Agilent Technologies 7890A Operating instructions

Agilent Technologies
Agilent 7890A
Gas Chromatograph
Troubleshooting

Notices
© Agilent Technologies, Inc. 2009
No part of this manual may be reproduced
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laws.
Manual Part Number
G3430-90014
Edition
Third edition, April 2009
Second edition, May 2008
First edition, March 2007
Printed in USA
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Safety Notices
CAUTION
A CAUTION notice denotes a hazard. It
calls attention to an operating
procedure, practice, or the like that, if
not correctly performed or adhered to,
could result in damage to the product
or loss of important data. Do not
proceed beyond a CAUTION notice
until the indicated conditions are fully
understood and met.
WARNING
A WARNING notice denotes a hazard.
It calls attention to an operating
procedure, practice, or the like that, if
not correctly performed or adhered to,
could result in personal injury or death.
Do not proceed beyond a WARNING
notice until the indicated conditions
are fully understood and met.

Troubleshooting 3
Contents
1 Concepts and General Tasks
Concepts 10
How to troubleshoot using this manual 10
The [Status] key 10
Configurable Items to Always Keep Current 11
Column configuration 11
Automatic Liquid Sampler configuration 11
Gas configuration 11
To View the Run Log, Maintenance Log, and Event Log 12
Information to Obtain Before Calling Agilent for Service 13
2 ALS and Detector Symptoms
Plunger Errors 16
Vial Mishandled by ALS 17
Syringe Needle Bends During Injection into Inlet 18
FID Does Not Ignite 19
FID Ignitor Does Not Glow During Ignition Sequence 20
Corrosion in FID Collector and Ignitor Glow Plug 21
FPD Does Not Ignite 22
NPD Adjust Offset Process Fails 23
3 Chromatographic Symptoms
Retention Times Not Repeatable 26
Peak Areas Not Repeatable 27
Contamination or Carryover 28
Isolate the source 28
Check possible causes—all inlet and detector combinations 28
Larger Peaks Than Expected 30
Peaks Not Displayed/No Peaks 31
Table 1. Detector troubleshooting 31

4Troubleshooting
Baseline Rise During Oven Temperature Program 32
Poor Peak Resolution 33
Peak Tailing 34
NPD 34
Peak Boiling Point or Molecular Weight Discrimination Poor 35
For any inlet operating in split mode with any detector 35
For any inlet operating in splitless mode with any detector 35
Sample Decomposition in Inlet/Missing Peaks 36
Peak Fronting 37
Noisy Detector, Including Wander, Drift, and Baseline Spikes 38
Noisy baseline 38
Baseline wander and drift 39
Baseline spiking 40
Figure 1. Cyclic spiking 40
Figure 2. Random spiking 40
Low Peak Area or Height (Low Sensitivity) 41
FID Flame Goes Out During a Run and Attempts to Reignite 43
FID Baseline Output Above 20 pA 44
FPD Flame Goes Out During a Run and Attempts to Reignite 45
FPD Output Too High or Too Low 46
FPD Low Peak Areas 47
FPD Large Peak Width at Half-Height 48
FPD Baseline Output High, > 20 pA 49
NPD Solvent Quenching 50
NPD Response Low 51
NPD Baseline Output > 8 million 52
NPD Adjust Offset Process Not Functioning Properly 53
NPD Low Selectivity 54
Negative Peaks Seen with TCD 55
TCD Baseline Has Dampened Sinusoidal Noise Trailing Peaks (Ringing
Baseline) 56
TCD Peaks Have Negative Dip on Tail 57
4 GC Not Ready Symptoms
GC Never Becomes Ready 60

Troubleshooting 5
Flow Never Becomes Ready 61
Oven Temperature Never Cools Down/Cools Very Slowly 62
Oven Never Heats Up 63
Temperature Never Becomes Ready 64
Cannot Set a Flow or Pressure 65
A Gas Does Not Reach Setpoint Pressure or Flow 66
A Gas Exceeds Pressure Setpoint or Flow 67
The Inlet Pressure or Flow Fluctuates 68
Cannot Maintain a Pressure as Low as the Setpoint on a Split Inlet 69
The Measured Column Flow Does Not Equal the Displayed Flow 70
FID Does Not Ignite 71
FID Ignitor Does Not Glow During Injection Sequence 72
NPD Adjust Offset Process Fails 73
FPD Does Not Ignite 74
5 Shutdown Symptoms
Column Shutdowns 76
Hydrogen Shutdowns 77
Thermal Shutdowns 79
6 GC Power On and Communication Symptoms
GC Does Not Turn On 82
GC Turns On, Then Stops During Startup (During Self-Test) 83
PC Cannot Communicate with GC 84
7 Checking for Leaks
Leak Check Tips 86
To Check for External Leaks 87
To Check for GC Leaks 89
Leaks in Capillary Flow Fittings 90
8 Troubleshooting Tasks
To Measure a Column Flow 92
Measuring FID, TCD, uECD, and FPD column flow 92
Measuring NPD column flow 94
To Measure a Split Vent or Septum Purge Flow 96

