Positive Electrospray Ionization Mass Spectrometry Research Articles

Rapid and sensitive quantification of levoglucosan in aerosols by high-performance anion-exchange chromatography with positive electrospray ionization mass spectrometry (HPAEC-positive ESI-MS)

Abstract A convenient quantification method for underivatized levoglucosan, which is a tracer for biomass burning influenced particulate matter (PM), has been established using high-performance anion-exchange chromatography (HPAEC) coupled to positive electrospray ionization mass spectrometry ((+)ESI-MS). Levoglucosan was chromatographically separated from its isomers (mannosan and galactosan) and detected selectively with positive ESI-MS. Limits of detection and quantification for this method were 0.40 and 1.3 ng mL −1 , respectively. A comparison of simultaneous measurements by this method and conventional derivatization gas chromatography/mass spectrometry showed a good linearity with a slope of 1.008 and a determination coefficient of 0.9932. The developed method was applied to ambient suspended particulate matter hourly collected by continuous particulate monitors at 10 stations. The hourly concentration of levoglucosan during August 9–11, 2011, was 1.7–918 ng m −3 and its distribution indicated the transportation of biomass burning aerosols of a forest fire. This is the first report of horizontal distribution of the hourly levoglucosan concentration in Japan.

Determination of thymopentin in beagle dog blood by liquid chromatography with tandem mass spectrometry and its application to a preclinical pharmacokinetic study.

The pentapeptide thymopentin (Arg-Lys-Asp-Val-Tyr, RKDVY) corresponds to amino acids 32-36 of the 49 amino acid immunomodulatory polypeptide, thymopoietin, whose biological activity is partially reproduced. Thymopentin is widely used in the clinic and represents a promising target for drug design but bioanalytical and pharmacokinetic data are limited due to its enzymatic instability. This paper reports a rapid and sensitive method based on liquid chromatography with tandem mass spectrometry for the determination of thymopentin in beagle dog blood. To inactivate peptidases and stabilize thymopentin, acetonitrile was added to blood samples immediately after collection followed by addition of stable isotope-labeled thymopentin as internal standard and washing with dichloromethane. Chromatography was carried out on an Ascentis Express Peptide ES-C18 column using gradient elution with methanol and aqueous 0.1% formic acid at a flow rate of 0.6 mL/min. Positive electrospray ionization mass spectrometry with selected reaction monitoring achieved linearity in the range of 1.5-800 ng/mL with good accuracy/precision and minimal matrix effects. The method was successfully applied to a pharmacokinetic study in beagle dogs after intravenous administration of 0.2 mg/kg thymopentin.

Determination of N-nitrosodiethanolamine, NDELA in cosmetic ingredients and products by mixed mode solid phase extraction and UPLC–tandem mass spectrometry with porous graphitic carbon column through systemic sample pre-cleanup procedure

A rapid, sensitive, accurate and specific ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) method for the detection of N-nitrosodiethanolamine (NDELA), a highly toxic contaminant in cosmetic raw materials and products was developed and validated. Systematized sample preparation steps were developed according to product types. Various SPE cartridges and columns were examined to establish the condition of SPE and chromatographic separation for NDELA. Sample cleanup steps consisting of solvent and liquid-liquid extraction tailored to the various sample matrix types were established prior to mixed mode SPE (Bond Elut AccuCAT). Chromatographic separation was achieved within 7 min on a porous graphitic carbon (PGC) column using a gradient elution with the mobile phase of 1mM ammonium acetate containing 0.1% acetic acid and methanol. NDELA was monitored using an electrospray positive ionization mass spectrometry in the multiple reaction monitoring (MRM) mode (m/z 134.9>103.7(quantifier) and 73.7(qualifier ion)) with d8-NDELA (m/z 143.1>111.0) as internal standard. The standard curves were linear over the concentration range of 1-100 ng/mL with a correlation coefficient higher than 0.99. The limit of detection (LOD) and the limit of quantification (LOQ) was 10 and 20 μg/kg, respectively (0.5 and 1 ng/mL in standard solution). The intra- and inter-day precisions were estimated to be below 11.1% and accuracies were within the range of 90.8-115.8%. The validated method was successfully applied to the analysis of real samples including raw materials, skin care, make-up, shampoos and hair products.

