Gas Chromatography (GC) (IUPAC Compendium of Chemical Terminology):
Lecture 3. Gas chromathography. Selectivity – Interaction strength Phase Dispersion Dipole H-Bonding Methyl -CH 3 Strong None None Phenyl -C 6 H 5 Strong None Weak Cyanopropyl -C 3 H 6 CN Strong Strong Moderate Trifluoropropyl -C 2 H 4 CF 3 Strong Moderate Weak PEG -OCH 2 CH 2 O- Strong Strong Moderate Compounds – Properties Compounds Polar Aromatic H-Bonding Dipole Toluene No Yes No Induced Hexanol Yes No Yes Yes OH Phenol Yes Yes Yes Yes OH Decane No No No No Naphtalene No Yes No Induced Dodecane No No No No 8
Lecture 3. Gas chromathography. Nonpolar to intermediate polarity stationary phases. BONDED PHASE Temp °C GENERAL USE OF PHASE O CH 3 Si * * X CH 3 Methyl polysiloxane Methyl 5% Phenyl Polysiloxane CH 3 * O Si O Si * X CH 3 Y 50-325 50-325 Nonpolar. Optima 1. Most frequently used phase in GC. Low selectivity, separates compounds according to boiling points. Excellent thermal stability. Nonpolar. Optima 5. Similar to methyl polysiloxane but slightly more selective due to phenyl content. Excellent thermal stability. Methyl 50% Phenyl Polysiloxane CH 3 * O Si O Si * 6% Cyanopropylphenyl 94% Methylpolysiloxane X CN CH 3 CH 3 * O Si O Si * X Y CH 3 Y 40-325 30-320 Intermediate polarity. Optima 17. Added selectivity due to higher phenyl content. Usually retains similar compounds longer than methyl silicone. Provides efficient separations of PAHS and biomedical samples such as drugs, sugars and steroids. Good thermal stability. Intermediate polarity. Optima 1701. An additional choice for a general purpose phase with nominal selectivity for polarizable and polar compounds. Good thermal stability. 9
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Lecture 3. <strong>Gas</strong> chromathography.<br />
Nonpolar to intermediate polarity stationary phases.<br />
BONDED PHASE Temp °C GENERAL USE OF PHASE<br />
O<br />
CH 3<br />
Si *<br />
*<br />
X<br />
CH 3<br />
Methyl polysiloxane<br />
Methyl 5% Phenyl Polysiloxane<br />
CH 3<br />
* O Si O Si *<br />
X<br />
CH 3<br />
Y<br />
50-325<br />
50-325<br />
Nonpolar. Optima 1.<br />
Most frequently used phase in <strong>GC</strong>. Low<br />
selectivity, separates compounds according to<br />
boiling points. Excellent thermal stability.<br />
Nonpolar. Optima 5.<br />
Similar to methyl polysiloxane but slightly<br />
more selective due to phenyl content. Excellent<br />
thermal stability.<br />
Methyl 50% Phenyl Polysiloxane<br />
CH 3<br />
* O Si O Si *<br />
6% Cyanopropylphenyl 94%<br />
Methylpolysiloxane<br />
X<br />
CN<br />
CH 3<br />
CH 3<br />
* O Si O Si *<br />
X<br />
Y<br />
CH 3<br />
Y<br />
40-325<br />
30-320<br />
Intermediate polarity. Optima 17.<br />
Added selectivity due to higher phenyl content.<br />
Usually retains similar compounds longer than<br />
methyl silicone. Provides efficient separations<br />
<strong>of</strong> PAHS and biomedical samples such as<br />
drugs, sugars and steroids. Good thermal<br />
stability.<br />
Intermediate polarity. Optima 1701.<br />
An additional choice for a general purpose<br />
phase with nominal selectivity for polarizable<br />
and polar compounds. Good thermal stability.<br />
9
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