测分析,结果显示,各种鱼肉中均有不同程度的氯酚类化合物检出,其中,黄花鱼检出的氯酚类化合物总量最大,为8.74 μg/kg;其次为鲫鱼7.59 μg/kg;米鱼的检出量最少,为1.59 μg/kg。所建立的方法简化了样品的前处理步骤,操作简单,方法灵敏度高、重复性好,可满足鱼肉中19种氯酚类化合物的高通量检测要求,能显著提高氯酚类化合物的检测效率。

Identification of chemical constituents in Simiao Yong'an Decoction based on UPLC-LTQ-Orbitrap-MS

This study aims to identify the chemical constituents of Simiao Yong'an Decoction based on ultra-performance liquid chromatography coupled with linear quadrupole ion trap-orbitrap mass spectrometry(UPLC-LTQ-Orbitrap-MS). The elution was performed through a UPLC BEH C_(18) column(2.1 mm × 100 mm, 1.7 μm) with the mobile phase of water(containing 0.1% formic acid)-acetonitrile at a flow rate of 0.4 mL·min~(-1). LTQ-Orbitrap-MS with heat electrospray ion(HESI) source was employed to collect MS fragment information in the negative ion mode. A total of 72 compounds were identified based on reference substance comparison, fragmentation rules, accurate molecular weight, related reports and databases(MassBank and HMDB), including 30 iridoid glycosides, 9 organic acids, 15 flavonoids, 10 phenylpropanoids, 7 triterpenoids, and 1 saccharide. The method established in this study is comprehensive, rapid, and accurate, which can help summarize the fragmentation rules of constituents and provide reference for revealing the active constituents and pharmacodynamic mechanism of Simiao Yong'an Decoction.

Supercritical fluid chromatography time-of-flight mass spectrometry enantiomeric determination of basic drugs in sewage samples

Many pharmacologically active compounds are chiral species, and their therapeutic or toxicological effects might differ between isomers. Herein, we develop a fast and sensitive chiral analysis methodology for the determination of eight pharmaceuticals, considered as emerging environmental pollutants and belonging to two different chemical classes, in wastewater and sludge samples. Compounds were separated using supercritical fluid chromatography (SFC) combined with time-of-flight mass spectrometry (TOF-MS) detection. The stationary phase, the modifier and the additive combined with supercritical carbon dioxide (CO2), in the SFC mobile phase, played a major effect in the enantiomeric resolution of selected compounds. Moreover, the composition of the mobile phase affected their ionization efficiency in the electrospray ionization source. Methanol (MeOH), containing a 0.1% of ammonia, was used as CO2 modifier for the separation of compounds in a polysaccharide-type column. Total analysis time was 15.5 min, achieving resolution factors between 1.03 and 2.49 for the eight pairs of enantiomers. In combination with mixed-mode solid-phase extraction and matrix solid-phase dispersion protocols, compounds were determined in wastewater and sludge samples, with limits of quantification in the range of 0.010–0.020 µg L−1 and 3.7–11.1 ng g−1, for aqueous and solid samples, respectively. The amine-type drugs (tramadol, propranolol and venlafaxine) were mostly found in wastewater samples, whilst azolic antimycotics were mainly quantified in sludge. The first group of compounds showed enantiomeric fractions significantly different to those existing in the commercial counterpart pharmaceuticals.

Determination of Dapoxetine Hydrochloride in Human Plasma by HPLC-MS/MS and Its Application in a Bioequivalence Study.

Dapoxetine is used for the treatment of premature ejaculation. The present study developed an HPLC–MS/MS method to determine the levels of dapoxetine in human plasma processed using simple protein precipitation. Dapoxetine-d7 was selected as the internal standard. The established method was performed using a mass spectrometer equipped with an electrospray ionization source in multiple positive ion reactions to monitor the mode using the precursor-to-product ion transitions of m/z 306.2–157.2 and m/z 313.2–164.2 for dapoxetine-d7 and dapoxetine, respectively. The method was evaluated based on its selectivity, linearity, limit of quantification, precision, accuracy, matrix effects, dilution integrity, stability, and extraction recovery. As a result of the model used in the present study, the validated linear ranges of dapoxetine were determined to be 2.00~1000 ng/mL in plasma, and the selectivity, precision, accuracy, dilution integrity, stability, and extraction recovery met the accepted standard. No matrix interference was observed. The method was successfully validated and applied to pharmacokinetic studies in healthy Chinese volunteers during the fasting and postprandial periods, respectively.