Multi-mycotoxin Analysis of Finished Grain and Nut Products Using Ultrahigh-Performance Liquid Chromatography and Positive Electrospray Ionization-Quadrupole Orbital Ion Trap High-Resolution Mass Spectrometry.

Ultrahigh-performance liquid chromatography using positive electrospray ionization and quadrupole orbital ion trap high-resolution mass spectrometry was evaluated for analyzing mycotoxins in finished cereal and nut products. Optimizing the orbital ion trap mass analyzer in full-scan mode using mycotoxin-fortified matrix extracts gave mass accuracies, δM, of < ± 2.0 ppm at 70,000 full width at half maximum (FWHM) mass resolution (RFWHM). The limits of quantitation were matrix- and mycotoxin-dependent, ranging from 0.02 to 11.6 μg/kg. Mean recoveries and standard deviations for mycotoxins from acetonitrile/water extraction at their relevant fortification levels were 91 ± 10, 94 ± 10, 98 ± 12, 91 ± 13, 99 ± 15, and 93 ± 17% for corn, rice, wheat, almond, peanut, and pistachio, respectively. Nineteen mycotoxins with concentrations ranging from 0.3 (aflatoxin B1 in peanut and almond) to 1175 μg/kg (fumonisin B1 in corn flour) were found in 35 of the 70 commercial grain and nut samples surveyed. Mycotoxins could be identified at δM < ± 5 ppm by identifying the precursor and product ions in full-scan MS and data-dependent MS/MS modes. This method demonstrates a new analytical approach for monitoring mycotoxins in finished grain and nut products.

Profiling Rat Brain Monoacylglycerol Lipase Activity Using an Ammonia- Adduct Enhanced Selected Ion Monitoring Liquid-Chromatography Positive Electrospray Ionization Mass Spectrometry Assay

2-Arachidonoylglycerols (2-AG) is one of the major endocannabinoids in the central nervous system. Upregulation of central endocannabinoids signaling by selective inhibition of brain monoacylglycerol lipase (MAGL) activity is a potential therapeutic approach in pain, obesity, and diabetes modulation to name a few. Thus, a sensitive and reliable analytical method for determination of endocannabinoid levels in the brain is essential for the discovery of MAGL inhibitors. Accurate measurement of monoacylglycerols (MAG) levels, using liquid chromatography positive electrospray ionization mass spectrometry (LC / +ESI / MS) and tandem MS, is a challenge since the brain endocannabinoids are not only susceptible to stress in the in-life phase of the study, but also prone to postmortem metabolism, acyl migration (i.e., conversion from 2-MAG to 1(3)-MAG), metal adduct ion formation and chemical hydrolysis generating the same products as those by the target enzyme. To avoid these artifacts, we have developed a simple LC / +ESI / MS method for direct detection of ammonium-adduct cations of the major MAGs in selected ion monitoring mode (SIM). For the in vitro MAGL inhibition assay, a LC isocratic elution was used for baseline separation of MAGs and their acyl migration isomers produced during the 37oC incubation with rat brain homogenate. To minimize the postmortem metabolism and isomerization of MAGs for in-vivo studies, rat brain was homogenized directly in four milliliters of ethanol for every gram of brain tissue and a linear LC gradient elution was applied for broad endocannabinoid profiling. The SIM LC / +ESI / MS method is shown to be useful for in-vitro brain evaluation of inhibitory potency of MAGL and fatty acid amide hydrolase (FAAH) inhibitors and for in-vivo brain assessment for target engagement studies.

