Search results for "Quantitative analysis."
showing 10 items of 304 documents
High-performance liquid chromatographic determination of spironolactone and its major metabolite canrenone in urine using ultraviolet detection and c…
1994
A rapid and simple column liquid chromatographic method involving a column-switching system for the determination of spironolactone and its main metabolite canrenone in urine is described. Purification and concentration was performed using an Hypersil ODS-C18, 30 microns (20 x 2.1 mm I.D.) pre-column. The most polar urinary compounds were removed by washing the pre-column with water, and the analytes were subsequently switched to a LiChrospher RP C18, 5 microns (125 x 4 mm I.D.) analytical column and separated by means of an acetonitrile-water mobile-phase. Under the proposed conditions, the extraction efficiency was approximately 100% over the 0.5-10.0 micrograms/ml concentration range. Th…
On-line trace enrichment for the determination of ethacrynic acid in urine by liquid chromatography and column-switching
1993
Abstract A chromatographic method based on liquid chromatography (LC) using column-switching for the determination of ethacrynic acid in urine samples, is described. The proposed system uses a Hypersil ODS-C18, 30 μm (20 mm × 2.1 mm i.d.) pre-column for the pre-concentration and separation of ethacrynic acid from the biological matrix. Polar urinary compounds are removed by flushing the pre-column with purified water, and the enriched analyte is then switched in back-flush mode onto an HP-LiChrospher RP C18, 5 μm (125 × 4 mm i.d.) analytical column, where it is chromatographed using an acetonitrile-acetate buffer gradient elution. The UV detector was set at 275 nm. The recovery of drug was …
A direct Capillary Liquid Chromatography with electrochemical detection method for determination of phenols in water samples
2010
A fast and direct method based on the use of Capillary Liquid Chromatography (LC) with electrochemical (EC) detection has been described for phenols pollutants in water samples. Concretely, phenol, o-cresol, 2-chlorophenol and bisphenol A have been selected as target analytes. The combination of Capillary LC with EC detection avoided the necessity of preconcentration steps typically used in environmental analysis. The sample injected volume was 2 μL. The achieved detection limits were between 1 and 2 μg/L and the linear dynamic range was up to 50 μg/L for all studied phenols. The precision and uncertainty were satisfactory. The analysis time per sample was 10 min. The proposed procedure has…
Automated high-performance liquid chromatographic determination of amphetamine in biological fluids using column-switching and on-column derivatizati…
1999
A rapid and simple liquid-chromatographic method has been developed for on-line quantification of amphetamine in biological fluids. Untreated samples (20 μL) are injected directly into the chromatographic system and purified on a 20 mm×2.1 mm i.d. pre-column packed with 30 μm Hypersil C18 stationary phase. After clean-up the analyte is transferred to the analytical column (125 mm×4 mm i.d., 5 μm LiChrospher 100 RP18) for derivatization and separation using a mixture of acetonitrile and the derivatization reagent (o-phthaldialdehyde andN-acetyl-L-cysteine) as the mobile phase. The experimental conditions for on-line derivatization and resolution of the amphetamine have been optimized, and th…
A sequential-injection system for spectrophotometric determination of p -aminobenzoic acid in sunscreens.
2002
A sequential injection method is proposed for spectrophotometric determination of p-aminobenzoic acid (PABA) in cosmetic formulations. The method is based on diazotization of the analyte, coupling with 8-hydroxyquinoline, and the subsequent formation of a colored product. The experimental conditions used (coupling reagent, sandwich arrangement, volumes aspirated, propulsion flow rate, reaction coil length) were studied. Response of the sequential injection method were linearly dependent on concentrations up to 25 micro g mL(-1) and the detection limit was 2 micro g mL(-1). Throughput was 51 measurements per hour and a complete cycle, including three measurement per sample and a washing step…
On-line bidirectional electrostacking of chromium(III) and chromium(VI) for flame atomic absorption spectrometry determination
2000
Abstract An on-line bidirectional electrostacking-flow injection-flame atomic absorption spectrometry method has been developed for the simultaneous separation, pre-concentration and determination of Cr(III) and Cr(VI). The electrostacking-flow injection unit was established, the pH and components of the support buffer and sample medium were investigated. Results indicated that the ionic mobility, electric field strength and sample area cross-section are the main influence factors on the electrostacking. The calibration range for both, Cr(III) and Cr(VI), was from 20 to 400 μg l −1 . The limit of detection was 7 μg l −1 for three-times the standard deviation of blank values using a electros…
Bioanalysis of digoxin and its metabolites using direct serum injection combined with liquid chromatography and on-line immunochemical detection.
1994
Abstract An automated dual-column liquid chromatographic assay for digoxin is described. Serum samples are directly injected onto a restricted-access solid-phase extraction support. After liquid chromatographic (LC) separation on a C18 analytical column, antigenic analytes are detected by means of post-column immunochemical detection (ICD) using fluorescein-labelled antibodies against digoxigenin. The detection limit of this assay is 160 pg/ml (preconcentration of 1.0 ml serum). With the present method digoxin and three of its cross-reactive metabolites were determined in serum taken from patients which were orally administered a 1-mg dose of digoxin. The results obtained with LC—ICD were c…
Determination of chromium(III) and chromium(VI) in mineral water by bidirectional electrostacking and electrothermal atomic absorption spectrometry
2001
Abstract A feasibility investigation was carried out on the use of bidirectional electrostacking for simultaneous separation and pre-concentration of Cr(III) and Cr(VI) and their electrothermal atomic absorption spectrometry (ETAAS) determination. The bidirectional electrostacking manifold was improved, and the effects of sample tube cross-section and electrostacking time on the pre-concentration factor were investigated. Results indicate that the sample tube cross-section and electrostacking time are the main influence factors on the electrostacking pre-concentration, as well as the electric field strength and ionic mobility. The method developed was suitable for the simultaneous separatio…
Determination of thyreostatics in animal feed by micellar electrokinetic chromatography
1999
The determination of the thyreostatics 2-thiouracil, its derivatives (4-methyl-2-thiouracil, 4-propyl-2-thiouracil and 4-phenyl-2-thiouracil) and methimazole in manufactured dried animal feed by micellar electrokinetic chromatography (MEKC) is described. A 99 +/- 5% extraction yield at the 20 micrograms g-1 level (n = 8) was achieved by shaking the milled fodder with methanol-1 M NaOH (80 + 20). Aliquots of the supernatant were injected in a 75 microns x 33.5 cm uncoated silica capillary using pressure; separation was performed at 23 degrees C with 15 kV (positive polarity) in a background electrolyte (BGE) containing 40 mM sodium dihydrogenphosphate, 50 mM sodium dodecyl sulfate and 15 mM …
Direct determination of lead in human milk by electrothermal atomic absorption spectrometry
1999
Abstract Infants are particularly sensitive to the toxic effects of lead. Since milk is their only or main food it is important to know the contribution of milk to lead intake. The purpose of this study was to develop a direct method for determining the lead content of human milk by electrothermal atomic absorption spectrometry when a deuterium lamp is the only background correction available. The optimum conditions for lead determination in breast milk: sample dilution in Triton ×-100, modifier (75 μg of palladium) and nitric acid contents (2%) and the graphite furnace program (mineralization: 1100°C; atomization: 2300°C) were selected. The analytical parameters are: linearity (20–300 ng m…