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Biomedical subjects

P Prognon

Publications and source records attributed to P Prognon.

At least 19 recordsLinked to original sources
PubMed1999

Flourescence-assay on traces of protein on re-usable medical devices: cleaning efficiency.

The cleaning of re-usable medical devices before disinfection or sterilization is recognized as being an essential phase. Detection of residual proteins can be used to validate the process, provided a sufficiently sensitive method is employed. A fluorescent method is presented, using orthophtalaldehyde (OPA) bound to N,N dimethyl-2-mercaptoethylammonium, to demonstrate the presence of amino acids on a medical device following cleaning. The sensitivity of this method (10-5 g/l) was assessed and the applicability of this detection technique is verified, using three types of carriers (steel blades, glass tubes or ceramic penicylinders), three types of contaminants (yeast extract, bovine albumin with native sheep's blood and formaldehyde fixed fibrin). In this context, studies involving formaldehyde-fixed fibrin are more sensitive and are to be recommended.

Disinfection↗
PubMed1998

Interaction between cyclodextrins and aflatoxins Q1, M1 and P1. Fluorescence and chromatographic studies.

The fluorescence properties of the aflatoxins M1, Q1, P1 in solution and the effect of various cyclodextrins (alpha-, beta-, gamma-, hydroxypropyl-beta- and alpha-beta-heptakis-di-O-methyl-beta-) on their fluorescence emission were studied. Among the aflatoxins, a substantial enhancement of the fluorescence emission of aflatoxin Q1 in the presence of aqueous solutions of alpha-, beta-, hydroxypropyl-beta, and alpha-beta-heptakis-di-O-methyl-beta-cyclodextrin, was observed. On the contrary, gamma-cyclodextrin proved to be inefficient to enhance the fluorescence properties of this compound. No important fluorescence enhancement was found for aflatoxins P1 or M1 for any of the cyclodextrin derivatives tested. The complex formation constant (Kf) of these compounds with beta-cyclodextrin was chromatographically determined, and from the results obtained, we can conclude that Kf cannot be used alone to explain the fluorescence increase. Thermodynamic studies showed that delta-H and delta-S parameters, associated with the partition of aflatoxins in RP-HPLC, increased when beta-cyclodextrin was added to the eluent.

Aflatoxin M1↗
PubMed1998

Determination of total cysteamine in human serum by a high-performance liquid chromatography with fluorescence detection.

A convenient, reliable and rapid method for determination of total cysteamine in human plasma by high-performance liquid chromatography with fluorescence detection is reported. This assay involves reduction of samples with dithiothreitol, derivatization of total cysteamine by addition of monobromobimane and protein precipitation by perchloric acid. The calibration curve was linear in the range 2-150 nmol ml-1 and the detection limit was 0.5 nmol ml-1. This method was successfully applied for a pharmacokinetic study of three cysteamine derivatives in healthy volunteers without any interference from coexisting substances.

Biological Availability↗
PubMed1997

Liquid chromatographic determination using lanthanides as time-resolved luminescence probes for drugs and xenobiotics: advantages and limitations.

Lanthanide sensitized luminescence is a very attractive alternative to UV detection and other luminescence techniques, i.e., fluorescence and phosphorescence, in separation science for the detection of drugs and xenobiotics because of the large Stokes shift, narrow emission bands and long lifetime. Some published applications of HPLC determination with lanthanide (Ln3+) sensitized luminescence detection are reviewed. Advantages and limitations of this technique are discussed. Normal-phase (NP) HPLC is not influenced by the quenching effect of water whereas reversed-phase (RP) HPLC is applicable to more compounds than NP-HPLC. However, pH adjustment and the quenching effect of water on Ln3+ luminescence are the main drawbacks of RP-HPLC. Elution properties and the need for pH adjustment are two arguments for selecting the mode of addition of Ln3+, i.e., pre- or post-column in the HPLC system. Sensitized Ln3+ luminescence detection is a much more specific method of detection than UV or fluorescence detection after HPLC separation but nevertheless, in some cases, does not always exhibit a significant increase in analytical performance when the donor itself is a strong fluorophore. The development of more powerful excitation sources could improve the limit of detection of the Ln3+ sensitized detection technique. This review suggests that it would be useful to obtain predicting factors about the drug to establish whether the latter is suitable to be measured using an HPLC-Ln3+ approach.