Simultaneous determination of glyphosate and glufosinate-ammonium residues in tea by ultra performance liquid chromatography-tandem mass spectrometry coupled with pre-column derivatization

A method was developed for the determination of glyphosate (GLY) and glufosinate-ammonium (GLUF) in tea using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The sample was extracted with ultrapure water and dichloromethane for 30 min under ultrasonication, followed by a simple cleanup with a C18 solid phase extraction (SPE) cartridge, and then GLY and GLUF were derivatized using 9-fluorenylmethoxycarbonyl (FMOC-Cl) in borate buffer for 2 h. The derivatives of GLY and GLUF were separated on a Waters C18 column (50 mm x 2.1 mm, 1.7 μm) in a gradient elution mode, and finally detected with positive electrospray ionization-mass spectrometry (ESI-MS/MS ) in multiple reaction monitoring (MRM) mode. The quantification analysis was performed by external standard method. The method showed a good linearity (r > 0. 990) in the range of 0.003 125-0.1 mg/L. The limits of detection (LODs) of GLY and GLUF were 0.03 mg/kg. At the spiked levels of 0.375, 1.5 and 4.5 mg/kg, the recoveries of GLY and GLUF were 87.37%-99.11% and 81.44% -86.17% respectively, and the relative standard deviations (RSDs) (n = 6) of GLY and GLUF were 0.68%-1.35% and 1.01%-2.33%, respectively. This method is simple, rapid and characterized with acceptable sensitivity and accuracy to meet the requirements for the analysis of GLY and GLUF simultaneously in tea.

The analysis of azocyclotin and cyhexatin residues in fruits using ultrahigh-performance liquid chromatography-tandem mass spectrometry

Ultrahigh-performance liquid chromatography coupled to electrospray positive ionization and tandem mass spectrometry (UHPLC-ESI(+)-MS/MS) was applied for the quantification and identification of azocyclotin and cyhexatin in fruit samples.

Tiliabisflavan A, a New Flavan‐3‐ol Dimer from Tilia amurensis with Cytotoxic and Anti‐Inflammatory Effects

