Waters IC-Pak Ion Exclusion Columns - Manual (Page 4)

[ Care and Use ManUal ]
4 Waters IC-PAK ™ Ion Exclusion Columns
Initial Efficiency Test
Before attempting the first analysis, perform an initial efficiency test.
To do this, run the test sample using the following procedure and
record the results and instrument settings:
1. Equilibrate the column with the appropriate mobile phase at
the desired flow rate.
2. Record the retention time, the instrument settings, and the
system configuration so these conditions can be reproduced
exactly for future comparison.
Measuring Efficiency
Waters uses the 5 sigma method, shown in Figure 2, to measure
column efficiency. Unlike the tangent method, this more stringent
method considers naturally occurring peak asymmetry.
If problems occur during normal operation of the column, repeat the
efficiency test and compare the results. This may help identify the
source of the problem.
Figure 2. 5 Sigma Test Method
N = Column efficiency (plates)
VR = Volume to peak apex (ml)
W = Volume at 4.4% of peak height (ml)
Test Conditions
Table 1 lists the conditions Waters uses to check the efficiency of
IC-Pak Ion Exclusion columns. Figure 3 is a representative chromato-
gram of flouride and short-chain weak organic acids.
Table 1. Column Test Conditions
Mobile Phase Flow Rate Sample
1 mM
octanesulfonic acid
1.0 mL/min
see standard
preparation
Figure 3. Chromatogram of Fluoride and Short-chain Weak Organic Acids
Working Standard
Fluoride 1 ppm
Acetate 5 ppm
Formate 5 ppm
Propionate 5 ppm
Butyrate 5 ppm
Eluent: 1 mM Octanesulfonic Acid
Pump: 590 Solvent Delivery Module
Injector: 710B WISP
Column: Ion Exclusion (300 mm X 7.8 mm)
Data: 840 Data System
Flow Rate: 1.0 mL/min
Injection: 100 µL of Working Standard
Detection: 430 Conductivity
Range: 500 µS
Temperature: On
Polarity:
+
Background: 320 µS