Chromatography detector

Thermal Conductivity Detector One of the earliest gas chromatography detectors, which is still widely used, is based on the mobile phase s thermal conductivity (Figure 12.21). As the mobile phase exits the column, it passes over a tungsten-rhenium wire filament. The filament s electrical resistance depends on its temperature, which, in turn, depends on the thermal conductivity of the mobile phase. Because of its high thermal conductivity, helium is the mobile phase of choice when using a thermal conductivity detector (TCD). 

R P W Scott, Liquid Chromatography Detectors Elsevier, Amsterdam, 1979... 

Liquid Chromatography Detectors" second edition, R.P.W.Scott, Journal of Chromatography Library, vol. 33, Elsevier, Amsterdam-Oxford-New York-Tokyo, (1986). 

Liquid Chromatography Detectors" (Ed. Thomas M. Vickrey) Chromatography Science Series,vol. 23, Marcel Dekker, Inc. New York (1983). 

Liquid Chromatography Detectors, edited by Thomas M. Vickrey... 

Munk, M., Refractive index detectors, in Liquid Chromatography Detectors, Vol. 23, Vickrey, T. M., Ed., Marcel Dekker, New York, 1983, chap. 5. 

Fenn, R. J., Siggia, S., and Curran, D. J., Liquid chromatography detector based on single and twin electrode thin-layer electrochemistry application to the determination of catecholamines in blood plasma, Anal. Client., 50, 1067,1978. 

R.P.W. Scott, Liquid Chromatography Detectors, Elsevier Science Publishers, Amsterdam (1986). 

Fig. 3. Diagrams of electrochemical cells used in flow systems for thin film deposition by EC-ALE. A) First small thin layer flow cell (modeled after electrochemical liquid chromatography detectors). A gasket defined the area where the deposition was performed, and solutions were pumped in and out though the top plate. Reproduced by permission from ref. [ 110]. B) H-cell design where the samples were suspended in the solutions, and solutions were filled and drained from below. Reproduced by permission from ref. [111]. C) Larger thin layer flow cell. This is very similar to that shown in 3A, except that the deposition area is larger and laminar flow is easier to develop because of the solution inlet and outlet designs. In addition, the opposite wall of the cell is a piece of ITO, used as the auxiliary electrode. It is transparent so the deposit can be monitored visually, and it provides an excellent current distribution. The reference electrode is incorporated right in the cell, as well. Adapted from ref. [113],...

Another variation on the method [4] with slightly higher sensitivity (several ng/1) used the liquid nitrogen cold trap and gas chromatography separation, but used the standard gas chromatography detectors or atomic absorption for the final measurement. These workers found four arsenic species in natural waters. 

Elimination of wet chemical sample preparation enables a complete analysis to be performed and data to be quickly analyzed. The detection limits are in the low part-per-million range using mass spectrometric detection. Alternatively, detection of compounds can be achieved by all common gas chromatography detectors (flame ionization detector, electron capture detector and flame photometric detector), and detection limits are determined by the method of detection employed. 

Gas chromatography detectors employed for the determination of volatile organics in soil are generally flame ionization detectors (FIDs), photoionization... 

Since the development of HPLC as a separation technique, considerable effort has been spent on the design and improvement of suitable detectors. The detector is perhaps the second-most important component of an HPLC system, after the column that performs the actual separation it would be pointless to perform any separation without some means of identifying the separated components. To this end, a number of analytical techniques have been employed to examine either samples taken from a fraction collector or the column effluent itself. Although many different physical principles have been examined for their potential as chromatography detectors, only four main types of detectors have obtained almost universal application, namely, ultraviolet (UV) absorbance, refractive index (RI), fluorescence, and conductivity detectors. Today, these detectors are used in about 80% of all separations. Newer varieties of detector such as the laser-induced fluorescence (LIE), electrochemical (EC), evaporative light scattering (ELS), and mass spectrometer (MS) detectors have been developed to meet the demands set by either specialized analyses or by miniaturization. 

Fujinari EM, Courthaudon LO. Nitrogen-specific liquid-chromatography detector based on chemiluminescence—Application to the analysis of ammonium nitrogen in waste-water. Journal of Chromatography 592, 209-214, 1992. 

Liquid Chromatography Detectors", Elsevier, Amsterdam New York, (1986)18. 

R. P. W, Scott," Lfgutd Chromatography Detectors, Elsevier, Amsterdam (1986)7... 

Table 23.1 Some Important Characteristics of the Gas Chromatography Detectors Specifically Used in Drug Residue Analysis...

In Figure 0-5, the area under each peak is proportional to the quantity of compound passing through the detector. The best way to measure area is with a computer that receives output from the chromatography detector. Denby and Scott did not have a computer linked to their chromatograph, so they measured the height of each peak instead. 

Table 24-5 Detection limits and linear ranges of gas chromatography detectors... 

Other gas chromatography detectors electron capture halogens, conjugated C=0, —C=N, -N02 nitrogen-phosphorus highlights R N flame photometer individual selected elements, such as R S, Sn, Pb photoionization aromatics, unsaturated compounds... 

To which kinds of analytes do the following gas chromatography detectors respond ... 

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