Search results for " High pressure liquid"

Variations of vitamin D-like reactivity in the crustacean Orchestia cavimana during the molt cycle

1991

An investigation into vitamin D-like molecules has been performed on whole extracts of the terrestrial amphipod Orchestia cavimana, using a sensitive nonequilibrium assay employing 1,25-(OH)2 D receptor from calf thymus. Relatively large amounts of these secosteroid-like molecules were observed and they varied in concentration according to the stages of the molt cycle. The amplitude of these variations reaches a ratio of about 40 from the minimum in premolt to the intermolt sharp peak.

Long-Term Administration of High Dose Vitamin A to Rats Does Not Cause Fetal Malformations: Macroscopic, Skeletal and Physicochemical Finds

1996

A rat model was used to investigate whether high oral doses of vitamin A lead to fetal malformations and to what extent retinyl esters (RES) are transferred from the mother to the fetuses. Retinol and RES concentrations in plasma behave similarly in rats and humans. When high concentrations of vitamin A are administered, plasma retinol concentrations remain relatively constant, whereas plasma RES increased in parallel with the dose. To achieve an elevation from approximately 150 to > 1525 nmol x L(-1) in the experimental group before mating, female Ibm: RORO (spf) rats were fed a maintenance diet enriched with 15.2 x 10(3) retinol equivalents (RE) x kg(-1) at the start and increased stepwis…

A simple high-performance liquid chromatography (HPLC) method for the measurement of pyridoxal-5-phosphate and 4-pyridoxic acid in human plasma.

2014

Abstract Background Low concentration of plasma pyridoxal-5-phosphate (PLP) is associated with hyperhomocysteinemia and inflammation. Most methods for the measurement of plasma PLP require large specimen volume and involve the use of toxic reagents. Methods We have developed a HPLC method for the measurement of PLP and 4-pyridoxic acid (4-PA) in plasma, which requires small specimen volume. The samples are prepared without adding any toxic reagents. Furthermore, we have examined whether intake of vitamin B 6 affects the concentration of plasma PLP and 4-PA. Results The coefficient of variation of the method was 6% and the recovery of the added vitamin in plasma was about 100%. The concentra…

Determination of 5-nitrofurylacrylic acid in wines by high-performance liquid chromatography

1988

Expressing forest origins in the chemical composition of cooperage oak woods and corresponding wines by using FTICR-MS.

2008

A non-targeted, ultra-high-resolution mass spectrometric, direct analysis of oak-wood extracts from two species (Quercus robur L. and Quercus petraea Liebl.) from three French forests, and of a wine aged in barrels derived therefrom has been performed to identify families of metabolites that could discriminate both the species and the geographical origin of woods. From 12 T ultra-high-resolution Fourier transform ion cyclotron resonance mass spectra of wood extracts, hundreds of mass signals were identified as possible significant biomarkers of the two species, with phenolic and carbohydrate moieties leading the differentiation between Q. robur and Q. petraea, respectively, as corroborated …

Purification method for the isolation of monophosphate nucleotides from Champagne wine and their identification by mass spectrometry

2001

Monophosphate nucleotides are difficult to identify in Champagne wine because they are present in small concentrations in a complex mixture. A method for the isolation, separation and identification of reference compounds, which achieved on average 79% recovery (except for cytidine derivatives), was developed and applied to wine. Some monophosphate nucleotides were then isolated from a Champagne wine aged on lees for 8 years, by ultrafiltration followed by a semi-preparative HPLC step using a strong anion-exchange column. The fraction obtained was subjected to HPLC in a reversed-phase column to remove the salt previously introduced, before identification of compounds by HPLC coupled to a ma…

Applications of liquid chromatography-mass spectrometry for food analysis.

2012

Abstract HPLC–MS applications in the agrifood sector are among the fastest developing fields in science and industry. The present tutorial mini-review briefly describes this analytical methodology: HPLC, UHPLC, nano-HPLC on one hand, mass spectrometry (MS) and tandem mass spectrometry (MS/MS) on the other hand. Analytical results are grouped together based on the type of chemicals analyzed (lipids, carbohydrates, glycoproteins, vitamins, flavonoids, mycotoxins, pesticides, allergens and food additives). Results are also shown for various types of food (ham, cheese, milk, cereals, olive oil and wines). Although it is not an exhaustive list, it illustrates the main current directions of appli…

Enhanced calculation of optimal gradient programs in reversed-phase liquid chromatography

2003

Abstract The resolution of a mixture of 16 β-blockers under gradient elution was optimised using both isocratic and gradient training sets, with a reversed-phase column and acetonitrile–water eluents. Error theory was applied to measure the information extracted from different gradient experimental designs. This allows checking the expected accuracy when gradient predictions exceed the initial solvent concentrations tested in the training set. This work applies the results on modelling found in a previous study [J. Chromatogr. A 1018 (2003) 169] where the performance of several retention models was compared. Enhanced retention predictions were applied to the optimisation of gradient program…

Peak dispersion in gradient elution: An insight based on the plate model.

2020

Gradient elution in liquid chromatography reduces the analysis time, improves the efficiency and increases the peak capacity. The study of this chromatographic mode has been based mainly on kinetic dispersion models. The plate model has been applied to a lesser extent, despite being the basis for the concepts of plate height and chromatographic efficiency. In this work, a general equation describing peak dispersion in HPLC gradient elution is derived from the plate model. This equation is studied and validated for three types of gradients: (i) a reference gradient without ramp in which the retention factor varies with time identically throughout the column, (ii) a gradient of stationary pha…

A Promising New Method to Estimate Drug-Polymer Solubility at Room Temperature

2016

The established methods to predict drug-polymer solubility at room temperature either rely on extrapolation over a long temperature range or are limited by the availability of a liquid analogue of the polymer. To overcome these issues, this work investigated a new methodology where the drug-polymer solubility is estimated from the solubility of the drug in a solution of the polymer at room temperature using the shake-flask method. Thus, the new polymer in solution method does not rely on temperature extrapolations and only requires the polymer and a solvent, in which the polymer is soluble, that does not affect the molecular structure of the drug and polymer relative to that in the solid st…