Temperature gas-liquid chromatography

Carboranes, These are used in neutron capture therapy (254), and as bum rate modifiers in gun and rocket propellants. They are used as high temperature elastomers and other unique materials, high temperature gas—liquid chromatography stationary phases, optical switching devises (256), and gasoline additives (257). 

R6. Ryhage, R., Use of a mass spectrometer as a detector and analyzer for effluents emerging from high temperature gas-liquid chromatography columns. Anal. Chem. 36, 759-764 (1964). 

These values are practically temperature independant, and they are very close to those found for the Apiezon L column. Comparison with the values of a series of alkybenzenes shows that the 5-position of thiazole possesses behavior analogous to that of a benzenic position in gas-liquid chromatography. 

Solution Polymers. Acryflc solution polymers are usually characterized by their composition, solids content, viscosity, molecular weight, glass-transition temperature, and solvent. The compositions of acryflc polymers are most readily determined by physicochemical methods such as spectroscopy, pyrolytic gas—liquid chromatography, and refractive index measurements (97,158). The solids content of acryflc polymers is determined by dilution followed by solvent evaporation to constant weight. Viscosities are most conveniently determined with a Brookfield viscometer, molecular weight by intrinsic viscosity (158), and glass-transition temperature by calorimetry. 

The malonaldehyde thus formed can be estimated quantitatively by the thiobarbituric acid method (58, 59). As a control of the method s reliability, we used, as primary standard, 1, 3, 3-tri-ethoxypropene (46, 47) purified by gas-liquid chromatography (56) and hydrolyzed to malonaldehyde at room temperature with IN sulfuric acid. The molar... 

The purity of 1 and 2 is assessed by analytical gas-liquid chromatography (GC) on a Hewlett-Packard 5890 gas chromatograph equipped with a flame-ionization detector and fitted with a 50 m x 0.2 mm HP-5 fused silica glass capillary column using linear temperature programming from an initial temperature of 150°C for 5 min to a final temperature of 200°C for 10 min at a rate of 5°C/min. 

Jaglan PS, Gunther FA. 1970. Single column gas liquid chromatography of methyl parathion and metabolites using temperature programming. Bull Environ Contam Toxicol 5 111-114. 

Halang, W. A., Langlais, R., and Kugler, E., Cubic Spline Interpolation for the Calculation of Retention Indices in Temperature-Programmed Gas-Liquid Chromatography, Ana/. Chem. 50, 1978, 1829-1832. 

In contrast to other organothallium(I) compounds, cyclopentadienyl-thallium(I) is a remarkably stable compound. Samples can be stored in sealed bottles for months without appreciable decomposition occurring it is unaffected by water and dilute alkali and it is only slowly oxidized by air at room temperature. Cyclopentadienyltballium(I) was first prepared by Meister in 1956 by addition of freshly distilled cyclopentadiene to a suspension of thallium(I) sulfate in dilute potassium hydroxide solution 101, 102). A number of variations of this procedure have been described (5, 25, 34, 56), and the compound has been made in other ways 35, 56,110, 164), but Meister s preparation, in which the yield of crude product is greater than 90%, remains the method of choice. Purification of crude cyclopenta-dienylthallium(I) is best accomplished by vacuum sublimation, and purity of samples can readily be assessed by gas-liquid chromatography on silicone oil at 170° C using hydrogen as carrier gas (7). 

The extracted fractions were esterified with either BF3-MeOH reagent or diazomethane and analyzed by GLC. Gas liquid chromatography (GLC) was conducted with a Perkin-Elmer Sigma 3 equipped with flame ionization detector. Separations were obtained on a Hewlett Packard 12 m x 0.2 mm i.d. capillary column coated with methyl silicon fluid (OV-101). The temperature was maintained at 80°C for 2 min then programmed from 80 to 220°C at 8°C/min. The injector temperature was 250°C. Mass spectra were obtained on a Hewlett Packard model 5995 GC-MS mass spectrometer, equipped with a 15 m fused silica capillary column coated with 5% phenyl methyl silicone fluid. Spectra were obtained for major peaks in the sample and compared with a library of spectra of authentic compounds. 

The reaction products were analyzed on-line by gas liquid chromatography (Varian 3400) on a 50 m CPSil-5 capillary column from Chrompack, hydrogen being the carrier gas (15 psi), with a temperature programming from 45 to 170°C (5°C.min 1) then from 170 to 180°C (2°C.mm1). 

The checkers used a 40-cm. spinning-band column. The product, n2bD 1.4237, was shown to be 98.9% pure by gas-liquid chromatography on a 6-ft. 20% fluorosilicone column. The retention time was 3.75 minutes with a flow rate of helium of 100 ml. per minute, and a column temperature of 125° with the injection port at 170°. The 19 F n.m.r. spectrum (56.4 MHz) consists of four lines of equal intensity centered at +3396 Hz from trichlorofluoromethane (internal) and two sets of two overlapping quartets centered at +4369 Hz and +4461 Hz, respectively. The integrated intensities of the three sets of fluorine resonances are 3 1 1. 

The procedure provides a sensitive derivative for analysis of Diclofopmethyl and of its hydrolysis product by gas-liquid chromatography. Standards of the derivative, stored in hexane at room temperature, were stable for at least one month. The method is rapid and permits the detection of 0.05mg kg-1 of diclofop in soil with minimum interference from coextractives. The alkylation product also provides a second method for verification of diclofop by gas-liquid chromatography. 

Figure 9.23 Separation of equimolar concentrations of methylglycosides by gas-liquid chromatography. The analysis was performed on an OV-1 stationary phase using a temperature gradient from 120 to 220 °C.

Letcher, T.M. et al.. Determination of activity coefficients at infinite dilution of solutes in the ionic liquid l-hexyl-3-methylimidazolium tetrafluoroborate using gas-liquid chromatography at the temperatures 298.15 K and 323.15 K, /. Chem. Eng. Data, 48, 1587, 2003. 

Lantz, A.W., Pino, V., Anderson, J.L., and Armstrong, D.W., Determination of solute partition behavior with room-temperature ionic liquid based micellar gas-liquid chromatography stationary phases using the pseudophase model, /. Chromatogr. A, 1115, 217-224, 2006. 

Why discuss distribution coefficients Most everyone is familiar with the demonstration of iodine distributed between an organic and an aqueous layer. However, distribution equilibria are at the heart of many separation processes from liquid-liquid extractions to virtually every type of chromatography in which the distribution of the solute between the mobile phase and the stationary phase determines the effectiveness of the separation. In the practice of analytical chromatography, distribution coefficients are often called partition coefficients but the concept is identical, only the names have changed. The temperature dependence of a distribution coefficient is at the heart of temperature programming in gas-liquid chromatography (GC), and analyses of the temperature behavior depend on the heats of solution of the distributed solutes. Indeed, GC measurements have been used to measure heats of solution. 

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