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1.
Anna Vesterlund Annika Tovedal Ulrika Nygren Henrik Ramebäck 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(3):951-955
Chemical yield determination can be a limiting source to the combined standard uncertainty in measurements of radionuclides.
Therefore, the combined standard uncertainties in yield determination in the measurement of radioactive strontium using two
methods were evaluated. The two methods compared were the measurement of stable strontium by atomic absorption spectrometry
(AAS) and the gamma spectrometric measurement of 85Sr. The evaluation showed that using gamma spectrometry for yield determination can reduce the combined standard uncertainty
by a factor of three compared to AAS. The expanded uncertainties of AAS and gamma spectrometry were calculated to be 10% and
3.3% (k = 2), respectively. 相似文献
2.
Dipl.‐Chem. Christian Pett M. Sc. Manuel Schorlemer Dr. Ulrika Westerlind 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(50):17001-17010
By displaying different O‐glycans in a multivalent mode, mucin and mucin‐like glycoproteins are involved in a plethora of protein binding events. The understanding of the roles of the glycans and the identification of potential glycan binding proteins are major challenges. To enable future binding studies of mucin glycan and glycopeptide probes, a method that gives flexible and efficient access to all common mucin core‐glycosylated amino acids was developed. Based on a convergent synthesis strategy starting from a shared early stage intermediate by differentiation in the glycoside acceptor reactivity, a common disaccharide building block allows for the creation of extended glycosylated amino acids carrying the mucin type‐2 cores 1–4 saccharides. Formation of a phenyl‐sulfenyl‐N‐Troc (Troc=trichloroethoxycarbonyl) byproduct during N‐iodosuccinimide‐promoted thioglycoside couplings was further characterized and a new methodology for the removal of the Troc group is described. The obtained glycosylated 9‐fluorenylmethoxycarbonyl (Fmoc)‐protected amino acid building blocks are incorporated into peptides for multivalent glycan display. 相似文献
3.
Gunilla Niklasson Ingemar Kvarnström Björn Classon Bertil Samuelsson† Ulrika Nillroth Helena Danielson 《Journal of carbohydrate chemistry》2013,32(5):555-569
ABSTRACT D-Mannitol was used as precursor for the synthesis of acyclic C 2 symmetric potential HIV-1 protease inhibitors. The 1- and 6-hydroxy groups of D-mannitol were substituted by -NHBoc, -NHValZ, -SAr, -SOAr and -SO2Ar and the 2-and 5-hydroxy groups were benzylated. In some products one of the central hydroxyl groups was either inverted or deoxygenated. Despite a close structural similarity to previously published inhibitors none of the products showed significant inhibitory activity against HIV-1 protease. 相似文献
4.
Ramón Batlle Anders Colmsjö Ulrika Nilsson 《Analytical and bioanalytical chemistry》2001,369(6):524-529
An SPME method was developed for sampling gaseous 2,4-toluene diisocyanate (2,4-TDI) involving derivatisation of the isocyanate
by reacting with dibutylamine (DBA). The TDI-DBA derivative thus formed was determined by LC–MS–MS utilising atmospheric pressure
chemical ionisation (APCI). As a first step, DBA was loaded onto a poly(dimethylsiloxane)/divinylbenzene (PDMS–DVB) fibre
coating by direct vapour-phase extraction of a highly concentrated diethyl ether solution of DBA. The DBA-loaded fibre was
then exposed to an artificially generated atmosphere of gaseous 2,4-TDI. The linearity of the method ranged from 52.8 to 3100
μg m–3 (6.8 to 400 ppbv) with a sampling time of 60 min. The proposed method has been applied to 2,4-TDI determination in an artificially
generated dynamic standard atmosphere, yielding an approximate method detection limit (MDL) of 2 μg m–3 (0.25 ppbv). This concentration is one twentieth of the Occupational Safety and Health Administration (OSHA) 8-hour time-weighted
average (TWA) exposure limit. The sampler with the PDMS–DVB-DBA coating was found to be stable and retains the required amount
of DBA for at least 10 days, an important feature for sampling systems with potential in-situ applications.
