Polymerization Kinetics: Monitoring Monomer Conversion Using an Internal Standard and the Key Role of Samplet0

2011 ◽  
Vol 88 (1) ◽  
pp. 116-121 ◽  
Author(s):  
Olivier Colombani ◽  
Ophélie Langelier ◽  
Ekkachaï Martwong ◽  
Patrice Castignolles
Keyword(s):  
Internal Standard ◽  
Monomer Conversion ◽  
Polymerization Kinetics ◽  
Kinetics Monitoring

Automated Carbohydrate Analysis of Physiologic Fluids

1968 ◽  
Vol 14 (6) ◽  
pp. 538-547 ◽  
Author(s):  
R L Jolley ◽  
M L Freeman
Keyword(s):  
Blood Serum ◽  
Research Laboratory ◽  
Exchange Resin ◽  
Clinical Laboratory ◽  
Anion Exchange Resin ◽  
Internal Standard ◽  
Carbohydrate Analysis ◽  
Basic Anion Exchange Resin ◽  
Basic Anion

Abstract Automated carbohydrate analysis can be useful clinically in the research laboratory as an aid in understanding the fundamental role of carbohydrates in metabolism, including their pathologic significance. An analytic system being developed at our laboratory utilizes an automated carbohydrate analyzer to chromatograph borated physiologic fluids while using strongly basic anion-exchange resin. The eluted carbohydrates are detected by sulfuric acid-phenol colorimetry. The carbohydrate analyzer used in this experimental work should become a useful tool in the clinical laboratory. Normal and diabetic human urine and blood serum have been chromatographed and significant differences established. As many as 38 peaks have been observed in the complex urine chromatograms. Using cochromatographic technics, 14 peaks have been tentatively identified as sucrose, raffinose, N-acetylglucosamine, maltose, lactose, ribose, fructose, arabinose, fucose, galactose, xylose, mannoheptulose, glucose, and glucose-1-phosphate. All except fucose have been quantified. Blood serum chromatograms consist of a major glucose peak and several smaller peaks indicating traces of other sugars. Melibiose has been used as an internal standard in chromatograms to determine recovery, resolution, and reproducibility. With the present technic, the lower limit of detectable sugar in physiologic fluids is in the 1-µg. range.

scholarly journals 1,3-Dioxolan-4-Ones as Promising Monomers for Aliphatic Polyesters: Metal-Free, in Bulk Preparation of PLA

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2396
Author(s):  
Stefano Gazzotti ◽  
Marco Aldo Ortenzi ◽  
Hermes Farina ◽  
Alessandra Silvani
Keyword(s):  
Molecular Weight ◽  
Thermal Properties ◽  
Acid Catalyst ◽  
Monomer Conversion ◽  
Reaction Conditions ◽  
Aliphatic Polyesters ◽  
Metal Free ◽  
Weight Growth ◽  
Double Activation

The first example of solvent-free, organocatalyzed, polymerization of 1,3-dioxolan-4-ones, used as easily accessible monomers for the synthesis of polylactic acid (PLA), is described here. An optimization of reaction conditions was carried out, with p-toluensulfonic acid emerging as the most efficient Brønsted acid catalyst. The reactivity of the monomers in the tested conditions was studied following the monomer conversion by 1H NMR and the molecular weight growth by SEC analysis. A double activation polymerization mechanism was proposed, pointing out the key role of the acid catalyst. The formation of acetal bridges was demonstrated, to different extents depending on the nature of the aldehyde or ketone employed for lactic acid protection. The polymer shows complete retention of stereochemistry, as well as good thermal properties and good polydispersity, albeit modest molecular weight.

scholarly journals Polymerization Kinetics Stability, Volumetric Changes, Apatite Precipitation, Strontium Release and Fatigue of Novel Bone Composites for Vertebroplasty

2018 ◽  
Author(s):  
Piyaphong Panpisut ◽  
Kirsty Main ◽  
Muhammad Adnan Khan ◽  
Mayda Arshad ◽  
Wendy Xia ◽  
...  
Keyword(s):  
Heat Generation ◽  
Glass Fibers ◽  
Monomer Conversion ◽  
Reaction Rates ◽  
Polymerization Kinetics ◽  
Fatigue Properties ◽  
Apatite Formation ◽  
Maximum Reaction ◽  
Urethane Dimethacrylate ◽  
Lower Temperature

