Chapter 9
Thermal Conductivity Detector (TCD)
TCD Overview
172
TCD Overview
The TCD is sensitive to any compound having thermal conductivity other than
that of the carrier gas used. The TCD is a universal type detector. It has a broad
range of uses in the analysis of permanent gases and other organic or inorganic
compounds for which the Flame Ionization Detector (FID) is practically non-
sensitive, such as CO
2
, CS
2
, H
2
O, H
2
, and N
2
.
While the FID is more sensitive to most organics, the simplicity of the TCD often
makes it the preferred detector when analyte concentrations are high enough. The
TCD typically requires only one type of gas, such as helium. The FID requires up
to four.
The TCD consists of a stainless steel block containing two filaments (generally
tungsten/rhenium filaments) which have the same electrical resistance. The block
is housed in an aluminum case that accommodates the heating elements and the
temperature sensor.
NOTE
TCD with polyimide coated filaments is optionally available for the analysis of very
aggressive gas matrices.
The filaments are electrically connected to a Wheatstone bridge. Two gas flows, a
reference flow and an analytical flow, enter the TCD cell, pass across the
filaments, and vent to the atmosphere. Figure 9-1 shows the filaments and gas
flows.
Содержание FOCUS GC
Страница 1: ...Thermo Scientific FOCUS GC Gas Chromatograph Instruction Manual PN 31709412 Revision May 2007 HOME ...
Страница 4: ...iv InstructionManual ...
Страница 70: ...Chapter 2 The FOCUS GC User Interface Info Diagnostics 70 Instruction Manual ...
Страница 92: ...Chapter 4 Column Oven Oven Parameters 92 Instruction Manual ...
Страница 124: ...Chapter 6 Purged Packed Column Injector PPKD PPKD Injector Menu 124 Instruction Manual ...
Страница 170: ...Chapter 8 Flame Ionization Detector FID Detector Signal Parameters 170 Instruction Manual ...
Страница 186: ...Chapter 9 Thermal Conductivity Detector TCD Detector Signal Parameters 186 Instruction Manual ...
Страница 242: ...Chapter 13 SOP number P0473 04 E 02 May 2007 242 Instruction Manual ...
Страница 320: ...Chapter 15 Maintenance and Troubleshooting Guide to Solve Analytical Problems 320 Instruction Manual ...
Страница 336: ...Chapter 16 LAN Option Set up Set Up 336 Instruction Manual ...
Страница 344: ...Glossary 344 Instruction Manual C min 1 instead of C min g L 1 instead of g L ...
Страница 350: ...Index 350 Instruction Manual ...