25,574 research outputs found
ESI-QqTOF-MS/MS and APCI-IT-MS/MS analysis of steroid saponins from the rhizomes of Dioscorea panthaica
No full textUsing high-resolution quadrupole time-of-flight mass spectrometry along with an electrospray ionization source (ESI-QqTOF-MS), accurate molecular weights of 13 steroid saponins extracted from the rhizomes of Dioscorea panthaica were acquired and the corresponding molecular formulae obtained. In order to elucidate the fragmentation pathways of steroid saponins in D. panthaica, 10 authentic samples were investigated using ESI-QqTOF-MS/MS. In addition, atmospheric pressure chemical ionization mass spectrometry combined with ion trap tandem mass spectrometry (APCI-IT-MS/MS) was used to analyze the structures of 13 steroid saponins in D. panthaica. Through the analysis of their tandem mass data, diagnostic fragment ions of the spirostanol and furostanol steroid saponins in D. panthaica were detected as m/z 271.2056 and 253.1951. In addition, four pairs of isomers were detected and the possible structures of four unknown steroid saponins in D. panthaica speculated. ESI-TOF and APCI-MSn have proved to be effective tools for research on fragmentation mechanism of steroid saponins and the rapid determination of native steroid saponins in extract mixture, thereby avoiding tedious derivation and separation steps. Copyright (c) 2006 John Wiley & Sons, Ltd
Zhou et al. PLOS ONE MS-Figures
No full textThis file contains seven figures as a part of research findings in Zhou et al. manuscript submitted to PLOS ONE journal. Each figure is well defined with title and legends. Moreover, all the figures are well described in the text of our manuscript
Ms. Courtney Chartier, RWWL AUC, August 2011
No full textThis video is a conversation with Ms. Courtney Chartier. Ms. Chartier talks about her work on the "New Georgia Encyclopedia" and "Online Voter Education Project." Andrea Jackson, AUC Woodruff Library, is the interviewer
Ms. Neely Terrell, RWWL AUC, March 2012
No full textThis video is a conversation with Ms. Neely Terrell. Ms. Terrell talks about her book, "Super Singles Activate". Anthony Kinsey and Jahnesta Horney, AUC Woodruff Library, are the interviewers
Ms. Felesha Love, Spelman College, January 2016
No full textThis video is a conversation with Felesha Love. Ms. Love talks about her book, "Brave Leap to Freedom: Integrating Mind, Body, and Spirit to Cultivate Healthy Relationships". Jordan Moore, AUC Woodruff Library, is the interviewer
ICP-MS data about heavy metal in dust aerosol generated by GAMEL
No full textICP-MS、APS data about heavy metal in dust aerosol generated by GAME
Configuration, optimization and evaluation of a novel instrumental platform for automated SPE-LC-MS/MS analysis of drugs in whole blood
No full textThe thesis describes the configuration, optimization and evaluation of a novel instrumental platform for fully automated SPE-LC-MS/MS analysis of small molecules, such as drugs, in whole blood.
The immunosuppressant Cyclosporine A was chosen as a model analyte, as this drug is predominantly bound to erythrocytes.
First, anticoagulated blood is converted into so-called Cell-Disintegrated Blood (CDB) by heat-shock or cryogenic treatment. CDB represents a homogenous blood sample and consists of subcellular particles which do not sediment on standing and do not clog capillaries, sieves or HPLC column packings.
For in-line treatment of anticoagulated whole blood, i.e. generation of CDB, a sample mixing unit, two special liquid handling units and two home-made sample processing modules were embedded into a XYZ-autosampler.
The module for heat-shock treatment consists of a stainless-steel capillary jacketed with a heating sleeve. Under optimal conditions for sampling and in-line processing of 20 µL of whole blood, it takes 13 seconds at 75 °C to generate CDB. The latter is stored in a holding loop before further treatment.
