Extra Questions for Test 2 Flashcards
What is the purpose of the septum?
to retain the high pressure carrier gas, and to purge the needle of any unwanted compounds
What is the septum made from?
silicone rubber
What is the typical volume injected into a packed GC column?
0.1 - 20 uL
What is the typical volume injected into a OTC?
0.001 - 1 uL
What is the function of the vaporization chamber and the heated metal block?
the vaporization chamber vaporizes the liquid sample immediately so if can be moved by the carrier gas
hence the heated metal block
Why is the injector temperature programmed in splitless GC system?
in order to trap the solute, and allow the solvent to elute from the column first
What types of compounds are analyzed using cold on column?
for thermolabile compounds (readily destroyed or deactivated by heat
What is the advantage of silanization of diatoms rock particles?
remains of diatoms is well suited as support material because of high surface area provided by the complex microscopic structure
What is the most nonpolar SP in GLC?
polydimethyl siloxane
What is the most polar SP in GLC?
50% cyanopropylpolymethyl siloxane
What is the advantage of cold on column over split and splitless?
trace analysis and good quantitation
resolution is not as good however
What is the chemical reaction for treating diatomaceous earth with silane reagent?
Si-OH + Cl2SiMe ——-> Si-O-Si(Cl)Me2 –> Si-O-SiMe3
What is the typical diameter of an OTC column?
0.1-0.5 mm
What is the typical diameter of a packed column?
2-4 mm
What is the typical length of an OTC ?
10-60 m
