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Analytical Characterization (analytical + characterization)
Selected AbstractsAnalytical characterization of PEG polymers by MEKCELECTROPHORESIS, Issue 4 2010María R. Plata Abstract Characterization of PEGs with average molecular masses of up to 2000 has been achieved using MEKC with UV detection. A rapid derivatization procedure with phenyl isocyanate using microwave radiation, in order to introduce chromophore groups in PEGs, has been developed involving a reaction time of 60,s. Different optimized conditions in accordance with the molecular weight have been studied to obtain the oligomer separation. The weight-average molecular mass the number-average molecular mass and the degree of polydispersity (molecular mass distribution) were calculated for the different PEGs obtaining similar results with those certified for standards. A good precision was obtained for characterizing the different oligomers. Ethylene glycol was used as the internal standard for the analysis of low-molecular-weight PEGs. The developed method was satisfactorily applied to the characterization of these polymers in several real samples, such as lubricant eye drops, toothpaste, tap water and eye make-up remover. [source] Analytical characterization of microfabricated SU-8 emitters for electrospray ionization mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2008Tiina Sikanen Abstract We present a detailed optimization and characterization of the analytical performance of SU-8-based emitters for electrospray ionization mass spectrometry (ESI/MS). The improved SU-8 fabrication process presented here enhances patterning accuracy and reduces the time and cost of fabrication. All emitters are freestanding and enable sample delivery by both pressure-driven and spontaneous flows. The optimized emitter design incorporates a sharp, double-cantilevered tip implemented to the outlet of an SU-8 microchannel and provides highly sensitive ESI/MS detection. Moreover, the optimized design allows the use of relatively large microchannel dimensions (up to 200 × 50 µm2, w × h) without sacrificing the detection sensitivity. This is advantageous with a view of preventing emitter clogging and enabling reproducible analysis. The measured limits of detection for the optimized emitter design were 1 nM for verapamil and 4 nM for Glu-fibrinopeptide B with good quantitative linearities between 1 nM and 10 µM (R2 = 0.9998) for verapamil and between 4 nM and 3 µM (R2 = 0.9992) for Glu-fibrinopeptide B. The measured tip-to-tip repeatability for signal intensity was 14% relative standard deviation (RSD) (n = 3; 5 µM verapamil) and run-to-run repeatability 4,11% RSD (n = 4; 5 µM verapamil) for all individual emitters tested. In addition, long-term stability of < 2% RSD was maintained for timescales of 30 min even under free flow conditions. SU-8 polymer was also shown to be chemically stable against most of the tested electrospray solvents. Copyright © 2008 John Wiley & Sons, Ltd. [source] Commercial manufacturing scale formulation and analytical characterization of therapeutic recombinant antibodiesDRUG DEVELOPMENT RESEARCH, Issue 3 2004Reed J. Harris Abstract Stable therapeutic antibody dosage forms present production technology challenges, particularly when high-concentration formulations are needed to meet the elevated dose requirements that are generally required for successful antibody therapy. Solid dosage forms, such as lyophilized powders, are generally more stable than liquid formulations. High-concentration drug products can be achieved by reconstitution of the lyophilisate in a smaller volume than its initial (pre-lyophilization) volume, but requires a significant vial overfill. High-concentration liquid formulations are becoming feasible as new techniques and technologies become available. Analytical methods to detect subtle molecular variations have been developed to demonstrate manufacturing consistency. Some molecular heterogeneity is contributed by conserved sites, such as Asn297 glycosylation and the loss of heavy chain C-terminal Lys residues. Characteristics that affect potency, stability, or immunogenicity must