Ion Electrospray Ionization-tandem Mass Spectrometry Research Articles

Record of North American boreal forest fires in northwest Greenland snow

We present boreal forest fire proxies in a northwest Greenland snowpit spanning a period of six years, from spring 2003 to summer 2009. Levoglucosan (C6H10O5) is a specific organic molecular marker of biomass burning caused by boreal forest fires. In this study, levoglucosan was determined via liquid chromatography/negative ion electrospray ionization-tandem mass spectrometry, wherein isotope-dilution and multiple reaction monitoring methods are employed. Ammonium (NH4+) and oxalate (C2O42−), traditional biomass burning proxies, were determined using two-channel ion chromatography. In the northwest Greenland snowpit, peaks in levoglucosan, ammonium, and oxalate were observed in snow layers corresponding to the summer–fall seasons of 2004 and 2005. Considered together, these spikes are a marker for large boreal forest fires. The levoglucosan deposited in the Greenland snow was strongly dependent on long-range atmospheric transportation. A 10-day backward air mass trajectory analysis supports that the major contributors were air masses from North America. In addition, satellite-derived carbon monoxide (CO) and ammonia (NH3) concentrations suggest that chemicals from North American boreal forest fires during the summer–fall of 2004 and 2005 were transported to Greenland. However, large boreal fires in Siberia in 2003 and 2008 were not recorded in the snowpit. The sub-annual resolution measurements of levoglucosan and ammonium can distinguish between the contributions of past boreal forest fires and soil emissions from anthropogenic activity to Greenland snow and ice.

Determination of Endocrine Disrupting Chemicals in Water and Wastewater Samples by Liquid Chromatography-Negative Ion Electrospray Ionization-Tandem Mass Spectrometry.

A liquid chromatography-negative ion electrospray ionization-tandem mass spectrometry method was developed for the simultaneous analysis of bisphenol A, 4-octylphenol, 4-nonylphenol, diethylstilbestrol, 17β-estradiol, estriol, estrone, 17α-ethinylestradiol, prednisone, and prednisolone. This method used solid-phase extraction with an elution solvent of acetonitrile to improve the stability of the analytes. To maintain the stability of analytes analyses were completed within five days. The recoveries ranged from 84 to 112% and the relative standard deviation of analysis of duplicate samples was <10%. The limits of quantitation were 1–10 ng/L. Surface water and wastewater were obtained from five wastewater treatment plants in Saskatchewan. Matrix effects were moderate to severe. Using standard addition calibration, all analytes except diethylstilbestrol and 17α-ethinyl estradiol were detected. There was a low frequency of detection of the target analytes in upstream and downstream water, indicating good removal efficiency during the wastewater treatment process. Bisphenol A and 4-nonylphenol were the only analytes detected downstream. Bisphenol A was the most frequently detected in raw wastewater (133 to 403 ng/L). Estriol was detected more often in raw wastewater than estrone or 17β-estradiol. This is the first Canadian study with the detection of prednisone and prednisolone with concentrations at 198–350 ng/L in raw wastewater at 60% of the wastewater treatment plants.

Pressurized Solvent Extraction with Ethyl Acetate and Liquid Chromatography-Tandem Mass Spectrometry for the Analysis of Selected Conazole Fungicides in Matcha.

The extraction of powdered nutraceuticals is challenging due to the low water content and high concentration of matrix components that can lead to significant matrix effects in liquid chromatography-positive ion electrospray ionization-tandem mass spectrometry (LC-ESI+-MS/MS). In this study we assess the feasibility of using pressurized solvent extraction with ethyl acetate to reduce the co-extraction of polar matrix components. Pigment attributed to chlorophyll was removed with in-cell clean-up utilizing Anasorb 747, Florisil®, and C18. Visible inspection of the extracts showed that pigment was removed from matcha, a powdered green tea sample. Pressurized solvent extraction with in-cell clean-up can be utilized to remove pigments from powdered samples such as nutraceuticals. Average matrix effect of the 32 target analytes that observed mass spectrometric signal suppression or soft MS signal enhancement was −41 ± 19% with the majority of analytes having a protonated molecular ion with m/z of 250 to 412. As generally moderate signal suppression was observed for conazole fungicides and structurally related compounds analyzed by LC-ESI+-MS/MS, it is recommended that matrix matched or standard addition calibration is used for quantitation. Catachins, other polyphenols, and caffeine are expected to contribute to the matrix effects observed in LC-ESI+-MS/MS. Diniconazole, fenbuconazole, and tebufenozide were the only target analytes with severe MS signal enhancement. Low levels (0.002–0.004 mg/kg) of prothioconazole-desthio and flusilazole were detected, along with trace levels of tebuthiuron in matcha.

