| {"likely_causes": ["Air in the pump inlet line, consistent with the note that air ingress can cause pressure fluctuation.", "A restricted or inadequately immersed inlet filter, which can interfere with solvent delivery.", "A loose accessible fitting or a pump-seal fault; the active leak-sensor message makes a liquid leak worth checking, but does not identify its location."], "evidence_basis": ["The case reports pressure oscillation; the troubleshooting note lists air in the inlet path and a restricted inlet filter as possible causes of pressure fluctuation.", "The case reports ‘Leak sensor active’; the note directs the operator to inspect accessible pump and tubing connections for liquid, while cautioning that the message does not identify a specific location.", "The note requires pressure to be released by the normal procedure before touching a pressurized fitting and refers persistent leakage or suspected seal faults to a qualified technician."], "case_description": "An HPLC sequence stopped after the pressure trace began oscillating during a gradient run. The instrument displayed ‘Pump pressure fluctuation’ and then ‘Leak sensor active.’ The operator reports that the solvent bottles are not empty and asks what to check before restarting.", "diagnosis_summary": "The pressure oscillation together with an active leak-sensor message points to a possible inlet-side air restriction or a leak in an accessible pump connection. The messages do not establish a specific failed component; check for visible bubbles, restricted inlet filters, and liquid at connections before considering service-level faults.", "uncertainty_notes": "The case does not state where liquid was detected, whether bubbles or a restricted filter were observed, or whether pressure stabilizes after inspection. The messages support a focused check of the inlet path and accessible connections, but do not confirm a failed component.", "recommended_actions": ["Do not restart the sequence until the leak-sensor condition has cleared and pressure behavior is stable.", "If an accessible inlet or fitting issue is found, correct it using the instrument’s normal operating procedure and recheck the system.", "Contact a qualified technician if leakage persists or a pump-seal fault is suspected."], "technical_materials": "Pump troubleshooting note: Pressure fluctuation may occur when air enters the pump inlet path or when an inlet filter is restricted. Check the solvent inlet lines for visible bubbles and confirm that the inlet filters are immersed and unobstructed. A loose fitting can admit air or allow solvent to escape. If the leak sensor is active, inspect the accessible pump and tubing connections for liquid. Before touching a pressurized fitting, stop the pump and release pressure using the instrument’s normal procedure. Persistent leakage or a suspected pump-seal fault requires service by a qualified technician.", "troubleshooting_steps": ["Stop the sequence and inspect accessible pump and tubing connections for liquid, without loosening any pressurized fitting.", "Stop the pump and release pressure using the instrument’s normal procedure before handling a connection.", "Check whether bubbles are visible in the solvent inlet lines and whether the inlet filters are immersed and unobstructed.", "After correcting any visible inlet or connection issue, observe whether pressure stabilizes and whether the leak-sensor message clears; if leakage persists, stop and request qualified service."]} | |
| {"likely_causes": ["The wash cycle may be disabled in the method, so the needle-wash step may not be performed.", "The wash solvent may be absent or the visible wash line may be obstructed, limiting the wash described in the note.", "Carryover may persist elsewhere in the autosampler fluid path; the note recommends service inspection if the listed checks do not resolve it."], "evidence_basis": ["The case reports a peak in a blank injected immediately after a concentrated sample; the note identifies that pattern as consistent with carryover, not conclusive proof of its source.", "The note states that the needle-wash cycle uses configured wash solvent and a wash station, and lists solvent presence, visible line obstruction, and method enablement as checks.", "The note recommends comparing blanks before and after the concentrated sample and referring persistent carryover to qualified service."], "case_description": "An LC autosampler sequence shows a small peak in a blank injected immediately after a concentrated sample. The blank was processed with the same method, and no autosampler alarm appeared. The operator asks whether the result points to carryover and what to inspect.", "diagnosis_summary": "The blank peak immediately following a concentrated sample is consistent with carryover, but does not establish where material is retained. The source note prioritizes checking wash-solvent availability, the visible wash line, and whether the method enables the wash cycle, then comparing blanks before and after the concentrated sample.", "uncertainty_notes": "The case does not report the wash-cycle setting, wash-solvent level, wash-line condition, or blank results from before the concentrated sample. The post-sample blank supports investigating carryover, but additional checks