Calibration Failure
There are a number of reasons why your calibration may fail. The following
is a list of common problem areas to check if you encounter problems with
your calibrations. If you still encounter difficulties, please contact
your local Agilent field service engineer.
The actions you take will depend upon whether the calibration tests
start, whether all of the lines in your calibration have failed, or whether
you experience difficulties with only some lines.
These troubleshooting suggestions are listed in order of the most common
to least common. It is suggested that you work through this list in the
order in which they are outlined.
When
the Instrument or Detector Calibration won't Start
Below is a list of possible causes why the calibration tests won't start.
Instrument calibration
Detector calibration
- Peltier is cooling - wait for the Peltier to come to temperature
- Water chiller is not turned on
- Instrument is busy - wait for the ICP-OES to complete the current
task
- Plasma is turned on. The plasma
must be turned off for this calibration procedure.
- Existing faults
When
All Your Wavelengths Fail
If you are using a new method:
- Check the uptake delay time
Ensure that enough time is allowed for introduction of the
solution to the spray chamber before readings are made. The uptake
delay time will need to be increased when the uptake tubing is lengthened,
which will occur if you are using the autosampler, or if the pump
rate is decreased. Using of the fast pump option will decrease the
time required for the sample uptake delay. The sample uptake delay
time and fast pump options are set on the Conditions
page.
- Check the replicate read time
Analytical signals are generally improved when you use a
larger number of long replicates. This is particularly important when
measuring at very low levels. The replicate read time is set in the
'Sample introduction settings' section on the Conditions
page.
If you are using a new or existing method:
- Check that the right analytical standards are being measured.
Sometimes the wrong analytical standards are used, resulting in a calibration
failure.
- Check the sample and drain tubing for wear
A failure of the pump drain tube may indicate that the solution
in the spray chamber is not being removed effectively, which will
affect the results of subsequent samples. Failure of the sample tube
will lead to ineffective introduction of sample into the spray chamber,
while progressive failure will result in a lowering of signal intensities.
- Check all hose connections
A loose or detached gas or sample tube will usually cause
the calibration to fail or the plasma to extinguish. Improperly connected
sample inlet tubes may also interfere with the sample introduction
process.
- Check your solutions
Ensure that your solutions were properly prepared and labeled.
If the standards you prepare are unstable, you will need prepare fresh
solutions regularly or add a stabilizer, if one is available. Be careful
not to contaminate the standard of blank solutions. If you are in
doubt as to the reliability of your solutions, you should always prepare
fresh ones.
- Check the torch injector tube
Deposits in the injector tube (the innermost tube of the
torch that carries the sample) may affect sample introduction to the
plasma, or may interfere in subsequent analyses. Blockage of the injector
tube should result in a decrease in signal intensities. Refer to the
procedures for cleaning the
torch for more information.
- Check the torch quartz tube
Deposits between the intermediate and outer tubes of the
torch may block the flow of gas to the plasma, which will eventually
extinguish the plasma altogether. Partial blockage in this area can
also cause localized torch overheating. Refer to the procedures for
cleaning the torch for
more information.
When
Some of Your Wavelengths Fail
If you are using a new method:
- Check your standards
Some elements are unstable or may be chemically incompatible
with other elements you are using. You can change the details of your
standards on the Standards
page.
- Check for spectral interferences
The wavelengths you are using may be causing spectral interferences,
which are affecting your results. Check the wavelength lines you are
using, and change them if necessary. You can check spectral interferences
in the Possible
Interferences graph.
- Check the calibration parameters
Verify the values included in the calibration parameters
meet your requirements. Ensure the limits set for the calibration
are not unrealistic. These parameters include the correlation coefficient
and whether you have selected linear or rational curve fitting. The
calibration parameters are set on the Standards
page.
- Low UV failed
Check that the snout purge (for radial measurements) and polychromator
boost purge are on and that the instrument has had adequate purge
time.
If you are using a new or existing method:
- Check the blank
Check your blank for possible contaminations. This is a common
problem, particularly if you are using alkaline and alkaline earth
metals. If you are in doubt as to the reliability of your blank,
you should always prepare a fresh one.
- Check the standard values
Verify that the standard values entered on the Standards
page reflect the values used in the analysis.
- Check the correlation coefficient limit
Use a reasonable correlation limit based on the accuracy
required by your analysis and the accuracy of the preparation of your
standard solutions. The correlation coefficient limit is set on the
Standards page.
- Check the wavelength selected
Try selecting an analytical line appropriate to the concentration
of the element under investigation. For example trace elemental analysis
may require the most sensitive line to be selected, however the same
element in high concentrations may require the selection of a less
sensitive line. Calibration failure on a number of analytical lines
for the same element either indicates a problem with the standards
used or samples introduction system.
- Check the method conditions
Ensure the conditions used for analysis are suitable for
the selected analytical lines.
- Check for nebulizer blockage
Blockage of the nebulizer will cause a decrease in the intensity
of the signal. Follow the nebulizer cleaning instruction to remove
any blockage. It is recommended that samples containing solid particles
are filtered before analysis or a digestion technique used to bring
solid particles in to solution for analysis. Refer to the procedure
on Cleaning the nebulizer
for more information.
- Check the spray chamber
Contamination of the spray chamber by elements present at
high levels may cause calibration failure. It is recommended the spray
chamber and sample introduction system be meticulously cleaned particularly
between measurements of an element in very high concentrations and
samples with low levels of the same element. Refer to the procedure
on Cleaning the spray
chamber for more information.
See also: