Taring, Weighing and Dissolution Systems for Library Compounds


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The management and analysis of compound libraries requires a variety of automation tasks and surrounding equipment. Even though automation of compound libraries dates back to the 1990s, there are still some tasks that have not been optimally automated and are being done manually. The latest systems from Zinsser handle all phases of work involved in compound management, including not only liquid and solid handling but also weighing operations, all in conjunction with capping or decapping as necessary.

Automated weighing platforms have been available for some time, and some of the older systems are nearing the end of their life spans without new versions available from the original manufacturer. Zinsser fills that gap with our latest weighing systems, and adds in the new "twist" of automated capping and decapping as an option. Taring, weighing, and dissolution with DMSO can all be combined together into one system or performed with separate modules depending on the desired workflow of each lab.

TARING

The taring operation is important in every compound management lab. It is possible that the library vials have been purchased with the tare weights which saves doing this step in the lab, but that does require greater expenditure for vials and also some labs prefer to maintain control over the taring operation. In order to successfully track the taring process, the vial not only needs to be weighed, the tare weight also needs to be stored along with the vial so it can be recalled later for the reweigh. This is typically done by associating the tare weight with a bar code ID that is attached to the vial. So in order to perform the taring operation, these tools are needed:

  • Balance. The balance is integrated onto the robotic system's deck, and can be a 4-place, 5-place or 6-place balance.
  • Bar code scanner. Reads the bar code ID for each vial.
  • Robotic gripper arm. Moves the vials from their racks to the bar code scanner and the balance.
  • Software. Stores the bar code ID and the tare weight together.

After the taring has been performed on a batch of vials, the associated data is stored in a table for easy future access. This table can be recalled by the Zinsser software to be used in future operations such as the weighing step, and can also be exported by the Zinsser software and subsequently imported into the customers compound management database system. Below is a typical example of a table of tare weight data. In this case, the system has already been provided with a reference table to start with that includes the barcode ID, the compound name, the molecular weight of the compound, and the percent free base of the compound. The taring system fills in the tare weight column after filling the vials.

 

WEIGHING - With Decapping and Recapping

In many compound management labs the library vials may be manually prepared by adding solid material from various sources. In this case, the lab technician would enter the final weight of the material by manually weighing the compound. This process can be semi-automated and made more efficient by using the Zinsser Moss system.

It is also common for the chemistry group to produce large numbers of compound vials via their internal synthesis schemes. In this case, the vials are typically dried down after the synthesis. If rated vials have been used to store these compounds, then those vials can be reweighed to determine the weight of compound that is in the vial. This can be accomplished with the same taring system described above, but often at this step the vials have been capped to protect the contents. So in order to fully automate this process the system should also include a decapper/recapper. Otherwise the lab technicians are required to manually uncap and then recap all of the vials, which is a tedious process that can also lead to repetitive stress injuries. For this operation, the system is configured as follows:

  • Balance. The balance is integrated onto the robotic system's deck, and can be a 4-place, 5-place or 6-place balance.
  • Capper/Decapper. Removes the cap before weighing, then puts it back on.
  • Bar code scanner. Reads the bar code ID for each vial.
  • Robotic gripper arm. Moves the vials from their racks to the bar code scanner and the balance.
  • Software. Stores the bar code ID and the tare weight together.

Prior to starting the run, the automated system imports the table with the tare weights, or if the same system was used for taring recalls it directly. The vials are scanned again to verify the identity, then decapped, weighed, and recapped. The weight is placed into an output table that can then be imported by the database system.

Dissolution

After the compound vials have been weighed and stored dry, at some point they need to be brought up into liquid form in order to create assay plates. Most typically this is done by adding DMSO to achieve a target concentration such as 10 millimolar, or a weight concentration if desired. This dissolution step can be performed on almost any liquid handling system, but again since the vials are capped, they will need to be decapped somehow before the dissolution step. Once again the Zinsser system solves the problem with the automated capper/decapper tool, allowing the entire process to be performed without manual intervention. The dissolution step can be performed on a separate platform with liquid handling capability and a capper/decapper, on on the same platform that is used for taring and weighing. This depends on the goals of the lab and whether it is desired to maintain separate modules for separate steps, or use a single platform for as many tasks as possible.

The Zinsser Lissy liquid handler will import the data table from the user's database which has the required volume for dissolution (last column in the table below). This is calculated from the previous weight data, the compound MW, and the free base factor. For dissolution, the system will decap the vial, read the bar code and then look up the dissolution volume for that bar code ID and dispense that amount of DMSO.

 

If desired, the Zinsser WinLissy Dissolution Module can be added which will perform the dissolution volume calculations on the fly, eliminating the need to import a database table. Either way, the software will produce a final table for export with all of the weight and dissolution data for the user's database system.

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