Received: 2 October 2000 / Revised: 4 December 2000 / Accepted: 6 December 2000 相似文献
5.
Backman Ulrika Jokiniemi Jorma K. Auvinen Ari Lehtinen Kari E.J. 《Journal of nanoparticle research》2002,4(4):325-335
We have prepared spherical non-agglomerated silver nanoparticles by an evaporation–condensation–dilution/cooling technique. Silver was evaporated from a crucible in a tubular flow reactor. A porous tube diluter was used to quench the carrier gas at the outlet of the reactor to enhance the formation of small particles and to suppress agglomeration and other particle growth mechanisms. The number size distribution of the prepared particles was measured with a differential mobility analyser–condensation nucleus counter combination and the size and the shape of the particles were analysed with transmission electron microscope. The system was modelled using a sectional aerosol dynamics computer code to estimate the importance of different aerosol processes. In all conditions the particles obtained were non-agglomerated and spherical. The mean particle diameter varied from 4 to 10-nm depending on boundary conditions. From the modelling studies it can be concluded that the nucleation rate is the most important parameter controlling the final particle size. 相似文献
6.
7.
Björklund J Isetun S Nilsson U 《Rapid communications in mass spectrometry : RCM》2004,18(24):3079-3083
Gas chromatography/ion trap mass spectrometry with in-source ionization and dissociation was used in positive-ion chemical ionization (PICI) mode for the determination of organophosphate triesters in indoor air. These compounds are widely used as additive flame retardants and plasticizers in different types of materials and have become ubiquitous pollutants in indoor environments. When using collision-induced dissociation in PICI mode the fragmentation of the organophosphate triesters can be performed in a more controllable way than in electron ionization (EI) mode. The developed selected-reaction monitoring method provided high selectivity for the investigated compounds. For 8-h air measurements (corresponding to 1.5 m3 of sampled air) the limit of detection of the method was determined to be in the range 0.1-1.4 ng m(-3), which is comparable with nitrogen-phosphorus detection and about 50-fold lower than when using EI in selected-ion monitoring mode. The presented method was applied to samples from three common indoor environments, in which a number of organophosphate triesters were identified and quantified. The dominating compound was found to be tris(2-chloropropyl) phosphate, which occurred at levels up to 0.8 microg m(-3). 相似文献
8.
Jansson B Elsherbiny D Simonsson US 《Rapid communications in mass spectrometry : RCM》2006,20(3):463-472
A sensitive method using enantiospecific liquid chromatography/tandem mass spectrometry detection for the quantitation of S- and R-mephenytoin as well as its metabolites S- and R-nirvanol and S- and R-4'-hydroxymephenytoin in plasma and urine has been developed and validated. Plasma samples were prepared by protein precipitation with acetonitrile, while urine samples were diluted twice with the mobile phase before injection. The analytes were then separated on a chiral alpha(1)-acid glycoprotein (AGP) column and thereafter detected, using electrospray ionization tandem mass spectrometry. In plasma, the lower limit of quantification (LLOQ) was 1 ng/mL for S- and R-4'-hydroxymephenytoin and S-nirvanol and 3 ng/mL for R-nirvanol and S- and R-mephenytoin. In urine, the LLOQ was 3 ng/mL for all compounds. Resulting plasma and urine intra-day precision values (CV) were <12.4% and <6.4%, respectively, while plasma and urine accuracy values were 87.2-108.3% and 98.9-104.8% of the nominal values, respectively. The method was validated for plasma in the concentration ranges 1-500 ng/mL for S- and R-4'-hydroxymephenytoin, 1-1000 ng/mL for S-nirvanol, and 3-1500 ng/mL for R-nirvanol and S- and R-mephenytoin. The validated concentration range in urine was 3-5000 ng/mL for all compounds. By using this method, the metabolic activities of two human drug-metabolizing enzymes, cytochrome P450 (CYP) 2C19 and CYP2B6, were simultaneously characterized. 相似文献
9.