Detectors systems Differential detector Flame

The flame ionization detector (FID) is the detector most often used in steroid analyses. For very low concentrations of steroids, the application of ECD is needed. Thermal conductivity detectors (TCDs) cannot be used in the analysis of steroids because of their very low sensitivity. For steroidal alkaloids, a nitrogen-specific detector (NPD) has also been used. By the use of dual detector systems (e.g., FID and NPD), closely related nitrogen-containing and non-nitrogen-containing steroids can be easily differentiated. The application of MS as detector was already discussed in a previous entry in this encyclopedia." By using a GC/MS system, the identity of the peak(s) can be determined in an undisputed manner. ... 

Other than phosgene and the cyanide agents, most chemical warfare agents are thought to have ionization potentials of less than 10.6 eV. Therefore screening with photo ionization detectors (PIDs) and flame ionization detectors (FIDs) is possible. However, because these systems will not differentiate... 

Self-condensation of acetone was carried out at 473 K and 100 kPa in a flow system with a differential fixed-bed reactor. Acetone was vaporized in H2 (H2/acetone =12) before entering the reaction zone. The standard contact time (6fc) was 0.84 g of cat h/g of acetone. Main reaction products were mesityl oxides (MO s), isophorone (IP) and mesitylene (MES). Traces of phorone and light hydrocarbons were also identified. The coke formed on the catalysts was characterized after reaction, ex-situ, in a temperature-programmed oxidation (TPO) unit. The TPO experiments were carried out in a microreactor loaded with 50 mg of catalyst and using a 3 % O2/N2 carrier gas. Sample temperature was increased linearly from room temperature to 973 K at 10 K/min. The reactor exit gases were fed into a methanator operating at 673 K to convert CO in methane and then analyzed by flame ionization detector. 

FI preconcentration system compared to one without preconcentration. For example, the response of a flame AAS detector may be influenced by a change in the solution introduction rate (cf. Sec, 2.4,2, equation 2.1). These effects should be differentiated from enrichment effects in order to obtain a valid evaluation of the preconcentration performance. This may be realized by separately determining the enhancement factor under similar operational conditions but without preconcentration. In this book the two factors will be differentiated whenever possible, otherwise the total enhancement factor, expressed as will be used instead of EF. Fang ei al.[10] have shown that when sensitivity enhancement factors exist, other than an increase in concentration of the analyte in solution, the enhancement effects will be multiplicative on EF. Provided that different factors have independent enhancement mechanisms, the total enhancement factor Nt, will be the product of the individual enhancement factors, N, and... 

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