Setting Dead Times for Optimum Linear Velocity
To set a dead time, inject 2.0 µL of a non-retained gaseous substance (compatible with the detector) via a standard 10 µL syringe with a PTFE-tipped plunger (cat.# 24557 or 24725) or draw 2 µL from the headspace over neat compounds. Accurately mark the injection starting time and peak elution time with an electronic integrator.
|Detector||Recommended Dead Volume Compounds|
|FID||methane, propane, butane|
|TCD||air*, methane, butane|
|NPD||acetonitrile headspace vapors, air*|
|ECD||air*, methylene chloride headspace vapors|
|ELCD||dichlorodifluoromethane or methylene chloride headspace vapors|
|MS||air*, propane, butane, argon|
* should be used only at lower oven temperatures
Some compounds may be slightly retained on thick-film phases (1.0 to 7.0µm) giving slightly erroneous dead volume times, however, they will be reproducible for similar column types.