How can I create and use Utility Methods in my ASTRA Sequence? - WKB319047

How can I create and use Utility Methods in my ASTRA Sequence?

Utility methods can be very useful for accomplishing regular maintenance of your SEC-MALS system. This guide article will show you how to set up and run these utility methods in your ASTRA Sequence, which can be easily run at the end of your sample sequence. Please note that these utility methods are not compatible with VISION Sequences.

What kinds of utility methods can I use?

There are a variety of utility methods accessible in ASTRA. All of these methods can be found in the System → Methods folder, which downloads automatically with ASTRA. The sections below provide a summary of some commonly used utility methods for MALS, RI, and UV instruments.

MALS Utility Methods

For utility methods pertinent to your MALS instrument, navigate to the System → Methods → Light Scattering → Utilities folder for HPLC (DAWN, miniDAWN, HELEOS, or TREOS) applications or System → Methods → Light Scattering - UHPLC → Utilities folder for UHPLC (microDAWN) applications. These utility methods include:

• COMET [comet duration]: Turns on the COMET ultrasonicator to help remove sticky residues from the inner bore of your MALS flow cell. A COMET must be present to use this method.
• Orbit On: Turns on the Orbit solvent recycler, useful to prevent pump and entire flow path from running dry while there is steady system flow. An Orbit must be present to use this method.
• APD off: Turns off the avalanche photodiode (APD) of the QELS module used for online DLS measurements. A QELS module must be present to use this method.
• Laser off: Turns off the MALS instrument laser.

Note that these utility methods are specific to the instrument type (DAWN vs. miniDAWN vs. HELEOS, for example).

RI Utility Methods

For utility methods pertinent to your RI instrument (Optilab, T-rEX), navigate to the System → Methods → RI Measurement → Utilities folder. These utility methods include:

• Flush: Cycles the purge valve open and close repeatedly to flush both the sample and reference cell of your RI instrument to aid dislodging bubbles or residues.
• Purge On: Opens the purge valve of your RI instrument to flush out the reference cell. We recommend toggling this on when you are not collecting data to help maintain a stable RI baseline. Additionally, while purge mode is toggled on, the absolute refractive index of the solvent/buffer will be reported on the front panel of the RI instrument.
• Purge Off: Closes the purge valve of your RI instrument. This seals off the fluid in the reference cell, so that the instrument can be used for sample data collection. Note that ASTRA will automatically do this upon starting data collection, however we recommend doing this 10–15 minutes prior to collection to provide equilibration time.
• Zero dRI: Zeroes the dRI baseline. This should only be done after purging with your intended solvent/buffer.

UV Utility Methods

UV utility methods are only available for HPLC CONNECT users; otherwise, there is no way for ASTRA to control the UV lamp. For utility methods pertinent to your Agilent UV/Vis lamp, navigate to the System → Methods → UV Measurement → Utilities folder. These utility methods include:

• Lamp Off [UV + Vis, UV, Vis]: Turns off the UV/Vis lamp to maintain the lifetime of the light source.

How do I use a utility method in an ASTRA sequence table?

Utility methods can be run individually but more commonly they are used at the end of an ASTRA sequence to provide regular maintenance and/or shutdown. We recommend the following to set up utilities methods for use in an ASTRA sequence:

1. Navigate to File → New → Experiment from Method.
2. Choose the utility method of interest and press Create. Please remember that choosing your desired utility method requires selecting the appropriate corresponding instrument within the System Methods folder (i.e., System → Methods → (Light Scattering or RI Measurement or UV Measurement) → Utilities).
3. Once opened in ASTRA, expand the configuration and double-click the respective instrument (Optilab in the example below).
4. Change the physical instrument to that of the instrument you are using for this system (the appropriate Optilab in this case). Press OK to save this change.
5. Right-click the experiment name and select Save as Method. If desired, rename this method to clarify its use/function (Optilab Purge On for example).
6. You can now use this method in your Sequence Table, feel free to choose it as you would another method by designating it in the Method section of the table. We recommend concatenating utility methods to the end of your Sequence like that shown in the screenshot below:

Note that because there is no sample being injected for utility methods, we don't need to provide additional information in the Sequence table nor does ASTRA need to wait for an auto-inject signal from the HPLC/UHPLC system.