Search results for "Spectrometry"

Proteomic investigations to unravel molecular physiology of the lantibiotic producer Microbispora sp. ATCC‐PTA‐5024

2013

Application of LA-ICP-MS as a rapid tool for analysis of elemental impurities in active pharmaceutical ingredients.

2014

The control of inorganic contaminants in active pharmaceutical ingredients has a significant role in the quality control of drug products. The concentration limits for metal residues in drug products have been defined by various regulatory guidelines. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is a powerful and fast analytical technique for multi-elemental analysis. A disadvantage in using LA-ICP-MS method is the lack of matrix reference materials for validation and calibration purposes. This article focuses on the handling strategy of laboratory-made matrix calibration standards for the quantification of elemental impurities in an active pharmaceutical ingredie…

A fluorescence spectroscopy study of the interaction of monocationic quinine with phospholipid vesicles Effect of the ionic strength and lipid compos…

1997

Abstract The interaction of monocationic quinine with zwitterionic dimyristoyl phosphatidylcholine (DMPC) and mixed negatively-charged dimyristoylphosphatidyl glycerol (DMPG) DMPC small unilamellar vesicles in the liquid-crystalline phase was investigated by steady-state fluorescence spectroscopy at pH 7 and 37°C. The maximum fluorescence emission peak at 383 nm, upon excitation at 335 nm, shifts to lower wavelength and decreases its intensity as the ratio between the total lipid and quinine concentrations increases. This indicates that in the membrane-bound state quinine is in an environment of low polarity, more deeply buried when anionic DMPG is present in the vesicle. For monoprotonated…

Binding of basic amphipathic peptides to neutral phospholipid membranes: a thermodynamic study applied to dansyl-labeled melittin and substance P ana…

1997

A thermodynamic approach is proposed to quantitatively analyze the binding isotherms of peptides to model membranes as a function of one adjustable parameter, the actual peptide charge in solution z(p)+. The main features of this approach are a theoretical expression for the partition coefficient calculated from the molar free energies of the peptide in the aqueous and lipid phases, an equation proposed by S. Stankowski [(1991) Biophysical Journal, Vol. 60, p. 341] to evaluate the activity coefficient of the peptide in the lipid phase, and the Debye-Huckel equation that quantifies the activity coefficient of the peptide in the aqueous phase. To assess the validity of this approach we have s…

NOseq: amplicon sequencing evaluation method for RNA m6A sites after chemical deamination

2020

Abstract Methods for the detection of m6A by RNA-Seq technologies are increasingly sought after. We here present NOseq, a method to detect m6A residues in defined amplicons by virtue of their resistance to chemical deamination, effected by nitrous acid. Partial deamination in NOseq affects all exocyclic amino groups present in nucleobases and thus also changes sequence information. The method uses a mapping algorithm specifically adapted to the sequence degeneration caused by deamination events. Thus, m6A sites with partial modification levels of ∼50% were detected in defined amplicons, and this threshold can be lowered to ∼10% by combination with m6A immunoprecipitation. NOseq faithfully d…

Micellar Liquid Chromatography:  A Worthy Technique for the Determination of β-Antagonists in Urine Samples

1998

Several beta-antagonists (acebutolol, atenolol, celiprolol, labetalol, metoprolol, nadolol, propranolol) were determined in urine samples with fluorometric detection after direct injection, in less than 15 min, with a micellar mobile phase of 0.1 M sodium dodecyl sulfate (SDS), 15% propanol, and 1% triethylamine at pH 3. The limits of detection (38 criterion) were usually between 3 and 30 ng/mL. The addition of propanol and triethylamine and the reduction of the pH of the mobile phase improved the efficiency of the chromatographic peaks that was rather low in pure micellar eluents. The selection of the composition of the mobile phase was easily performed through the use of an interpretive p…

Characterization of NOM

2015

Worldwide reports over the last few decades have shown that the amount of natural organic matter (NOM) in surface water is continuously increasing, which has an adverse effect on drinking water purification. For many practical and hygienic reasons, the presence of NOM in drinking water is undesirable. Various technologies have been proposed for NOM removal with varying degrees of success. The properties and amount of NOM, however, can significantly affect the process efficiency. To improve and optimize these processes, it is essential to characterize and quantify NOM at various points during purification and treatment. It is also important to be able to understand and predict the reactivity…

Study of Selective Adsorption of Gases by Calorimetry

2013

This chapter is devoted to the study of coadsorption of gases in nanoporous solids by using the differential calorimetry. In the first part, the thermodynamic principles of adsorption of gases are recalled. Some of them have already presented in chapter one. However a special attention has been paid here to the determination of the adsorption enthalpies and entropies and we focused on the selective adsorption of binary mixtures. Then the specific experimental technique based on the combination of differential calorimetry with manometry and gas phase chromatography or mass spectrometry is shown in details. In the last part, the thermodynamic concepts on coadsorption are illustrated with expe…

Multi-occurrence of twenty mycotoxinsin pasta and a risk assessment in the moroccan population

2018

In the present study, the multi-occurrence of twenty (20) mycotoxins in pasta samples consumed in Morocco was assessed. For this, a modified Quick, Easy, Cheap Effective, Rugged, and Safe method was validated. The mycotoxins studied were identified and quantified by liquid chromatography&ndash

Determination of four parabens and bisphenols A, F and S in human breast milk using QuEChERS and liquid chromatography coupled to mass spectrometry

2018

Abstract For the first time, a multiresidue, sensitive and high throughput method for determination of bisphenol A, F and S and 4 parabens (methyl paraben, ethyl paraben, propyl paraben and butyl paraben) in human breast milk was developed. The proposed method includes an extraction and clean-up procedure based on QuEChERS methodology followed by liquid chromatography coupled to triple quadrupole mass spectrometry determination. Negative atmospheric pressure chemical ionization in the selected reaction monitoring mode was used for mass detection. During the method validation the recoveries varied between 83 and 115% with a precision lower than 20% for all analytes using spiked levels from 0…