25_GC-page6 - We need a way to measure our eluents as they evolve from the column Each can be roughly classified based on Destructive vs

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Unformatted text preview: We need a way to measure our eluents as they evolve from the column. Each can be roughly classified based on Destructive vs. nondestructive Virtually every method of directly or indirectly observing eluents as been looked at. We’ll cover some of the more common types. General vs. some discrimination vs. very discriminating Let’s start by reviewing some general concepts such as detection limit and sensitivity. AED High sensitivity - possible selectivity TCD Rapidly respond to concentration changes FID ECD NPD (N) NPD (P) FPD (S) FPD (P) Large linear range Stable with respect to noise and drift Low sensitivity to variations in flow, pressure and temperature Produces an easily handled signal MS (SIM) 10-15 g General purpose Nondestructive Limit of detection Linear range ~ 400 pg/ml carrier ~ 106 Mode of detection Change in resistance of a wire based on variations in the thermoconductivity of the gas evolving from a column. 10-12 g Species hydrogen helium nitrogen ethane water benzene acetone chloroform FTIR MS (Scan) 10-9 g 10-6 g Thermal conductivity 105 cal/cm sec oC 49.93 39.85 7.18 7.67 5.51 4.14 3.96 2.33 10-3 g ...
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This note was uploaded on 01/07/2012 for the course CHEM 290 taught by Professor Harvey during the Fall '08 term at SUNY Stony Brook.

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