Search results for "EXTRACTION"

Derivatization of amphetamine and methamphetamine with 1,2-naphthoquinone 4-sulfonic acid into solid-phase extraction cartridges. Determination of am…

1997

The derivatization of amphetamine and methamphetamine with 1,2-naphthoquinone-4-sulfonate (NQS) into solid-phase extraction cartridges (C 18 ) is described. Optimum conditions were the use of carbonate–hydrogencarbonate buffer of pH 10, a 10 min reaction time at 25 °C and an NQS concentration of 9.6 × 10 - 3 M. The accuracy and the precision of the method were tested. The results obtained with the proposed liquid–solid procedure were compared with those obtained with a traditional liquid–liquid extraction with hexane–ethyl acetate. The procedure was used to measure amphetamine in pharmaceutical and urine samples

Machine-readable entailments with the Italian 'prendere' construction expressing hitting and insulting events

2022

The Italian language features a little debated transitive construction with prendere ‘to take/to catch’ in which a prepositional phrase (PP) with an adverbial value occurs mandatorily (e.g. Lui prese a pugni Leo ‘He punched Leo’). Semantically, this construction often implies the use of physical force or verbal offence. In the hitting or insulting event, the notional subject generally is a [+ Human] Agent, whilst the notional direct object generally is a [+ Animate] Affectee ([1]: 4). It can be contended that prendere, which carries no literal meaning, is zero-valent and that the predicate assigning semantic roles is the PP. A computational tool will be illustrated, …

Ultrasound-assisted extraction for food and environmental samples

2013

Abstract In recent years, ultrasound-assisted extraction (UAE) has attracted growing interest, as it is an effective method for the rapid extraction of a number of compounds from food and environmental samples, with extraction efficiency comparable to that of classical techniques. In particular, recently, numerous analytical applications of this technique dealt with the extraction of natural compounds and pollutants from food and environmental samples. This review gives a brief presentation of the theory of UAE, discusses recent advances that influence its efficiency, and summarizes the main results in selected applications published in the period 2010–12. There is discussion of the advanta…

Computer-aided study of the gas flow within a natural gas storage and the associated collection network

2017

The current paper presents a computer-aided analysis of the way in which a natural gas storage created in a depleted gas deposit and the associated gas collection network are operated, both during the extraction phase and during the injection phase. In a first step, an analysis is carried out on a two-dimensional, nonstationary model for the gas storage, based on the deposit’s geometry and the rock properties, but also on the gas motions. Also, a dynamic simulation of the injection and extraction processes is unfolded, allowing the study and optimisation of elements such as well placement and gas flows through the wells with the goal of maximising the storable gas quantities. A second model…

Extraction and fusion of spectral parameters for face recognition

2011

This is the copy of journal's version originally published in Proc. SPIE 7877: http://spie.org/x10.xml?WT.svl=tn7. Reprinted with permission of SPIE. Many methods have been developed in image processing for face recognition, especially in recent years with the increase of biometric technologies. However, most of these techniques are used on grayscale images acquired in the visible range of the electromagnetic spectrum. The aims of our study are to improve existing tools and to develop new methods for face recognition. The techniques used take advantage of the different spectral ranges, the visible, optical infrared and thermal infrared, by either combining them or analyzing them separately …

Supervised reference region extraction for the quantification of [11C]-(R)-PK11195 brain studies

2006

Flow injection Fourier transform infrared determination of nicotine in tobacco

2000

A fully automated procedure is proposed for the Fourier transform infrared (FTIR) determination of nicotine in tobacco. The method is based on the on-line extraction of nicotine with CHCl3. Samples, weighed inside empty extraction cartridges, were humidified with NH3 and the cartridges were installed in a flow manifold in which they were extracted with 2 ml CHCl3 for 2 min, then 400 microliters of the extract were introduced into a micro-flow cell using a carrier of CHCl3 and the IR spectrum was registered continuously. The absorbance, in the wavenumber range 1334-1300 cm-1, was measured, obtaining a peak as a function of time. The area of this peak was interpolated on a calibration line es…

Analysis of Nicotine and Its Oxidation Products in Nicotine Chewing Gum by a Molecularly Imprinted Solid-Phase Extraction

2000

Chromatographic stationary phases showing exceptional selectivity for nicotine can be prepared by the technique of molecular imprinting. Such phases were used in the search for a rapid cleanup step for nicotine and some of its oxidation products in chewing gum formulations. Thus, using an organic mobile phase, the nicotine analytes from chewing gums dissolved in nonpolar solvent were retained, whereas the nonpolar matrix eluted close to the void peak. A subsequent switch to an acidic mobile phase resulted in elution of the analytes as one sharp peak. Due to weak binding of the less basic oxidation products, other imprinted polymers were tested, and the solid-phase extraction procedure was o…

Combining poly(dimethyldiphenylsiloxane) and nitrile phases for improving the separation and quantitation of benzalkonium chloride homologues: In-tub…

2013

The retention and separation of four homologues of benzalkonium chloride (alkyl (C12, C14, C16, C18) dimethylbenzylammonium chloride) have been studied in poly(dimethyldiphenylsiloxane) (TRB) and nitrile capillary phases, respectively. Under the optimized conditions (50% acetonitrile in processed samples, 35% of diphenyl content of the TRB, capillary length 43 cm and water:methanol 60:40 as replacing solvent), the extraction efficiency was similar for all the homologues with satisfactory reproducibility and independently of the amount and proportion of homologues. Industrial samples with high viscosity or with complex composition and washes waters have been analyzed without previous treatme…

Solid-phase extraction disks for determining pesticides from soil leachates

1997

Abstract Analytical techniques are essential for identifying and quantifying the chemicals present in environmental samples. A method for extracting pesticides from soil leachates was developed. The proposed method is based on solid-phase extraction and uses 47-mm disks of octyl-bonded silica. Analysis was carried out by gas chromatography with nitrogen–phosphorus and electron-capture detectors. Several factors that can provide better pesticide recoveries with this extraction method are discussed. These factors are: the kind and percentage of organic solvent used in the extraction procedure, the volume and the ionic strength (adding 15% of NaCl) of the aqueous phase which passes through the…