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July 01, 2010 (Vol. 30, No. 13)

Enhancing the Visibility of Sample Quality

Vision Technology Is Being Used to Facilitate Liquid Volume Auditing and Precipitate Detection

  • Making Sample Quality Visible

    Click Image To Enlarge +
    Figure 1. Cap detection, volume, and precipitate level detection as measured by the Tube Auditor

    A new solution to this challenge uses high-resolution vision technology to audit both volume and precipitate in racks containing up to 96 tubes. An advantage of this approach is that auditing can take place without de-capping of the tube, thus minimizing any exposure of the sample and helping reduce potential degradation or cross-contamination.

    A high-speed vision system incorporated into a benchtop instrument is used to image multiple sample tubes simultaneously—up to a full column of eight tubes in a standard SBS footprint rack. The captured image is analyzed, and the liquid meniscus detected for each tube being audited.

    Advanced image processing routines  take into account variations between different liquid types, for example DMSO or aqueous solutions.

    Once the position of the meniscus has been determined, the volume of liquid is calculated, taking into account the tube type. Further algorithms are used to detect the presence of a cap and any precipitate in the base of the tube.

    Figure 1 illustrates a column of eight tubes following image capture, with various regions of interest depicted, with detection of caps, meniscus, and precipitate (in two of the tubes).

    Benefits of this approach include: speed, less than two minutes to audit a 96 tube rack; accurate, volume measurement better than +/-10 µL; precipitate and cap detection; no need for tare-weighing of tubes; noncontact and operates with capped tubes.

  • Click Image To Enlarge +
    Figure 2. The Tube Auditor is a benchtop or integrated unit for volume measurement and precipitate detection in SBS format microtubes.

    The RTS Tube Auditor™ (Figure 2) can be used manually, with racks of tubes presented by the user, or integrated into a fully automated system, with racks of tubes being loaded/unloaded by a robot. This allows end users to audit small or large numbers of tubes according to the needs of their organization.

    By integrating the instrument into an automated system, typically where the liquid sample is aspirated from the source tube and dispensed into a plate, it is possible to perform auditing following selected, or indeed every, access to the sample. Users can determine the frequency at which they audit samples based on their own quality control processes.

    Although originally intended to facilitate in-process auditing, this technology is also finding applications at an earlier stage in the drug discovery process. Having an accurate record of the volume prior to putting the sample into storage is clearly important.

    The Tube Auditor can be used to measure volume at the time of initial sample dissolution (and also give an indication of how well it has been solubilized). During early trials the technology reliably identified samples with lower volumes than had been anticipated. Upon investigation, this was found to be a result of blocked tips in the liquid handler used to perform the solubilization.

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