Search results for "Chemical analysis"

Lung myofibroblasts are characterized by down-regulated cyclooxygenase-2 and its main metabolite, prostaglandin E2.

2013

Background: Prostaglandin E2 (PGE(2)), the main metabolite of cyclooxygenase (COX), is a well-known anti-fibrotic agent. Moreover, myofibroblasts expressing alpha-smooth muscle actin (alpha-SMA), fibroblast expansion and epithelial-mesenchymal transition (EMT) are critical to the pathogenesis of idiopathic pulmonary fibrosis (IPF). Our aim was to investigate the expression of COX-2 and PGE(2) in human lung myofibroblasts and establish whether fibroblast-myofibroblast transition (FMT) and EMT are associated with COX-2 and PGE(2) down-regulation. Methods: Fibroblasts obtained from IPF patients (n = 6) and patients undergoing spontaneous pneumothorax (control, n = 6) and alveolar epithelial ce…

Bloodstains on Leather: Examination of False Negatives in Presumptive Test and Human Hemoglobin Test.

2017

Presumptive tests for blood are very simple and sensitive tests used in the search for evidence. They also provide initial information on the nature of stains. A second test can confirm their nature. However, these tests can present false–negative results for different reasons. Some of those reasons have been studied, while others, those caused by the substrate material that contains the stain, are less well known. This work studies the effect of one component of a leather substrate—quebracho extract—on presumptive and human hemoglobin blood tests. Assays were performed using samples of blood dilutions contaminated with quebracho extract and others formed on a substrate containing the conta…

Novel Source of Ubiquitous Phthalates as Analytical Contaminant

1981

Procedures for Antibiotic Residues in Bovine Muscle Tissues

2011

Abstract Acetonitrile extraction followed by primary-secondary amine dispersive SPE cleanup QuEChERS (quick, easy, cheap, effective, rugged, and safe), was compared to pressurized liquid extraction (PLE) using water at 70°C for 10 min at 1500 psi for the determination of 16 veterinary drugs in bovine muscle tissues by LC/MS/MS. PLE was significantly more effective for the extraction of veterinary drugs (ranging from 69 to 103% with RSD ≤ 18%) than QuEChERS (ranging from 19 to 89% with RSD ≤ 19%). Linearity of the calibration curves was obtained over the range considered (from 10 μg/kg or LOQ to 1000, μg/kg) with r2 ≥ 0.99 for all the analytes by both methods. Although an internal standard w…

Determination of Boron in Fertilizers by Inductively Coupled Plasma-Atomic Emission Spectrometry: Studies of Some Spectral Interferences at Different…

1995

Abstract The most sensitive analytical wavelengths of boron cannot be used in the determination of boron in fertilizers by inductively coupled plasma-atomic emission spectrometry because of spectral interference by potassium, phosphorus, and iron. For the 4 wavelengths of boron investigated, it was noticed that, at the same wavelength, the pattern of spectral interference changes according to fertilizer composition. The spectral interference patterns at the 4 analytical boron wavelengths were studied by adding matrix elements typically found in fertilizers to real fertilizer samples. When levels of added matrix elements correlate less than 0.2 to each other, the effect of added matrix eleme…

Determination of fluoxetine enantiomers in pharmaceutical formulations by electrokinetic chromatography-counter current technique

2012

In this work, an electrokinetic chromatography–counter current procedure for the separation of fluoxetine enantiomers using highly sulfated β-cyclodextrin was optimized and applied to the determination of the enantiomers in three pharmaceutical formulations according to the matrix features. Quality criteria were applied to facilitate its transferability to testing laboratories. Fluoxetine was used therapeutically as the racemate, although a stereospecificity associated with its interactions with the neuronal serotonin-uptake carrier was demonstrated. In this context, the development of enantioselective methods for the chiral analysis of pharmaceuticals allowing stereoisomer ratio estimation…

Determination of Magnesium in Fertilizers by Inductively Coupled Plasma Atomic Emission Spectrometry: Studies of Some Spectral and Interelement Effec…

1995

Abstract Four analytical wavelengths of magnesium were tested for determination of Mg from fertilizers by inductively coupled plasma atomic emission spectroscopy (ICP-AES): 202.528, 285.213, and 383.826 nm (Mg I) and 279.553 (Mg II). The effects of fertilizer matrix elements on Mg determination were examined by adding matrix elements to fertilizer solutions. Multiple linear regression calculations proved a valuable technique for evaluating the effects of matrix elements on Mg determination. The observed interferences at Mg wavelengths may be both spectral and interelement. Interelement effects were typically caused by Na, K, and Ca, and spectral effects, by P, Fe, and S. The best wavelength…

Monitoring of five postharvest fungicides in fruit and vegetables by matrix solid-phase dispersion and liquid chromatography/mass spectrometry

2002

Abstract A method was developed for monitoring dichloran, flutriafol, o-phenylphenol, prochloraz, and tolclofos-methyl in fruits and vegetables, using matrix solid-phase dispersion and liquid chromatography with mass spectrometry detection. The method was used to determine fungicide content in 200 samples of chards, onions, peppers, bananas, lemons, and oranges. Of the samples examined, 54% contained o-phenylphenol with concentrations ranging from 0.005 to 3.34 mg/kg and 35% showed prochloraz in the range of 0.06–1.95 mg/kg. Dichloran, flutriafol, and tolclofos-methyl were detected only occasionally. Only 4% of the samples exceeded the European Union maximum residue limits. The pesticides i…

Effects and future trends of casein phosphopeptides on zinc bioavailability

2007

This review focuses on studies of the effects of CPPs on zinc bioavailability. It evaluates the main differences in studies performed in the last two decades, such as methodology used to measure zinc, food matrix, CPP preparation, CPP dose, CPP:Zn molar ratio and presence and concentration of zinc absorption inhibitors, such as phytate, iron and calcium. The future trends of CPPs as functional ingredients in zinc-enriched or zinc-containing foods are also discussed.

Chemically selective imaging of overlapping C-H stretching vibrations with time-resolved coherent anti-stokes Raman scattering (CARS) microscopy.

2014

Chemically selective imaging of spectrally overlapping compounds is studied with a time-resolved, femtosecond approach on coherent anti-Stokes Raman scattering (CARS) microscopy taking advantage of time-dependent oscillating CARS amplitude which is sensitive to different chemical components at different time points. Chemically selective imaging is demonstrated for composite material of polypropylene (PP) matrix and om-POSS (octamethyl polyhedral oligomeric silsesquioxane) microparticles having partly overlapping CH stretching vibrations. Inverse Fourier transformation (IFT) was applied to Raman spectra of PP and om-POSS, indicating that the oscillatory structures of the vibrational decays d…