be elucidated for each therapeutic antibody. Drug Dev. Res. 61:137,154, 2004. © 2004 Wiley-Liss, Inc. [source] A Microbial Biosensor for p -Nitrophenol Using Arthrobacter Sp.ELECTROANALYSIS, Issue 14 2003Yu Lei Abstract This article reports the construction, optimization of performance variables and analytical characterization of a sensitive and selective microbial amperometric biosensor for measurement of p -nitrophenol (PNP), a U.S. Environmental Agency priority pollutant. The biosensor consisted of PNP-degrading/oxidizing bacteria Arthrobacter sp. JS443 as biological sensing element and a dissolved oxygen electrode as the transducer. The best sensitivity and response time were obtained using a sensor constructed with 1.2,mg dry wt. of cells and operating in pH,7.5, 50,mM citrate-phosphate buffer. Using these conditions, the biosensor was able to measure as low as 28,ppb (0.2,,M) of PNP selectively without interference from structurally similar compounds, such as phenol, nitrophenols and chlorophenols. The service life of the microbial biosensor is around 5,days when stored in the operating buffer at 4,°C. The applicability to lake water is demonstrated. [source] On the Risk,Downside Risk TradeoffTHE MANCHESTER SCHOOL, Issue 2 2004Carmen F. Menezes In the last decade the literature has established the empirical importance of the tradeoff between risk and downside risk in a variety of economic settings. While the notions of risk and downside risk have been generalized in the theoretical literature, the literature has yet to provide a choice-theoretic characterization of their tradeoff. This paper provides an analytical characterization of the risk,downside risk tradeoff and shows its relevance in the analysis of optimal decisions under uncertainty, such as the precautionary savings decision. [source] Development of a high throughput protein a well-plate purification method for monoclonal antibodiesBIOTECHNOLOGY PROGRESS, Issue 5 2009Jennifer Hopp Abstract We have developed a new high throughput method for the purification of monoclonal antibodies from harvested cell culture fluid for analytical characterization. This method uses Protein A resin in a 96 well-plate format with protein loading sufficient to perform multiple analyses per well. Resin and buffer conditions were optimized to obtain aggregate and charge variant comparability with three preparative Protein A purified monoclonal antibodies. We are able to successfully demonstrate comparability for aggregate within 0.25% based upon size-exclusion chromatography. Acidic species were found to be within 2% from the preparative purified control based upon cation-exchange chromatography, 5% based upon capillary zone electrophoresis, and 3% based upon imaged capillary isoelectric focusing. Glycan distribution was analyzed and was within 1% of the preparative purified controls. A tryptic digest was performed and all peaks in the preparative purified control were found in the first elution from the well-plate format. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Der globale Kohlenstoffkreislauf im Anthropozän.CHEMIE IN UNSERER ZEIT (CHIUZ), Issue 2 2010Betrachtung aus meereschemischer Perspektive Abstract Durch die Verbrennung fossiler Brennstoffe werden durch die Menschheit jährlich über 8 Milliarden Tonnen Kohlenstoff (Gt C) in Form von CO2 in die Atmosphäre emittiert. Die kumulativen Emissionen seit Beginn der industriellen Revolution haben zu einem Anstieg der atmosphärischen CO2 -Konzentration geführt, die einen zusätzlichen anthropogenen Treibhauseffekt zur Folge hat. Von den drei auf der Zeitskala von Jahrhunderten austauschenden Kohlenstoffreservoiren Atmosphäre, terrestrische Biosphäre und Ozean ist der Ozean bei weitem das größte. Das CO2 -System des Meerwassers umfasst die chemischen Spezies HCO3,, CO32, und CO2(aq). Daraus resultiert die pH-puffernde Eigenschaft des Meerwassers sowie seine hohe Aufnahmekapazität für anthropogenes CO2. Mit Hilfe von vier chemischen Messgrößen kann das marine CO2 -System analytisch sehr präzise beschrieben werden. Diese Messgrößen dienen als sensitive "Sensoren" für physikalische, chemische und biologische Vorgänge im Meer. Im