Serum Calcitriol Concentrations and Kidney Function Decline, Heart Failure, and Mortality in Elderly Community-Living Adults: The Health, Aging, and Body Composition Study

Lower 25-hydroxyvitamin D concentrations have been associated with risk for kidney function decline, heart failure, and mortality. However, 25-hydroxyvitamin D requires conversion to its active metabolite, calcitriol, for most biological effects. The associations of calcitriol concentrations with clinical events have not been well explored. Case-cohort study. Well-functioning community-living older adults aged 70 to 79 years at inception who participated in the Health, Aging, and Body Composition (Health ABC) Study. Serum calcitriol measured using positive ion electrospray ionization-tandem mass spectrometry. Major kidney function decline (≥30% decline in estimated glomerular filtration rate from baseline), incident heart failure (HF), and all-cause mortality during 10 years of follow-up. Baseline calcitriol concentrations were measured in a random subcohort of 479 participants and also in cases with major kidney function decline [n=397]) and incident HF (n=207) during 10 years of follow-up. Associations of serum calcitriol concentrations with these end points were evaluated using weighted Cox regression to account for the case-cohort design, while associations with mortality were assessed in the subcohort alone using unweighted Cox regression. During 8.6 years of mean follow-up, 212 (44%) subcohort participants died. In fully adjusted models, each 1-standard deviation lower calcitriol concentration was associated with 30% higher risk for major kidney function decline (95% CI, 1.03-1.65; P=0.03). Calcitriol was not significantly associated with incident HF (HR, 1.16; 95% CI, 0.94-1.47) or mortality (HR, 1.01; 95% CI, 0.81-1.26). We observed no significant interactions between calcitriol concentrations and chronic kidney disease status, baseline intact parathyroid or fibroblast factor 23 concentrations. Observational study design, calcitriol measurements at a single time point, selective study population of older adults only of white or black race. Lower calcitriol concentrations are independently associated with kidney function decline in community-living older adults. Future studies will be needed to clarify whether theseassociations reflect lower calcitriol concentrations resulting from abnormal kidney tubule dysfunction or direct mechanisms relating lower calcitriol concentrations to more rapid loss of kidney function.

Simultaneous quantification of proposed anti-malarial combination comprising of lumefantrine and CDRI 97–78 in rat plasma using the HPLC–ESI-MS/MS method: application to drug interaction study

BackgroundLumefantrine is the mainstay of anti-malarial combination therapy in most endemic countries presently. However, it cannot be used alone owing to its long onset time of action. CDRI 97–78 is a promising trioxane-derivative anti-malarial candidate that is currently being investigated as a substitute for artemisinin derivatives owing to their emerging resistance.MethodsIn the present study, a sensitive, simple and rapid high-performance liquid chromatography coupled with positive ion electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) method was developed for the simultaneous determination of lumefantrine and CDRI 97-78’s metabolite, 97–63, in rat plasma using halofantrine as an internal standard. Lumefantrine and 97–63 were separated on a Waters Atlantis C18 (4.6 × 50 mm, 5.0 μm) column under isocratic condition with mobile phase consisting of acetonitrile: methanol (50:50, v/v) and ammonium formate buffer (10 mM, pH 4.5) in the ratio of 95:5 (v/v) at a flow rate of 0.65 mL/min.ResultsThe method was accurate and precise within the linearity range 3.9-500 ng/mL for both lumefantrine and 97–63 with a correlation coefficient (r2) of ≥0.998. The intra- and inter-day assay precision ranged from 2.24 to 7.14% and 3.97 to 5.90%, and intra- and inter-day assay accuracy was between 94.93 and 109.51% and 96.87 and 108.38%, respectively, for both the analytes. Upon coadministration of 97–78, the relative bioavailability of lumefantrine significantly decreased to 64.41%.ConclusionsA highly sensitive, specific and reproducible high-throughput LC-ESI-MS/MS assay was developed and validated to quantify lumefantrine and CDRI 97–78. The method was successfully applied to study the effect of oral co-administration of lumefantrine on the pharmacokinetics of 97–78 in male Sprague–Dawley rats and vice versa. Co-administration of 97–78 significantly decreased the systemic exposure of lumefantrine.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-015-0684-5) contains supplementary material, which is available to authorized users.

