GC Control
Injecting Two GC Samples Simultaneously (Agilent 7890 GC)

The 7890 GC can be used to simultaneously inject two samples from different positions (dual operation mode). Thus, the sample throughput can be doubled.

Overview

The following conditions must be met to run the GC in dual operation mode:

• the GC must be fitted with the required hardware components,

• the GC must be installed in two timebases (refer to  Agilent 6890/7890 GC: Dual Operation),

• the PGM Files for the two timebases must match, i.e., the shared commands and properties must be identical,

• a batch must be available for each timebase,

• either two gas sampling valves or two injectors can be used for injection,

• if the GC is operated with an external autosampler, the autosampler must support dual operation, too.

After installing the GC, follow the steps below to set up the dual operation mode.

1. Create two PGM Files

Create a PGM File for each timebase, observing the following:

• Enable dual operation with the following command (this can be done only from the control panel):

• DualOperation

  = Shared

   

• Enable dual operation for the related sample(s) (this can be done only in a PGM):

• Sharable

  = ON

   

   Tip: 

  When a batch is running, you cannot perform manual commands in the Shared mode. To control the GC via manual commands while a batch is running, assign the GC to only one timebase:

  DualOperation

  = FrontOnly or BackOnly

   

• Make sure that all commands and properties shared by the timebases have the same values at the same retention times. This is especially important for the temperature, injection, data acquisition, and running batches. If the values and/or retention times are different, the samples will be processed one after the other.

   Note: 

  The ReadyCheck cannot always establish exactly in which order the samples are processed. Therefore, more or less warnings than appropriate may appear during the ReadyCheck.

• In general, commands and properties that are assigned to only one timebase can be set independently of the setting in the PGM File for the other timebase. The Inject command is an exception: It must be available in both programs at the same time. (In special cases, it may be missing in both programs; it must not be missing in only one program.)

2. Create a sequence and a batch for each timebase

• When using two 7683 B injectors, it is not possible to simultaneously inject two samples from the same tray position.

• When using two gas sampling valves, both valves must use the same sample position.

• The batches do not have to include the same number of samples. If all samples of one batch are processed, sample processing will continue for the remaining samples of the other batch.

•  Tip: 

  You can add new samples or sequences to the finished batch and restart the batch. Sample processing is resumed when the next sample of the running batch is started.

• Two blank run samples are run in parallel, however, if only one of the two samples is a blank run, samples are processed one after another.

3. Start the batches

In dual operation mode, a batch must be started on both timebases simultaneously:

• Create the two batches and perform the Ready Check on both timebases. Afterward, start the two batches.

  A message may appear in the Audit Trail advising you to start a batch on the other timebase, too.

• Start the batch on the other timebase.

  The two batches run in synchronization. The Ready Check checks that the shared properties, temperature gradient, and run time for the sample pairs match. During run time, the sample positions and sample types of each batch are compared against each other.

Observe the following restrictions:

• Emergency programs can only be run in parallel, but the Ready Check cannot check if emergency programs are suited for parallel operation. Therefore, make sure that the used emergency programs are suited for your application.

• The Ready Check can check only the active sequences.

• The Ready Check does not report samples which cannot be processed simultaneously due to their sample positions or sample type. Refer to the Audit Trail for the current sequence for information on sequentially processed samples.

• The Ready Check can detect changes to the running sequence on the other timebase only when you stop and restart the batch on the other timebase. If the Ready Check reports an error on the other timebase, follow the steps below.

• 1. In the timebase for which the error was reported:

  2. Stop the batch.

  3. Eliminate the error.

  4. For the first sample, change the status from Interrupted to Single, if necessary.

  5. Restart the batch.

  6. Return to the original timebase.

  7. Run the Ready Check again.

Examples

a) To analyze a pair of sequences (e.g., Front1 and Back1) simultaneously on two instruments (e.g., Front and Back) and then run another sequence (Front2) only on the Front instrument:

• For the pair of sequences, set Sharable = On.

• In the instrument method for the Front2 sequence, set Sharable = Off.

b) Use the following settings if you want to process sequences in dual operation mode whenever possible but also analyze them one after the other if required:

• Accept the default setting: DualOperation = Shared, however

• Do not enter the Sharable command in the instrument method.

c) If you want to run a queue only on one instrument (e.g., on the front instrument), proceed as follows:

• In the instrument method, set Sharable = Off and start the queue on the front instrument.

The queue is started immediately and does not wait for a queue on the Back instrument.