Search results for " Liquid"

Comparison of high-pressure liquid chromatography (HPLC) and Griess reagent-spectroscopic methods for the measurement of nitrate in serum from health…

2008

Bioavailability of NO can be estimated by measuring the concentration of nitrate (NO(3)) in serum. However, the methods used for the measurement NO(3) in plasma or serum show a great degree of variation. Therefore, we compared two analytical methods for the measurement of NO(3) in serum.The concentration of NO(3) in 600 serum samples collected from healthy individuals was determined by the HPLC and by the Griess reagent-spectroscopic method.The concentration of NO(3) in the samples was 29.4+/-16.1 micromol/L and 26.2+/-14.0 micromol/L (mean+/-SD) measured by HPLC and Griess reagent-spectroscopic method respectively (p0.0001). We detected a significant correlation between the two methods (R=…

Estradiol counteracts oxidized LDL-induced asymmetric dimethylarginine production by cultured human endothelial cells.

2006

Objective: Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide (NO) synthase, is a novel cardiovascular risk factor produced by endothelial cells. ADMA levels are mainly regulated by the activity of dimethylarginine dimethylaminohydrolases (DDAH). Endothelial release of ADMA is increased in the presence of oxidized LDL cholesterol (oxLDL), whereas estrogens stimulate NO production by endothelial cells by increasing both expression and activity of NO synthase and by reducing ADMA levels. Thus, the aim of the present study was to evaluate the estradiol effects on the DDAH/ADMA/NO pathway in cultured human umbilical vein endothelial cells (HUVEC) exposed to LDL. Methods…

Sympathetic activity at rest and motor brain areas: FDG-PET study.

2008

Although recent studies identified brain areas which are involved in short term activation of the sympathetic nervous system, little is known about brain mechanisms which generate the individual variability of basal autonomic activity. In this fluorodeoxyglucose positron emission tomography study (FDG-PET), we aimed to identify brain regions, which covary with function parameters of the autonomic nervous system at rest. Therefore, FDG-PET (Siemens, Germany) was performed twice in 14 healthy resting subjects (7 m, 7 f; mean age 29.5 years) while different parameters of autonomic function were assessed simultaneously: Blood pressure, heart rate, power spectra of heart rate variability (HF/LF …

Modulation of oestrogen excretion profiles by adjuvant chemotherapy in pre- and postmenopausal breast cancer.

1985

Modulation of steroid status by conventional chemotherapy was studied in 31 breast cancer patients receiving CMF and in 31 age-matched breast cancer patients without any therapy, taken as controls. This was achieved through the study of oestrogen excretion profiles using previously identified parameters and referring not only to classical but also to the “other”, namely catechol and unusual, oestrogen metabolites. After CMF treatment the premenopausal patients exhibit a modified excretion pattern, mainly concerning a marked and significant reduction of classical oestrogens, as shown by pattern indices. Because there is evidence that oestriol metabolism is not markedly affected by CMF treatm…

Effective Henry's law partitioning and the salting constant of glyoxal in aerosols containing sulfate.

2013

The reversible partitioning of glyoxal was studied in simulation chamber experiments for the first time by time-resolved measurements of gas-phase and particle-phase concentrations in sulfate-containing aerosols. Two complementary methods for the measurement of glyoxal particle-phase concentrations are compared: (1) an offline method utilizing filter sampling of chamber aerosols followed by HPLC-MS/MS analysis and (2) positive matrix factorization (PMF) analysis of aerosol mass spectrometer (AMS) data. Ammonium sulfate (AS) and internally mixed ammonium sulfate/fulvic acid (AS/FA) seed aerosols both show an exponential increase of effective Henry's law coefficients (KH,eff) with AS concentr…

Towards comprehensive non-target screening using heart-cut two-dimensional liquid chromatography for the analysis of organic atmospheric tracers in i…

2021

Abstract Non-target screening of secondary organic aerosol compounds in ice cores is used to reconstruct atmospheric conditions and sources and is a valuable tool to elucidate the chemical profiles of samples with the aim to obtain as much information as possible from one mass spectrometric measurement. The coupling of mass spectrometry to chromatography limits the results of a non-target screening to signals of compounds within a certain polarity range based on the utilized stationary phases of the columns. Comprehensive two-dimensional liquid chromatography (LCxLC) introduces a second column of different functionality to enable the analysis of a broader range of analytes. Conventional LCx…

Comparison of UV and charged aerosol detection approach in pharmaceutical analysis of statins

2009

Abstract CAD (charged aerosol detector) has recently become a new alternative detection system in HPLC. This detection approach was applied in a new HPLC method for the determination of three of the major statins used in clinical treatment—simvastatin, lovastatin and atorvastatin. The method was optimized and the influence of individual parameters on CAD response and sensitivity was carefully studied. Chromatography was performed on a Zorbax Eclipse XDB C18 (4.6 mm × 75 mm, 3.5 μm), using acetonitrile and formic acid 0.1% as mobile phase. The detection was performed using both CAD (20 pA range) and DAD (diode array detector—238 nm) simultaneously connected in series. In terms of linearity, …

Characterization of oligomeric compounds in secondary organic aerosol using liquid chromatography coupled to electrospray ionization Fourier transfor…

2009

The components of secondary organic aerosols (SOAs) generated from the gas-phase ozonolysis of two C(10)H(16)-terpenes (alpha-pinene; sabinene) and a cyclic C(6)H(10) alkene (cyclohexene) were characterized by the use of a Fourier transform ion cyclotron mass spectrometer equipped with an electrospray ionization source operated in the negative ion mode. Reversed-phase high-performance liquid chromatography was used to achieve chromatographic separation of highly oxidized organic compounds. In addition to the well-known group of low molecular weight oxidation products (monomers; e.g. dicarboxylic acids), higher molecular weight compounds (dimers) were also detected and their exact elemental …

Dissolution and hydrolysis of fibre sludge using hydroxyalkylimidazolium hydrogensulphate ionic liquids

2014

Abstract The dissolution and hydrolysis of wet fibre sludge in ionic liquids (ILs) with different reaction conditions are performed in this study. Novel types of hydroxyalkylimidazolium hydrogensulphate ILs, [glymim]HSO 4 , [hemim]HSO 4 and [hpmim]HSO 4 , are especially designed and aimed to combine the dissolution and hydrolysis of wet fibre sludge in a one-step pretreatment. The results were obtained based on the analysis of total reducing sugars (TRS) with the DNS method. The dissolution and hydrolysis of fresh wild horse chestnut fruit ( Aesculus hippocastanum ) with the same ILs were also carried out as a comparison reference. Since fibre sludge is cellulose based and horse chestnut fr…

L'affitto d'azienda nel fallimento

La proposta esegetica del presente lavoro si articola su due livelli. Sul primo, l'affitto endofallimentare è visto come strumento di riallocazione del rischio di impresa nell'insolvenza, dai creditori al terzo affittuario, e di ripristino del fisiologico rapporto tra potere gestorio e business risk, tipico dell'impresa in bonis. Sul secondo, l'istituto è inquadrato non come anomalia sistematica, ma come coerente momento di valorizzazione della massa attiva da liquidarsi, in una mutata concezione della fase liquidatoria fallimentare, necessariamente integrante un momento gestionale che, per la res azienda, coincide con la continuazione dell'impresa.