Detectors gases used with

A technique known as selective electron capti sensitization has been used to increase the response of the BCD weakly electron-capturing compounds [117]. In this mode a standard electron-capture detector is used with a supply of makeup gas doped with a specific sensitizing reagent such as oxygen nitrous oxide. In this way the BCD functions as an ion-aoleculSj... 

Kirkland, J. J., A high-performance ultraviolet photometric detector for use with efficient liquid chromatographic columns. Anal. Chem. 40, 391-396 (1968). Kirkland, J. J., Controlled surface porosity supports for high speed gas and liquid chromatography. Anal. Chem. 41, 218-220 (1969). 

The purpose of an online detector is to sense and measure the separated analytes as they elute from the column. A variety of sensitive detectors are used with gas chromatographs. These include universal units that detect most analytes and extremely selective devices that detect only spe-... 

Liquid anhydrous ammonia is used extensively as a coolant in heat exchange systems because of its chemical stability, low corrosiveness, and high latent heat of vaporization. However, anhydrous ammonia is readily contaminated during handling and storage. The gas chromatographic analysis of trace contaminants (O2, N2, CO, CH4, CO2, and water) in liquid ammonia was described by Mindmp and Taylor. An F M Model 5750 equipped with a Carle Microcavity Thermistor detector was used with dual columns for analysis. Table 9.3 lists the experimental parameters for both columns, which were conditioned for a minimum of 12 h at a temperature of 180°C and a... 

The relative distribution of aromatic hydrocarbons in xylene products can be quantitatively determined by gas chromatography. A flame ionization or thermal conductivity detector is used with a capillary or packed column containing crosslinked polyethylene glycol as the stationary phase. The peak area of each component is measured and the weight percentage concentration is calculated by dividing the peak area of the component by the sum of the areas of all peaks. 

These workers also studied the gas chromatography of the four butyltin chlorides on a variety of stationary phases. Of the 12 stationary phases tested, separation was achieved only with 20% of G1 7100 FF or 18% of OE 4007 D or OE 4011, supported on Sterchamol (column diameter =0.25 mm) and operated at 175°C, 178 C or 194°C, respectively. A thermal-conductivity detector was used, with hydrogen as carrier gas. 

A F M Model 720 dual-column, linear-temperature programmed gas chromatograph equipped with a four-filament hot wire thermal conductivity cell detector was used with a 1-mv recorder. Samples were delivered to the instrument with a Hamilton 50- y1 syringe. 

Despite their importance, gas chromatography and liquid chromatography cannot be used to separate and analyze all types of samples. Gas chromatography, particularly when using capillary columns, provides for rapid separations with excellent resolution. Its application, however, is limited to volatile analytes or those analytes that can be made volatile by a suitable derivatization. Liquid chromatography can be used to separate a wider array of solutes however, the most commonly used detectors (UV, fluorescence, and electrochemical) do not respond as universally as the flame ionization detector commonly used in gas chromatography. 

A gas ionization detector consists of a tube filled with a high pressure gas and two electrodes. A tube filled with 2 MPa (20 atm) of xenon is common. The gas in the tube ionizes when x-rays pass through the tube causing a current to flow between a high voltage potential placed across the electrodes. This concept is similar to that used in a Geiger tube detector. Gas ionization detectors are utilized in some CT scanners. 

Solvent extraction followed by gas chromatographic analysis is used to determine paraffin wax antioxidants (qv), ie, butylated hydroxyanisole and butylated hydroxytoluene and other volatile materials. Trace amounts of chlorinated organic compounds, eg, polychlorinated biphenyls, can be deterrnined by using a gas chromatograph with an electron-capture detector (22). 

Corrosion. Anticorrosion measures have become standard ia pipeline desiga, coastmctioa, and maintenance ia the oil and gas iadustries the principal measures are appHcation of corrosion-preventive coatings and cathodic protection for exterior protection and chemical additives for iaterior protectioa. Pipe for pipelines may be bought with a variety of coatiags, such as tar, fiber glass, felt and heavy paper, epoxy, polyethylene, etc, either pre-apphed or coated and wrapped on the job with special machines as the pipe is lowered iato the treach. An electric detector is used to determine if a coatiag gap (hoHday) exists bare spots are coated before the pipe is laid (see Corrosion and corrosion control). 

AH gas-fired power plants require oxygen analy2ers to ensure that air has not been drawn into the piping system. Oxygen intake can lead to the presence of an explosive mixture in the pipeline before the fuel reaches the burner or combustor 2one. When gas-fired units are located in an enclosed area, multiple ultraviolet flame detectors are used to shut down equipment and flood the area with CO2 or a chemical fire suppressant whenever a spark or flame is detected. 

SPME has been utilized for deterrnination of pollutants in aqueous solution by the adsorption of analyte onto stationary-phase coated fused-siUca fibers, followed by thermal desorption in the injection system of a capillary gas chromatograph (34). EuU automation can be achieved using an autosampler. Eiber coated with 7- and 100-p.m film thickness and a nitrogen—phosphoms flame thermionic detector were used to evaluate the adsorption and desorption of four j -triazines. The gc peaks resulting from desorption of fibers were shown to be comparable to those obtained using manual injection. 

Epichlorhydrin (ECH) detection starts with detecting epoxide cycle using hydrochloric acid in combination with sodium chloride the reaction product - 1,3-dichlorhydrin - is extracted in diethyl ether and concentrated by removing the latter. Gas-liquid chromatography with a flame-ionization detector is used to detect glycerin 1,3-dichlorhydrin. The sensitivity of the method is 0.01 mg/dm. ... 

Gas chromatographic analysis at 79° using a flame detector in conjunction with a 183 x 0.32 cm. stainless-steel column containing Dow-Corning 550 fluid on silanized support gave peaks for l-bromo-3-chloropropane (6.5 minutes) and 6-chloro-2-hexyne (9.3 minutes) whose areas were shown to be proportional to the mole fractions. The latter were determined by integration of the expanded (50 Hz sweep width)... 

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. 

The gas chromatograph (GC) is a Hewlett-Packard 5890 GC with a thermal conductivity detector. A 5A mole sieve column is used with argon carrier gas this gives peaks going in the same direction for both hydrogen and nitrogen. 

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