In the search for anticancer compounds from Korean medicinal plants, themethanolic extract from the trunk ofTilia amurensis Rupr. (Tiliaceae) was found to have significant cytotoxicity against A549 (lung carcinoma), SK-OV-3 (ovary malignant ascites), SK-MEL-2 (skinmelanoma), andHCT-15 (colon adenocarcinoma) in our screening test. T. amurensis is commonly known as “bee tree” and widely distributed in the mountainous areas of Korea, China, and Japan. T. amurensis has been used to treat various diseases as a Korean traditional medicine from ancient times. Its flowers have been applied for alleviating a fever, and its leaves have also been traditionally used for analgesia and rheumatoid arthritis. Importantly, an extract of this tree has been used to treat stomach cancer without any side effects. A recent pharmacological study revealed the potential of T. amurensis as an anticancer agent by evaluating the DNA topoisomerase inhibitory activity. However, only a few constituents associated with the anticancer activity from T. amurensis have been reported. Recently, our phytochemical investigations on T. amurensis revealed the presence of bioactive lignan constituents with antitumor and anti-inflammatory activities. Our continuing interest in further research on the bioactive constituents from T. amurensis led us to investigate bioactive metabolites of T. amurensis trunk. A bioassay-guided fractionation and chemical investigation of its MeOH extract resulted in the isolation and identification of four flavan-3-ols, including a new flavan-3-ol dimer, tiliabisflavanA (1) (Figure 1). The isolated compounds were evaluated for their antiproliferative activities against A549, SK-OV-3, SK-MEL-2, and HCT-15 cell lines, as well as their inhibitory effects on NO production in a lipopolysaccharide (LPS)-activated BV-2 cell line. Compound 1 was obtained as a colorless gum. The molecular formula of 1 [ α 1⁄2 25 D +31.5 (c 0.35, MeOH)] was determined to be C31H28O12 based on positive high-resolution electrospray ionization mass spectrometry (HR-ESIMS) data (m/z 615.1479 [M +Na], calcd for C31H28NaO12, 615.1478). The infrared (IR) spectrum showed absorption bands for hydroxyl group (3358 cm) and aromatic rings (1614 and 1450 cm). The structure of 1 was further elucidated by detailed analysis of H and C NMR chemical shifts and by heteronuclear multiple-quantum correlation (HMQC) and heteronuclear multiple-bond correlation (HMBC) experiments. The H and CNMR spectra of 1were similar to those of2 except for the particular signals assigned tomethylene carbon [δH 3.88 (s); δC 15.5]. The assigned proton and carbon resonances of 1 in CD3OD are summarized in Table 1. The H, C NMR, and HMQC spectra of 1 displayed the characteristic signals for theC-ring of flavan-3-ol [δH4.75 (br s,H-2), 4.10 (br s, H-3), 2.82 (dd, J = 16.5, 4.5, H-4a), and 2.67 (dd, J = 16.5, 3.5, H-4b); δC 79.2 (C-2), 66.0 (C-3), and 27.7 (C-4)]. In addition, the 1,3,4-trisubstituted B ring signals [δH 6.94 (d, J = 1.5,H-20), 6.72 (overlap,H-50, H-60); δC144.7 (C-30, C-40), 130.5 (C-10), 118.5 (C-60), 114.7 (C-50), and 114.2 (C-20)] were observed, together with the A-ring carbon signals [δC 154.6 (C-5), 154.0 (C-7), 152.4 (C-9), 105.5 (C-8), 99.3 (C10), and 95.6 (C-6)]. The NMR data were closely related to those of 2; however, instead of the two A ring aromatic methines (C-6, C-8) in 2, the NMR spectra of 1 showed only one aromatic methine (δC 95.6, CH) for the A ring and an additional quaternary aromatic carbon (δC 105.5, C) as well as particular benzylic methylene signals [δH 3.88 (s); δC 15.5 (CH2)]. This indicated that compound 1 is comprised symmetrically of two epicatechin units connectingC-6 andC-8 positions through amethylene bridge. In theHMBCspectrum (Figure 2), the CH2 proton signal at δH 3.88 showed HMBC correlations with δC 154.0 (C-7), 152.4 (C-9), and 105.5 (C-8), which revealed that the two epicatechin units in 1 were linked between their C-8 position through amethylenebridge.Theother partial structures of 1 were clearly elucidated by the interpretation of the H–H correlation spectroscopy (COSY) and HMBC, and thus, the gross structure of 1 was established as shown in Figure 1 and named tiliabisflavan A. The relative configurations of C-2 and C-3 in 1 were determined to be cis for (2R,3R) or (2S,3S) configuration [δC 79.2 (C-2)/66.0 (C-3) and J3,4a = 4.5 Hz, J3,4b = 3.5 Hz for 1] on the basis of the comparison with the chemical shifts of C-2/ C-3 [δC 79.9/67.5 for (+)-epicatechin (2) and δC 82.6/68.7 for (+)-catechin (3)] and the coupling constants of H-3/H-4 Note DOI: 10.1002/bkcs.10011 K. H. Kim et al. BULLETIN OF THE KOREAN CHEMICAL SOCIETY

A simple method for simultaneous determination of N-arachidonoylethanolamine, N-oleoylethanolamine, N-palmitoylethanolamine and 2-arachidonoylglycerol in human cells.

The endocannabinoid system has been considered as a target for pharmacological intervention. Accordingly, inhibition of fatty acid amide hydrolase (FAAH), a degrading enzyme of the endocannabinoids N-arachidonoylethanolamine (anandamide; AEA) and 2-arachidonoylglycerol (2-AG) as well as of the endocannabinoid-like substances N-oleoylethanolamine (OEA) and N-palmitoylethanolamine (PEA), can cause augmented endogenous cannabinoid tone. Using liquid chromatography coupled with positive electrospray ionisation mass spectrometry, we herein describe a method to simultaneously quantify levels of AEA, OEA, PEA and 2-AG in cultured cells. The procedure was developed according to the FDA guidelines for bioanalytical methods validation. The limits of quantification (LOQs) were 0.05 pmol for AEA, 0.09 pmol for OEA, 0.10 pmol for PEA and 0.80 pmol for 2-AG when molecular ion monitoring was used. In H460 human lung carcinoma cells, basal levels of all four analytes ranged between 2 and 17 pmol mg(-1) protein with PEA showing the lowest and OEA the highest concentrations. Endocannabinoid levels observed in mesenchymal stem cells were of the same order of magnitude when compared to those in H460 human lung carcinoma cells.