Liquid chromatography–tandem mass spectrometry for simultaneous measurement of thromboxane B2 and 12(S)-hydroxyeicosatetraenoic acid in serum

Arachidonic acid (AA) is metabolized in human platelets by two main pathways: via cyclooxygenase (COX-1) to prostaglandins and thromboxane (TX)A2 and via 12-lipoxygenase (12-LOX) to 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE). While COX products are known to regulate platelet reactivity, the role of 12-LOX metabolites is still controversial. To better understand the platelet enzymatic pathways, we developed a simple and sensitive liquid chromatography–tandem mass spectrometry (LC–MS/MS) assay for the simultaneous measurement of both platelet metabolites in human serum. After the addition of deuterated d4-TXB2 and d8-12(S)-HETE as internal standards and the solid-phase extraction of serum samples, analytes were resolved using reversed-phase C18 column and quantified using negative ion electrospray ionization-tandem mass spectrometry. Intra and interassay imprecisions were less than 10% for both analytes. The lower limits of quantification were 0.244ng/ml and 0.976ng/ml for TXB2 and 12(S)-HETE, respectively. This method was applied to measure platelet metabolites in healthy subjects (n=35). LC–MS/MS allows rapid, simultaneous, sensitive and accurate quantification of both platelet AA products in human serum with a small sample volume required and a minimal sample preparation.

Development and validation of a liquid chromatography–tandem mass spectrometry method for simultaneous determination of amlodipine, atorvastatin and its metabolites ortho-hydroxy atorvastatin and para-hydroxy atorvastatin in human plasma and its application in a bioequivalence study

A sensitive, simple and rapid high-performance liquid chromatography coupled with positive ion electrospray ionization-tandem mass spectrometry (HPLC–ESI-MS/MS) method was developed for the simultaneous determination of amlodipine, atorvastatin and its metabolites ortho-hydroxy atorvastatin and para-hydroxy atorvastatin in human plasma. The analytes were extracted from human plasma through liquid–liquid extraction method. A mixture of methyl tert-butyl ether and ethyl acetate (50:50, v/v) was used as the extractant. The chromatographic separation was achieved on a CAPCELLPAK CR 1:4 (5μm, 150mm×2.0mm i.d.) column within 6.0min with the mobile phase consisted of acetonitrile and ammonium acetate buffer (20mM) containing 0.3% formic acid (50:50, v/v). Data acquisition was carried out in multiple reaction monitoring (MRM) mode. The method was validated and was successfully applied to the bioequivalence study of combination tablets containing AM and AT with coadministered individual drugs in 50 healthy Chinese male volunteers.

RAPID METHOD FOR THE DETECTION OF METABOLITE OF SULFUR MUSTARD 1,1′-SULFONYLBIS[2-S-(N-ACETYLCYSTEINYL)ETHANE] IN PLASMA AND URINE BY LIQUID CHROMATOGRAPHY-NEGATIVE ELECTROSPRAY-TANDEM MASS SPECTROMETRY

A method for detection of an important biological marker, 1,1′-sulfonylbis[2-S-(N-acetylcysteinyl)ethane] (SBSNAE) of sulfur mustard agent [bis-(2-chloroethyl)sulfide] (HD) in human plasma and rat urine to quantify HD exposure, is presented. It employs solid-phase extraction sample preparation, followed by liquid-chromatography-negative ion-electrospray ionization-tandem mass spectrometry. The method limit of detection (LOD) for SBSNAE is 0.05 ng/mL for rat urine samples with relative standard deviations of less than 10%. Application of this procedure was demonstrated in the HD animal exposure model. Rats were exposed intravenously to 5 mg/kg HD, and SBSNAE levels in urine samples were analyzed for 22 days post-exposure.

Development and Validation of a Liquid Chromatography-Tandem Mass Spectrometry Method for the Identification and Quantification of JWH-018, JWH-073, JWH-019, and JWH-250 in Human Whole Blood

A sensitive and specific method for the quantification of JWH-018, JWH-073, and JWH-250 and the qualitative identification of JWH-019 in whole blood was developed and validated. Samples fortified with JWH-018-d₉ and JWH-073-d₉ underwent liquid-liquid extraction and were analyzed by liquid chromatography-positive ion electrospray ionization-tandem mass spectrometry. Two transitions were monitored for all analytes except JWH-250, for which there was only one available transition. JWH-019 did not meet the stringent requirements for quantitative analysis, and thus this method is only appropriate for the qualitative identification of this compound in whole blood. The linear range was 0.1-20 μg/L for all quantitative analytes. The maximum average within and between-run imprecision was 7.9% and 10.2%, respectively, and all controls quantified within 8.2% of target concentrations. Process efficiency, a measurement that takes into effect extraction efficiency and matrix effect, was ≥ 32.0% for all quantitative analytes; similar results were obtained for the deuterated internal standards. All analytes were stable at room, refrigerated, and frozen temperatures for at least 30 days. The method was used to quantify JWH-018 and JWH-073 in a blood specimen collected from a person known to have used an herbal incense blend containing these substances.

