1,721,051 research outputs found
Comprehensive 2D GC combined with novel MS instrumentation: powerful unified tools for the analysis of complex samples
No full textFlow-modulated GC × low-pressure-GC: a novel approach fro high resolution/sensitivity separations in gas chromatography
No full textUse of solid-phase micro extraction (SPME) for determination of mineral oil and polycyclic aromatic hydrocarb0ns by mono dimensional GC or GCxGC
No full textSolid-phase microextraction (SPME) is a rapid, easy and solvent-free or low-solvent consuming technique. Several kind of different fibers are available commercially, thus the most suitable selectivity may be chosen according to the specific application. In the present work, the potential of a particular and low exploited fiber (carbopack Z/PDMS) was investigated for determination of mineral oil (MO) and polycyclic aromatic hydrocarbons (PAHS) in foods. The prevalent sorption mechanism of the carbopack Z/PDMS fiber depends on the extraction conditions. In a non-polar solvent the effect of carbopack Z is predominant, which is particularly prone to the extraction of planar compounds by π- π interaction. While sampling the head-space (HS) the sorption mechanism of the PDMS predominates. Therefore, two independent approaches were studied, one using the direct-immersion (DI) extraction, the other by HS-SPME to exploit the carbopack Z and the PDMS selectivity, respectively.
A method to analyze parent PAHs was developed by direct immersion of the fiber in a hexane solution, following by GC-MS analysis for the determination of benzo[a]pyrene, or by comprehensive GC (GCxGC) coupled to time-of-flight (ToF) MS detector for the determination of the 16 PAHs highlighted by the European Union. Very good repeatability, limit of detection (LOD), and limit of quantification (LOQ) values were obtained.
The same fiber was employed to sampling the HS of food samples, thus exploiting, as prevalent sorption mechanism, the PDMS affinity. A good selectivity for MO components was observed, thus a rapid screening method was developed with satisfactory results
Comprehensive Two-Dimensional Gas Chromatography Combined with Single and Triple Quadrupole Mass Spectrometry: Powerful Unified Tools for the Analysis of Food Volatiles
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A comprehensive gas chromatography system with flow modulation under vacuum conditions
No full textThe invention relates to the exploitation of low pressure conditions in the second analytical dimension of flow-modulated comprehensive two-dimensional gas chromatography (GCxGC) systems to reduce the requirements of high gas flows exiting the modulator. The invention specifically relates to flow modulators (3) characterized by the necessity of high gas flows (e.g.,>10 mL/min), to efficiently release effluent accumulated from the first column (12), onto the second column (20). The use of a second analytical column (20), with an internal diameter (ID) equal to, or exceeding 0.30 mm (e.g., 0.32 mm, 0.53 mm), along with vacuum outlet conditions, reduces the pressure conditions inside the second analytical column. Such intra-column low pressure conditions enables efficient release of effluent from the modulator, using lower gas flows (e.g., 7-8 mL/min)
Flow-modulation low-pressure comprehensive two-dimensional gas chromatography
No full textThe present research is specifically based on the use of greatly-reduced gas flows, in flow-modulator (FM) comprehensive two-dimensional gas chromatography systems. In particular, focus of the present research is directed to FM devices characterized by an accumulation stage, and a much briefer re-injection step. It has been widely accepted that the operation of such FM systems requires high gas flows (≥20. mL/min), to re-inject the gas-phase contents of sample (or accumulation) loops, onto the second column. On the contrary, it will be herein demonstrated that much lower gas flows (≈ 6-8. mL/min) can efficiently perform the modulation step of re-injection. The possibility of using such improved operational conditions is given simply by a fine optimization of the processes of accumulation and re-injection. The application of lower gas flows not only means that second-dimension separations are carried out under better analytical conditions, but, even more importantly, greatly reduces problems which arise when using mass spectrometry (i.e., sensitivity and instrumental pumping capacity)
A new analytical perspective in flow-modulated comprehensive two-dimensional gas chromatography
No full textA powerful four-dimensional separation-science tool: on-line liquid chromatography-comprehensive two dimensional gas chromatography-triple quad mass spectrometry
No full textGC multidimensionale “comprehensive” con modulazione a flusso: è questo il futuro delle separazioni GC ad alta risoluzione?
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