AbstractPurposeThe aim was to determine effects of diluent monomer and monocalcium phosphate monohydrate (MCPM) on polymerization kinetics and volumetric stability, apatite precipitation, strontium release and fatigue of novel dual-paste composites for vertebroplasty.Materials and methodsPolypropylene (PPGDMA) or triethylene (TEGDMA) glycol dimethacrylates (25 wt%) diluents were combined with urethane dimethacrylate (70 wt%) and hydroxyethyl methacrylate (5 wt%). 70 wt% filler containing glass particles, glass fibers (20 wt%) and polylysine (5 wt%) was added. Benzoyl peroxide and MCPM (10 or 20 wt%) or N-tolyglycine glycidyl methacrylate and tristrontium phosphate (15 wt%) were included to give initiator or activator pastes. Commercial PMMA (Simplex) and bone composite (Cortoss) were used for comparison.ATR-FTIR was used to determine thermal activated polymerization kinetics of initiator pastes at 50-80 °C. Paste stability, following storage at 4-37 °C, was assessed visually or through mixed paste polymerization kinetics at 25 °C. Polymerization shrinkage and heat generation were calculated from final monomer conversions. Subsequent expansion and surface apatite precipitation in simulated body fluid (SBF) were assessed gravimetrically and via SEM. Strontium release into water was assessed using ICP-MS. Biaxial flexural strength (BFS) and fatigue properties were determined at 37 °C after 4 weeks in SBF.ResultsPolymerization profiles all exhibited an inhibition time before polymerization as predicted by free radical polymerization mechanisms. Initiator paste inhibition times and maximum reaction rates were described well by Arrhenius plots. Plot extrapolation, however, underestimated lower temperature paste stability. Replacement of TEGDMA by PPGDMA, enhanced paste stability, final monomer conversion, water-sorption induced expansion and strontium release but reduced polymerisation shrinkage and heat generation. Increasing MCPM level enhanced volume expansion, surface apatite precipitation and strontium release. Although the experimental composite flexural strengths were lower compared to those of commercially available Simplex, the extrapolated low load fatigue lives of all materials were comparable.ConclusionsIncreased inhibition times at high temperature give longer predicted shelf-life whilst stability of mixed paste inhibition times is important for consistent clinical application. Increased volumetric stability, strontium release and apatite formation should encourage bone integration. Replacing TEGDMA by PPGDMA and increasing MCPM could therefore increase suitability of the above novel bone composites for vertebroplasty. Long fatigue lives of the composites may also ensure long-term durability of the materials.

scholarly journals P38 Identification of Nifurtimox metabolites in urine of pediatric Chagas disease patients by UHPLC-MS/MS

2019 ◽  
Vol 104 (6) ◽  
pp. e32.3-e33
Author(s):  
CA Pérez Montilla ◽  
S Moroni ◽  
N González ◽  
G Moscatelli ◽  
JM Altcheh ◽  
...  
Keyword(s):  
Chagas Disease ◽  
Pediatric Patients ◽  
Neutral Loss ◽  
Multiple Reaction Monitoring ◽  
Internal Standard ◽  
Research Unit ◽  
Therapeutic Drug ◽  
List Type ◽  
Monitoring Strategies

BackgroundNifurtimox (NFX) is one of the only 2 available drugs for the treatment of Chagas disease, a parasitic disease endemic to Latin America. In spite of widespread use of this medication, little is known regarding its metabolism, particularly in children.The objective of this study was to develop a method to identify NFX metabolites in human samples, and apply it to the discovery of NFX metabolites in urine from pediatric patients undergoing treatment for Chagas disease.MethodsUrine was collected from 12 pediatric patients and 8 healthy volunteers (controls), and anonymized before analysis. Informed consent was obtained from all participants. Samples were aliquoted, deproteinized with ACN (BNZ as internal standard) and centrifuged in cold. 10% of supernatant in water was injected into a 1.8 µm C18 column and chromatographed in 3.5 min under a water/ACN gradient at 0.4 mL/min in a Shimadzu Nexera X2 UHPLC equipment. Species were positively ionized by a Turbo IonSpray source. Metabolites were identified and characterized by an ABSciex 6500 QTRAP spectrometer through Enhanced-Mass-Screening (EMS), Neutral-Loss (NL), Precursor-Ion (PREC), Enhanced-Product-Ion (EPI) and MS3 experiments. For chromatographic monitoring, parameters were optimized and the three most intense Multiple-Reaction-Monitoring (MRM) transitions were selected.ResultsDenitrated NFX conjugated with cysteine (M1) and N-acetyl-cysteine (M2), as well as other phase I metabolites like saturated nitrile (M3), hydroxyamide (M4), carboxylic acid (M5) or aldehyde (M6) were identified in most samples. The final MS/MS detection method was high reproducible and sensitive for all metabolites.ConclusionsWe found the main NFX metabolites in pediatric urine using a fast MS/MS method that can allow us to efficiently study the role of NFX and its metabolites in pediatric treatment response and the adverse drug reactions, and in combination with PK/PD experiments will facilitate future clinical trials, and possibly develop new therapeutic drug monitoring strategies.ReferenceThe research was carried out in the Translational Research Unit (IMIPP-CONICET), located in the Buenos Aires Children´s Hospital ‘Dr. Ricardo Gutiérrez’, and financed by the Fund for Scientific and Technological Research (FONCyT, Project BID-PICT 2015–0168).Disclosure(s)Nothing to disclose

scholarly journals Endogenous L-Carnosine Level in Diabetes Rat Cardiac Muscle

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Yali Liu ◽  
Dan Su ◽  
Ling Zhang ◽  
Shaofeng Wei ◽  
Kuangyi Liu ◽  
...  
Keyword(s):  
Cardiac Muscle ◽  
Reliable Method ◽  
Internal Standard ◽  
Muscle Carnosine ◽  
Relative Standard ◽  
Healthy Control ◽  
Novel Method ◽  
Interday Precision ◽  
Carnosine Level

