EA Troubleshooting

This section should be used to help diagnose problems with the elemental analyzer. If, after following the guidance below, you are unable to resolve the issue on your instrument, please contact the customer service department at Elementar.

Operating pressure for the EA cannot be obtained

It is important to operate the EA with the correct operating helium gas pressure. Listed below are possible reasons for not being able to attain the operating pressure. See the EA user manual for further details. 

Gas supply

  • Is the helium cylinder nearly empty? If so, replace with a new one.
  • Is the secondary gas regulator that controls the helium pressure feeding the EA set to the correct pressure? This should be set to 1.25 bar.

Leaks

  • Is there is a large leak in the EA instrument? If so, use the EA software’s built in method for leak checking; Options > Diagnostics > Leak Test. See the EA user manual for more details.

Background gas levels higher than recommended

An overview of the background gas levels can be achieved by running a ‘Background Scan’ method (Background gas levels); during the method the magnet current changes and the ion source typically has trap current of 200uA to allow direct comparison of target background levels (Ion Beam Background Levels). If background levels are too high it can adversely affect your analysis. Possible reasons could be:

Leaks

  • A leak in the system results in the ingress of atmospheric air into the system and can be identified by elevated N2 (m/z28) and Ar (m/z 40) levels, typically these backgrounds should be <1e-10 A and <1e-11 A, respectively.
  • A convenient way to identify leaks within the centrION / isoprime precisION IRMS is to tune the isoprime precisION IRMS to m/z 40 and direct a stream of argon gas around various fittings.
  • The most efficient way to locate leaks within the EA is to use the built in leak check methods, here the system is initially pressurized and then the system is monitored for any drops in pressure. See the EA software and EA user manual for details.

After routine maintenance

  • After routine maintenance, e.g. changing an ash finger, furnace tube or water trap, etc. the background may be temporarily high due to an ingress of atmospheric air into the system (high N2, H2O and Ar). Assuming there are no leaks the levels should return to normal.
  • After a combustion, reduction or pyrolysis tube has been changed and is heated to its operating temperature the background gas levels may increase temporarily due to degassing from the reactor chemicals. Background levels should return to normal without intervention within 30 minutes for combustion modes, but up to several hours if in EA-O pyrolysis mode; this is due to degassing from the carbon black component.

High water backgrounds

  • High water backgrounds can potentially cause issues, particularly with d13C measurements, due to protonation in the ion source. Elevated water levels are often evident after routine maintenance, particularly if the IRMS has been vented for extended periods, but should reach normal levels without intervention.
  • If water levels remain high check that the ‘Nafion flush flow is on’, as indicated in the software under system status, and that the drying tubes containing phosphorus pentoxide (sicapent®) are not exhausted.

Gas supply

  • High background gas levels could also be due to the purity of the gases. We recommend the helium carrier gas should have a purity of greater than N5.0 (99.999%). Please refer to the site requirements documentation.
  • Although unlikely, there is the potential that the actual gas supply cylinder may be contaminated. This is can be identified by swapping the cylinder

No sample peak

If no sample peaks are detected at the IRMS, but are present at the thermal conductivity detector (TCD), then the issue will be after the EA, probably in the centrION / isoprime precisION IRMS. Please refer to Error Reporting.

If no peaks are detected at the TCD, then the issue will be either in the EA, a problem with the sample or a communication issue. For further information, please refer to the EA user manual.

Leak or Blockage

  • Is there carrier gas flow through the TCD? If not, and assuming the helium is switched on, there is likely to be a blockage or leak in the EA flow pathway. Use the EAs built in method for leak checking; Options > Diagnostics > Leak Test. See the EA user manual for more details.

EA not functioning or in a ready state

  • Does the autosampler carousel turn during analysis? Or is the ball valve mechanism working? If not, please refer to the EA user manual or contact service at Elementar
  • Are the combustion, reduction and pyrolysis tubes at their operating temperatures? This can be set within the EA software under Options > Settings > Parameters. If the furnace does not heat up, please contact service at your regional Elemental office or your local Elementar representative.
  • Ensure that the APT and TPD column standby temperatures are set correctly, Options > Settings > Parameters. The desorption temperatures are set within each of the EA methods, this can be edited by selecting Options > Settings > Methods

Communication issues

Poor sensitivity

If there is a loss in sample peak sensitivity, it is advisable to first check if the IRMS has also lost sensitivity when a monitoring gas is introduced; please refer to Error Reporting. If the monitoring gas sensitivity is as expected then the problem will likely be associated with the EA.

Leaks

Incomplete combustion/pyrolysis

  • Is the correct furnace tube and chemicals being used and is the furnace at the correct temperature? Please refer to the EA user manual for more details.
  • Are the furnace tube chemicals exhausted and require replacement? The EA software contains a useful tool to be able to record how many samples have been analyzed using particular consumables, see Options > maintenance > intervals. This provides an indication of when maintenance may be required, however these intervals can be altered to suit the user’s particular application / sample type. For details on how to replace the furnace tube please refer to the EA user manual.
  • Is the ash finger or crucible full? If so, remove and replace; please refer to the EA user manual
  • Is the oxygen lance blocked? If so, please refer to the EA user manual and replace the lance.

