5
c.
Simultaneously, depress the syringe plunger and select Collect to begin data
collection. Pull the needle out of the injection port immediately.
8. While the data collection proceeds, repeat Step 4 to thoroughly clean the
syringe and needle. It may take more than three flushes to feel the syringe
plunger move smoothly again, which is your indicator that the syringe and
needle are both suitably clean.
9. Data collection will end after 15 minutes.
10. Analyze your chromatogram.
a.
Choose Peak Integration from the Analyze menu.
b.
Select and integrate the left-most peak. To do this, drag from a little before
the peak to a point far enough to the right that includes all of the peak. Then
choose Add.
Note:
Prior to integrating, it is also possible to drag across a
peak and then use the Zoom button to zoom in on the peak.
Figure 4
Peak integration in Vernier software
c.
To analyze another peak on the same graph, repeat Step b.
d.
When you are finished with all peaks, select OK to return to the graph.
11.
Using
Logger
Pro
or LabQuest App, you can do any of the following.
You can choose to Store a run. (In Logger
Pro
, choose Store Latest Run
from the Experiment menu. In LabQuest App, tap the File Cabinet icon.)
You can choose to save this chromatogram and peak analysis for later use,
with a unique file name, by choosing Save from the File menu.
Print your chromatogram and peak analysis table.
You can rename run names, or peak names in the software.
6
1.0 Product Description and Principles of Operation
Figure 5
Side view of Vernier Mini GC
Figure 5 shows a side view of the Vernier Mini GC. The power input jack, power
switch, USB connection to the computer or LabQuest, and column ventilation grill
are shown in this view.
Principles of Operation
: The Vernier Mini GC is designed to separate mixtures of
gases or volatile liquids and identify components of the mixtures by their specific
retention times. The chromatograph uses ambient air supplied from a pump to carry
a small sample of vapor through a stainless steel column.
The column is a general purpose column designed to study solvent impurities,
distillation, gases, natural gas odorants, sulfur compounds, essential oils,
hydrocarbons, semivolatiles, pesticides, and oxygenates. The column is heated using
an electric current. Temperature of the column is monitored by a built-in resistance
temperature detector (RTD) for accurate temperature measurement. The column
assembly also has an independent thermistor to protect against overheating.
At the end of the column is a Seacoast Science chemicapacitor sensor. The sensor is
a micromachined sensor chip coated with a chemoselective polymer. The polymer
absorbs analytes exiting the column. Analyte absorption by the polymer coating is
measured by the detector circuitry.
While the sensor is designed to detect a wide
range of analytes, it does not detect low-polarity compounds such as alkanes.
2.0 Specifications
The Vernier Mini GC is designed for use in an educational or research laboratory.
Ambient temperature range for safe operation is 5°C to 40°C, and safe range of
ambient relative humidity of 0 to 95%. The Mini GC should not be immersed or
sprayed with liquids. Power for the chromatograph is supplied by an external power
supply. The Mini GC has a back-lit liquid-crystal display that advises the user as to
its current status.
