5
–
Troubleshooting
Thermo Scientific
Product Manual for IonPac AS31 Columns
Page 37 of 45
155007-01
For Research Use Only. Not for use in diagnostic procedures.
5.4.2
Analyte Specific Efficiency Loss
If a specific analyte exhibits an efficiency problem this could be due to contamination. For
example, iron oxide causes sulfate and phosphate to tail; aluminum causes poor recovery and peak
shape for phosphate; magnesium and calcium hydroxide precipitation in the suppressor cause poor
recovery and peak shape for magnesium and calcium (refer to the Product Manual for the
suppressor for product specific troubleshooting); nonionic surfactants can cause sulfate to tail.
A.
Purge system of suspected contamination. Refer to the Operator’s Manual for the system for
details.
B.
Check sample as source of contamination.
C.
Employ the use of an appropriate guard or trap column to remove contaminants. Contact your
local representative for current product specific information.
5.4.3
Shortened Retention Times
Shortened retention times will cause peaks to elute closer together and may be due to one or more
factors. Fast eluent flow will cause quicker elution of analytes. Higher eluent concentration or a
contaminated column (which results in loss of capacity) will reduce the analyte retention causing
peaks to elute early.
Even with adequate system and column efficiency, resolution of peaks will be compromised
if analytes elute too fast due to elevated flow rate or eluent concentration.
A.
During gradient analysis the column must be equilibrated with the starting eluent prior to
analysis. The time required is dependent on the difference in concentration between the start
and the end of the gradient. If the ion concentration on the column is higher than the starting
eluent concentration, then peaks may elute early or with inconsistent retention time.
Typically, 3-5 column volumes of eluent are suggested for equilibration. Increase the length
of time the column is in the starting eluent prior to injection to ensure adequate equilibration.
B.
Check the flow rate. Ensure the eluent flow rate is equivalent to the flow rate specified by the
analytical protocol. Confirm the eluent flow rate after the column using a stopwatch and
graduated cylinder.
C.
Ensure the eluent compositions and concentrations are correct. An eluent that is too
concentrated will cause the peaks to elute sooner. Prepare fresh eluent.
D.
Diluting the eluent will improve peak resolution but will also increase the analytes’ retention
times. If a 10% dilution of the eluent is not sufficient to obtain the desired peak resolution,
or if the resulting increase in retention times is unacceptable, clean the column (see,
Section
6, “Column Care”).
If you are using a gradient pump to proportion the eluent, components from two or three
different eluent reservoirs, the resulting eluent composition may not be accurate enough
for the application. Use one reservoir containing the correct eluent composition to see if
this resolves the problem. There may be a problem when one of the proportioned eluents is
less than 5%.
NOTE
!
NOTE
!