Chromatography, High Pressure Liquid↗
PubMed1997

Study protocol: stability of morphine injected without preservative, delivered with a disposable infusion device.

BACKGROUND AND OBJECTIVE: Morphine hydrochloride, a major analgesic drug, is being increasingly administered using portable disposable infusion devices. The objective of this study was to investigate the stability of morphine in such a system at two concentrations (2.50 and 5.00 mg/ ml) over a 30-day period. METHOD: High-performance liquid chromatography of stored morphine solutions. RESULTS: The best stability was observed with disposable infusion devices filled with a morphine solution containing sodium metabisulphite as a preservative. No breakdown products were detected after 1 month of storage at room temperature, in light or darkness. On the other hand, 2.50 and 5.00 mg/ml morphine solutions without sodium metabisulphite, stored in the infusion device led to the formation of 0.205% and 0.235% of pseudomorphine, respectively, after 6 days of storage in the light, and 1.50% and 0.94% after 30 days storage. CONCLUSION: Morphine hydrochloride solutions stored in disposable infusion devices degraded very slowly, particularly when preserved with sodium metabisulphite. The solutions are stable over 5 days, the maximum period of storage normally required when using disposable infusers.

Analgesics, Opioid↗
PubMed1997

Rapid semi-quantitative fluorimetric determination of citrinin in fungal cultures isolated from cheese and cheese factories.

A new rapid semi-quantitative fluorimetric assay for citrinin production testing in mould cultures has been developed. The chemical structure of the citrinin makes it a weak native fluorophore. This fluorescence can be strongly enhanced in an acidic environment. A standard curve where the concentration of HCl needed to show the yellow fluorescence signal of different concentrations of citrinin was established, thus providing a semi-quantitative method to prove the capacity of toxin production of fungal cultures. Two Penicillium strains from the Spanish National Collection of Type Cultures, were studied for the toxin production on YES broth at 25 degrees C for 21 d. The culture was assayed daily for the presence/absence and quantification of citrinin by adding the HCl concentration set, and also quantified by RP-HPLC as a confirmation procedure. Experiments demonstrate that 5 d are necessary to show the presence of citrinin. As an illustration, a total of 48 strains of Penicillium isolated from cheese and cheese factories were analysed with the proposed method.

Cheese↗
PubMed1996

Simple and sensitive high-performance liquid chromatography--fluorescence method for the determination of citrinin application to the analysis of fungal cultures and cheese extracts.

A new and highly sensitive method for the detection of the important mycotoxin, citrinin, has been developed. Spectroscopic studies demonstrate that the fluorescence of this metabolite is influenced by the pH of the environment. This fact was exploited in the chromatographic determination of citrinin with fluorescence detection. The proposed method, based on the addition of 1 M hydrochloric acid as an acidic post-column reagent, has a limit of detection of 0.9 center dot 10(-7) M. Analytical validation shows that linearity can be assumed from 2 center dot 10(-7) to 10(-4) M citrinin. The repeatability and reproducibility are satisfactory, with R.S.D. = 5.1% (n = 9, c = 10(-5) M) and R.S.D. = 7.2% (n = 9, c = 10(-5) M). The method was also applied to the determination of this mycotoxin produced by mould cultures isolated from soft cheese and also from soft cheese and also from cheese extracts spiked with citrinin. The specificity of the method is demonstrated and the necessity for post-column acidification is illustrated on real samples.

Cheese↗
PubMed1996

Postcolumn excitation of aflatoxins using cyclodextrins in liquid chromatography for food analysis.