6Troubleshooting
To Measure a Detector Flow 98
Measuring FID, TCD, uECD, and FPD flows 98
Measuring NPD flows 100
To Perform the GC Self-Test 102
To Adjust the FID Lit Offset 103
To Verify That the FID Flame Is Lit 104
To Verify FID Ignitor Function During Ignition Sequence 105
To Measure FID Leakage Current 106
To Measure FID Baseline Output 107
To Measure NPD Leakage Current 108
To Verify That the NPD Bead Is Ignited 109
To Verify That the FPD Flame Is Lit 110
To Adjust the FPD Lit Offset 111

Troubleshooting 7

8Troubleshooting

9
Agilent 7890A Gas Chromatograph
Troubleshooting
Agilent Technologies
1
Concepts and General Tasks
Concepts 10
Configurable Items to Always Keep Current 11
To View the Run Log, Maintenance Log, and Event Log 12
Information to Obtain Before Calling Agilent for Service 13

10 Troubleshooting
1Concepts and General Tasks
Concepts
This manual provides lists of symptoms and corresponding
tasks to perform should you experience errors associated
with GC hardware or chromatographic output, GC Not Ready
messages, and other common issues.
Each section describes a problem and provides a bulleted list
of possible causes for you to troubleshoot. These lists are not
intended for use in the development of new methods.
Proceed with troubleshooting under the assumption that
method(s) are working properly.
This manual also includes common troubleshooting tasks as
well as information needed prior to calling Agilent for
service.
How to troubleshoot using this manual
Use the following steps as a general approach to
troubleshooting:
1Observe the symptoms of the problem.
2Look up the symptoms in this manual using the Table of
Contents or the Search tool. Review the list of possible
causes of the symptom.
3Check each possible cause or perform a test that narrows
the list of possible causes until the symptom is resolved.
The [Status] key
Be sure to also use the [Status] and [Info] keys on the GC
keypad while using this troubleshooting information. These
keys will display additional useful information related to the
status of the GC and its components.

Concepts and General Tasks 1
Troubleshooting 11
Configurable Items to Always Keep Current
Certain configurable items in the GC must always be kept
current. Failure to do so will lead to reduced sensitivity,
chromatographic errors, and possible safety concerns.
Column configuration
Reconfigure the GC every time a column is trimmed or
changed. Also verify that the data system reflects the correct
column type, length, id, and film thickness. The GC relies on
this information to calculate flows. Not updating the GC
after altering a column causes incorrect flows, changed or
incorrect split ratios, retention time changes, and peak
shifts.
Automatic Liquid Sampler configuration
Keep the Automatic Liquid Sampler (ALS) configuration
up- to- date to ensure proper operation. ALS items to keep
current include injector position, installed syringe size, and
solvent and waste bottle usage.
Gas configuration
Reconfigure the GC every time the gas type is changed. If
the GC is configured to a gas other than what is actually
being plumbed, incorrect flow rates will result.
WARNING Always configure the GC appropriately when working with
hydrogen. Hydrogen leaks quickly and poses a safety concern if
too much of it is released into the air or into the GC oven.

12 Troubleshooting
1Concepts and General Tasks
To View the Run Log, Maintenance Log, and Event Log
The GC maintains internal event logs, each of which holds
up to 250 entries. Use these logs to troubleshoot problems,
especially when a message no longer appears on the display.
To access the logs, press [Logs] to toggle to the desired log.
The display will indicate the number of entries the log
contains. Scroll through the list.
Run Log For each run, the run log records deviations from
the planned method. This log is overwritten at the start of
each run. The run log information can be used for Good
Laboratory Practice (GLP) standards and can be uploaded to
an Agilent data system. When the Run Log contains entries,
the Run Log LED lights.
Maintenance Log The maintenance log contains an entry for
each time an Early Maintenance Feedback limit is reached,
reset, or changed. The log records details such as the
counter item, the counter value, the new counter value, and
whether or not the counter was reset (indicating a part
replacement). When the maintenance log is full, the GC
overwrites entries, beginning with the oldest.
Event Log The event log records events such as shutdowns,
warnings, faults, and GC state changes (start run, stop run,
and so forth) that occur during GC operation. When the
event log is full, the GC overwrites entries, beginning with
the oldest.

