Error Reporting

Software errors may manifest themselves in several different ways, and are not always attributed to problems directly linked to the software packages. If errors are reported by lyticOS then the following areas should be referenced:

• System Status (lyticOS default display)
• System Status (Layout>Common>System Status)
• System Messages (Layout>System Messages)
• Export Information (Home>Actions>lyticOS>Utilities>Export Logs / Export Readbacks)

All terminal and persistent errors should be reported to your regional Elementar office or your local Elementar representative at the earliest opportunity and the log and readbacks exported.

Communication

If there are communication errors reported by lyticOS, normally a device not being found, then both the connection settings within lyticOS and the ports allocated within Device Manager should be checked.

If communication to an inlet is the problem then also check the communication settings within the peripherals control software. Restarting the PC, MS and inlet system may also be an option, as can removing the USB cables to the PC and then refitting the cable. Elementar should be contacted for persistent problems or if the basic checks fail to regain stable communication.

Electronics

The electronic “error” messages will be reported within lyticOS. For a live display of all readbacks, an engineer’s license must be applied to lyticOS. The readbacks may then be accessed via Layout > isoprime visION > Advanced > Readbacks (Advanced). Otherwise the readback logs should be exported at the earliest available opportunity. All terminal and persistent errors should be reported to Elementar at the earliest opportunity as the log files are constantly overwritten with new information.

Vacuum Read-backs

A mass spectrometer must operate in a vacuum for two reasons:

To reduce ion scattering. If the ions collide with any residual gas molecules their trajectories will be modified, resulting in peak broadening.

To limit contamination. Any residual gases in the ionizing chamber would also be ionized, giving rise to an instrument background

The vacuum read-backs are displayed on the System Status panel within lyticOS. These read-backs will alter depending on the system status and the gas loads present, with a higher vacuum being achievable under a lower gas load. The normal operational vacuum readings (Nupro open and SIV open) should be in the ranges shown. These require a stable helium flow. If the helium carrier flow is disturbed (EA replace parts or GC service) or there is a leak then the readings will be higher and thus require fault diagnosis.

Pirani Gauge Troubleshooting

If the low vacuum is greater than normal, then the most common faults include a pumping system problem, a leak, high moisture or lack of helium carrier flow.

Helium Carrier

The helium carrier is from two sources when it is incident on the source.

• Direct from the inlet system*
• From the MOVPT injector valve in the form of the monitoring gas carrier flow.

*Inlet system also includes the diluter

Firstly, check that helium is flowing through both the monitoring gas injector and the inlet system.

Note: After breaking vacuum it may take some time to reach this pressure. In particular, if the atmospheric moisture levels were high at the time of venting, it could take one day to return to correct levels.

If the Pirani reading does not decrease after a suitable length of time, then a leak must be suspected.

• Close the Nupro isolation valve

• If the Pirani reading does not decrease, the leak is in the mass spectrometer and must be found.
• If the Pirani reading falls to ~5E^-2 mbar, the leak is either in the monitoring gas injector, the inlet, SIV or the Nupro isolation valve.
• Close off the sample capillary by taking it out of the sample Open Split and plugging it into a septum.
• If the Pirani reading decreases, the leak is the sample inlet system. If necessary, consult the manuals for the specific sample inlet system.
• If the Pirani reading falls to ~5E^-2 mbar, the leak is either in the monitoring gas injector, or the isolation valve.

Find and repair the leak, do not over tighten ferruled joints. If a ferrule appears damaged, it must be replaced.

Cold Cathode (High Vacuum) Gauge Troubleshooting

The normal operating pressure as read on the HV gauge (depending on the length of the fused silica capillary) is ~3E^-6 mbar.

The Cold Cathode gauge will not reach its normal operating pressure if:

• There is a leak on the mass spectrometer vacuum enclosure.
• There is a high content of atmospheric gases drawn into the mass spectrometer via any of the inlet capillaries.
• Helium is not flowing out of either the monitoring or the sample open split (Check the helium supply bottle)
• The turbomolecular pump is faulty and not pumping efficiently.

Background Levels

The background levels are the acquired ion beams shown for the relevant display map. The minor beams aren’t normally reported, since it is the major which influences the system status the most. The ion beams witnessed by the collector are proportional to the system state and tuning.

A background scan is the preferred method of checking the ion beam background levels.

Background Scan

If the background levels are unexpected, then it is recommended you run a Background Scan (Ion source tuning and background check). This method produces a spectra across a wide range, normally 10-50 AMU, dependent on tuning.

This allows you to not only see the isotopes we’re measuring but all of the others for the given approximate range as mentioned. Due to the variations in systems, and tuning, an AMU range cannot be predetermined, and some familiarity is required to decipher the trace that is produced.

Ratios

The ratio of beams displayed within lyticOS effectively show that the source tuning, magnetic filter and collector positioning is all correct for a given species. This system tuning should give consistent ratios between isotopes for each said given species. Absolute ratio values will differ between gases and the country of origin. If the ratios are vastly different to those expected check:

• Beam coincidence and Accelerating Voltage tuning
• Background scan
• System tuning
• Gas supply
• System leaks.

isoprime visION Mass Spectrometer Tuning

The default tuning parameters, as set during installation, should be noted and referred to during troubleshooting. If, for whatever reason, a beam cannot be found or the ratios have vastly altered then known good tuning should be reapplied to the system. It is common, however, that the tuning may alter if the following procedures have be carried out on the MS:

• Filament change
• Source clean & rebuild
• Magnet reposition
• Collector realignment

Note: Neither the magnet reposition nor the collector alignment should be attempted .

