Search results for "efficient"
showing 10 items of 1603 documents
Spectral attenuation of solar ultraviolet radiation in humic lakes in Central Finland
2003
The attenuation of solar ultraviolet (UV) radiation in five lakes in Central Finland was evaluated through field measurements and/or by determining the optical properties of the lake water during summer 1999. Spectral UV irradiance in the air and at several depths underwater was measured in three lakes (Lake Palosjärvi, Konnevesi, and Jyväsjärvi) with dissolved organic carbon (DOC) ranging from 4.9 to 8.7 mg l(-1) and chlorophyll a ranging from 1.6 to 16 g l(-1). According to the field measurements, 99% of the UV-B radiation was attenuated in approximately a half meter water column in the clearest lake. In the UV-A region at 380 nm, the corresponding attenuation occurred in the upper one me…
Influence of ground tire rubber on the transient loading response of a peat biofilter
2010
Abstract The effect of using ground tire rubber (GTR) as an adsorptive material in the removal of a 2:1:1 weight mixture of n-butyl acetate, toluene and m-xylene by using a peat biofilter under different intermittent conditions was investigated. The performance of two identical size biofilters, one packed with fibrous peat alone and the other with a 3:1 (vol) fibrous peat and GTR mixture, was examined for a period of four months. Partition coefficients of both materials were measured. Values of 53, 118 and 402 L kg −1 were determined for n-butyl acetate, toluene and m-xylene in peat, respectively; and values of 40, 609 and 3035 L kg −1 were measured for the same compounds in GTR. Intermitte…
Influence of template basicity and hydrophobicity on the molecular recognition properties of molecularly imprinted polymers
1996
Abstract Triazine herbicides were used as model templates for a basic study of the molecular recognition process in imprinted polymers. Five structurally related triazine herbicides (atrazine, ametryn, cyanazine, prometryn and terbutylazine) that differ in basicity and hydrophobicity were imprinted. Chromatographic evaluation of the resulting materials in an aqueous-poor mobile phase showed that the selectivity for the template increased with its Bronsted basicity whereas it did not correlate with template hydrophobicity. Thus, the highest and lowest affinity and selectivity for the template was observed using the ametryn-imprinted (p K a =4.1) and the cyanazine-imprinted polymers (p K a =1…
Interaction of polyelectrolytes with oppositely charged micelles studied by fluorescence and liquid chromatography
2005
It is studied by spectrofluorimetry the association of ionized cationic micelles (cetyltrimethylammonium bromide, CTAB) with oppositely charged polyelectrolyte [sodium poly(styrenesulfonate), PSSNa]. CTAB provokes a change in the fluorescence intensity emitted by PSSNa. The investigated surfactants form micelle-like aggregates before critical micellar concentration (CMC). Two approaches (binding and partition equilibrium) are used to obtain the association constant, KA, number of CTAB molecules in a binding site, N, and apparent partition coefficient, Γ. Analysis of the parameters as a function of polymer concentration and ionic strength μ is performed. The effect of μ shows an enhancement …
Validation of a high-performance chromatographic method for determination of cefotaxime in biological samples
1999
An analytical method for detecting and quantifying cefotaxime in plasma and several tissues is described. The method was developed and validated using plasma and tissues of rats. The samples were analyzed by reversed phase liquid chromatography (HPLC) with UV detection (254 nm). Calibration graphs showed a linear correlation (r > 0.999) over the concentration ranges of 0.5–200 μg/mL and 1.25–25 μg/g for plasma and tissues, respectively. The recovery of cefotaxime from plasma standards prepared at the concentrations of 25 μg/mL and 100 μg/mL was 98.5 ± 3.5% and 101.8 ± 2.2%, respectively. The recovery of cefotaxime from tissue standards of liver, fat and muscle, prepared at the concentration…
Separation Efficiency of Two SEC Packings: Comparison of Chromatographic, Thermodynamic, and Fractal Parameters
2004
Abstract The size‐exclusion chromatographic (SEC), thermodynamic, and fractal behavior of two organic packings, named TSK‐Gel HHR and TSK‐Gel HXL, has been compared in order to assess their separation efficiency. The different experimental elution trends of five solvent/polymer systems have been evidenced through the universal calibration curves, and the existence of secondary mechanisms (such as adsorption) has been quantified by the chromatographic partition coefficient K p. From a thermodynamic point of view, the swelling and crosslinking degrees have been evaluated and compared in the two gels assayed. Moreover, the values of some fractal parameters (fractal dimension of the surface and…
Liquid chromatographic procedure for the evaluation of β-blockers in pharmaceuticals using hybrid micellar mobile phases
1997
Abstract A reversed-phase chromatographic procedure with a micellar eluent is proposed for the determination of several β-blockers (acebutolol, atenolol, carteolol, celiprolol, labetalol, metoprolol, nadolol, oxprenolol, propranolol, and timolol) in pharmaceutical formulations (tablets, capsules, and ophthalamic solutions). A study is shown on the chromatographic behaviour of these drugs with mobile phases containing sodium dodecyl sulphate (0.075–0.15 M ) and propanol (0–15%, v/v), at different pH values (3–7). The excellent correlation between log of the octanol-water partition coefficient and log of capacity factor, for the ten drugs in mobile phases of SDS and propanol, suggested that t…
Quantitative structure-retention and retention-activity relationships of beta-blocking agents by micellar liquid chromatography.
2001
Abstract Sixteen β-blocking agents (acebutolol, alprenolol, atenolol, bisoprolol, carteolol, celiprolol, esmolol, labetalol, metoprolol, nadolol, oxprenolol, pindolol, practolol, propranolol, sotalol and timolol) showing a large range of hydrophobicity (octanol–water partition coefficients, log P between −0.026 and 2.81) were subjected to micellar liquid chromatography with sodium dodecyl sulfate as micelle forming agent, and n-propanol as organic modifier. The correlation between log P and the retention factor extrapolated to a mobile phase free of micelles and organic modifier was investigated. The use of an interpolated retention factor or the retention factor for specific individual exp…
The solubilization site of 5,10,15,20-tetrakis-(2,6-dichlorophenyl)-porphyrin-Mn(III) in DPPC vesicles: A spectrophotometric and tensiometric study
2006
Abstract The solubilization site of 5,10,15,20-tetrakis-(2,6-dichlorophenyl)-porphyrin-Mn(III) (MnTDPPC) in l -α-dipalmitoylphosphatidyl choline (DPPC) vesicles was determined in a systematic UV–vis spectrophotometric study. Measurements of the MnTDPPC absorbance have been conducted at constant temperatures (in the interval 30 °C ≤ T ≤ 48 °C) and varying concentrations of phospholipid. In the entire temperature range, the absorption due to MnTDCCP was found to increase with increasing DPPC concentration, until it reaches a plateau value. The data have been analyzed using a pseudo-phase model yielding the binding constant of MnTDCPP to vesicular aggregates. No significant temperature depende…
Micellar liquid chromatography: suitable technique for screening analysis.
2002
The screening capability of micellar liquid chromatography (MLC) is discussed using the reported chromatographic data of several sets of compounds (amino acids, beta-blockers, diuretics, phenethylamines, phenols, polynuclear aromatic hydrocarbons, steroids and sulfonamides) and new results (sulfonamides and steroids). The chromatographic data are treated with an interpretive optimisation resolution procedure to obtain the best separation conditions. Usually, the pH and the concentration of surfactant (sodium dodecyl sulfate, SDS, or cetyltrimethylammonium bromide) for the optimal mobile phase were 2.5-3 and0.12 M, respectively. The nature and concentration of organic solvent depended on the…