Quantification of 1α,25-Dihydroxy Vitamin D by Immunoextraction and Liquid Chromatography–Tandem Mass Spectrometry

1α,25-dihydroxy vitamin D [1,25(OH)(2)D] is the active metabolite of vitamin D. Antibody-based detection methods lack specificity, but when combined with isotope dilution/ultra-performance liquid chromatography (UPLC)-tandem mass spectrometry, immunoextraction provides an attractive method for 1,25(OH)(2)D. We developed a method for simultaneous quantification of 1,25(OH)(2)D(2) and 1,25(OH)(2)D(3) with a 4.6-min instrument cycle time. Results are available 36 h after sample preparation begins. Sample preparation consisted of protein precipitation, immunoextraction with solid-phase anti-1,25(OH)(2)D antibody, and derivatization with 4-phenyl-1,2,4-triazoline-3,5-dione. Analytes were resolved using reversed-phase UPLC and quantified using positive ion electrospray ionization-tandem mass spectrometry. We used hexadeuterated 1,25(OH)(2)D(3) and 1,25(OH)(2)D(2) as internal standards and performed method comparisons against the DiaSorin RIA and an LC-MS/MS method available at a reference laboratory. 1,25(OH)(2)D(3) intraassay and interassay imprecision was 5.6% and 8.0% (120 pmol/L) and 8.7% and 13% (48 pmol/L). Limits of detection and quantification were 1.5 pmol/L and 3.0 pmol/L, respectively. 1,25(OH)(2)D(2) intraassay and interassay imprecision was 8.7% and 11% (186 pmol/L) and 11% and 13% (58 pmol/L). Limits of detection and quantification were both 1.5 pmol/L. Comparison with RIA had a proportional bias of 0.75, constant bias of -4.1, and Pearson correlation (r(2)) of 0.31. Comparison with a reference LC-MS/MS assay had a proportional bias of 0.89, constant bias of 3.7, and r(2) of 0.88. Protein precipitation with antibody-based extraction is effective for sample preparation before LC-MS/MS analysis of derivatized 1,25(OH)(2)D. This method appears to have improved specificity over a clinically used RIA with low imprecision and limits of detection.

Analysis of alkaloids in Coptis chinensis Franch by accelerated solvent extraction combined with ultra performance liquid chromatographic analysis with photodiode array and tandem mass spectrometry detections

A new method based on accelerated solvent extraction (ASE) followed by ultra performance liquid chromatography (UPLC) analysis has been developed for the identification and quantification of major alkaloids in extracts of Coptis chinensis Franch. The UPLC system consisted of a dual detection system of photodiode array detector (PDA) and positive ion electrospray ionization-tandem mass spectrometry (ESI-MS/MS) in sequential configuration. The operational parameters of ASE including extraction solvent, extraction temperature, static extraction time and extraction cycles were optimized. UPLC analysis was performed on an ACQUITY UPLC BEH C 18 column eluted by a mobile phase of acetonitrile spiked with a buffer solution consisting of 0.50% acetic acid and 20 mmol L −1 ammonium acetate. A tandem quadrupole spectrometer operating in either full scan mode or in MS/MS mode for multiple reaction monitoring (MRM) was used for the identification and quantitative analysis of eight major alkaloids in C. chinensis Franch extracts. The samples were also analyzed on a high-performance liquid chromatography–electrospray ionization-time-of-flight mass spectrometry (HPLC-ESI-TOF-MS) system to confirm the identification results. Three of the eight major alkaloids, berberine, palmatine and jatrorrhizine were quantified by UPLC–PDA and UPLC–MS/MS. The results indicated that both UPLC–PDA and UPLC–MS/MS methods were simple, sensitive and reliable for the determination of alkaloids in C. chinensis Franch. Seven Huanglian samples from different locations were analyzed using the established methods. UPLC fingerprints based on the distribution of the eight major alkaloids can serve as a rapid and reliable method for the authentication and quality evaluation of traditional Chinese medicine (TCM) herbs.

