PubMed Health⌕ Search

Biomedical subjects

M Valcárcel

Publications and source records attributed to M Valcárcel.

At least 91 records · Page 5Linked to original sources
PubMed1987

Direct quantification of coproporphyrins and uroporphyrins in urine by derivative synchronous fluorescence spectroscopy.

The second-derivative synchronous fluorescence spectroscopic technique is applied to the simultaneous and direct assay of coproporphyrins and uroporphyrins in human urine. This technique resolves the overlapping conventional spectra, obviating the need for pre-analysis sample separation techniques, and measurements can be made in a single scan. The amplitudes of the derivative peaks are linearly related to uroporphyrin (0.4 to 300 micrograms/L) and coproporphyrin (0.4 to 250 micrograms/L) concentrations. The detection limit for both porphyrins is 0.1 microgram/L. Analytical recoveries range between 98 and 101%. Within- and between-assay CVs are reported. Results for 24-h urine specimens correlated well with those obtained by an extraction-ion-exchange chromatography combined method. The proposed method is inexpensive and requires no sophisticated detection equipment.

Coproporphyrins↗
PubMed1986

Simultaneous and direct determination of pyridoxal, pyridoxal-5'-phosphate, and pyridoxic acid in serum by derivative synchronous fluorescence spectroscopy.

Simultaneous and direct assays of pyridoxal, pyridoxal-5'-phosphate, and pyridoxic acid in human serum are described. The method applied is based on the reaction of these compounds with beryllium in an ammoniacal medium to yield highly fluorescent derivatives. Overlapping of conventional fluorescence spectra is resolved by using second-derivative fluorescence spectroscopy, thus making the use of separation techniques unnecessary. The proposed method is simple (only beryllium and an ammoniacal buffer are needed to develop fluorescence), rapid (the derivative formation is instantaneous and serum treatment only requires deproteinization), and inexpensive (no sophisticated detection equipment is necessary, any conventional modern spectrofluorimeter being adequate for use). The analytical recovery achieved was of about 96% for pyridoxal, 97% for pyridoxal-5'-phosphate, and 100% for pyridoxic acid. Measurements were carried out in a single scan.

Beryllium↗
PubMed1985

Simultaneous determination of epinephrine and norepinephrine in urine by derivative synchronous fluorescence spectroscopy.

The combination of synchronous and derivative fluorimetry, potentially useful in resolving mixtures that present strongly overlapping conventional fluorescence spectra, appears suitable for determining epinephrine and norepinephrine in urine. We describe a simple, rapid, and inexpensive method for simultaneous assay of these compounds in a single scan of urine specimens from normal adults. The catecholamines are extracted from the sample on cation-exchange columns and subsequently determined by formation of trihydroxyindoles. Analytical recovery is about 94% for epinephrine, 91% for norepinephrine, with a CV of approximately 5%. No sophisticated detection equipment is necessary, a conventional modern fluorimeter being adequate.

Adult↗