Commands and Tips for Third-Party Devices
Agilent 7890 GC: Application

General

In Chromeleon, short descriptions of the GC commands are available in the Command dialog box or the Properties/Link box.

Inlet

The inlet is usually controlled by the use of Inlet.* commands. However, the inlet can be connected to the column via the PGM File or via a direct command, e.g., using

Column.Inlet = Front

The column commands also control the inlet.

Generally, either an Inlet.* command (e.g., Inlet.Flow orInlet.Pressure) or a Column.*command (e.g., Column.Flow oderColumn.Pressure) is allowed per PGM. A combination of both Inlet.* and Column.* commands is not possible. In addition, using a Flow and Pressure command in the same PGM is not possible.

A combination of the following commands is therefore invalid:

Inlet.Flow.Nominal = 20.0

Column.Pressure.Nominal = 5.00

Also, refer to  Agilent 7890 GC: PGM File - Entering Pressure or Flow?

Cool On-Column Inlet

It is not recommended to set both the temperature and Mode = TrackOven in the same program. If you attempt to do so, the following error message appears:

[Warning]{FrontInlet} Assignment for Temperature.Nominal has no effect. Set Mode to the following mode(s): RampedTemperature.

Setting a temperature ramp automatically selects the RampedTemperature mode.

For a constant temperature, set Mode = RampedTemperature and enter a temperature value.

Column

It is possible to enter column dimensions and connections, but not the calibration. If column dimensions and connections are not defined, certain commands such as Flow cannot be executed.

It is not possible to modify column dimensions and connections in an automatic sample program (batch). These parameters can only be modified manually using the F8 command box.

Valves

Chromeleon supports the following valve types: multi-position valve, gas sampling valve, switching valve, other valves.

Gas sampling valves can be used for performing gas injections. If used with a multi-position valve, 32 sample positions are provided.

Aux

For the 7890 GC, a maximum of three auxiliary EPC devices for pressure control can be installed. Devices for pressure (PCM) and auxiliary temperature control, however, can be controlled by the GC, but not by Chromeleon.

Sampler

The 7890 GC can be used with the following autosamplers: Agilent 7650A, 7683B, 7693A, G1888 Headspace Sampler (= external autosampler), or any non-Agilent sampler with a signal transmission similar to that of the G1888 Headspace sampler.

Parking the Sample Tray (7693A Autosampler)

To move the sample tray to the park position, press the park button [P] on the front panel of the tray (for details, also refer to the operating manual of the sampler).

If you later want to perform injections, you must press the [P] button again to move the gripper from the park to the Home position.

FID Detector (GC 7890A+ and 7890B only)

When operating a FID detector with a GC 7890 B or a GC 7890 A+ (firmware version B.02.00 or later), the GC system provides the following FID modes:

• Constant Makeup & fuel flow
• Column + makeup = constant
• Column + fuel = constant

The above FID modes (in the following referred to as "GC FID modes") correspond to the following FID Mode values in Chromeleon:

• Makeup

• Combined

Depending on the GC FID mode that is set on the GC before the GC driver is connected in Chromeleon, the Mode property in Chromeleon will then be set to either Makeup or Combined. The table below shows how the GC FID modes are mapped to the Chromeleon FID Mode values:

Example 1:

The GC driver is not connected in Chromeleon and the GC FID mode is Column + fuel = constant.

Connecting the driver in Chromeleon sets the Chromeleon Mode property for the FID to Makeup.

If you change the Mode property in Chromeleon to Combined, the FID detector will run in Column + makeup = constant mode.

When setting the Mode property back to Makeup again, the FID detector runs in Column + fuel = constant mode.

Example 2:

The GC driver is not connected in Chromeleon and the GC FID mode is Column + makeup = constant.

Connecting the driver in Chromeleon sets the Chromeleon Mode property for the FID to Combined.

If you change the Mode property in Chromeleon to Makeup, the FID detector will run in Constant makeup & fuel flow mode.

When setting the Mode property back to Combined, the FID detector runs in Column + makeup = constant mode again.

 Tip:

Due to changes in the Agilent GC 7890 firmware, inconsistencies in existing PGMs with regard to the FID mode may occur. Thermo Fisher Scientific therefore recommends to double-check the FID mode setting on the GC before starting a run.

To verify that PGMs which have originally been created for a GC 7890A are executed correctly with an 7890B or 7890A+, do the following:

1. Connect the GC to Chromeleon (if not yet done so).

2. In Chromeleon, set FID Mode property to Makeup (if not yet done so).

3. Check on the GC display whether the GC FID mode is Constant makeup & fuel flow. If the mode is not correct, disconnect the GC, select Constant makeup & fuel flow on the GC, then connect the GC with Chromeleon again.

