Waters Carbamate Analysis Column - Manual (Page 4)

[ Care and Use ManUal ]
Carbamate Analysis Column 4
e. Particular Contamination
Filter all mobile phases. Never use turbid or cloudy solvents or
solutions.
f. Shock
Protect column from vibration, mechanical shock, and rapid changes in
operating pressure. Any thermal, physical, or chemical shock (such as
changing solvent composition rapidly) may cause the particles to shift and
may result in void and a loss of efficiency.
Protect the column from rapid changes in solvent composition which may
alter the mobile phase viscosity, and thereby, the system back pressure
drastically.
g. Efficiency Testing
Waters columns are tested in our quality control laboratories for
adherence to our specifications. Slight variations in your results will
occur depending on:
• Equipment Used
• Test System makeup
• Equipment settings and experimental conditions
Each new column’s performance should be checked on your system to
provide an initial efficiency standard for future comparison. After the
column has been installed and equilibrated, run the test sample as
described in the Waters Carbamate Analysis System Manual.
Choose a peak for one of the following analytes: aldicarb sulfoxide,
aldicarb sulfone, oxamyl, or methomyl. Measure the column effi-
ciency as shown in Figure 3.
NOTE: For convenience, VR and W can be expressed in units of length
rather than volume as measure with a scale from the chromatogram.
The “5-Sigma” method shown in Figure 3 is a more stringent way
to calculate plate count, N, than “half-peak height” and “tangent”
methods. It takes into account naturally occurring peak asymmetry
which can significantly reduce the resolution between adjacent peaks.
Save the chromatogram from this test. With the calculated column
efficiency, record the retention times, system settings, and all
experimental conditions so that they can be reproduced exactly in
the future. If problems occur during normal operation of the column,
repeat the initial efficiency test under the original conditions and
compare the results.
Differences in the results may indicate the source of the problem.
Refer to Table 1 and also the Waters Carbamate Analysis System
Manual for troubleshooting guidelines.
Figure 3: 5-Sigma Method for Measuring Column Efficiency
V. Care and MaIntenanCe
a. Troubleshooting
Table 1 provides the corrective action for some typical column
problems that may occur with the Carbamate Analysis Column.
Refer also to the Waters Carbamate Analysis System Manual for
more detailed information on troubleshooting Waters Carbamate
Analysis Method.
NOTE: Eventually, column performance will degrade over time below
an acceptable level as determined by periodic efficiency testing.
When this happens, replace the old column with a new Waters
Carbamate Analysis Column. See Section VI. for reorder information.
IN
JE
CT
W
V R
= Column efficency (plates)
= Volume to peak apex (mL)
= Volume at 4.40% of peak height (mL)
N 25 =
( )
2
V
R
W