Preliminary UHPLC–PDA–ESI-MS screening of light-accelerated autoxidation products of the tetrapyrrole biliverdin

The application of phycobiliproteins, e.g. blue C-phycocyanin, as natural water-soluble food colourants is emerging. The chromophore of these proteins comprises a number of tetrapyrroles (or phycocyanobilins), which have an extensive conjugated system, vulnerable to autoxidation. To assess the autoxidation products, a simplified model system was used in which the free tetrapyrrole biliverdin, instead of phycobiliprotein, was subjected to light-accelerated autoxidation. Degradation products of biliverdin were subsequently annotated by reversed-phase ultra-high performance liquid chromatography with a photo diode array and positive mode in-line electrospray ionization mass spectrometry. To facilitate the analysis of degradation products, autoxidation of the three methine bridges in biliverdin was mimicked in silico. It was found that both the peripheral and central methine bridges of biliverdin were susceptible to light-accelerated autoxidation. Scission products tentatively annotated with MS2 and MS3 were propionic acid-containing pyrroles. From this, it can be speculated that tetrapyrroles attached to phycobiliproteins are susceptible to autoxidative degradation.

Quick and simple LC-MS/MS method for the determination of simvastatin in human plasma: application to pharmacokinetics and bioequivalence studies

A simple, rapid, and sensitive method based on liquid chromatography-tandem mass spectrometry for the quantitative determination of simvastatin in human plasma was developed and validated. After a simple extraction with methyl tert-butyl ether, the analyte and internal standard (lovastatin) were analyzed using reverse-phase liquid chromatography, on a Kinetex C18column (100 × 4.6 mm, 2.6 μm) using acetonitrile: ammonium acetate (2 mM + 0.025 % formic acid) (70: 30, v/v) as a mobile phase in a run time of 3.5 min. Detection was carried out using electrospray positive ionization mass spectrometry in the multiple-reaction monitoring mode. The method was linear over 0.04-40.0 ng/mL concentration range. The mean extraction recovery of simvastatin was 82% (RSD within 15%). Intraday and interday precisions (as relative standard deviation) were all ≤8,7% with accuracy (as relative error) of ±8%. This rapid and reliable method was successfully applied for a bioequivalence study of 40 mg of simvastatin orally disintegrating tablets in 44 healthy volunteers, showing that this method is suitable for the quantification of simvastatin in human plasma samples for pharmacokinetics and bioequivalence studies.

Novel formation of [2M-H](+) species in positive electrospray mass spectra of indoles.

When subjected to positive ion electrospray ionisation (ESI+) mass spectrometry (MS), indoles with a 3-alkyl substituent show a propensity to form novel [2M-H](+) 'covalently bound dimers'. This process, which appears to be initiated in the nebuliser of the instrument, is mechanistically interesting, analytically useful and potentially significant in organic synthesis. A selection of 2- and 3-substituted indoles have been synthesised and analysed by ESI-MS. The formation of the 'homo' and 'hetero' dimers of these compounds has been investigated using ESI+ mode. The mechanism of formation of the observed 'dimeric' species has been probed by synthesising authentic samples of the dimeric compounds. 'Dimeric' species corresponding to [2M-H](+) have been observed for all 3-substituted indoles studied, but not for indoles substituted in just the 2-position. By infusing equimolar mixtures of labelled and unlabelled indoles through the instrument, the expected approximately statistical mixture of homo- and heterodimeric species has been observed. Further experiments have established that this novel dimerisation occurs in the droplets formed in the nebuliser of the instrument. It has been shown that 3-substituted indoles form [2M-H](+) dimers in high abundance in the spray obtained from the nebiliser of an ESI+ instrument. The mechanism for the dimerisation does not involve the known 2M dimeric species that is readily formed in the solution-phase chemistry of indoles.

