Calibration Failure Troubleshooting on ICP-OES Systems

Answer

This Information Applies To: Agilent 5000 series ICP-OES systems

Issue

Instrument calibration (wavelength), detector calibration (dark current, or method calibration (worksheet) failure.

Resolution

There are several reasons why a calibration may fail. The following is a list of common areas to check if problems are encountered with calibrations.

The steps to follow will depend upon whether the calibration tests start, whether all the lines in your calibration have failed, or whether difficulties are only encountered with some lines. 

• When the instrument or detector calibration won't start 
• When all the wavelengths fail
• When some of the wavelengths fail

These troubleshooting suggestions are listed in order of the most common to least common. It is suggested to work through this list in the order in which they are outlined. If you are experiencing method (worksheet) calibration failures, please complete the detector calibration, followed by the instrument calibration before proceeding. See ICP-OES Detector and Instrument Calibration for more information on these calibrations.

When the instrument or detector calibration won't start

Detector or dark current 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. See ICP-OES Detector and Instrument Calibration for step-by-step instructions.

Instrument or Wavelength Calibration

• Plasma is not lit
• Peltier is cooling - wait for the Peltier to come to temperature
• Polychromator is heating
• No detector calibration
• Instrument is busy - wait for the ICP-OES to complete the current task.
• Existing faults. See ICP-OES Detector and Instrument Calibration for step-by-step instructions.

When all of the wavelengths fail

• 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 an autosampler is being used, or if the pump rate is decreased. Using the fast pump option will decrease the time required for the sample uptake. The sample uptake delay time and fast pump options are set on the Conditions page.
• Check the replicate read time
  Analytical signals are usually improved with a larger number of long replicates. This is important when measuring at very low levels. The replicate read time is set in the Sample introduction settings section on the Conditions page.
• 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, which will result in a lowering of signal intensities.
• Check all tube 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 the solutions
  Ensure that the solutions were properly prepared and labeled. If the standards prepared are unstable, fresh solutions need to be prepared regularly or add in a stabilizer, if one is available. Be careful not to contaminate the standard or blank solutions. If in doubt as to the reliability of the solutions, new fresh ones should always be prepared.
• 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 of signal intensities. See the procedures for cleaning the torch in the article: Cleaning the 5000 Series ICP-OES Torch, Acid and Aqueous Matrices.
• 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. 
• Check the nebulizer
  Run the nebulizer backpressure test (See Checking for a Blocked ICP-OES Nebulizer) to check for a nebulizer blockage or leak. If the nebulizer backpressure fails high, the nebulizer is likely blocked. Blockage of the nebulizer will cause a decrease in the intensity of the signal. Follow the nebulizer cleaning instruction to remove any blockage (Cleaning a Blocked Nebulizer in the Agilent ICP-OES System). It is recommended that samples containing solid particles are filtered before analysis or a digestion technique used to bring solid particles into solution for analysis. If the nebulizer backpressure fails low, there is likely a leak between the nebulizer and the nebulizer gas line. Reconnect the nebulizer and retest. Replace the gas line and fitting if the backpressure is still low.

When some of the wavelengths fail

• Check the standards
  Some elements are unstable or may be chemically incompatible with other elements that are being used. Update the details of the standards on the Standards page.
• Check for spectral interferences
  The wavelengths selected may be causing spectral interferences, which are affecting the results. Check the wavelength lines previously selected in the method and change them if necessary. You can check spectral interferences in the Possible Interferences graph.
• Check the calibration parameters
  Verify that the values included in the calibration parameters meet requirements. Ensure that 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, a minimum of approximately 10 minutes.
• 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, calibration error, and %RSE limit set on the Standards page
  Use a reasonable correlation limit, calibration error, and %RSE limit based on the accuracy required by your analysis and the accuracy of the preparation of your standard solutions. These parameters are set on the Standards page and can be modified after the worksheet run is completed.
• 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 several analytical lines for the same element either indicates a problem with the standards used or sample introduction system.
• Check the method conditions
  Ensure that the conditions used for analysis are suitable for the selected analytical lines.
• Check the nebulizer
  Run the nebulizer backpressure test (See Checking for a Blocked ICP-OES Nebulizer) to check for a nebulizer blockage or leak. If the nebulizer backpressure fails high, the nebulizer is likely blocked. Blockage of the nebulizer will cause a decrease in the intensity of the signal. Follow the nebulizer cleaning instruction to remove any blockage (See Cleaning a Blocked Nebulizer in the Agilent ICP-OES System). It is recommended that samples containing solid particles are filtered before analysis or a digestion technique used to bring solid particles into solution for analysis. If the nebulizer backpressure fails low, there is likely a leak between the nebulizer and the nebulizer gas line. Reconnect the nebulizer and retest. Replace the gas line and fitting if the backpressure is still low. 
• Check the spray chamber
  Contamination of the spray chamber by elements present at high levels may cause calibration failure. Agilent recommends the spray chamber and sample introduction system be meticulously cleaned or replaced, particularly between measurements of an element in very high concentrations and samples with low levels of the same element. See the procedure on the article Cleaning the Agilent ICP-OES Spray Chamber for more information.

Learn how to effectively troubleshoot your Agilent ICP-OES system: ICPOES-MULTI-2210e - Agilent 5000 Series ICP-OES Troubleshooting System Issues e-learning course available from Agilent education