Concepts and General Tasks 1
Troubleshooting 13
Information to Obtain Before Calling Agilent for Service
Gather the following information before contacting Agilent
for service:
•Symptoms
•Problem description
•Hardware installed and parameters/configuration when
the error occurred (sample, supply gas type, gas flow
rates, detectors/inlets installed, and so forth)
•Any messages that appear on the GC display
•Results of any troubleshooting tests you have run
•Instrument details. Obtain the following information:
•GC serial number, which can be found on a sticker
located beneath the keypad on the bottom right corner
of the GC.
•GC firmware revision (press [Status], then [Clear])
•GC power configuration (located on a label on the back
panel of the GC to the left of the GC power cable)
•Oven configuration (fast- or slow- heating)
•Press the [Status] key to display previous Error, Not Ready,
and Shutdown messages.
To obtain service/support contact numbers, see the Agilent
Web site at www.agilent.com/chem.

14 Troubleshooting
1Concepts and General Tasks

15
Agilent 7890A Gas Chromatograph
Troubleshooting
Agilent Technologies
2
ALS and Detector Symptoms
Plunger Errors 16
Vial Mishandled by ALS 17
Syringe Needle Bends During Injection into Inlet 18
FID Does Not Ignite 19
FPD Does Not Ignite 22
NPD Adjust Offset Process Fails 23

16 Troubleshooting
2ALS and Detector Symptoms
Plunger Errors
If the ALS reports a front or back plunger error, check the
following possible causes:
•The syringe plunger is sticking or is not securely
connected to the plunger carrier.

ALS and Detector Symptoms 2
Troubleshooting 17
Vial Mishandled by ALS
Refer to your sampler installation manual for additional
information.
When you find a mishandled sample vial, do the following:
•Check for folds or wrinkles in the crimp cap, especially
near the neck of the sample vial.
•Use Agilent- recommended sample vials.
•Check sample labels (if applicable).
•Check that they are the correct size.
•Verify that the labels do not interfere with the gripper.
•Check that the tray vial racks are clean and snapped into
the tray base.

18 Troubleshooting
2ALS and Detector Symptoms
Syringe Needle Bends During Injection into Inlet
Refer to your ALS documentation for additional information:
7683B Automatic Liquid Sampler Installation, Operation
and Maintenance
7693A Automatic Liquid Sampler Installation, Operation
and Maintenance
•Check that the GC septum nut is not too tight.
•Check that the syringe is installed correctly into the
syringe carriage.
•Check that the needle support and guide are clean.
Remove any residue or septum deposits.
•If using the cool on- column inlet, check that the correct
insert for the syringe is installed.
•Check that you are using the proper syringe. The
combined length of the syringe barrel and needle should
be approximately 126.5 mm.
WARNING When troubleshooting the injector, keep your hands away from
the syringe needle. The needle is sharp and may contain
hazardous chemicals.

ALS and Detector Symptoms 2
Troubleshooting 19
FID Does Not Ignite
•Verify that the Lit Offset is < 2.0 pA.
•Check that the FID ignitor glows during ignition sequence.
(See To Verify FID Ignitor Function During Ignition
Sequence.)
•Check for a plugged or partially plugged jet.
•Check the FID flow rates. The hydrogen:air ratio greatly
impacts ignition. Nonoptimal flow settings can prevent
flame ignition. (See To Measure a Detector Flow.)
•There could be a large leak in the system if the flame still
will not light. Large leaks result in measured flow rates
being different from actual flow rates, causing nonideal
ignition conditions. Thoroughly leak check the whole
system, especially the column fitting at the FID.
•Check the column flow rate.
•Check for leaks at the FID column fitting.
•Ensure that the FID temperature is high enough for
ignition (>150 °C).

20 Troubleshooting
2ALS and Detector Symptoms
FID Ignitor Does Not Glow During Ignition Sequence
1Remove the detector top cover.
2Turn the FID flame On.
3Observe the ignitor plug though the FID chimney. The
small hole should glow during ignition sequence.
If the test fails, check for the following possible causes:
•The ignitor may be bad; replace the ignitor.
•Detector temperature is set to < 150 °C. Agilent
recommends operating the FID at > 300 °C.
•The ignitor is not making a good connection to the
ground:
•The ignitor must be tightly screwed into the FID castle
assembly.
•The three T- 20 Torx screws that hold the collector
assembly in place must be tight.
•The brass knurled nut that holds the FID castle
assembly in place must be tight.
Perform FID maintenance if these parts are corroded or
oxidized.
WARNING Keep body parts at a safe distance from the FID chimney while
performing this task. If using hydrogen, the FID flame will not be
visible.
T-20 Torx screws (3)
Ignitor
Knurled nut