For cryogenic treatment of a blood sample, a stainless-steel processing needle with a large inner diameter was installed in one of the liquid handling units. The autosampler was programmed to introduce the processing needle containing the blood sample (40 µL) into a stand-pipe, which is located in a thermo-flask filled with liquid nitrogen. The processing needle therefore contacts liquid nitrogen and the blood sample is snap-frozen. Optimal conditions were found to be 10 seconds for snap-freezing at -196 °C and 60 seconds for thawing at room temperature.
A CDB sample obtained either by heat-shock or cryogenic treatment is further processed by being pumped via a switching-valve through an in-line filter to retain cell nuclei and “cell debris”. It was found that a depth filter packed with spherical hydrophilic silica is optimal. This filter allows at least 200 analysis cycles before it has to be replaced.
Next, the CDB sample is pumped on-line via another switching-valve through a SPE column (50 x 0.5 mm ID) at a high flow rate. Due to the special packing material and the very small inner diameter, a high linear flow velocity is achieved and turbulent flow is generated. By this, high-molecular matrix components such as proteins are eluted in the void volume to waste. The low-molecular weight target analyte Cyclosporine A and the Internal Standard Cyclosporine D are retained and extracted by reversed phase partitioning chromatography (RPC).
After fractionation of CDB on the SPE column, the analyte and the IS are transferred to a series-connected analytical column and separated from residual matrix components by RPC. Finally, the analyte is detected by a tandem mass spectrometer applying electrospray ionization (ESI) and multiple reaction monitoring (MRM).
The optimized method has a total analysis time of less than 11 minutes. The analytical procedure and the instrumental platform were validated for heat-shock treated blood samples with respect to linearity, range (10 - 1000 ng/mL), lower limit of quantitation (10 ng/mL), intra-day and inter-day accuracy and precision, as well as matrix-independent and matrix-dependent recovery (around 100 %). It was shown that the electrospray induced ionization is suppressed by approximately 25 %. These matrix effects, however, can be totally compensated for by the addition of an Internal Standard, i.e. Cyclosporine D.
A comparison with a semi-automated SPE-LC-MS/MS method, established in the Institute, revealed a very good agreement. This was shown by Passing and Bablok plots.
The robustness of the fully automated SPE-LC-MS/MS analysis platform was monitored during 500 consecutive analysis cycles with heat-shock treated blood samples. The relative standard deviation for the signal response was 15.6 % for Cyclosporine A and 15.2 % for Cyclosporine D. The back pressure of the total system rose only by 52 bar.
These findings show that, despite its instrumental and chromatographic complexity, the described analysis platform fulfills the prerequisites to be used in routine clinical-chemical analysis.Die Doktorarbeit beschreibt die Konfiguration, Optimierung und Evaluierung einer neuartigen instrumentellen Plattform für die vollständig automatisierte SPE-LC-MS/MS Analyse von kleinen Molekülen, wie beispielsweise Arzneistoffe, im Vollblut.
Das Immunsuppressivum Cyclosporin A wurde als Modellanalyt gewählt, da dieser Arzneistoff vorwiegend an Erythrozyten gebunden ist.
Zunächst wird antikoaguliertes Blut durch eine Hitze- oder Kälteschock Behandlung in sogenanntes Zell-desintegriertes Blut (Cell-Disintegrated Blood, CDB) überführt. CDB stellt eine homogene Blutprobe dar und besteht aus subzellulären Partikel, die beim Stehen nicht sedimentieren und keine Kapillaren, Siebe und HPLC- Packungsmaterialien verstopfen.
Für die in-line Behandlung von antikoagulierten Vollblut, d.h. für die Herstellung von CDB, wurde ein Gerät zum Mischen der Probe, zwei spezielle Bauteile für die Handhabung von Flüssigkeiten und zwei selbst-gebaute Module für die Probenprozessierung in einen XYZ-Probengeber eingebaut.
Das Modul für die Hitze-Schock Behandlung besteht aus einer Edelstahlkapillare, die mit einer Heizmanschette ummantelt ist. Unter optimalen Bedingungen für die Probenahme und in-line Prozessierung von 20 µL Vollblut werden 13 Sekunden und 75 °C benötigt um CDB herzustellen. Letzteres wird vor einer weiteren Behandlung in einer Rückhalteschleife gelagert.