If required, tuning from a known good previously-run task, can be applied directly from either the task list in question or from a batch. If the “old” tuning doesn’t improve the beam response then the problems lies elsewhere, such as within electronic supplies (thus incorrect voltages etc. are applied) or from the gas introduction (from anywhere between and including the gas cylinder and the source inlet tube).

Performance Troubleshooting

Monitoring Gas Stability

Degradation in the shape of monitoring pulses may have several causes, including a contaminated gas supply, but almost all of these require that the monitoring gas injector be re-built. The following list indicates how problems may arise within the monitoring gas injection assembly:

• The GVF 003/004 ferrule, which constitutes the seal for the ON/OFF action of the MOVPT valve, is of a relatively soft material. This valve is used intensively and after prolonged usage, the sealing face of the ferrule becomes damaged. It needs to be replaced.
• The 25 mm capillary used to inject the monitoring gas into the monitoring flow of helium, is becoming partially blocked with ferrule or glass dust and needs replacing.
• If instability has occurred, immediately after the monitoring gas injector has been rebuilt, then check
  • the correct size capillary has been used,
  • the 0.006" stainless steel capillary has been mounted back into the assembly,
• • and that all the recommendations described in the rebuilding the monitoring gas injector section have been observed.
• Check that there are no leaks at any of the connectors within the entire assembly.

If stability cannot be achieved and the monitoring gas pulses have a normal shape, the problem almost certainly lies with the mass spectrometer and not the gas introduction system.

Please make the following checks:

• Using argon, leak check the entire system.

• Check that the mass spectrometer is tuned correctly, in particular, that the accelerating voltage is centered on the peak. If the ambient temperature changes significantly, it is possible to drift off peak center. This is a very common cause for instability.
• If the mass spectrometer has recently been switched off, please, allow at least one day for all the components to stabilize.
• If the vacuum enclosure has recently been exposed to atmospheric gases then it may take up to an hour, or more, for stability to be achieved on the monitoring gas ratios. This is usually indicated by steadily falling ratio values
• Check the long term stability of the ratios by performing a time scan of the ratios. The long term behavior of the ratio trace is very indicative of the reason for mass spectrometer instability. The ratio trace obtained may display any of the following characteristics:

• Random glitches on an otherwise steady noise band could indicant a source filament problem (assuming other external factors such as knocking the bench or movement from other devices has been eliminated).
• The ratio trace has a slow sinusoidal shape. This is normally indicative of a pumping problem.

Monitoring Gas Linearity

Effects other than non-linearity may lead the operator to assume that the instrument is not linear. These effects usually have a trivial cause and must be checked for, before assuming that there is indeed a non-linearity problem.

• Check that the symptom is not caused by drifting of the ratios. Drifting always occurs whenever the mass spectrometer has been vented to atmosphere or the system has not been used for a long time. To do this, plot a Time Scan as described in the section entitled Stability of the instrument. If the ratios are drifting, do nothing, simply wait for them to stabilize. After drifting has stopped, re-check for linearity.
• Check helium is not leaking from the injection valve head, into the body of the valve, thus contaminating the monitoring gas. A constant contamination beneath pulses of differing intensities will show the same effect as non linearity.
• Check that the helium pressure is set at 55 psi.

• The best way to make the check for a leak between the head and the body is to connect argon gas to the pneumatic head of the injection valve, instead of the helium. If there is a leak between the head and the body, argon pulses will be seen on the mass spectrometer every time the injection valve opens. (Remember to tune the mass spectrometer to m/z 40)
• If there is a leak for a pressure of 55 psi, the seal on the valve stem must be replaced.

Monitoring Gas Sensitivity

If the sensitivity is fine for sample peaks, but poor for monitoring peaks, then the most likely causes are:

The helium pressure set at the monitoring gas injector module is too high.

The monitoring gas is contaminated.

There is a partial blockage in the monitoring line or the 25 μm injection capillary, which is connected to the MOVPT valve.

General notes on fault finding

Here are a few very brief guidelines, when fault finding:

• ALWAYS check every possibility outside the vacuum enclosure before opening up the mass spectrometer.
• ALWAYS allow plenty of time for the vacuum to stabilize before assuming that there is a problem.
• ALLOW the head amplifier to warm up for at least one hour before starting to take measurements.
• ALLOW the magnet to warm up for at least one hour before starting to take measurements.
• ALWAYS bear in mind that poor results are very rarely caused by mass spectrometer or electronics problems, or by any hardware faults within associated sample inlet systems. The cause is usually of a very trivial nature. Poor results are often symptomatic of a need for maintenance of the sample inlet itself. Inlet systems are constantly exposed to a wide variety of real life samples, they include many connections, some of which may undergo frequent temperature variations, and they involve catalysts that are necessary for the sample processing. As a consequence, all sample inlet systems require very regular maintenance to ensure they are free from contamination, free from leaks and that the chemicals that they use are in good condition. Ensure that meticulous maintenance is carried out before looking for a hardware fault.