Reduction tube issues

  • Is the reduction tube at the correct operating temperature? The temperature should be set to 600°C and 850°C for CN and CNS modes, respectively.
  • Is the correct amount of copper in the furnace tube and is it positioned correctly? Please refer to the EA user manual for details on how to pack the furnace tubes.  In CNS mode, it is crucial for the reduction tube to contain less copper (cf. CN mode) and only having it positioned in the hottest zone of the furnace. If this is not the case, colder Cu can react with the SO2 to form Cu2S and thus reduce the SO2 signal peak height.
  • Are the reduction chemicals exhausted? i.e. has  the Cu metal been oxidized? If this is the situation the N2 formation from the reduction of NOx will be incomplete and the N2 signal will be reduced. An indication that the reduction tube is near exhaustion can be seen as an increase in the m/z 30 (NO) signal at the IRMS or as a second peak eluting after the N2 on the TCD trace (‘oxygen breakthrough’). This second peak is O2 and its breakthrough occurs when there is not enough Cu metal to react with the excess amount of O2 during analysis. It is advisable to replace the Cu before it is totally exhausted; please refer the EA user manual for instructions

Advanced purge and trap columns

  • For the PYRO cube and ISOTOPE cube, are the APT columns set with the correct adsorption (‘standby’) and desorption temperatures? The standby temperatures can be set at Options > Settings > Parameters, while the temperatures for desorption are set within each of the EA methods, this can be set by selecting Options > Settings > Methods. Please refer to the EA user manual.

Temperature programmed  desorption column (TPD)

  • For the ISOTOPE select, is the TPD column set to the correct adsorption (‘standby’) and desorption temperatures? The standby temperatures can be set at Options > Settings > Parameters, while the temperatures for desorption are set within each of the EA methods, this can be set by selecting Options > Settings > Methods. Please refer to the EA user manual.

Dilution

  • Is your sample being diluted in error or by an incorrect amount? In IonOS, under ‘dilution type’ within the EA method the level of dilution of each gas species can be specified. If a dilution method is not selected each sample gas will be diluted (or undiluted) by the global ‘sample percent’ value that is defined under the ‘centrION’ tab. If the sample is not to be diluted, then please ensure that the ‘sample percent’ value is set to 100%.

EA blanks are high

For the very best analytical data it is important to establish that the system produces low EA blanks. Listed below are potential reasons for particularly high blanks, for further details please refer to the EA user manual.

Nitrogen

  • Is ball valve leaking? A leak in the ball valve assembly can result in the ingress of atmospheric air and produce a significant N2 blank. Refer to the EA user manual and perform a leak check and, if necessary, maintenance on the ball valve.
  • Is the flush flow sufficiently high to remove atmospheric air from the ball valve? This is typically set to around 600 ml/min for a duration of 15s, please refer to the EA user manual for further details.
  • Is the oxygen gas used of good quality? A significant N2 blank can be observed if the quality of the oxygen gas is particularly poor. This can be determined by running blanks with and without the introduction of oxygen.
  • Is the capsule packed tightly? It is important to compress the capsules tightly to minimize inclusion of atmospheric air.

Carbon dioxide

  • Are the capsules contaminated? Running blanks without a capsule can help diagnose if the capsules are the source of organic contamination.
  • Does the CO2 APT column require conditioning? Please refer to the EA user manual and follow the procedure in the software for heating out the column, Options > Maintenance > CO2 – column heat-out.

Sulfur Dioxide

  • Does the SO2 APT column require conditioning? Please refer to the EA user manual and follow the procedure in the software for heating out the column, Options > Maintenance > SO2 – column heat-out.

Carbon monoxide

  • Is the pyrolysis tube fully conditioned? It is advisable to leave the furnace at operating temperature for a few hours and afterwards check if the CO blank has reduced and is stable. Repeat this procedure until an acceptable blank value is attained.
  • Does the CO APT column require conditioning? Please refer to the EA user manual and follow the procedure in the software for heating out the column, Options > Maintenance > CO – column heat-out’.

Poor isotope ratio measurements (precision, linearity and accuracy)

If system is producing poor isotopic data, it is important to try and diagnose the problem by first determining if the IRMS is functioning as expected. This can be done by introducing monitoring gas pulses into the IRMS and measuring their stability and linearity; if the data from the monitoring gas pulses are also poor then please refer to Error Reporting.

If the IRMS is performing well with the monitoring gas pulses, then the next step is to investigate the EA including potential issues with the samples / standards being analyzed.

Incomplete combustion/pyrolysis and reduction of samples

  • For reliable stable isotopic data it is important that samples undergo efficient combustion, pyrolysis and reduction. For more information on the furnace tubes, as well as advice on ash fingers / crucibles and oxygen lances, please refer to Poor sensitivity and the EA user manual.

High water backgrounds

  • Ensure that the water backgrounds are low by confirming that the drying tubes are not exhausted and the ‘Nafion flush flow is on’ in the centrION. Please refer to Ion Beam Background Levels for more information.

Sample issues

  • It is very important the sample being analyzed is homogeneous. Sample homogeneity can be improved by grinding the sample into a fine powder using a pestle and mortar or an automatic grinder.
  • To improve combustion efficiency it is recommended that samples are packed in tin capsules as tin burns easily and aids the combustion reaction by elevating the local temperature to approximately 1800°C. For pyrolysis, it is recommended to use silver capsules as these have a lower oxygen content.
  • Some samples are more challenging to analyze and may require an additive to be included into the capsule. For example, the combustion of alkaline samples, such as some soils, may require the addition of WO3 to aid the combustion and bind to disruptive substances. In pyrolysis mode, the d18O analysis of inorganic phosphates or nitrate samples may require the addition of extra carbon into the capsule, e.g. graphite or polyethylene.

Sample integration and calibration

  • A possible reason for poor stable isotope sample data could be due to inappropriate sample integration. These settings can be optimized in IonOS.
  • If sample precision is good, but the accuracy is not, this could be due to the calibration methodology. We recommend to use multi-point calibration techniques employing a principle of identical treatment, i.e. samples are calibrated against standards that are analyzed in the same way as the samples. See Analyzing Blanks & Standards (EA) for more details.