Für die Tieftemperatur Behandlung einer Blutprobe wurde eine weitlumige Edelstahlnadel zur Prozessierung in eines der Bauteile für die Handhabung von Flüssigkeiten eingebaut. Der Probengeber wurde so programmiert, dass die Nadel, welche die Blutprobe (40 µL) enthält, in ein Steigrohr, welches sich in einem mit flüssigem Stickstoff gefüllten Isolierbehälter befindet, eingeführt wird.
Hierdurch wird die Nadel mit flüssigem Stickstoff kontaktiert und die Blutprobe schockgefroren. Als optimale Bedingungen wurden 10 Sekunden für das Schockgefrieren bei -196 °C und 60 Sekunden für das Auftauen bei Raumtemperatur gefunden.
Eine CDB Probe, die entweder durch Hitze- oder Kälteschock-Behandlung gewonnen wurde, wird weiter prozessiert, indem sie über ein Schaltventil durch einen in-line Filter gepumpt wird, um Zellkerne und „Zellbruchstücke“ zurückzuhalten. Es stellte sich heraus, dass ein Tiefenfilter, der mit sphärischem hydrophilem Kieselgel gepackt ist, optimal ist. Dieser Filter ermöglicht mindestens 200 Analysen-Zyklen bevor er ausgetauscht werden muss.
In einem weiteren Schritt wird die CDB Probe on-line über ein weiteres Schaltventil mit einer hohen Flussrate durch eine SPE Säule (50 x 0.5 mm ID) gepumpt. Aufgrund des speziellen Packungsmaterials und dem sehr kleinen Innendurchmesser wird eine hohe lineare Flussgeschwindigkeit erreicht und eine turbulente Strömung erzeugt. Hierdurch werden hochmolekulare Matrixkomponenten wie beispielsweise Proteine im Totvolumen in den Abfall eluiert. Niedermolekulare Zielanalyte wie Cyclosporin A und der interne Standard Cyclosporin D werden über Umkehrphasen- Verteilungschromatographie (RPC) reteniert und extrahiert.
Nach der Fraktionierung von CDB auf der SPE Säule, wird der Analyt und der interne Standard auf eine in Serie geschaltete analytische Säule überführt und von restlichen Matrixbestandteilen über RPC abgetrennt. Zum Schluss wird der Analyt in einem Tandem-Massenspektrometer über eine Elektrospray Ionisation (ESI) und Multiple Reaction Monitoring (MRM) detektiert.
Die optimierte Methode weist eine Gesamtanalysezeit von weniger als 11 Minuten auf.
Das Analysenverfahren und die instrumentelle Plattform wurden für Hitzeschock behandelte Blutproben hinsichtlich Linearität, Messbereich (10 – 1000 ng/mL), unterer Bestimmungsgrenze (10 ng/mL), Richtigkeit und Präzision innerhalb eines Tages und von Tag zu Tag, sowie Matrix-unabhängiger und Matrix-abhängiger Wiederfindung (um 100 %) validiert. Es konnte gezeigt werden, dass die über Elektrospray induzierte Ionisation um ca. 25 % unterdrückt wird. Diese Matrixeffekte können jedoch durch Zugabe des internen Standards Cyclosporin D vollständig kompensiert werden.
Ein Vergleich mit einer teilautomatisierten SPE-LC-MS/MS Routinemethode, die im Institut etabliert ist, ergab eine sehr gute Übereinstimmung. Dies konnte anhand von Passing und Bablok Plots aufgezeigt werden.
Die Robustheit der vollständig automatisierten SPE-LC-MS/MS Analysenplattform wurde während 500 aufeinander folgenden Analysezyklen mit Hitzeschock behandelten Blutproben überprüft. Die relative Standardabweichung für das MS-signal betrug 15.6 % für Cyclosporin A und 15.2 % für Cyclosporin D. Der Rückdruck des gesamten Systems stieg nur um 52 bar an.
