Search results for "Desorption"
showing 10 items of 340 documents
Critical assessment of ionization patterns and applications of ambient desorption/ionization mass spectrometry using FAPA-MS
2016
Ambient desorption/ionization mass spectrometry (MS) has gained growing interest during the last decade due to its high analytical performance and yet simplicity. Here, one of the recently developed ambient desorption/ionization MS sources, the flowing atmospheric-pressure afterglow (FAPA) source, was investigated in detail regarding background ions and typical ionization patterns in the positive as well as the negative ion mode for a variety of compound classes, comprising alkanes, alcohols, aldehydes, ketones, carboxylic acids, organic peroxides and alkaloids. A broad range of signals for adducts and losses was found, besides the usually emphasized detection of quasimolecular ions, i.e. […
A new interface to couple thin-layer chromatography with laser desorption/atmospheric pressure chemical ionization mass spectrometry for plate scanni…
2005
An interface to allow on-line qualitative and quantitative full-plate detection and analysis of compounds separated by thin-layer chromatography (TLC) is presented. A continuous wave diode laser is employed as a desorption source. Atmospheric pressure chemical ionization mass spectrometry ionizes and subsequently identifies the desorbed sample molecules. Besides direct laser desorption on untreated TLC plates, graphite particles were used as a matrix to couple in the laser power and improve the efficiency of desorption.
Measurement of nanoparticle mass distributions by laser desorption/ionization time-of-flight mass spectrometry.
2011
In this paper, access to the mass distribution analysis of nanoparticles is described based on laser desorption/ionization and time of flight mass spectrometry. Two examples are given, demonstrating the accurate mass distribution analysis of nanoparticles fabricated both ex situ and in situ during the laser-assisted desorption process. The potentials and the limitations of the method are discussed, with special emphasis on carbonaceous clusters and molecules.
Stir bar sorptive-dispersive microextraction mediated by magnetic nanoparticles-nylon 6 composite for the extraction of hydrophilic organic compounds…
2016
A new and sensitive analytical method based on the recently developed approach termed stir bar-sorptive dispersive microextraction (SBSDME) using a magnetic CoFe2O4@SiO2-nylon 6 composite as sorbent material is presented for the extraction of hydrophilic organic compounds. The simultaneous determination of four hydrophilic UV filters in environmental water samples has been chosen as a model analytical application due to the increasing awareness regarding the occurrence of sunscreen residuals in natural waters. The developed SBSDME approach combines the principles and benefits of stir bar sorptive extraction (SBSE) and dispersive solid phase extraction (DSPE) but allows for lower extraction …
Determination of 129I/127I isotope ratios in liquid solutions and environmental soil samples by ICP-MS with hexapole collision cell
2003
The determination of I-129 in environmental samples at ultratrace levels is very difficult by ICP-MS due to a high noise caused by Xe impurities in argon plasma gas (interference of Xe-129(+)), possible (IH2+)-I-127 interference and an insufficient abundance ratio sensitivity of the ICP mass spectrometer for I-129/I-127 isotope ratio measurement. A sensitive, powerful and fast analytical technique for iodine isotope ratio measurements in aqueous solutions and contaminated soil samples directly without sample preparation using ICP-MS with a hexapole collision cell (ICP-CC-QMS) was developed. Oxygen is used as reaction and carrier gas for iodine thermal desorption via the gas phase from solid…
Determination of n-alkanes, polycyclic aromatic hydrocarbons and hopanes in atmospheric aerosol: evaluation and comparison of thermal desorption GC-M…
2019
Organic aerosol (OA) constitutes a large fraction of fine particulate matter (PM) in the urban air. However, the chemical nature and sources of OA are not well constrained. Quantitative analysis of OA is essential for understanding the sources and atmospheric evolution of fine PM, which requires accurate quantification of some organic compounds (e.g., markers). In this study, two analytical approaches, i.e., thermal desorption (TD) gas chromatography mass spectrometry (GC-MS) and solvent extract (SE) GC-MS, were evaluated for the determination of n-alkanes, polycyclic aromatic hydrocarbons (PAHs) and hopanes in ambient aerosol. For the SE approach, the recovery obtained is 89.3 %–101…
Improvement of the detection limit for determination of 129I in sediments by quadrupole inductively coupled plasma mass spectrometer with collision c…
2004
The previously developed sample introduction device for the hot extraction of iodine from environmental samples (soils or sediments) and on-line introduction of analyte via the gas phase in quadrupole inductively coupled plasma mass spectrometry with hexapole collision cell (ICP-CC-QMS) was equipped with a cooling finger, which allowed intermediate iodine enrichment and improved the detection limits for I-129 down to 0.4 pg g(-1) without any additional sample preparation. A mixture of oxygen and helium as reaction gases in the hexapole collision cell was used for reducing the disturbing background intensity of Xe-129(+). Oxygen was also used as the carrier gas for iodine thermal desorption …
Simple and commercial readily-available approach for the direct use of ionic liquid-based single-drop microextraction prior to gas chromatography
2009
A simple and commercial readily-available approach that enables the direct use of ionic liquid (IL)-based single-drop microextraction (SDME) prior to gas chromatography (GC) is presented. The approach is based on thermal desorption (TD) of the analytes from the IL droplet to the GC system, by using a robust and commercially-available thermodesorption system. For this purpose, a two-glass-tube concentrically disposed system was designed. The inner tube is a laboratory-cut Pyrex tube (20mm length) that houses the ionic liquid droplet from the SDME process, and the outer tube is a commercially-available TD glass tube (187 mm length) commonly employed for stir-bar sorptive extractions (SBSE). I…
Analysis of organic pollutants in water at trace levels using fully automated solid-phase extraction coupled to high-performance liquid chromatography
1997
A method has been developed for the determination of trace levels of 32 pesticides, 19 explosives and 16 polycyclic aromatic hydrocarbons (PAH) in water in three individual steps. Solid-phase enrichment (SPE) is coupled to high-performance liquid chromatography (HPLC) with a fully automated system. The organic pollutants are enriched on reusable cartridges packed with adsorbent materials: pesticides and explosives on a mixed bed of divinylbenzene-ethylvinylbenzene copolymers (LiChrolut EN®) and perfluorinated polyethylene (PolyF®), and polycyclic aromatic hydrocarbons on C18-modified silica (Zorbax® ODS1). Thermally assisted desorption (TAD) has been shown to increase the recovery of analyt…
Solid-Phase Microextraction Liquid Chromatography/Tandem Mass Spectrometry To Determine Postharvest Fungicides in Fruits
2003
A method to determine five postharvest fungicides (dichloran, flutriafol, o-phenylphenol, prochloraz, tolclofos methyl) in fruits (cherries, lemons, oranges, peaches) has been developed using solid-phase microextraction (SPME) coupled to liquid chromatography (LC) with photodiode array (DAD), mass spectrometry (MS), or tandem mass spectrometry (MS/MS) with ion trap detection. Extraction involved sample homogenization with an acetone/water solution (5:1), filtration, and acetone evaporation prior to fiber extraction. The pesticides were isolated with a fused-silica fiber coated with 50-microm Carbowax/template resin. The effects of pH, ion strength, sample volume, and extraction time were in…