Search results for "sample preparation"
showing 3 items of 343 documents
Stability of Ascorbic Acid in Several Blood Collecting Procedures
2003
Purpose: There is good evidence that ascorbic acid (AA) status influences the onset of post-operative complications in intensive care patients. Light and room temperature cause the spontaneous oxidation of AA. Therefore, the stability of AA during modified sample preparation was investigated. Design: Prospective, single centre study. Methods: The AA plasma concentration was analysed in arterial and venous blood with added ethylene-diamine-tetra-acetic acid (EDTA) from 165 subjects. In addition, EDTA or heparin was added as an anticoagulant in venous blood of 79 subjects. Analyses were carried out using high performance liquid chromatography with ultraviolet detection. Results: In samples of…
Effect of sample preparation on gel permeation chromatography results of determination of molecular weight of polyethylene obtained with using of zir…
2003
Molecular weights of polyethylene (PE) obtained with using of zirconocene catalyst activated with large excess of methylaluminoxane (MAO) were determined by gel permeation chromatography (GPC) method. It was found that repeatability of the measurements is strongly influenced by MAO remained in PE samples as well as time of sample keeping in the apparatus (dissolution + measurement time) at temp. 142 °C. A method of MAO removing from PE samples, before GPC measurement, based on additional washing of the sample with HF in methanol solution has been proposed. This modification leads to better both authenticity and repeatability of the results. Studies on the influence of time of sample keeping…
Determination of glyphosate and its metabolite aminomethylphosphonic acid in fruit juices using supported-liquid membrane preconcentration method wit…
2005
Abstract The application of supported-liquid membrane (SLM) technique for effective extraction of N -(phosphonomethyl)glycine (glyphosate) and its primary metabolite aminomethylphosphonic acid (AMPA) from juices (orange, grapefruit, apple and blackcurrant) in combination with HPLC-UV detection after derivatization with p -toluenesulphonyl chloride (TsCl) is presented. The influence of various parameters such as the composition of acceptor phase, flow-rate, concentration of analytes, on the performance of extraction procedure, was studied. It was shown that by appropriate manipulation of SLM parameters the level of detection could be significantly improved. The influence of SLM conditions on…