Signal enhancement of glucuronide conjugates in LC-MS/MS by derivatization with the phosphonium propylamine cation tris(trimethoxyphenyl) phosphonium propylamine, for forensic purposes.

Although chemical derivatization for signal enhancement in drug testing is most often associated with gas chromatography, it also has the potential to improve the detection of analytes poorly ionized by atmospheric pressure ionization techniques, such as electrospray ionization used in liquid chromatography-mass spectrometry. A number of acidic compounds, namely drug glucuronides (e.g. conjugates of temazepam, oxazepam, lorazepam, morphine, testosterone, epitestosterone, 5-α-dihydrotestosterone, androsterone, p-nitrophenol, and paracetamol) were successfully derivatized with tris(trimethoxyphenyl) phosphoniumpropylamine to introduce a quaternary cation functionality to the analytes. Benzodiazepine glucuronides were more specifically investigated, and following positive mode electrospray ionization mass spectrometry, average improvements to peak areas as a result of derivatization were 67-, 6-, and 7- fold for temazepam, oxazepam, and lorazepam glucuronides. Average improvements to the signal-to-noise ratios for temazepam, oxazepam, and lorazepam glucuronides were 1336-, 371- and 217-fold, respectively. The values obtained for the derivatized conjugate were also typically higher than those for the underivatized parent drug. Urine containing benzodiazepine glucuronides was also successfully derivatized. The data indicates potential for the use of charge derivatization to improve the detection of molecules with acidic functionalities by liquid chromatography-mass spectrometry (LC-MS) techniques in certain scenarios.

Nanocrystalline ZnO Doped on Lanthanide Oxide Dy2O3: A Novel and UV Light Active Photocatalyst for Environmental Remediation

Doping of ZnO on Dy2O3 was studied for its enhanced photocatalytic activity under UV light irradiation. Various doping concentrations were prepared employing precursor nitrates, and 20 mol % ZnO-doped Dy2O3 was found to be highly active under UV irradiation for the degradation of a model pollutant, Orange G dye. The photocatalyst was highly crystalline with a particle size of 40–50 nm and possessed a highly porous and rough surface (26.12 nm) as evidenced by X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, and atomic force microscopy analysis. The band alignment and surface area were determined by X-ray photoelectron spectroscopy and Brunauer–Emmett–Teller analyses. The band gap energy of the prepared photocatalyst was found to be 3.15 eV from UV–diffuse reflectance spectroscopy measurements, and the metal oxide stretching frequencies were analyzed by Fourier transform infrared analysis. Free radical formation by the photocatalyst during the in situ process was confirmed by electron paramagnetic resonance studies. The photocatalytic degradation of Orange G dye was monitored with a UV–visible spectrophotometer, COD, and positive mode electrospray ionization mass spectrometry analyses.

Influence of electrolytes and a supercharging reagent on charge state distribution and response of neuropeptide ions generated during positive electrospray ionisation mass spectrometry.

To aid in the detection of trace quantities of neuropeptides in a biological matrix (as saliva), the influence of different electrolytes and a supercharging reagent on the positive electrospray ionisation mass spectrometry (ESI-MS) response was investigated. Ammonium acetate, sodium chloride and sodium bicarbonate (10(-7) M to 10(-3) M) and the supercharging reagent m-nitrobenzyl alcohol (m-NBA) was added to the mobile phase and the effect on the ESI response and charge-states distribution (CSD) was studied in a group of peptides (molecular weight range 2.2kDa to 3.5kDa; CGRP, VIP, GLP1, CRF and PrRP). As expected, the result indicates that the ESI response is affected by the presence of additives: ammonium acetate shifted the observed charge states ratio whereas the addition of m-NBA resulted in the appearance of higher maximum charge state ions. This increase in higher charge state for all the peptide ions, [M + nH]n+ to [M + (n + 1)H](n+1), was atttributed to protonation of the C-terminal. However, when the composition of MeCN in a mobile phase containing m-NBA was increased, an enhancement of the total ion signal was observed for non-polar peptide samples. This is a very interesting observation as this is not observed in samples without m-NBA and could be a result of how these peptide ions are solubilised and positioned relative to the droplet surface/air interface.

