Search results for "reference standards"
showing 10 items of 156 documents
Selective determination of trimethylamine in air by liquid chromatography using solid phase extraction cartridges for sampling.
2004
Abstract The selective determination of trimethylamine (TMA) in air by liquid chromatography is reported. Sampling is effected by flushing air through C18-packed solid-phase extraction (SPE) cartridges at a flow rate of 15 mL/min for 15 min. Next, TMA is desorbed from the cartridges and injected into the chromatographic system. The analyte is then selectively retained on a precolumn ( 20 mm ×2.1 mm i.d., packed with 30 μm, Hypersil C18 phase), and derivatized on-line by injecting 9-fluorenylmethyl chloroformate (FMOC). Finally, the TMA-FMOC derivative is transferred to the analytical column ( 125 mm ×4 mm i.d., LiChrospher 100 RP18, 5 μm), and monitored at 262 nm. The method was applied to …
Diffusion technique for the generation of gaseous halogen standards
2009
Abstract Halogens are known to play an important role in the tropospheric ozone-depletion chemistry and are of special interest because of their influence on the atmospheric oxidation capacity. In this paper, we investigate the application of a capillary diffusion technique for the generation of gaseous halogen standards like Br 2 , IBr, ICl and I 2 . The influence of capillary dimension (i.e. length and inner diameter), ambient pressure and headspace volume of the diffusion vessel on the test gas output has been evaluated. The experimental output rates are determined from the mass loss of the analyte vessel on a regular schedule and compared with their respective theoretical predictions. W…
Environmentally friendly LC for the simultaneous determination of ascorbic acid and its derivatives in skin-whitening cosmetics
2008
Ascorbic acid (AA), also known as vitamin C, is a very popular skin-whitening agent used in cosmetics. However, the use of AA (and also its sodium or magnesium salts) in cosmetic products is limited owing to its labile oxidative properties. In order to avoid its early degradation, different derivatives have been designed, such as ascorbyl phosphate (APH; as magnesium or sodium salts) and ascorbyl palmitate (AP), and more recently the ascorbyl glucoside (AG). Bearing in mind that all these chemicals in skin-whitening cosmetic products must be determined in order to control the efficacy of such products, this paper focuses on developing a wide-ranging LC analytical method able to determine th…
Comparison between micellar liquid chromatography and capillary zone electrophoresis for the determination of hydrophobic basic drugs in pharmaceutic…
2007
[EN] The determination of highly hydrophobic basic compounds by means of conventional reversed-phase liquid chromatographic methods has several drawbacks. Owing to the characteristics of micellar liquid chromatography (MLC) and capillary electrophoresis (CE), these techniques could be advantageous alternatives to reversed-phase chromatographic methods for the determination of these kinds of compounds. The objective of this study was to develop and compare MLC and CE methods for the determination of antipsychotic basic drugs (amitryptiline, haloperidol, perphenazine and thioridazine) in pharmaceutical preparations. The chromatographic determination of the analytes was performed on a Kromasil…
Determination of low-molecular-mass aliphatic carboxylic acids and inorganic anions from kraft black liquors by ion chromatography.
2007
An ion chromatographic (IC) method with suppressed conductivity detection (CD) was developed and validated for the quantitative determination of several low-molecular-mass aliphatic mono- and dicarboxylic acids as their carboxylate anions together with some inorganic anions (chloride, sulfate, and thiosulfate) from kraft black liquors. To confirm the identification of some carboxylate anions which lack commercial model substances, a qualitative IC method with suppressed electrospray ionization mass spectrometry (ESI-MS) was also developed. The separations were performed on an IonPac AS 11-HC anion-exchange column operated at 25 degrees C within 25 min by a gradient elution with aqueous pota…
Aceites esenciales: productos antimicrobianos y antioxidantes naturales en la industria agroalimentaria
2020
[ES] Los consumidores son conscientes del peligro derivado del uso de antioxidantes y antimicrobianos sintéticos en la industria agroalimentaria, demandando alternativas más seguras y ecológicas. En este estudio, se ha determinado la actividad antioxidante de aceites esenciales comerciales mediante el método DPPH y su efecto antimicrobiano frente a la bacteria Pseudomonas syringae y el hongo fitopatógeno Fusarium oxysporum a través del empleo del método estandarizado de disco. Los aceites esenciales de clavo, ajedrea, canela y orégano, así como carvacrol, mostraron la máxima actividad antioxidante, comparable a antioxidantes establecidos. El aceite esencial de gaulteria fue el más potente i…
Identifying the Unknown Content of an Ancient Egyptian Sealed Alabaster Vase from Kha and Merit’s Tomb Using Multiple Techniques and Multicomponent S…
2020
This article highlights the multianalytical study of exuded liquid from an ancient Egyptian sealed alabaster vase by Master's students in an applied chemistry for cultural heritage course. Master students are introduced to the field of Archaeometry that see the collaboration of experts in different areas of research such as conservators, curators of museums, physicists, chemists, etc. The sample is a residue exuded on the linen strip sealing an ancient Egyptian alabaster vase (inventory number S.8448) from the collection of the Museo Egizio in Turin (Italy). The students start to plan the noninvasive investigation by X-ray fluorescence (XRF), transmission electron microscopy (TEM), and ener…
Comparison of pulsed-field gel electrophoresis and whole-genome-sequencing-based typing confirms the accuracy of pulsed-field gel electrophoresis for…
2020
Summary Aim To determine whether pulsed-field gel electrophoresis (PFGE) accurately recognizes isolates belonging to clusters defined by techniques based on whole-genome sequencing (WGS) using Pseudomonas aeruginosa as a model. Methods We selected 65 isolates of ST395 P. aeruginosa isolated in seven European hospitals between 1998 and 2012. Isolates were typed by PFGE and sequenced by WGS. A core genome multi-locus sequence typing (cgMLST) analysis based on 3831 genes was performed with a homemade pipeline. Findings PFGE identified eight pulsotypes and cgMLST differentiated nine clusters and nine singletons. Five cgMLST clusters and pulsotypes (31/65 isolates) coincided perfectly. Isolates …
Determination of phenytoin in plasma by molecularly imprinted solid-phase extraction.
2001
Abstract A molecularly imprinted polymer (MIP) using phenytoin as template and methacrylamide as the functional monomer was prepared. The selectivity was measured by comparing capacity factors of phenytoin and other structurally related compounds. The polymer was evaluated as a selective sorbent in molecularly imprinted solid-phase extraction (MISPE). Several washing solvents were tested to study their ability to disrupt the non-specific interactions occurring between the sample and the polymer matrix and the role of water in the recognition process was also investigated. It was shown that the key step of successful sample extraction is the right choice of the washing solvent. Plasma sample…
Towards the development of a fossil bone geochemical standard: An inter-laboratory study
2007
Ten international laboratories participated in an inter-laboratory comparison of a fossil bone composite with the objective of producing a matrix and structure-matched reference material for studies of the bio-mineralization of ancient fossil bone. We report the major and trace element compositions of the fossil bone composite, using in-situ method as well as various wet chemical digestion techniques. For major element concentrations, the intra-laboratory analytical precision (%RSDr) ranges from 7 to 18%, with higher percentages for Ti and K. The %RSDr are smaller than the inter-laboratory analytical precision (%RSDR; 100% was found for the high field strength elements (Hf, Th, Zr, Nb). The…