Diese Ergebnisse zeigen, dass – trotz der instrumentellen und chromatographischen Komplexität – die beschriebene Analysenplattform die Anforderungen, die in der klinisch-chemischen Routineanalytik gestellt werden, erfüllt
Development of an UPLC-QTOF-MS method for Qualitative and Quantitative Analysis of Saussurea eopygmaea
No full textAn ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry UPLC-QTOF-MS method has been developed for qualitative and quantitative analysis major compounds in Saussurea eopygmaea Hand-Mazz, which has long been used as a traditional Tibetan medicine. This method was validated to be sensitive, precise, and accurate with the limits of detection of compounds 2, 3, 4, 6, and 7 with 0.67-1.90 mu g mL(-1), the overall intra-day and inter-day variations less than 8.45%, and the overall recovery over 93.8%, respectively. The correlation coefficients (R-2) of the calibration curves were higher than 0.998. In addition, by comparison MS and MS/MS spectra with those of authentic compounds and literatures, a total of 14 main peaks were identified within 6 min. These results demonstrate that this approach has the potential for quality control of S. eopygmaea and other Tibetan herbal medicines
sj-pdf-1-opp-10.1177_10781552221127698 - Supplemental material for Comparison of permeabilities of eight different types of cytotoxic drugs to five gloves with different materials by LC-MS/MS methods to reduce occupational exposure of medical personnel
No full textSupplemental material, sj-pdf-1-opp-10.1177_10781552221127698 for Comparison of permeabilities of eight different types of cytotoxic drugs to five gloves with different materials by LC-MS/MS methods to reduce occupational exposure of medical personnel by Hailong Zhou, Yunyun Li and Fan Xu in Journal of Oncology Pharmacy Practice</p
LC-API/MS in Drug Metabolism and Pharmacokinetic Studies
No full textThe use of API interfaces with quadrupole mass spectrometers has been shown to give rise to good sensitivity, selectivity, and robustness for the interfacing of LC to MS. Since their introduction in the 1990s the technique has rapidly become widespread, but at the outset of this research programme, there were still a number of problems associated with it, particularly when dealing with complex sample matrices. The aim of this research programme was to study illustrative examples of the kinds of problems associated with the analysis of biological samples using LC-API-MS in an attempt to arrive at strategies which could be employed to eliminate, or at least compensate for, the problems.
Commonly reported problems include the occurrence of matrix effects - a change in response of the target analyte(s) as a result of the presence in the samples of co /late eluting interferences. An investigation which compared ESI with APCI ionisation illustrated a significant drawback in the accepted methodology for the elimination of matrix effects.
Optimal LC conditions for a number of assays may use non-MS-friendly mobile phases. A simple and convenient solution to this problem was found to be the post column addition of organic modifier, which reproducibly and reliably enhanced sensitivity. This approach was initially used for a range of dihydropyridine calcium channel blockers and was subsequently applied to a range of chiral compounds from different therapeutic groups to illustrate that this was applicable as a generic technique for increasing sensitivity (typically by around an order of magnitude) in low organic mobile phases.
Strategies to develop and validate methods for the determination of endogenous analytes in a biological fluid were investigated. This involved the use of a surrogate matrix, to develop a method for the determination of endogenous testosterone in human serum and the use of non-matrix calibration standards for the successful development and validation of a method for the analysis of indolyl 3 acryloylglycine (IAG) in human urine.
As a result of observations suggesting promotion of ionisation of deltamethrin in liver tissue sample extracts, it was postulated that this was due to the presence of high concentrations of surfactants. After confirming the effect, a series of systematic investigations were performed to attempt to understand the mechanism to be able to utilise this as a general method for the enhancement of signal with low sensitivity analytes. It was found that the type of surfactant and concentration used was directly associated with an increased (or decreased) response.
Although there remain a number of problems associated with the use of LC-API-MS, the work undertaken for this thesis has successfully demonstrated a number of techniques that can be applied to overcome these problems. Knowledge of the nature of the sample undergoing analysis, the required analytical conditions, and where required careful application of one of the techniques described will ensure that a robust method can be readily developed
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