The krypton and xenon contents of atmospheric air

1956 ◽  
Vol 234 (1199) ◽  
pp. 557-565 ◽  
Keyword(s):  
Gas Chromatography ◽  
Low Temperature ◽  
Atmospheric Air ◽  
Dry Air

The proportion of krypton and xenon in dry air has been measured by a method using distillation and low-temperature gas-chromatography for the isolation of krypton and xenon. The separation has been controlled by the use of radioactive 85 Kr tracer. The krypton content of dry air is 1⋅139 ± 0⋅01 x 10 -6 by volume. The xenon content of dry air is 0⋅086 ± 0⋅001 x 10 -6 by volume.

Profile of Volatile Metabolites in Human Urine

1971 ◽  
Vol 17 (7) ◽  
pp. 592-594 ◽  
Author(s):  
Albert Zlatkis ◽  
Hartmut M Liebich
Keyword(s):  
Mass Spectrometry ◽  
Gas Chromatography ◽  
Low Temperature ◽  
Ethyl Ether ◽  
High Efficiency ◽  
Allyl Isothiocyanate ◽  
Reduced Pressure ◽  
Dietary Changes ◽  
Volatile Metabolites ◽  
Diagnostic Use

Abstract Volatile constituents of 30 urines from 10 adults have been studied by gas chromatography, and two also by mass spectrometry. The sample was prepared by extracting urine with ethyl ether, distilling the extract at low temperature under reduced pressure, and concentrating the distillate to a few microliters. High-efficiency capillary columns, 150 m x 0.5 mm i.d., provide the resolution necessary to indicate the presence of some 300 compounds, 40 of which have been identified by mass spectrometry. These include ketones, alcohols, lactones, terpenes, furans, dimethyl sulfone, pyrrole, and allyl isothiocyanate. Dietary changes have a relatively small effect on the profile of the volatiles, and interindividual patterns are very similar. These facts make analyses of this kind of potential diagnostic use.

Enantiomer separation of 1,4-sulfanylalcohols by conventional and low-temperature gas chromatography

Chirality ◽  
2006 ◽  
Vol 18 (7) ◽  
pp. 558-561 ◽  
Author(s):  
Jean-Jacques Filippi ◽  
Xavier Fernandez ◽  
André-Michel Loiseau ◽  
Louisette Lizzani-Cuvelier ◽  
Uwe J. Meierhenrich
Keyword(s):  
Gas Chromatography ◽  
Low Temperature ◽  
Enantiomer Separation

Experimental Study of a Laminar Flow Solid Desiccant Dehumidifier Driven by a Low Temperature Heat Source

2016 ◽  
Vol 819 ◽  
pp. 361-365 ◽  
Author(s):  
Seung Jin Oh ◽  
Kyaw Thu ◽  
Muhammad Wakil Shahzad ◽  
Wongee Chun ◽  
Kim Choon Ng
Keyword(s):  
Experimental Study ◽  
Low Temperature ◽  
Laminar Flow ◽  
Heat Source ◽  
Silica Gel ◽  
Average Diameter ◽  
Hot Water ◽  
Dry Air ◽  
Temperature Heat ◽  
Adsorption Desorption

In this paper, an experimental study of a laminar flow solid desiccant dehumidifier has been presented. The cyclic steady state performance of adsorption-desorption processes was analyzed at various heat source temperatures and typical ambient humidity conditions in tropics. The desiccant dehumidification system consists of two beds filled with silica gel, two heat exchangers operating at 30 oC and 80 oC respectively, three humidity stations for measurement of the temperature and humidity conditions of the system and a blower to make airflow throughout the system. Type-RD silica gel of 0.3 mm average diameter was used as the working desiccant in the dehumidification system. This system has no moving parts rendering less maintenance compared with a rotary type. It is also energy-efficient means of dehumidification by adsorption process with low temperature heat source as compared to the conventional methods. As a result, it was observed the humidity ratio of inlet air is reduced from 24 g/kg of dry air to about 17 g/kg of dry air. Concomitantly, hot water at 80 oC is used to regenerate the adsorbent.

scholarly journals The low temperature oxidation of copper

1926 ◽  
Vol 111 (757) ◽  
pp. 210-219 ◽  
Keyword(s):  
Low Temperature ◽  
Metallic Surface ◽  
Low Temperature Oxidation ◽  
Protective Oxide ◽  
Temperature Oxidation ◽  
Dry Air ◽  
Protective Oxide Film ◽  
Oxygen Surface ◽  
Mechanism Of The Reaction ◽  
Number Of Authors

The attack of dry air or oxygen upon copper becomes appreciable somewhere in the neighbourhood of 200° C. The mechanism of the reaction in this temperature range has been studied by a number of authors but the absence of unanimity in their conclusions is remarkable. It is evident that the oxidation of a metallic surface may result in the formation of a protective oxide film, and that continued oxidation may be controlled by the diffusion of oxygen through the film rather than by factors which are normally described as chemical. Under these circumstances the progress of oxidation is precisely similar to the flow of heat and is subject to the same laws. If c is the concentration of oxygen at a distance y from the oxide—oxygen surface after a time t then D δ 2 c /δ y 2 = δ c /δ t .

Gas chromatography of high boiling compounds on low temperature columns

1960 ◽  
Vol 32 (13) ◽  
pp. 1730-1733 ◽  
Author(s):  
Chales. Hishta ◽  
John P. Messerly ◽  
Robert F. Reschke
Keyword(s):  
Gas Chromatography ◽  
Low Temperature

scholarly journals MINIATURIZED LIQUID-LIQUID EXTRACTION WITH LOW-TEMPERATURE PARTITIONING TECHNIQUE (LLE/LTP) FOR PESTICIDE ANALYSIS IN A BIOLOGICAL MATRIX BY GAS CHROMATOGRAPHY

Química Nova ◽  
2021 ◽  
Author(s):  
Thaís Silva ◽  
Maria Eliana Queiroz ◽  
Antônio Neves ◽  
Patrícia Vieira ◽  
André Oliveira ◽  
...  
Keyword(s):  
Gas Chromatography ◽  
Low Temperature ◽  
Blood Serum ◽  
Liquid Extraction ◽  
Serum Samples ◽  
Biological Matrix ◽  
Rural Workers ◽  
Extraction Solvent ◽  
Liquid Liquid Extraction ◽  
Partitioning Technique

The liquid-liquid extraction with low-temperature partitioning technique (LLE/LTP) was miniaturized to determine the pesticides chlorpyrifos, bifenthrin, λ-cyhalothrin, and deltamethrin in a biological matrix, by gas chromatography. The method was proposed for fetal-bovine serum samples (500 μL), by using a full factorial design (23) with one center point. The evaluated factors included the volume of water added to the sample (1000 μL), volume of extraction solvent (500 μL) and stirring time (60 s) – a cleanup step was not necessary. The method was validated for the main figures of merit. The results indicated that the LLE/LTP/GC/ECD miniaturized method was efficient in extracting pesticides from blood-serum samples (75 to 115%). It showed both selectivity and sensitiveness, with limits of quantification (LOQ) ranging from 8 at 17 μg L-1. Once validated, the method was applied to blood-serum samples of rural workers from a city in the Brazilian state of Minas Gerais. In that case, the presence of chlorpyrifos was detected in two of the samples.

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