9
Turning the instrument off
The Vernier Mini GC should be turned off with the power switch when not in use.
We recommend unplugging and disconnecting the power supply, and disconnecting
the USB cable while the instrument is not in use. The chromatograph has a built-in
timer to turn off heating of the column and pressure from the pump after 2 hours
with no communication from the LabQuest 2, LabQuest, or computer.
4.0 Maintenance
To extend the life and ensure the proper functioning of the Vernier Mini GC, there
are some routine cleanings and replacements that should be followed.
4.1 Column maintenance and/or replacement
The Restek MXT
®
–1 column is a general-purpose column that performs very well
for our recommended families of reagents and laboratory exercises. It is a stainless-
steel capillary column, 11 meters in length, and coated with Siltek® to make the
stainless steel unreactive. MXT-1 is a nonpolar phase that has excellent properties
for separating polar compounds. If separation efficiency deteriorates, conditioning
the column with 0.5
μ
L of acetone or methanol, or running the chromatograph for
1–2 hours at 120°C and 20 kPa with air or an inert carrier gas will help to restore
proper function.
If you use our recommended procedures and substances with your Mini GC, we
think you will get many years of use from the high-quality Restek column. But, if
performance deteriorates after time, such that the column must be replaced, contact
Vernier for an RMA number (the column cannot be replaced by the user). You will
then send the unit to an RMA address, and be charged a fee for the replacement.
Vernier Order Information:
Column Assembly Replacement, order code GC-COL
4.2 Cleaning the exterior of the case
Before cleaning the case, disconnect power. For routine cleaning of the exterior of
the case, use mild detergent and a damp cloth. Do not allow water to leak inside of
the case as this may result in electrical shock or shorts. Abrasive cleansers should not
be used to clean the instrument.
4.3 Replacing the septum
The septum should be replaced after approximately 150 injections. The septum may
be replaced by unscrewing (counterclockwise) the septum retainer nut using a coin
or a large screwdriver.
Note:
Two additional Septa were shipped with your new
Mini GC (in a small Ziploc bag). With the retainer nut removed, spear the defective
septum with a syringe needle and lift it out. Place a new septum flat in the cavity.
Screw the retainer nut to snug tightness. Overtightening the retainer nut will not give
a better seal of the septum but will damage the instrument. After you have used your
original septum, and the two replacements, you can order additional septa.
Vernier Order Information:
Septa Replacement, pkg of 4, order code GC-SEP
4.4 Replacing the MEMS sensor
The Seacoast Science MEMS chemicapacitor 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.
10
The MEMS sensor should last for more than 2000 hours of operation. If performance
deteriorates after time, such that the MEMS sensor must be replaced, contact Vernier
for an RMA number (the column cannot be replaced by the user). You will then send
the unit to an RMA address, and be charged a fee for the replacement.
Vernier Order Information:
Sensor Replacement, order code GC-SENS
4.5 Storing the instrument
Proper storage of the Vernier Mini GC will protect it from damage and maintain the
life of the instrument. The manufacturer recommends flushing the column with
0.4
L acetone or methanol followed by 15 min purge at 120°C and 20 kPa. Store
the instrument in the protective case provided with instrument. Store in a cool, dry
environment.
5.0 GC Troubleshooting
Error Possible
causes
Inconsistent flow
Check and replace septum
Inconsistent peak areas
Check injection volume, septum
Inconsistent retention times
Check septum, pump
No communication
Check USB cables. Or, make sure you
are using correct software versions.
No power
Check to make sure power plugs are
plugged in properly.
Appendix A
Classes of Compounds That Can Be Used in Vernier Mini GC
Compound Type
Typical Compounds
Range of Acceptable
Boiling Points
(°C)
Alcohols C
1
–C
8
65
–195
Aldehydes C
2
–C
8
20
–170
Aromatic hydrocarbons
C
6
–C
10
80
–165
Carboxylic Acids
C
1
–C
4
100
–165
Esters C
2
–C
10
30
–120
Ethers C
4
–C
8
35
–
145
Ketones C
3
–C
8
55
–175
Nitriles C
2
–C
5
80
–140
