Search results for "liquid"
showing 10 items of 4351 documents
Comparison of several methods used for the determination of cephalosporins. Analysis of cephalexin in pharmaceutical samples
2002
The precision of UV absorbance of intact and acid degraded cephalosporins, ninhydrin, high performance liquid chromatography and iodometric methods used for analysis of cefoxitin, cefotaxime, cephazolin and cephalexin were compared. To obtain the calibration graphs the analytical signal used were: absorbance, first derivative absorbance, second derivative absorbance and H-point Standard Additions Method by using absorbance values at two selected wavelengths as analytical signal. These methods and calibration graphs were also used for the determination of cephalexin in pharmaceutical samples.
Furosemide assay in pharmaceuticals by Micellar liquid chromatography: study of the stability of the drug.
2000
A simplified high-performance liquid chromatographic procedure is described for the determination of furosemide (4-chloro-N-furfuryl-5-sulphamoylanthranillic acid), which makes use of UV detection, a C18, reversed-phase column, and micellar mobile phases of sodium dodecyl sulphate (SDS) and 1-propanol at pH 3 buffered with phosphate system. The most adequate experimental conditions to handle furosemide solutions in the analytical laboratory are studied. The mixture of furosemide and its degradation products which are formed upon light exposition was resolved with a mobile phase of 0.04 M SDS-2% propanol. Separation of furosemide from its common impurities and the hydrolytic product, 4-chlor…
Determination of pharmaceutical residues in wastewater using high performance liquid chromatography coupled to quadrupole-Orbitrap mass spectrometry
2016
Abstract A multi-class method for the determination of 24 emerging pharmaceutical residues has been developed and validated. The method is based on solid-phase extraction of wastewater samples using Strata-X cartridges followed by high performance liquid chromatography coupled to hybrid quadrupole − Orbitrap high resolution mass spectrometry (HPLC-Q-Orbitrap-HRMS). A single-laboratory validation procedure showed satisfactory analytical performance. The analysis of 21 samples collected at the wastewater treatment plant in Riga revealed the occurrence of 20 compounds of different therapeutic classes. The highest concentration was found for the central nervous system stimulator caffeine − up t…
Efficiency of antidepressant drugs as monoamine reuptake inhibitors: analysis of the hydrophobicity influence using biopartitioning micellar chromato…
2004
The reuptake blockade of biogenic amines by antidepressants is related not only to their therapeutics effects, but also to their side effects and potential drug-drug interactions. As an alternative to classical quantitative structure-activity relationships studies, in this work we propose different quantitative retention-activity relationships (QRAR) models that are able to describe the monoamine reuptake inhibition by antidepressants. The retention of compounds is measured using a biopartitioning micellar chromatography (BMC) system that can simulate the same hydrophobic, electronic and steric molecular interactions as those that condition drug activity. Since all the compounds considered …
Determination of queuosine derivatives by reverse-phase liquid chromatography for the hypomodification study of Q-bearing tRNAs from various mammal l…
2004
Three queuosine derivatives (Q-derivatives) have been found at position 34 of four mammalian so-called Q-tRNAs: queuosine (Q) in tRNA(Asn) and tRNA(His), mannosyl-queuosine (manQ) in tRNA(Asp), and galactosyl-queuosine (galQ) in tRNA(Tyr). An analytical procedure based on the combined means of purified tRNA isolation from liver cells and ribonucleoside analysis by reverse-phase high performance liquid chromatography coupled with real-time UV-spectrometry (RPLC-UV) was developed for the quantitative analysis of the three Q-derivatives present in total tRNA from liver tissues and liver cell cultures. Using this analytical procedure, the rates of Q-tRNA modification were studied in total tRNAs…
Liquid Biopsy and Lymphoma Monitoring in Clinical Practice
2021
Abstract INTRODUCTION Lymphomas represent the fourth most frequent type of cancer, 90% of them arising from B cell lymphocytes. Despite their high prevalence, around 40% remain incurable because of refractoriness to current chemoimmunotherapy or disease relapse after obtaining response (Li et al., 2018; Meng et al., 2020). The cell of origin is a B lymphocyte with a unique B cell receptor (BCR). The BCR is an immunoglobulin composed of two heavy chains (IgH) and two light chains (IgL) whose genes have multiple coding segments that through rearrangement first and further somatic hypermutation in the germinal center, generate a unique sequence that could be used to monitor the treatment respo…
Influence of heterogeneous freezing on the microphysical and radiative properties of orographic cirrus clouds
2013
The influence of heterogeneous freezing on the microphysical and optical properties of orographic cirrus clouds has been simulated with the large eddy simulation model EULAG. Idealised simulations with different concentrations of ice nuclei (IN) in a dynamically dominated regime with high vertical velocities have been performed. Furthermore the temperature at cloud formation as well as the critical supersaturation for initiation of heterogenous freezing have been varied. The shortwave, longwave and net cloud forcing has been calculated under the assumption that the clouds form between 06:00 and 12:00 local time (LT) or between 12:00 and 18:00 LT. In general it can be seen that the onset of …
A numerical model of the cloud-topped planetary boundary-layer: Impact of aerosol particles on the radiative forcing of stratiform clouds
1997
In a numerical sensitivity study, the microphysical model of stratus MISTRA, is used to investigate the impact of aerosol particles on the evolution of stratiform clouds. Four model runs are presented, each for a different type of background aerosol. Two include aerosol particle size-distributions which are typical of marine and rural continental air masses; a third represents a mixture of marine and rural continental aerosol particles, and the fourth rural continental aerosol particles with a reduced solubility in water. The results show that the microphysical structure of layer clouds was strongly affected by the physico-chemical properties of the aerosol particles from which the cloud dr…
A numerical model of the cloud-topped planetary boundary-layer: radiative forcing of aerosols in stratiform clouds
1998
In a numerical sensitivity study with the microphysical stratus model MISTRA the impact of aerosol particles on the time evolution of stratiform clouds is investigated. Four model runs with different aerosol size distributions are presented. Two size distributions are typical for maritime and continental air masses. The third model run consists of a mixture of maritime and rural aerosol particles, while in the fourth case study rural aerosol particles with a reduced water solubility are utilized. The numerical results show that the microphysical structure of the clouds is strongly affected by the physico-chemical properties of the aerosol particles. In the maritime case, with a relatively l…
Riming of Graupel: Wind Tunnel Investigations of Collection Kernels and Growth Regimes
2009
Abstract Laboratory experiments were carried out in the vertical wind tunnel in Mainz, Germany, to study the collision coalescence growth of single spherical ice particles having initial radii between 290 and 380 μm while they were freely floated in a laminar flow containing a cloud of supercooled droplets with radii between 10 and 20 μm. The experiments were performed in a temperature range between −8 and −12°C, where riming proceeds in the atmosphere, and with cloud liquid water contents lying between 0.9 and 1.6 g m−3 (i.e., values typically found in mixed-phase clouds). The collection kernels were calculated from the mass increase of the rimed ice particles and the average liquid water …