Search results for "Detector"
showing 10 items of 3491 documents
Stability of Plant Sterols in Ingredients Used in Functional Foods
2011
The content of plant sterol (PS) and their oxidation products (POPs) in eight ingredients used to enrich functional foods was studied. A gas chromatographic (GC) technique with mass-spectrometric detection was used for identification, while GC with a flame ionization detector (GC-FID) was used for quantification. β-Sitosterol was the most abundant phytosterol, and the main POPs found were derived from this compound (7α/β-hydroxysitosterol, 7-ketositosterol, and sitostanetriol). The total amount of POPs found in the ingredients ranged from 29.03 to 110.02 μg/100 g PS. The β-sitosterol oxidation rates ranged from 10 to 50 μg β-sitosterol oxides/100 g of β-sitosterol. In view of this low rate …
Comparison of photodiode array, evaporative light scattering, and single-quadrupole mass spectrometric detection methods for the UPLC analysis of pyr…
2017
ABSTRACTIt is important to analyze pyrolysis liquids to evaluate the yield of valuable products as well as unfavorable by-products. This work focuses on choosing detectors for reversed-phase ultra high-performance liquid chromatography analysis of pyrolysis liquids. The linearity, sensitivity, precision, and recovery of photodiode array (PDA) detector, single-quadrupole mass spectrometer (MS), and evaporative light scattering (ELS) detector were compared for the quantitative determination of several typical compounds found in pyrolysis liquids. PDA and MS detectors were found to be suitable for the quantification of furans and phenol derivatives (furfural, vanillin, syringol), but sugars an…
Gas chromatographic and mass spectrometric analysis of chlorinated catechols occurring in pulp bleach liquors
1982
Chlorination step (C-step), spent bleach liquor from a kraft pulp mill and the product from the chlorination of guaiacol in aqueous solution have been investigated for their content of chlorinated catechols. After separation the samples were derivatized with diazoethane and analysed by glass capillary gas chromatography with an electron capture detector. The external standard mixture of all ethylated chlorocatechols was used in the measurements. The structures of the compounds identified were confirmed by gas chromatography/mass spectrometry. Eight chlorinated catechols were identified from a sample prepared by chlorination of guaiacol with Cl2 in aqueous solution. However, only four of the…
High-resolution pyrolysis–gas chromatography with a movable reaction zone
1997
Abstract A new device was constructed for pyrolysis–gas chromatography and it was laboratory tested. The device enables the thermal degradation of polymers inside a capillary pre-column and transfer of the reaction zone into a column oven. The pyrolysis procedure described protects the thermally sensitive compounds prior to pyrolysis, prevents the process of irreversible condensation of high-boiling pyrolysis products during the chromatographic process and eliminates extracolumn effects on the peak broadening.
Packing technology, column bed structure and chromatographic performance of 1-2-μm non-porous silicas in high-performance liquid chromatography
1989
This work is aimed at further elucidating the aggregation behaviour of micron- and submicron-size non-porous silicas and the column performance of 1–2-μm C18 silicas in reversed-phase high-performance liquid chromatography of low-molecular weight compounds. It is demonstrated that highly ordered, dense, porous aggregates of such silica beads were obtained by gravity settling and centrifugation. The slurry techniques applied at constant flow-rate and a pressure up to 50 MPa provided less-ordered aggregates, but generated an acceptable performance of columns when 1–2-μm C18 silica beads were employed. To operate columns of 53 mm × 4.6 mm I.D., the maximum flow-rate needs to be ca. 2.5 ml/min …
Lipid hydroperoxides determination in milk‐based infant formulae by gas chromatography
2003
A simple gas chromatograph using a flame ionization detector and a polar capillary column method is proposed for determining hydroperoxides in the lipid fraction of milkbased infant formulas. Tricosanoic acid is used as internal standard. The method includes the following steps: a) the extraction of fat with chloroform/methanol (2:1, v/v), b) the reduction of hydroperoxide acids to hydroxide acids with hydrogen gas and palladium as a catalyst, c) the transmethylation to obtain the methyl esters with acetyl chloride and methanol/ hexane (4:1, v/v), and d) an acetylation with acetic anhydride/ pyridine (4:1, v/v) to obtain an acetoxy derivate of the hydroxide present. Two chromatography runs,…
Determination of triazines and organophosphorus pesticides in water samples using solid-phase extraction.
1991
Abstract Octadecyl (C 18 )-bonded porous silica was evaluated for the extraction of triazine and organophosphorus pesticides from natural water. The extraction results showed an effective performance when 1 l of water was passed through small glass columns containing 500 mg of 50–100-μm C 18 bonded porous silica. The absorbed compounds were removed with ethyl acetate, evaporated to 200 μl and determined by gas chromatography. The overall average recoveries were greater than 85% except for dimethoate and trichlorfon. Application of this procedure to the analysis of natural water samples gave results that agree well with those obtained by solvent extraction methods.
Filter-based infrared detectors for high temperature size exclusion chromatography analysis of polyolefins: calibration with a small number of standa…
2012
Infrared detection has been shown to be very appropriate for high temperature analysis of polyolefins. After some early reports in which dispersive or single-band filter-based detectors were applied, Fourier transform detectors have been described for this application, in order to improve the method sensitivity. Modern simple filter-based detectors prove, however, comparable sensitivity while providing a number of practical advantages when coupled to chromatographic systems: reduced cell volume, simplified hardware, continuous generation of absorbance chromatograms, as well as simpler data collection and processing. A practical method for calibration, using multiple-band signals obtained wi…
Isolation and concentration of organophosphorus pesticides from water using a c18 reversed phase
1989
Abstract A simple, rapid and effective method for the extraction and enrichment of organophosphorus pesticides based on the use of Sep-Pak C 18 cartridges was studied as alternative method to those based on extraction with organic solvents. The influence of the elution solvent, pH, salinity and volume of water filtered was studied for ten organophosphorus pesticides. The pesticides were determined by gas chromatography with a BP-1 capillary column and a thermionic detector. Recoveries at the 100 and 200 ng/1 spiking levels were greater than 85%, except for disulfoton.
Critical study of and improvements in chromatographic methods for the analysis of type B trichothecenes
2001
Various analytical methods used in the analysis of type B trichothecenes (deoxynivalenol, nivalenol, 3- and 15-acetyldeoxynivalenol) in cereals were compared and optimised in this work. These methods use either GC-electron-capture detection (ECD) of trimethylsilyl, trifluoroacetyl and heptafluorobutyryl derivatives or HPLC with UV or photodiode array detection of analytes. A new HPLC procedure using fluorescence detection prior derivatisation with coumarin-3-carbonyl chloride has been also tested. Five extraction solvents and two solid-phase extraction cartridges (silica, Florisil) plus a especial clean-up column (MycoSep 225) were compared in order to obtain the best recovery of the mycoto…