摘要:
Herein is described an apparatus for adaptation to existing GC/MS systems, utilizing a splitless injector as the desorption oven with a liquid CO2 cooled low thermal mass cryo trap that eliminates the need for flash heating of volatile compounds.
摘要:
A method for the cryogenic fractionation of air, in which a liquid volume present in a vaporization chamber in a distillation column system of an air fractionation plant is fed by means of a cryogenic liquid and in which a proportion of the liquid volume is continuously transferred into the gas phase by vaporization, wherein, in addition to oxygen, the cryogenic liquid contains components, including xenon, which are higher-boiling than oxygen. The content of xenon in the cryogenic liquid is determined and used as a measure of any enrichment of the components which are higher-boiling than oxygen in the cryogenic liquid. A corresponding air fractionation plant is also described.
摘要:
This invention relates to a modulator for use in gas chromatographic analysis, adopted for alternatively trapping and releasing fractions of solutes in a length of a capillary column within a chromatographic oven, characterized in that it comprises at least one nozzle placed to spray at least one jet in at least one corresponding place along said capillary column length, said nozzle(s) being connected each to a source of liquid CO2 via a related valve, and means for alternatively opening said valve(s) for a predetermined time, to cause a jet of liquid CO2 to impinge for said predetermined time on said column place and to leave the oven atmosphere to heat said column place after said predetermined time. The modulator can be used in a conventional GC system or in a two dimensional GC system, for modulating the analytes fed to the second capillary column.
摘要:
A flow of a carrier gas through a column is provided. A sample is provided in the column, and a temperature of a longitudinally short portion of the column is raised to a predetermined controlled high temperature at which volatile substances are released from the sample packing and are carried by the carrier gas. The column is cooled on each side of the short portion to a low temperature at which the volatile substances condense or adsorb on the column packing. By continuously moving the heated short portion from an inlet end to an outlet end of the packing in a direction of carrier gas flow the volatile substances selected by the controlled high temperature are released. Four particularly useful and advantageous applications can be identified for the invention. Firstly, it provides an improved gas chromatograph (GC) injector. Secondly, it provides an improved thermal separator or extractor. Thirdly, it provides an efficient way to analyze target compounds suspected of being contained within a complex mixture by allowing for the GC analysis to be carried out only on those compounds or substances falling within the same or similar thermal desorption characteristics as those of the target compound. Lastly, by operating in a full time-coupled time-resolved (TCRC) mode, a complete three-dimensional analysis output can be obtained giving better power of separation of the analyzed sample, which is of particular importance when the substance to be analyzed is a complex organic material.
摘要:
A simplified method for solid phase extraction of components of interest from a sample employing a syringe in which the inner surface of the cannula or needle is at least partially coated with a stationary phase such that aspirating the sample into the needle results in adsorption of the components of interest into the stationary phase. Aspiration of a solvent may be employed for removing the components of interest from the stationary phase for direct injection into a chromatographic instrument, or the components of interest may be removed by thermal desorption, wherein the needle is placed in the injection port of the chromatographic instrument and heated.
摘要:
The invention provides a method and apparatus for efficiently measuring and analyzing volatile and relatively non-volatile flavor components released during oral processing of food or other products. The subject exhales a breath sample into one or more temperature-controlled collection chambers, preferably at predetermined time intervals during the oral processing of the product. Each breath sample is then purged from its collection chamber with a non-reactive gas flow into an adsorbent, absorbent or other trap containing an interface that separates and collects the volatile and relatively non-volatile components from the breath sample. The trap is then transferred to a thermal desorber to release the volatile and relatively non-volatile flavor components from the interface surface into a measuring and analysis apparatus.
摘要:
A gas trap apparatus is disclosed for trapping gaseous fraction of mixtures. The apparatus includes a gas column chamber into which a tubular column, such as a capillary tube, may extend. A cooling chamber is provided into which a coolant may be introduced for solidifying or liquefying a gas sample. A heating element in surrounding relationship to the cooling chamber is used for vaporizing the solidified/liquified gas. A Dewar flask surrounds the gas trap apparatus to prevent thermal leakage to the atmosphere.
摘要:
A practical device and method of performing comprehensive multi-dimensional chemical separation using a first dimension of a two-dimensional chromatograph to generate a chromatogram in a time comparable to or even faster than common practice while the second dimension generates multiple chromatograms each in a time comparable to the fastest prior art chromatography. The transfer of sample portions from the first dimension to the second dimension is by any one of several sample stream modulation techniques. These techniques accumulate portions of sample between the first and the second dimensions transferring them as very sharp concentration pulses analogous to fast injections, without loss of sample and with a substantial improvement in sensitivity.
摘要:
A highly selective, sensitive, fast detection system and method are disclosed for detecting vapors of specific compounds in air. Vapors emanating from compounds such as explosives, or stripped from surfaces using heat and suction from a hand-held sample gun, are collected on surfaces coated with gas chromatograph (GC) material which trap explosives vapors but repel nitric oxide, then are desorbed and concentrated in one or more cold spot concentrators. A high speed gas chromatrograph (GC) separates the vapors, after which specific vapors are decomposed in two pyrolyzers arranged in parallel and the resulting nitric oxide is detected. A low temperature pyrolyzer with silver produces NO from nitramines or nitrite esters; a high temperature pyrolyzer decomposes all explosives vapors to permit detection of the remaining explosives. Also disclosed is a series arrangement of pyrolyzers and gas chromatographs and an NO detector to time-shift detection of certain vapors and facilitate very fast GC analyses. The use of hydrogen as a carrier gas, plus unique collectors and concentrators, high speed heaters, NO detectors, and very fast, temperature-programmable GC's enhance selectivity, sensitivity and speed of detection.
摘要:
A gas chromatography plus mass spectrometry system implements a scan strategy in which each full range scan alternates between a normal measurement mode and a survey mode based on a block/gap map made during the previous scan. Survey mode is used within regions that were determined in the previous scan to lack signal above a predetermined threshold. Spectral data is generated during measurement mode operation. Each scan serves both measurement and mapping functions in a way that avoids mass filter jumps, since each scan is monotonic over the entire scanning range.