Concentration dependent Electrospray Ionisation Mass Spectrometry and Tandem Mass Spectrometry (MS/MS ) studies on (E,E)-1-[5-(1,3-benzodioxol-5yl)-1-oxo-2,4-pentadienyl]- piperidine (Piperine) and its analogues.

Studies on piperine ((M1)) and its synthetic analogues (M2–18) by positive electrospray ionisation mass spectrometry were carried out in the flow injection mode of analysis in methanol. The MS experiments on these compounds at concentration 5 ng/μL or above yielded dimeric ionic species [2 M + Na]+ which revealed that piperine and its analogues exhibit clustering of ions when the solutions of these compounds at concentrations 5 ng/μL or above were allowed to move through the electrospray interface of the mass spectrometer. The same clustering of the ions was not observed when the solutions of the same compounds at concentrations below 5 ng/μL were used for similar studies. The formation of the clusters was further confirmed by tandem mass spectrometry (MS/MS) studies wherein the fragmentation of dimeric ionic species [2 M + Na]+ led to the formation of sodium adducted monomeric ionic species [M + Na]+. The MS measurements of these compounds by Atmospheric Pressure Chemical Ionisation (APCI) were on expected lines as there was no clustering of the ions in case of APCI-MS measurements.

An UFLC-MS/MS Method for Quantification of Panaxadiol in Rat Plasma and Its Application to a Pharmacokinetic Study

Panaxadiol is a novel antitumor agent extracted from the Chinese medical herb Panax ginseng. This agent is being developed for the treatment of tumor diseases. A rapid, selective, and simple method based on ultrafast liquid chromatography-tandem mass spectrometry was established and validated to determine panaxadiol in rat plasma following oral and sublingual intravenous administration of panaxadiol. The plasma samples were pretreated with acetic ether, and chromatographic separation was achieved on a Shim-pack XR-ODS III column using isocratic elution with the mobile phase of 0.1 % formic acid and acetonitrile. Analytes and protopanaxadiol (internal standard) were analyzed and identified using electrospray positive ionization mass spectrometry in the multiple reaction-monitoring mode. The MS/MS detection was carried out by monitoring the fragmentation of m/z 461.45 → m/z 127.1 for panaxadiol and m/z 425.4 → m/z 95.1 for protopanaxadiol (internal standard) on a triple-quadrupole mass spectrometer. The result showed good linearity over a wide concentration range (0.1-20 ng/mL) (R2 > 0.999) and its lower limit of detection and quantification were 0.03 and 0.1 ng/mL, respectively. The intra- and interday precision (RSD %) was within 15 % and the accuracy ranged from 94.9 % to 112.0 %. The absolute bioavailability was 12.5 %. The method was fully validated and successfully applied to the pharmacokinetic study of a single dose of panaxadiol.

Monitoring Haloperidol Exposure in Body Fluids and Hair of Children by Liquid Chromatography–High-Resolution Mass Spectrometry