marinen Kohlenstoffkreislauf sind größere natürliche Prozesse aktiv, die Kohlenstoff mit der Atmosphäre austauschen und im Innern der Ozeans umverteilen. Diese Prozesse werden auch als "Pumpen" bezeichnet und sowohl durch physikalische als auch biologische Faktoren angetrieben. Während die "physikalische Pumpe" unmittelbar durch die Aufnahme von anthropogenem CO2 aus der Atmosphäre verstärkt wird, ist dieses für die beiden "biologischen Pumpen" bisher ungeklärt. Eine Vielzahl von potenziellen Konsequenzen des globalen Wandels (Temperaturanstieg, marine CO2 -Aufnahme, Ozeanversauerung) auf marine Ökosysteme sind identifiziert worden. Diese werden gegenwärtig intensiv hinsichtlich ihrer Klimasensitivität sowie ihres Rückkopplungspotenzials auf das Klima untersucht. Es ist jedoch kaum vorstellbar, dass die "biologischen Pumpen" sich unter dem Einfluss des globalen Wandels nicht verändern werden. By burning of fossil fuels humankind emits more than 8 billion tons of carbon (Gt C) in the form of CO2 to the atmosphere. Since the onset of the industrial revolution the cumulative emissions have led to an increase of the atmospheric CO2 concentration which corresponds to an additional radiative forcing in the atmosphere. Of the three reservoirs which exchange carbon on the time scale of centuries , atmosphere, terrestrial biosphere, and ocean , the ocean is by far the largest. The marine CO2 system comprises the chemical species HCO3,, CO32,, and CO2(aq). This gives rise to the pH-buffering nature of seawater as well as its high uptake capacity for anthropogenic CO2. Four measurement parameters of the marine CO2 system are available for an accurate analytical characterization. These parameters also provide a means of sensing the role of physical, chemical, and biological drivers for the marine carbon cycle. The marine carbon cycle features major natural processes that exchange carbon with the atmosphere and re-distribute it throughout the ocean. These are known as "pumps" and driven by physical and biological factors. While the "physical pump" is inevitably enhanced by the oceanic uptake of anthropogenic CO2, even the sign of the response is currently not clear for the "biological pumps". A host of potential consequences of global change (temperature rise, ocean carbonation, ocean acidification) have been identified. These are currently studied intensively with respect to their climate sensitivity as well as the climate feedback potential. [source] Generation of Cationic [Zr-{tert -Butyl Enolate}] Reactive Species: Methyl Abstraction versus Hydride AbstractionCHEMISTRY - A EUROPEAN JOURNAL, Issue 17 2004Bing Lian Dr. Abstract Treatment of the neutral methyl,Zr,enolate [Cp2Zr(Me){O(tBuO)CCMe2}] (1) with one equivalent of B(C6F5)3 or [HNMe2Ph][B(C6F5)4] as a methyl abstractor in THF at 0,°C leads to the selective formation of the free ion pair complex [Cp2Zr(THF){O(tBuO)CCMe2}]+,[anion], (2) (anion=MeB(C6F5)3,, B(C6F5)4,), which is relevant to the controlled polymerization of methacrylates. Cation 2 rapidly decomposes at 20,°C in THF with release of one equivalent of isobutene to form the cationic Zr,carboxylate species [Cp2Zr(THF)(O2CiPr)]+ (3), through a proposed intramolecular proton transfer process from the tert -butoxy group to the enolate. The reaction of 1 with one equivalent of B(C6F5)3 or [HNMe2Ph][B(C6F5)4] in CH2Cl2 leads to the direct, rapid formation of the dimeric ,-isobutyrato,Zr dicationic species [{Cp2Zr[,-(O2CiPr)]}2]2+ (4), which gives 3 upon dissolution in THF. Contrastingly, when [Ph3C][B(C6F5)4] is used to generate the cationic Zr,enolate species from 1 in CD2Cl2, a 15:85 mixture of dicationic complexes 4 and [{Cp2Zr[, -(O2CC(Me)CH2)]}2]2+[B(C6F5)4] (5 -[B(C6F5)4]2) is obtained quantitatively. The formation of 5 is proposed to arise from initial hydride abstraction from a methyl enolate group by Ph3C+, as supported by the parallel production of Ph3CH, and subsequent elimination of methane and isobutene. In addition to standard spectroscopic and analytical characterizations for the isolated complexes 2,5, complexes 4 and 5 have also been structurally characterized by X-ray diffraction studies. [source] | |||||||||||||