Search results for "Chemical analysis"
showing 10 items of 324 documents
Adsorptionsvoltammetrische Molybd�nbestimmung in biologischen Proben nach nassem Hochdruckaufschlu\
1989
The transfer of an (known from literature [141 and till now only applied to seawater) adsorption-voltammetric determination of molybdenum with oxine to biological samples, is described. The herewith accomplished changes of base solution resulted simultaneously in an optimization of the method with regard to interpretability and sensitivity. Special care was taken in the problem of decomposition. Best results are obtained with a high-pressure decomposition. Accuracy of analyses is confirmed with trials of recovery also in the biological matrix.
Univariate method for background correction in liquid chromatography–Fourier transform infrared spectrometry
2007
An univariate method is proposed for background correction in on-line gradient liquid chromatography-Fourier transform infrared (LC-FTIR) spectrometry using acetonitrile:water as mobile phase components. The method is based on the calculation of the ratio of absorbances (AR) at two characteristic wavenumbers for each spectrum. This parameter is subsequently used to locate the most appropriated eluent spectrum within a reference spectra matrix (RSM) to be subtracted from each spectrum included in the sample chromatogram. To correct minor changes in eluent spectra intensity during the elution of analytes, a correction factor (Kf), defined as the ratio of the absorbance of the sample and the s…
Solid-Phase Extraction Techniques for Assay of Diuretics in Human Urine Samples
1991
Abstract Solid-phase extraction techniques were evaluated for the treatment of urine samples in the analysis of diuretics before injection into an HP-Hypersyl ODS-C18 column. Six different reversed-phase extraction columns were tested, and the results obtained are compared with those obtained in a classical liquid-liquid extraction with ethyl acetate. The solid-phase extraction procedures are the best overall choice for all the diuretics tested, due to their versatility, the minor time-consuming, and the good recovery percentages obtained. C18 and C8 packings give the highest recoveries for a majority of the diuretics studied. However, CH or PH columns, due to their greater selectivity, can…
Electrothermal Atomic Absorption Spectrometric Diagnosis of Familial Hypercholesterolemia
2000
We have developed a new nonradioactive assay to identify human low-density lipoprotein receptor defects. It is based on the incubation of cultured cells with colloidal gold-LDL conjugates and quantitation of the gold associated with the cells by electrothermal atomic absorption spectrometry. After an oxidative treatment with nitric and hydrochloric acids, the biological matrix interferes neither with the gold recovery nor with the gold measurements, which are linear, at least from 0.15 to 3 ng of gold. When cells expressing a functional LDL receptor are incubated with increasing amounts of colloidal-gold LDL conjugates, the obtained saturation curve parallels that described when [125I]LDL i…
An automated on-line multidimensional HPLC system for protein and peptide mapping with integrated sample preparation.
2002
A comprehensive on-line two-dimensional 2D-HPLC system with integrated sample preparation was developed for the analysis of proteins and peptides with a molecular weight below 20 kDa. The system setup provided fast separations and high resolving power and is considered to be a complementary technique to 2D gel electrophoresis in proteomics. The on-line system reproducibly resolved approximately 1000 peaks within the total analysis time of 96 min and avoided sample losses by off-line sample handling. The low-molecular-weight target analytes were separated from the matrix using novel silica-based restricted access materials (RAM) with ion exchange functionalities. The size-selective sample fr…
Error analysis and performance of different retention models in the transference of data from/to isocratic/gradient elution.
2003
The transferability of retention data among isocratic and gradient RPLC elution modes is studied. For this purpose, 16 beta-blockers were chromatographed under both isocratic and gradient elution with acetonitrile-water mobile phases. Taking into account the elution mode where the experimental data come from, and the mode where the retention should be predicted, the following combinations are possible: isocratic predictions from (i) isocratic or (ii) gradient experimental designs; and gradient predictions from (iii) isocratic or (iv) gradient data. Each of these possibilities was checked using three retention models that relate the logarithm of the retention factor: (a) linearly and (b) qua…
Optimization of iron speciation (soluble, ferrous and ferric) in beans, chickpeas and lentils
2001
Abstract A spectrophotometric method with bathophenanthroline for iron determination that makes it possible to differentiate between iron (II) and iron (III) in total soluble iron in legumes (beans, chickpeas and lentils) was optimized. Sample size, volumes of reducing agent and bathophenanthroline were selected. Matrix interferences made it necessary to apply the addition’s method. To check the quality of the method, linearity and precision (RSD%) were determined. A linear response between 0.1 and 1.8 μg Fe/ml in the assay and precision values ranging from 2.1 to 6 for instrumental precision, and from 1.6 to 1.7 and 2.7 to 9.1, for intra- and inter-day assays, respectively were obtained. T…
Development of a species-unspecific isotope dilution GC-ICPMS method for possible routine quantification of sulfur species in petroleum products.
2008
Inductively coupled plasma mass spectrometry (ICPMS) hyphenated with capillary gas chromatography was applied for sulfur multispecies determination in petroleum products by species-unspecific isotope dilution mass spectrometry (IDMS). To guarantee a stable and continuous addition of the spike into the GC-ICPMS system, a special dosing unit was designed and synthesis of a (34)S-labeled dimethyldisulfide spike from (34)S-enriched elemental sulfur in the milligram range was developed. The sample was mixed with an internal standard for spike mass flow calibration. From the mass flow chromatogram obtained by species-unspecific GC-ICP-IDMS, determination of all separated sulfur species and of the…
Development and validation of a micellar liquid chromatographic method to determine three antitumorals in plasma
2017
Aim: A micellar liquid chromatographic method to determine several anticancer drugs (pazopanib, dabrafenib and regorafenib) in plasma was developed and validated by the guidelines of the EMA. Experimental: Plasma samples were directly injected, after a 1/5-dilution in a micellar solution. The drugs were resolved in <18 min using a C18 column. The mobile phase was an aqueous solution of 0.12 M SDS – 2% 1-pentanol, buffered at pH 7. The detection was performed by absorbance at 260 nm. Results: The values of the main validation parameters were: LOD (0.1–1 mg/l), calibration range (0.2–2 to 80 mg/l), accuracy (-12.5 to +11.7%) and precision (<11.9%). Conclusion: The procedure was conduct…
In situ generation of Co(II) by use of a solid-phase reactor in an FIA assembly for the spectrophotometric determination of penicillamine
2005
[EN] A flow injection analysis (FIA) manifold for the determination of penicillamine in pharmaceutical preparations is proposed. The manifold includes a solid-phase reactor for the in situ production of the derivatizing reagent, Co(II) ion, which forms a coloured complex with penicillamine in an alkaline medium. The reactor is prepared by natural immobilization of cobalt carbonate on a polymer matrix, which endows it with a high mechanical and microbiological stability. The cobalt released by passage of a 5 x 10(-4) Mol l(-1) sulphuric acid stream at a flow-rate of 2.3 ml min(-1) is merged with a volume of 314 mu l of sample containing penicillamine in ammonium-ammonia buffer at pH 9.5 to m…