Haloperidol, 4-[4-(4-chlorophenyl)-4-hydroxy-1-piperidinyl]-1-(4-fluorophenyl)-1-butanone (HP), one of the most widely used antipsychotics in the treatment of schizophrenia, mania, and other psychiatric disorders, is frequently encountered in cases of unintentional pediatric intoxication because the ingestion of a small amount can cause significant toxic effects in children. For monitoring HP in suspected ingestions, a liquid chromatography-high-resolution mass spectrometry method has been developed and validated in urine, blood, and hair samples. The analyte was extracted from 1 mL blood or urine by liquid/liquid extraction and from 5 mg of hair by micropulverized extraction; gradient elution on an Atlantis T3 column was realized using HP-d4 as an internal standard. Positive ion electrospray ionization and high-resolution mass spectrometry determination were performed in an Orbitrap mass spectrometer. The method exhibited a r > 0.999 in the studied ranges (0.1-50 ng/mL in urine and blood and 0.1-50 ng/mg in hair) and a limit of quantification of 0.1 ng/mL for urine and blood and 0.1 ng/mg for hair; intra-assay and interassay relative SDs were always more than 18%. The method was applied to determine haloperidol in 3 children who were admitted to emergency departments. HP concentrations ranged from 2 to 21 ng/mL in urine, from not detected to 4.9 ng/mL in blood, and from 0.37 to 0.73 ng/mg in hair samples. The utilization of high-resolution/high-accuracy mass spectrometry in full scan mode allowed the identification of HP metabolites in urine and blood, thus unequivocally documenting the exposure to the drug. HP metabolites were structurally characterized by high-resolution multiple mass spectrometry. For the first time, a HP metabolite was detected in hair.

Elimination pathways of cyclosarin (GF) mediated by β-cyclodextrin in vitro: Pharmacokinetic and toxicokinetic aspects

Cyclodextrins (CD) are promising small molecular scavengers showing favourable degradation of extremely toxic organophosphorus compounds (OP) such as tabun (GA), soman (GD) or cyclosarin (GF). For β-CD derivatives as potential OP antidotes with low intrinsic toxicity it is of great interest to completely understand the modes of interaction of both compounds in terms of OP detoxification. The mechanisms of CD action are not completely understood which prompted us to investigate the interactions of GF and β-cyclodextrin (β-CD) as model compounds. Using positive electrospray ionization mass spectrometry (ESI/MS), the formation of covalent conjugates of β-CD with O-cyclohexylmethylphosphonate (CHMP) residue was detected for the first time and was examined in vitro. With a newly developed LC–MS method the formation of O-cyclohexylmethylphosphonic acid (CHMPA) (i.e. GF hydrolysis) and covalent CHMP-β-CD conjugates was analyzed. Compared to water, tris(hydroxymethyl)aminomethane (TRIS) reduced the formation of covalent conjugates but amplified formation of CHMPA. Depending on experimental conditions the degradation of GF by β-CD may be preferably catalytic or stoichiometric. For illustrating different possible reaction pathways a scheme was established that could support the idea of β-CD acting as an artificial enzyme. These results provide an important insight into the β-CD mediated detoxification pathways of GF.

The relationship between electrospray ionization behavior and cytotoxic activity of [MI(P)4]+‐type complexes (M = Cu, Ag and Au; P = tertiary phosphine)

To try to find a correlation between the antiproliferative activity of a series of [M(I)(P)4](+) complexes (M = Cu, Ag and Au; P = tertiary phosphine) and their stability at micromolar concentration under mass spectrometric conditions. [M(I)(P)4](+) complexes were investigated by positive ion electrospray ionization mass spectrometry with multiple collisional experiments using an ion trap mass spectrometer. The displacement of P from native [M(I)(P)4](+), previously described for the copper derivative, is common for the triad complexes leading to the formation of [M(P)3](+) and [M(P)2](+) adducts. Further dissociation of [M(P)2](+) depends on the nature of the metal (Cu ~ Ag > Au). More labile [Cu(P)2](+) and [Ag(P)2](+) are more cytotoxic against HCT-15 human colon carcinoma cells compared to less labile [Au(P)2](+) species. The dissociation of P ligand(s) from the [M(I)(P)4](+) complexes is the driving force for the triggering of the antiproliferative activity. The more favored is the displacement of P from the [M(P)2](+) active form, the more favored is in turn the possibility for the metal to interact with biological substrates related to cancer proliferation.