are needed to determine whether the wash setup or another part of the fluid path is involved.", "recommended_actions": ["Correct any confirmed method or wash-supply issue, then repeat the blank comparison described in the technical note.", "If carryover persists after the listed checks, request qualified service inspection of the autosampler fluid path.", "Do not assign the observed peak to a specific component unless further inspection supports that conclusion."], "technical_materials": "Autosampler carryover note: A peak in a blank following a concentrated sample is consistent with carryover, but the observation alone does not locate its source. The needle-wash cycle uses the configured wash solvent and wash station. Check that the wash solvent is present, that the wash line is not visibly obstructed, and that the wash cycle is enabled in the method. If these checks do not resolve the observation, compare a blank after the wash cycle with a blank injected before the concentrated sample. Persistent carryover after the listed checks should be referred to qualified service for further inspection of the autosampler fluid path.", "troubleshooting_steps": ["Confirm that the wash cycle is enabled in the method used for the sequence.", "Check that wash solvent is present and inspect the visible wash line for obstruction.", "Run a blank after the wash cycle and compare it with a blank injected before the concentrated sample, as described in the note.", "If the post-sample blank continues to show a peak after these checks, refer the autosampler fluid path for qualified service inspection."]} | |
| {"likely_causes": ["A gas-delivery or connection issue that is not ruled out by the reported setpoint indicators; the note calls for an approved leak check of accessible connections.", "Contamination or obstruction at the accessible detector assembly, both listed in the troubleshooting note.", "An unresolved ignition or detector fault if the flame still does not ignite after the specified checks; the provided information does not identify a particular failed part."], "evidence_basis": ["The case reports ‘Flame not detected’; the note says this indicates that flame presence was not confirmed, not that a specific cause has been diagnosed.", "The operator has not checked the detector assembly or performed a leak check, while the note explicitly lists both as checks.", "The reported setpoint indicators are not described by the note as a substitute for inspecting connections or checking the assembly.", "The note prohibits loosening gas lines or servicing the detector while hot and directs persistent ignition failure to the site gas-shutdown procedure and qualified service for repairs."], "case_description": "During a GC run, the detector signal disappeared and the instrument displayed ‘Flame not detected.’ The operator says the gas-supply indicators are showing their configured setpoints, but has not checked the detector assembly or performed a leak check. What should be investigated first?", "diagnosis_summary": "The detector has not confirmed flame presence, but the displayed message alone does not distinguish a gas-delivery issue from an obstruction or contamination at the accessible detector assembly. Since the case reports setpoint indicators but no leak check or assembly inspection, those checks remain necessary before attributing the problem to a component failure.", "uncertainty_notes": "The case provides no leak-check result, direct observation of the detector assembly, or outcome of an ignition attempt after inspection. The available message confirms only that flame presence was not detected; the cause remains undetermined until the listed checks are completed.", "recommended_actions": ["Complete the gas-indicator, accessible-assembly, and approved leak checks before attempting to resume operation.", "If flame presence is still not confirmed, stop the run and follow the site procedure for shutting off detector gases.", "Have a qualified service person handle any gas-line or detector repair."], "technical_materials": "Detector troubleshooting note: A ‘Flame not detected’ message means the detector did not confirm flame presence; it does not by itself identify the cause. The checks listed are to verify the gas-supply indicators, inspect the accessible detector assembly for contamination or obstruction, and perform the approved leak-check procedure on accessible gas connections. If the flame does not ignite after these checks, stop the run and follow the site procedure for shutting off detector gases. Do not loosen gas lines or service the detector while it is hot. Gas-line or detector repairs must be performed by qualified service personnel.", "troubleshooting_steps": ["Stop the run and confirm the gas-supply indicators, recording what they show rather than treating the setpoints as proof of gas delivery.", "Following the approved procedure, inspect the accessible detector assembly for contamination or obstruction.", "Perform the approved leak-check procedure on accessible gas connections.", "If the flame still does not ignite, stop the run and follow the site procedure for shutting off detector gases; do not loosen gas lines or service the hot detector.", "Arrange qualified service for gas-line or detector repairs."]} | |