Detector carbon composite

Sun, X., Yan, J., Yang, X., Wang, E., Electrochemical detector based on sol-gel-derived carbon composite material for capillary electrophoresis microchips. Electrophoresis 2004, 25, 3455-3460. 

The vacuum chamber that contains the detector is made of stainless steel. The chamber protects the detector from dirt and, by being evacuated, prevents condensation of vapor on the detector surface or electrical discharge when high voltage is applied to the detector. A metal envelope, with a very thin window at its end for the passage of the incident photons, surrounds the detector. The window is made of beryllium, aluminum, or a carbon composite fiber. Transmission characteristics of several window thicknesses are shown in Fig. 12.23. Most commercial cryostats include the preamplifier as a standard component. 

D.E. Tallman and D.E. Weisshaar, Carbon composite electrodes for liquid-chromatography electrochemistry - Optimizing detector performance by tailoring the electrode composition, J. Liquid Chromatogr., 1983, 6, 2157-2172. 

Lead sesquioxide is used as an oxidation catalyst for carbon monoxide ia exhaust gases (44,45) (see Exhaust control), as a catalyst for the preparation of lactams (46) (see Antibiotics, P-lactams), ia the manufacture of high purity diamonds (47) (see Carbon, diamond-natural), ia fireproofing compositions for poly(ethylene terephthalate) plastics (48), ia radiation detectors for x-rays and nuclear particles (49), and ia vulcanization accelerators for neoprene mbber (50). 

Thermal Conductivity Detector In the thermal conductivity detector (TCD), the temperature of a hot filament changes when the analyte dilutes the carrier gas. With a constant flow of helium carrier gas, the filament temperature will remain constant, but as compounds with different thermal conductivities elute, the different gas compositions cause heat to be conducted away from the filament at different rates, which in turn causes a change in the filament temperature and electrical resistance. The TCD is truly a universal detector and can detect water, air, hydrogen, carbon monoxide, nitrogen, sulfur dioxide, and many other compounds. For most organic molecules, the sensitivity of the TCD detector is low compared to that of the FID, but for the compounds for which the FID produces little or no signal, the TCD detector is a good alternative. 

Lewis, N. S., Comparisons between mammalian and artificial olfaction based on arrays of carbon black polymer composite vapor detectors, Acc. Chem. Res. 2004, 37, 663 672... 

Beyond the density changes that can be used to control method modifications in SFC, the mobile phase composition can also be adjusted. Typical LC solvents are the first choice, most likely because of their availability, but also because of their compatibility with analytical detectors. The most common mobile phase modifiers, which have been used, are methanol, acetonitrile and tetrahydrofuran (THF). Additives, defined as solutes added to the mobile phase in addition to the modifier to counteract any specific analyte-column interactions, are frequently included also to overcome the low polarity of the carbon dioxide mobile phase. Amines are among the most common additives. 

Ordinarily electrical amplification is used to compensate for differences in isotope abundances in the gas being measured. Thus, for carbon dioxide all three Faraday collectors are used with relative signal amplification at m/z = 44, 45, and 46 of 1 91 500 (since the normal abundance ratios 12C/13C 91, and 160/180 500). The amplified signals from all three detectors are thus comparable in intensity. Because of this feature, however, IRMS should only be used on gases with isotope composition close to natural abundance. Enriched material should not be used without careful recalibration since there is no guarantee of a linear response of electric signal to ion current for widely different isotope ratios. 

Elemental composition Ba 69.58%, C 6.09%, O 24.32%. The compound is digested with nitric acid under heating and the solution is analyzed for barium by atomic absorption or emission spectrometry (see Barium). Carbon dioxide may be determined by treating a small amount of the solid with dilute HCl and analyzing the evolved gas by GC using a thermal conductivity detector or a mass spectrometer. The characteristic mass of CO2 is 44. 

Elemental composition C 15.77%, S 84.23% carbon disulfide. It may be analyzed by GC using a sulfur chemiluminescence detector or by GC/MS. A concentration of 1 ppm in the air may be measured by mass spectrometry. The primary characteristic ionic mass for identification of this compound by mass spectrometry is 76. Many GC columns are available commercially. 

Elemental composition C 42.88%, O 57.12%. Carbon monoxide may be identified and determined quantitatively at low ppm level by infrared sensors. Such CO detectors are commercially available. Also, it can be analyzed by GC using TCD or FID or by GC/MS. The characteristic ion mass for CO identification is 28 (same as N2 or ethylene, both of which can interfere). 

The gases exiting the reactor pass through a Beckman 565 infrared CO2 analyzer, which continuously monitored the production of carbon dioxide. Gas composition analysis was performed on-line using a Hewlett Packard 5890 II gas chromatograph, equipped with both a thermal conductivity and a flame ionization detector and a Porapak-Q column. Additional experimental details are given elsewhere (9). 

They studied the effect of the mass detectors drift tube temperature on the low-molecular-mass TGs. Solutions of 10 mg/ml of tributyrin, tricaproin, tricaprylin, tricaprin, and trilaurin were injected twice at each of the following drift tube temperatures 20,25, 30,45, and 60°C. Five replications of the HPLC analysis were performed for one sample of ewe s milk fat to determine the reproducibility of the HPLC method. The TG composition was estimated in accordance with the method based on the calculation of the equivalent carbon numbers (ECNs) of the HPLC chromatographic peaks and in the molar composition in fatty acids, analyzed by GLC, collected at the HPLC chromatograph outlet. The HPLC fractions were collected every 40 s at the outlet of the column after 14 min there were no peaks before that time. 

G. A. Sotzing, J. N. Phend, R. H. Grubbs, and N. S. Lewis, Highly sensitive detection and discrimination of biogenic amines utilizing arrays of polyaniline/ carbon black composite vapor detectors , Chemistry of Materials 12, 593 (2000). 

E. S. Tillman and N. S. Lewis, Mechanism of enhanced sensitivity of linear poly(ethylenimine) - carbon black composite detectors to carboxylic acid vapors , Sensors And Actuators B - Chemical 96, 329 (2003). 

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