Application Tips

Entering a Temperature Gradient

You can enter a temperature gradient directly by including a command in the PGM File.

For the 7890 GC, the oven temperature profile can include a maximum of 20 ascents or descents. The maximum temperature change (ascent) is up to 120°C per minute, depending on the oven type.

Up to 3 gradient profiles for inlet and columns can be defined. Gradients are entered in the Program Wizard by specifying the rates, end temperatures, and dwell time. In the program, however, the "base point philosophy" is used (similar to entering a flow or percent gradient in HPLC). Each temperature command is a base point of the gradient program. The wizard automatically converts the entered rates into the base point representation.

Temperature Setting Commands

Use the following commands to enable or disable temperature control of the oven, two inlets, and two detectors:

(Note: GC_1 = Front Detector, GC_2 = Back Detector)

Use the following commands to set the temperature of each module:

It may take some time for the instrument to reach the nominal temperature. Please note that the oven heats faster than the injector and the detector system. As soon as the nominal temperature is reached, the GC sends a Ready signal. An injection via the autosampler is possible only after this signal.

Example:

The following program waits until the nominal temperature of 150°C is reached before the Inject command is executed:

  0.000 GC.Temperature = 150

   Wait GC.Ready

   Inject

  ...... ..............

 Tip:

After the instrument has received the nominal temperature value from Chromeleon, it implements the desired value as quickly as possible. When the value is "almost" reached, the instrument waits until the user-defined Equilibration Time has elapsed before sending a confirmation message to Chromeleon.

Manual Injections

To perform manual injections, proceed as follows:

1. Add a Remote Inject driver to the timebase (for instructions, refer to  Agilent 7890 GC: Installation - Settings for manual injections).

2. Start a batch.

3. The GC is automatically set into pre-run state for the current sample.

4. Wait until the audit trail message "Waiting for inject response on ExtStart' appears.

5. Perform the injection and then press the Start key (press ON/YES if a gas sampling valve is used).

6. Wait until the run is finished. Repeat steps 3 to 5 for each additional sample in the batch.

Notes:

The manual command buttons Inject and Stop Flow provided on the online toolbar of the Chromeleon client are currently not supported for the 7890 GC.

Manual injections may lead to a time delay between sample start and recording time resulting in a lower reproducibility of retention times in chromatogram peaks. To prevent a time delay you may use a Remote cable for synchronizing external instruments. For details, refer to 7890 GC: Instrument Synchronization.

Multiple Injections

The 7650A, 7683B and 7693A injectors support multiple injections for injection of large volumes.

• Use the InjectCount property to set the number of required injection repetitions. To disable the multiple injections functionality, set the value of the property to 1.

• If a delay time between injections is needed, use the InjectDelay property to define the required delay time.

Note:

• In the sample list in the Chromeleon Browser, specify the total injection volume (not the volume to be injected with each individual repetition).

• Make sure that the volume to be injected with each individual repetition (= total injection volume/number of repetition (InjectCount)) can be handled by the injector.

The GC run is started with the first injection of the current sample.

7650A and 7693A Injectors

In addition to setting the InjectCount and InjectDelay properties described above, the 7650A and 7693A injectors also provide the Mode property.

• To enable multiple injections: Set the value of the Mode property to LVI.

• To disable multiple injections: Set the Mode to any value other than LVI.

Using an 7650A, 7683B or 7693A alternately as front or back injector

If the GC is equipped with only one 7650A, 7683B or 7693A injector, you can use this injector to perform batch runs alternately on the front and back inlet. For that, you have to configure the injector as front and back injector on the Sampler tab page in the Chromeleon Server Configuration:

• In the Chromeleon Server Configuration, click the Sampler tab page of the 7890 GC.

• In the Front Injector and Back Injector sections, select the Installed check box. Also, make sure to select the same injector type in both Type boxes.

Caution:

(7683B or 7693A injectors only) The GC is not able to detect whether an injector is mounted on the correct mounting post or not. To avoid possible damage to the GC, double-check settings on the GC if the injector is installed on the correct mounting post.

The following example describes how to change from the back to the front injector on a 7683B or 7693A injector:

1. After the batch is finished, remove the back injector from the back mounting post.

2. On the GC key pad, press 'Config -> Back Injector'. The cursor is now displayed on the first line 'Back tower'.

3. Press the 'Off/No' key to configure the injector as the front injector. The message 'Injector not installed' appears on the display of the GC.

4. Install the injector on the front injector mounting post.

5. You can now run batches on the front injector. For that, verify that the PGM contains a FrontInjector.Inject command instead of a BackInjector.Inject command.

For installation instructions for the GC, refer to  Agilent 7890 GC: Installation.