Search results for "Analytical"

<strong>QUANTITATIVE QUANTUM MECHANICAL NMR ANALYSIS: THE SUPERIOR TOOL FOR ANALYSIS OF BIOFLUIDS</strong>

2016

Almost automatic quantitative analysis of biofluids is now behind only a few clicks from sample to EXCEL table after minimal sample preparation (move 0.3 ml sample into NMR tube and add buffer), without separations, calibration and reference materials, even for unknown compounds!  Each organic compound with protons gives a highly diagnostic and unique NMR spectrum which is practically identical with any spectrometer operating at certain field. A distinctive feature of high-resolution 1D NMR spectra is that even the most complex spectrum of a compound can be described by a few spectral parameters within experimental accuracy, employing a quantum mechanical theory. The NMR spectral parameters…

Altérations du métabolisme de l'homocystéine et maladies cardiovasculaires

1998

Resume L'homocysteine est un produit intermediaire du metabolisme de la methionine. L'augmentation moderee ou intermediaire de la concentration totale en homocysteine circulante, detectee dans les conditions basales ou apres le test de surcharge orale en methionine, est maintenant reconnue comme un facteur de risque important des maladies cardiovasculaires et des thromboses, chez les femmes comme chez les hommes, au meme titre que les facteurs de risques conventionnels. L'hyperhomocysteinemie, qui depend d'une inhibition de la voie de remethylation, d'une inhibition ou d'une saturation de la voie de transsulfuration, resulte d'une alteration de la regulation coordonnee du metabolisme de l'h…

Rapid fluorimetric assay for primary amine groups in water samples

2003

Bond Elut C(18) solid-phase extraction cartridges were used for pre-concentration followed by derivatization with o-phthaldialdehyde-N-acetylcysteine (OPA-NAC) of primary amines in water. Optimal conditions were: conditioning the cartridges with borate buffer pH 10.4, retention of the primary amines, addition of the OPA-NAC(3.7 mmol L(-1)) 1:1 molar ratio and borate buffer pH 8, elution of the isoindol with MeOH-borate buffer (9:1) pH 10.2 and fluorescence measurement. The equations of the calibration graphs for methylamine, ethylamine, propylamine, butylamine, pentylamine, and beta-phenylethylamine at lambda(excitation)=330 nm and lambda(emission)=440 nm, in the optimal conditions are pres…

Refractive Indices and Deviations in Refractive Indices of Trifluoromethanesulfonate-Based Ionic Liquids in Water

2011

Refractive indices were determined for four different ionic liquid + water binary systems, from (288.15 to 338.15) K, and covering the entire composition range. The four ionic liquids used were 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, 3-butyl-1-ethylimidazolium trifluoromethanesulfonate, 3-butyl-1-methylimidazolium trifluoromethanesulfonate, and 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate, all of them being completely miscible in water. From the experimental data, deviations in refractive indices, defined on a volume fraction basis, have been calculated and fitted to an extended version of the Redlich–Kister equation. The behavior of the deviations in refractive in…

Methacrylate ester-based monolithic columns for nano-LC separation of tocopherols in vegetable oils

2010

The separation and determination of tocopherols (Ts) in vegetable oils by nano-LC chromatography with UV-vis detection using lauryl methacrylate ester-based monolithic columns has been developed. The separation of Ts was optimized in terms of mobile phase composition on the basis of the best compromise among efficiency, resolution and analysis time. Using a mobile phase composed of ACN/methanol/water, an excellent resolution between Ts was achieved within 18 min. The LODs were lower than 0.26 μg/mL, being repeatability values of retention time and peak area below 0.15 and 3.1%, respectively. The method was applied to the quantification of Ts and tocotrienols present in several vegetable oil…

Quantification of DNA and RNA: A Spectrophotometric Method

2003

Spectophotometric quantification is a very exact method of quantifying the content of nucleic acids in any sample. The purity of the sample can be simultaneously checked very easily. Keywords: DNA; RNA; spectrophotometric quantification

Some observations on the determination of the methyl parathion-parathion ratio in binary mixtures by infrared spectroscopy

1989

Abstract The determination of the methyl parathion/parathion ratio in binary mixtures has been carried out by infrared spectroscopy using a simple and easy model for the treatment of the spectra obtained from sample thin films using sodium chloride windows. The model is based on the use of two bands, one at 974 cm−1, characteristic of parathion, and other at 1348 cm−1, common to both compounds. From the spectra of pure parathion samples and mixtures of known composition of methyl parathion and parathion, two constants have been obtained. These constants relate the absorption of each compound at 1348 cm−1 to the absorption of parathion at 974 cm−1. Eighteen synthetic samples have been analyz…

Investigations of the Microstructure of Lipid Interface Films

1990

The phase behaviour of phospholipid monolayers at electrolyte/gas interfaces is studied by fluorescence microscopy. At the LE/LC phase transition, phase separation leads to a Wigner-type lattice structure. The observations are quantified using digital image processing. The results show that the phase transition comprises three different regimes.

1988

Hydrolysis of Phytic Acid by Microwave Treatment: Application to Phytic Acid Analysis in Pharmaceutical Preparations

1998

Abstract The acid hydrolysis of phytic acid in a Teflon reactor using a domestic microwave oven has been studied and compared with other reported procedures. In 0.44 M HCl quantitative hydrolysis was achieved with six heating stages of 2 min each. A lower yield was obtained with H 2 SO 4 and HNO 3 . The analytical use of this hydrolysis to determine phytic acid by indirect determination of phosphate has been demonstrated by analysis of three pharmaceutical formulations. No sample pretreatment other than obtaining a homogeneous suspension was necessary.