Measurement of fluorescence increase was used for the comparative quantification of the effect that several cyclodextrins (alpha-, beta-, heptakis-2,6-beta-omicron-dimethyl- and gamma-) produce on the fluorescent response of aflatoxins B1 and G1. This constitutes a new chromatographic method with stability of the mobile phase, and shows general improvements in the chromatographic conditions with respect to other methods (especially those using an iodine reservoir as a postcolumn reactor). A C18-type column was used, with methanol-water (60:40, v/v) as the mobile phase. The excitation phase of the natural fluorescence of aflatoxins, a 10(-2) M solution of each cyclodextrin, was introduced postcolumn. The determination of the elution order aflatoxin G2 > G1 > B2 > B1 was performed for each phase in less than 15 min. As expected using an aqueous-alcoholic medium, an increase in the fluorescence response of aflatoxins with an unsaturated furanic ring was found to occur with all the cyclodextrins studied, except gamma-cyclodextrin. The observed increase was larger for heptakis-2,6-beta-omicron-dimethyl- than for beta-cyclodextrin (to our knowledge, the only cyclodextrin previously described in the literature to serve for the determination of aflatoxins). The difference is of the order of 70.1-fold in the case of aflatoxin G1 and 45.2-fold in the case of aflatoxin B1. The detection limit in the mobile phase used was determined (for aflatoxin B1) for beta-cyclodextrin and 2,6-beta-omicron-dimethylcyclodextrin (signal-to-noise ratio 1:3) to be 4 and 9 mg 1(-1), respectively.

Aflatoxin B1↗
PubMed1996

Effects of pH and solvent on the fluorescence properties of biomedically important benzamides. Application to determination in drugs and in human urine.

The fluorescence properties of five substituted benzamides, including alizapride, metoclopramide, sulpiride, sultopride and tiapride, were investigated at several pH values and in various solvents (dimethyl sulfoxide, ethanol, ethylene glycol, methanol, propan-2-ol, tetrahydrofuran and water). Except for alizapride, the fluorescence intensities were found to be higher at acidic (1-6) than at alkaline (8-12) pH values. Using the optimum solvent (aqueous solutions) and appropriate pH conditions, linear spectrofluorimetric calibration curves were established over a concentration range of about two orders of magnitude, with correlation coefficients larger than 0.996. Limits of detection were between 1 and 13 ng ml-1, depending on the compound. The method was applied to the determination of benzamides in pharmaceutical preparations and in human urine, with recoveries ranging from 94 to 108% and from 93 to 104%, respectively.

Benzamides↗
PubMed1996

[Contribution to the study of phenothiazine detection by inhibition of phosphorescence in liquid chromatography].

Diacetyl, in deaerated solutions, is a major room temperature phosphorescent compound. Its phosphorescence quenching is proposed in order to quantify results on phenothiazine derivatives. It is established from the luminescent data on phenothiazines that diacetyl phosphorescence can be quenched quantitatively by these compounds. This detection mode is applied to liquid chromatography limitations as well as the mechanism of the quenching are discussed.

Chromatography, High Pressure Liquid↗
PubMed1995

Roles of divalent cations and pH in mechanism of action of nitroxoline against Escherichia coli strains.

The antibacterial activity of nitroxoline (NIT), an antibiotic used in the treatment of acute or recurrent urinary tract infections caused by Escherichia coli, is decreased in the presence of Mg2+ and Mn2+ but not Ca2+. In order to elucidate the interaction between this drug and the divalent cations, spectrophotometric studies based on the natural absorption of the nitroxoline moiety were conducted. In the presence of the divalent metal ions, a shift in the NIT A448 suggested the formation of drug-ion complexes, for which the stability followed the order Mn2+ > Mg2+ > Ca2+. A clear correlation was found between the chelating property and antibacterial activity of NIT; both were pH dependent. A convenient colorimetric method for the determination of NIT uptake by bacterial cells was also developed. Uptake was energy independent and showed biphasic kinetics: a rapid association with cells and then a slower increase in cell-associated NIT which reached a plateau. NIT uptake was reduced in the presence of magnesium. The implications of metal ion complexation and pH on the clinical efficacy of NIT are discussed.