A novel method for quantitation of cardiac muscle carnosine levels using HPLC-UV is described. In this simple and reliable method, carnosine from the rat cardiac muscle and the internal standard, thymopentin, were extracted by protein precipitation with acetonitrile. The method was linear up to 60.96 μg·mL−1for L-carnosine. The calibration curve was linear in concentration ranges from 0.5 to 60.96 μg·mL−1. The relative standard deviations obtained for intra- and interday precision were lower than 12% and the recoveries were higher than 90% for both carnosine and internal standard. We successfully applied this method to the analysis of endogenous carnosine in cardiac muscle of the diabetes rats and healthy control rats. The concentration of carnosine was significantly lower in the diabetes rats group, compared to that in the healthy control rats. These results support the usefulness of this method as a means of quantitating carnosine and illustrate the important role of L-carnosine in cardiac muscle.

The Strategic Imperative of Quality Assurance

2022 ◽  
pp. 212-227
Author(s):  
Ahmed M. Abdel-Meguid
Keyword(s):  
Higher Education ◽  
Quality Assurance ◽  
Higher Education Institutions ◽  
Internal Standard ◽  
Fundamental Question ◽  
New Normal ◽  
American University ◽  
Standard Procedures ◽  
Strategic Imperative

This chapter focuses on the fundamental question: What is the strategic importance of quality assurance (QA) for higher education institutions (HEIs)? Divided into four main segments, the chapter begins by defining QA within the context of a continuum, ranging from entirely voluntarily QA—as a part of the HEI internal standard procedures—to more ‘prescriptive' models, as mandated by ranking and accreditation bodies. Secondly, the chapter engages in identifying specific strategic functions of QA in light of two inherent objectives of HEIs: competitiveness and sustainable impact. Next, the chapter showcases the role of QA played in advancing the American University in Cairo (AUC) School of Business to the renowned triple-crown accreditation status (AACSB, EQUIS, AMBA), while highlighting both challenges encountered and implementable solutions. Last of all, the chapter discusses potential future changes to QA, given the ‘new normal' of the higher education landscape.

l-Lactide polymerization studied by 1H NMR with diffusion-ordered spectroscopy (DOSY): a “One NMR Tube Experiment” providing data on monomer conversion, polymer structure, Mn and Mw

2015 ◽  
Vol 6 (24) ◽  
pp. 4353-4357 ◽  
Author(s):  
P. Lewinski ◽  
S. Sosnowski ◽  
S. Kazmierski ◽  
S. Penczek
Keyword(s):  
1H Nmr ◽  
Molar Mass ◽  
Monomer Conversion ◽  
Polymer Structure ◽  
Polymerization Kinetics ◽  
Average Molar Mass ◽  
On Line ◽  
First Time ◽  
Lactide Polymerization

The standard NMR and DOSY techniques allowed for the first time the on-line study of the polymerization kinetics together with the determination of number average molar mass Mn and mass average molar mass Mw.

Study on the Role of Surfactants to Aqueous Two-Phase Synthesizing CPAM

2013 ◽  
Vol 781-784 ◽  
pp. 511-514
Author(s):  
Ya Feng Cao ◽  
Mei Jun Qu ◽  
Feng Zhi Tan ◽  
Zhao Li Liu ◽  
Yuan Li
Keyword(s):  
Monomer Conversion ◽  
Continuous Phase ◽  
Ionic Surfactants ◽  
Process Conditions ◽  
Phase System ◽  
Two Phase ◽  
Optimum Reaction ◽  
Optimum Reaction Condition ◽  
Better Than

In this paper,cationic polyacrylamide (CPAM) was synthesized by using aqueous two-phase polymerization. The Role of surfactants to aqueous two-phase synthesizing CPAM was studied, including the effect of the type,the composition and the concentration of the surfactants. The results showed that non-ionic surfactants had a better stabilizing impact on the polymer aqueous two-phase system. And the effect of the compound surfactant was better than that of a single surfactant. Take the chemical compound of Tween80 and OP10 as the polymerization auxiliaries, the optimum reaction condition of synthesis were as follows:wTween80:ѡOP10=1.5,w=1.6%, 50°C.In this process conditions, the distribution coefficient was the most appropriate in the continuous phase, the total monomer conversion rate and the intrinsic viscosity number of the product reached the maximum.

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