Commands and Tips for Third-Party Devices
CTC Analytics PAL Samplers: Tips for Headspace Operation

Chromeleon supports two headspace injection modes:

HS_Single:  Standard headspace injection

HS_Progr:  Progressive headspace injection

In HS_Single mode, the sampler performs a standard headspace injection, including sample preparation. You must specify an incubation time (IncubationTime parameter) for every sample in the sequence.

In HS_Progr mode, you do not have to explicitly set the incubation time for samples. Instead, you can increase the incubation time of the previous sample by a certain value (IncubOffset). The IncubTimeStart parameter determines the start of the incubation time of the first sample in a sequence. Thus, the incubation time for the sample number n is calculated as follows:

IncubTimeStart + (n-1) * IncubOffset .

 Tip:  

You are not allowed to change the IncubOffset or IncubTimeStart parameters in a sequence, i.e., they can be set before the start of the sequence or they must have the same value in each sample program that is used in the sequence.

In both modes, Chromeleon needs information about the minimum time difference between two sample injections. Use the GCCycleTime parameter to specify the time required by the GC after injection until the instrument is ready for the next injection.

 Tip:  

Make sure the cycle time is long enough for completion of all actions by the GC (injection procedure, chromatographic separation, cleaning, warming up of the inlet, etc.) and the sampler (cleaning before and after injection, preparation of new samples, etc.).

The PAL sampler automatically places the vials in the agitator for sample preparation. After the injection procedure, the vials are moved back to their original positions in the tray.

• If you start a new sequence, make sure that no samples were left in the agitator. If necessary, remove all vials from the agitator manually before starting a new sequence.

 Caution:  

Always run an emergency program to cool down the agitator (or other temperature-controlled components) before removing the samples manually from the agitator.

• If you interrupt a current sequence (immediately or after current sample) or if an abort error occurs, Chromeleon attempts to remove all remaining samples from the agitator. This attempt may fail in case of a general device error. In this case, remove the vials manually.

 Caution:  

Always run an emergency program to cool down the agitator (or other temperature-controlled components) before removing the samples manually from the agitator.

• Chromeleon checks whether the specified GC cycle time of a sample exceeds the program end time minus the start time of the next sample. Nevertheless, Dionex recommends allowing for some extra time.

 Tip:  

The GC may require more time, e.g., to heat up the inlet, column, and/or detector until it has reached the new temperature. In this case, certain commands, such as Wait and Inject, delay the execution of the program, possibly even beyond the sample incubation time. Therefore, Dionex recommends setting the real time of the GC cycle to GCCycleTime and adding 30 to 60 seconds for safety reasons. (You might have to add more time, depending on the GC running conditions; for more information, refer to the GC instruction manual.)

• Do not use the TRANSP_VIAL command to transport vials to or from the agitator while the sequence is being processed in HS_Inject mode. The mechanism for sample preparation is not connected with this command. If you use this command while a sample is being processed, Chromeleon may attempt to place a vial in a position that is already occupied or to fetch a vial from a position where no vial is present.

• In headspace injection mode, you can assign the tray to be used either manually or explicitly in the PGM File via the tray name (e.g., TrayName = Tray1 or Tray = Tray1). If you use the Tray and TrayName parameters, it is not possible to make assignments via user-defined columns or formulae.

• Actions for the current sample have priority over preparation steps for the next sample. Therefore, sample preparation steps are only performed when the sampler is idle. The injection is performed when the PAL sampler has completed sample preparation. Chromeleon does not place a new sample in the agitator if the remaining preparation time for the running sample (marked green) is less than 30 seconds.

• If you use the headspace mode for injection, all samples must use the same injection mode. It is not possible to change the headspace mode during a sequence or use non-headspace and headspace modes in one sequence.

• The following applies to blank samples (the Blank sample type, for which the inject command contains the Skipped parameter) and samples without an inject command: Sample preparation is simulated, i.e., the system waits for the incubation time but the sample is not placed in the agitator and no injection is performed.

 Note:  

The Audit Trail messages for sample preparation are displayed both in the currently running sample and in the sample that is prepared.

For more information, refer to  PGM File for HS_Progr Inject Mode.