Search results for "chromatography"
showing 10 items of 5037 documents
Determination of 21 perfluoroalkyl substances and organophosphorus compounds in breast milk by liquid chromatography coupled to orbitrap high-resolut…
2018
Abstract The human exposure to perfluoroalkyl (PFASs) and organophosphorus (OPs) compounds is a cause of concern and its determination in biological matrices, including human milk, is an emergent approach for evaluate their exposure. A comprehensive strategy for the quantitative determination of 21 PFASs and OPs compounds in breast milk was developed. The proposed method includes an extraction and clean-up procedure based on the QuEChERs methodology followed by an ultra-high performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-HRMS) determination. The full-scan mass data were acquired with a resolution of 50000 FWHM and a mass accuracy better than 5 ppm. Met…
On-Capillary Surface-Enhanced Raman Spectroscopy: Determination of Glutathione in Whole Blood Microsamples.
2018
Oxidative stress monitoring in the neonatal period supports early outcome prediction and treatment. Glutathione (GSH) is the most abundant antioxidant in most cells and tissues, including whole blood, and its usefulness as a biomarker has been known for decades. To date, the available methods for GSH determination require laborious sample processing and the use of sophisticated laboratory equipment. To the best of our knowledge, no tools suitable for point-of-care (POC) sensing have been reported. Surface-enhanced Raman spectroscopy (SERS), performed in a microvolume capillary measurement cell, is proposed in this study as a robust approach for the quantification of GSH in human whole blood…
Human liver cytosolic epoxide hydrolases.
1988
Human liver epoxide hydrolases were characterized by several criteria and a cytosolic cis-stilbene oxide hydrolase (cEHcso) was purified to apparent homogeneity. Styrene oxide and five phenylmethyloxiranes were tested as substrates for human liver epoxide hydrolases. With microsomes activity was highest with trans-2-methylstyrene oxide, followed by styrene 7, 8-oxide, cis-2-With methylstyrene oxide, cis-1,2-dimethylstyrene oxide, trans-1, 2-dimethylstyrene oxide and 2, 2-dimethylstyrene oxide. With cytosol the same order was obtained for the first three substrates, whereas activity with 2, 2-dimethylstyrene oxide was higher than with cis-1,2-dimethylstyrene oxide and no hydrolysis occurred …
Differences in platelet growth factor release and leucocyte kinetics during autologous platelet gel formation.
2006
Three commercial systems for whole blood separation were compared to obtain the buffy coat composed of platelet-rich plasma (BC-PRP) and leucocytes . These samples of the buffy coat were used to make a platelet gel (PG), which was used to measure platelet growth factor (PGF) release, to perform a white blood cell (WBC) count and to measure myeloperoxidase (MPO) release from WBCs. Aliquots of whole blood obtained from ten volunteers were distributed either to a blood cell separator (The Electa Cell-Separator (TM), E-CS) or to a tabletop centrifuge (Gravitational Platelet Sequestration System (TM), GPS) to prepare the BC-PRP. The third system combines the BC-PRP production by E-CS with a micr…
The Use of Frozen-Thawed Platelet-Derived Phospholipids as a Confirmatory Test for the Diagnosis of Lupus Anticoagulants. Comparison with Two Commerc…
1999
Lupus anticoagulants (LAs) belong to acquired circulating anticoagulants interfering with phospholipid-dependent coagulation tests. Owing to the remarkable variability among patients, SSC guidelines recommend more than one test to detect and confirm the presence of LAs. However, this is an expensive procedure and greatly raises the work load of the laboratory. A standardised platelet-derived phospholipid preparation was obtained and platelet neutralisation (PNP) procedures with APTT and DRVVT reagents were performed on plasmas from 16 patients with LAs and from 41 control subjects. In comparisons, STAclot-PNP and DVVconfirm clotting assays were conducted. PNP by using APTT or DRVVT reagents…
Quantification of thrombocyte growth factors in platelet concentrates produced by discontinuous cell separation.
2002
Platelet concentrates (PC) are increasingly used to increase bone regeneration in pre-prosthetic surgery. Although it is generally appreciated that certain growth factors (PDGF, TGF, EGF, and ECGF) are present in thrombocyte preparations, relatively little is known about these components in quantitative terms. The study reported here analysed the amounts of growth factors in PC produced under standard conditions from healthy volunteers. All the blood samples (237 in total) were analysed using Quantikine ELISA kits (R and D). The mean +/- SD platelet count in whole blood from these donors was 262,000+/-58,000/microl, while in PC produced by discontinuous cell separation it was 1.419,000+/-33…
Enhancing effect of alpha-hydroxyacids on "in vitro" permeation across the human skin of compounds with different lipophilicity.
2005
The percutaneous penetration-enhancing effects of glycolic acid, lactic acid and sodium lauryl sulphate through the human epidermis was investigated using 5-fluorouracil as a hydrophilic model permeant and three compounds belonging to the phenylalcohols: 2-phenyl-ethanol, 4-phenyl-butanol and 5-phenyl-pentanol. The lipophilicity values of the compounds ranged from log Poct -0.95 to 2.89. The effect of the enhancer concentration was also studied. Skin pretreatment with aqueous solutions of the three enhancers did not increase the permeability coefficient of the most lipophilic compound (log Poct = 2.89). For the other compounds assayed, the increase in the permeability coefficients depended …
Absorption, excretion, and distribution of dietary antioxidant betalains in LDLs: potential health effects of betalains in humans
2004
Background: Betalains were recently identified as natural antioxidants. However, little is known about their bioavailability from dietary sources. Objective: The objective was to evaluate the bioavailability of betalains from dietary sources. Design: The plasma kinetics and urinary excretion of betalains were studied in healthy volunteers (n 8) after a single ingestion of 500 g cactus pear fruit pulp, which provided 28 and 16 mg indicaxanthin and betanin, respectively. The incorporation of betalains in LDL and the resistance of the particles to ex vivo–induced oxidation was also researched. Results: Betanin and indicaxanthin reached their maximum plasma concentrations 3 h after the fruit me…
Comparative column chromatographic estimations of phenylalanine in plasma, whole blood, native and paper-dried capillary blood of healthy children an…
1984
The concentration of phenylalanine in plasma, whole venous and capillary blood, and paper-dried blood of 75 probands (25 healthy adults, 27 healthy children, and 23 patients with hyperphenylalaninaemia) were measured by use of a sensitive short column chromatography method. The comparison of the values in each group of probands by several statistic methods showed an excellent correlation of the phenylalanine concentration in paper-dried whole blood to those measured in venous plasma. Evaluation of the analytical method revealed a high sensitivity and accuracy by use of a sample volume of 50 microliter. We would therefore suggest that the estimation of phenylalanine for the diagnosis and the…
New spectrophotometric procedure for determining cefotaxime based on derivatization with 1,2-naphthoquinone-4-sulphonate into solid-phase extraction …
1998
Cefotaxime was derivatised with 1,2-naphthoquinone-4-sulphonate (NQS), extracted into solid-phase cartridges (C18) and detected using a UV-visible detection system. Optimum conditions for this new procedure were: hydrogencarbonate-carbonate buffer, pH 10.5, 5-min reaction time at 25 degrees C and an NQS concentration of 7.1x10(-3) mol l(-1). The accuracy and the precision of the liquid-solid procedure were tested. The procedure was used to measure cefotaxime in pharmaceutical and urine samples. The results obtained were contrasted with those reported for a HPLC method for urine samples. The generalized H-point standard additions method was used to measure cefotaxime in urine samples.