Anti-Infective Agents, Urinary↗
PubMed1994

[Microbiological consequences of chelation of bivalent metal cations by nitroxoline].

The present work deals with the physico-chemical and microbiological investigations made in order to explain the role of divalent cations in the mechanism of the action of nitroxoline (NIT), an antibiotic used in the treatment of uncomplicated urinary tract infections. Preliminary studies reported that bacteriostatic and bactericidal activities of NIT on Escherichia coli strains are decreased in the presence of Mg2+ and Mn2+ but not with Ca2+. A spectrophotometric study, conducted in order to elucidate the interaction between metal ions and NIT, showed the formation of drug-metal ion complexes. In addition, we examined the relationships between the metal ions-chelating property of NIT and its effects on the decrease of the mannose sensitive hemagglutination titer and the production of siderophores from E. coli. The results suggested that these antimicrobial activities of NIT would also be due to the complexation of metal ions by this molecule.

Anti-Infective Agents, Urinary↗
PubMed1994

[Luminescence and detection in liquid chromatography: III. Chemiluminescence].

Chemiluminescence avoiding the fluctuations of the light of excitation, Rayleigh and Raman scattering, allows to get detection threshold 100 to 1,000 times lower than fluorimetry. Processes using the luminol, lucigenin, aryloxalic esters and ozone are employed in liquid chromatographic detection. Some pharmaceutical, biological and toxicological examples illustrate their applications.

Acridines↗
PubMed1993

[Luminescence and detection in liquid chromatography. II--Energy transfer from a stimulated molecule: indirect potentialization or sensitized luminescence].

Under the words of sensitized luminescence, the processes who include the transfers of energy from a donor to an acceptor are described. They are to the origin of new possibilities of detection in liquid chromatography by emission or inhibition of phosphorescence and fluorescence. These news technologies are illustrated by examples in pharmaceutic, biologic or food applications.

Chromatography, Liquid↗
PubMed1993

[Luminescence and detection in liquid chromatography. I: Change of environment of analytes].

The emissions of light by biorganisms or these obtained by alchemists were known since long time ago but the are used in analytical chemistry only when STOKES discovered that the intensity of this light was proportional to the quantity of the matter. The very large sensibilities reached, associated with the great separation's ability of the liquid chromatography allows to develop new processes for quantification of very low concentrations of luminescent or no luminescent molecules. Many pharmaceutical, biological toxicological environmental or alimentary applications show that it is possible in liquid chromatography to obtain a detection limit about the pico or femtomole when simple chemical process are used: direct potentialization of luminescence by addition of modifiers of the chemical environment of the analytes: solvents, cyclodextrins, surfactants, metallic ions, indirect potentialization of the luminescence by transfer of energy from an excited molecule: sensitized fluorescence and phosphorescence, excitation of the molecule by a chemical reaction or chemiluminescence. These aspects are emphasized and illustrated by some examples in three articles.

Chromatography, Liquid↗
PubMed1989

A rapid and specific extraction procedure for folates determination in rat liver and analysis by high-performance liquid chromatography with fluorometric detection.

The native fluorescence of the main biological derivatives of folic acid is maximal at acidic pH. The intensities obtained with 5-methyltetrahydrofolic acid, tetrahydrofolic acid, and formyltetrahydrofolic acid are in the ratio 10/5/1. After separating the metabolites by reversed phase high-performance liquid chromatography, the fluorometric detection limit varied between 0.4 and 20 pmol per injection. Rat liver extract (about 2 g/50 ml of 1% ascorbate solution) could be analyzed after incubation at 37 degrees C overnight, deproteinizing with acetone, and purification and concentration in an ion exchange column. The concentrations obtained varied from 1.27 to 7.96 nmol/g depending on the derivative. Recovery varied from 89 to 113%.

Animals↗