A sensitive method for quantitation of β-lyase metabolites of sulfur mustard as 1,1′-sulfonylbis[2-(methylthio)ethane] (SBMTE) in human urine by isotope dilution liquid chromatography–positive ion-electrospray-tandem mass spectrometry

A method for measurement of an important biological marker, 1,1′-sulfonylbis[2-(methylthio)ethane] (SBMTE) of sulfur mustard agent HD [bis-(2-chloroethyl)sulfide] in human urine, to quantify HD exposure, is presented. It employs TiCl 3 reduction of β-lyase metabolites to SBMTE, and automated solid-phase extraction sample preparation, followed by isotope dilution liquid chromatography–positive ion-electrospray ionization-tandem mass spectrometry with 7.5 min/sample cycle time, to achieve SBMTE quantitation of up to 200 samples/24 h a day. Percent relative standard deviations over the calibration range varied from 12.0% at 0.1 ng/mL to 0.9% at 100 ng/mL, and the limit of detection from a 0.5 mL sample was below the lowest level calibration standard of 0.1 ng/mL.

Development of a mass fingerprinting tool for automated interpretation of oligosaccharide fragmentation data.

The bioinformatic tool GlycosidIQ was developed for computerized interpretation of oligosaccharide mass spectrometric fragmentation based on matching experimental data with theoretically fragmented oligosaccharides generated from the database GlycoSuiteDB. This use of the software for glycofragment mass fingerprinting obviates a large part of the manual, labor intensive, and technically challenging interpretation of oligosaccharide fragmentation. Using 130 negative ion electrospray ionization-tandem mass spectrometry fragment spectra from identified oligosaccharide structures, it was shown that the GlycosidIQ scoring algorithms were able to correctly identify oligosaccharides in the great majority of cases (correct structure top ranked in 78% of the cases and an additional 17% were ranked second highest in the sample set).

Automated solid phase extraction and quantitative analysis of human milk for 13 phthalate metabolites

While the demonstrated benefits associated with breastfeeding are well recognized, breast milk is one possible route of exposure to environmental chemicals, including phthalates, by breastfeeding infants. Because of the potential health impact of phthalates to nursing children, determining whether phthalates are present in breast milk is important. We developed a sensitive method for measuring 13 phthalate metabolites in breast milk using automated solid phase extraction (SPE) coupled to isotope dilution–high-performance liquid chromatography (HPLC)–negative ion electrospray ionization–tandem mass spectrometry. We used D 4-phthalate diesters to unequivocally establish the presence in human breast milk of enzymes capable of hydrolyzing the ubiquitous phthalate diesters to their respective monoesters. The analytical method involves acid-denaturation of the enzymes after collection of the milk to avoid hydrolysis of contaminant phthalate diesters introduced during sampling, storage, and analysis. The method shows good reproducibility (average coefficient of variations range between 4 and 27%) and accuracy (spiked recoveries are ∼100%). The detection limits are in the low ng/ml range in 1 ml of breast milk. We detected several phthalate metabolites in pooled human breast milk samples, suggesting that phthalates can be incorporated into breast milk and transferred to the nursing child.

Calcium-dependent Protein Interactions in MUC5B Provide Reversible Cross-links in Salivary Mucus

The macromolecular organization within saliva was investigated by tracer diffusion measurements of fluorescent polystyrene microspheres by fluorescence recovery after photobleaching using a confocal microscope (confocal-FRAP). There was a concentration-dependent reduction in microsphere diffusion; this was much greater in the presence of calcium (10 mm) and was reduced by the addition of EGTA (10 mm). These effects on tracer diffusion showed that native saliva contained a macromolecular organization that was sensitive to free calcium concentrations. This was supported by a major increase in the weight average molecular weight of the high molecular weight mucin fraction in saliva (10-62 x 106) and an increase in intrinsic viscosity of saliva (733 to 1203 ml/g) both caused by calcium. Analysis of the change in tracer diffusion in saliva showed a 20-fold increase in the apparent pore size (from 130 nm in 10 mm CaCl2 to 2600 nm in 10 mm EGTA at physiological concentration). The effect was specific for calcium and was unaffected by up to 2 m NaCl. The calcium binding activity was contained in a high buoyant density fraction of saliva excluded from Sepharose CL-2B. Calcium binding to this fraction gave an approximate Kd of 7 x 10-6 m, and the binding was irreversibly destroyed by treatment with 6 m guanidinium chloride and by mild reduction, suggesting it to be to a protein site. This fraction of saliva was shown to contain MUC5B as the single major protein species by positive ion electrospray ionization-tandem mass spectrometry analysis. The results suggested that oligomeric MUC5B in saliva is assembled into much larger linear or branched assemblies through calcium-mediated protein cross-links.