Impurities in Commercial Cyclohexane on Rtx-DHA-100

Peaks
1.Isopentane
2.n-Pentane
3.2,2-Dimethylbutane
4.Cyclopentane
5.2,3-Dimethylbutane
6.2-Methylpentane
7.3-Methylpentane
8.n-Hexane
9.2,2-Dimethylpentane
10.Methylcyclopentane
11.Benzene
12.2,4-Dimethylpentane
13.3,3-Dimethylpentane
Peaks
14.Cyclohexane (solvent)
15.2-Methylhexane
16.2,3-Dimethylpentane
17.1,1-Dimethylcyclopentane
18.3-Methylhexane
19.3-Ethylpentane
20.Isooctane
21.n-Heptane
22.cis-1,2-Dimethylcyclopentane
23.Methylcyclohexane
24.Ethylcyclopentane
25.Toluene
26.p-Xylene
27.Isopropylcyclohexane
image
GC_PC1356
ColumnRtx-DHA-100, 100 m, 0.25 mm ID, 0.50 µm (cat.# 10148)
SampleImpurities commonly found in commercial cyclohexane
Diluent:Cyclohexane
Injection
Inj. Vol.:0.6 µL split (split ratio 100:1)
Liner:Topaz 4.0 mm ID Precision inlet liner w/wool (cat.# 23305)
Inj. Temp.:250 °C
Oven
Oven Temp.:35 °C (hold 15 min) to 65 °C at 5 °C/min (hold 5 min) to 200 °C at 20 °C/min (hold 2 min)
Carrier GasHe, constant flow
Flow Rate:2.4 mL/min
DetectorFID
InstrumentAgilent 7890B GC
NotesSample is a synthetic blend prepared with impurities known to be present in cyclohexane at concentrations expected to be found in commercial samples.

Note that the distorted peak shape of 3,3-dimethylpentane is an example of "solvent effect." Solvent effect occurs when the analytical starting temperature is much lower than the boiling point of the solvent. When that occurs, the solvent peak affects the chromatography of compounds eluting near it. Peak shape for the compounds eluting prior to the solvent peak are usually distorted, while compounds eluting after the solvent peak will have somewhat increased retention.
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