Overview: Using 3 Zaber stepper motors and a Hamilton Microlab 500 series syringe pump we’ve assembled a home-built autosampler and written custom software for it. The software is written in Labview (originally version 8.2 but currently in Labview 2016) and the software is available here (you’ll need the LabVIEW Runtime Engine to run the executable). We’ve used the unit for automated titrations (urea and guanidineHCl denaturation of proteins) using time-resolved fluorescence and small-angle x-ray scattering (SAXS) and obtained data that would have been very difficult and laborious to obtain manually. Many thanks to Sagar Kathuria for helping
with the development and debugging of the autosampler and software.
Scheduling wells on a microplate:
The program works with the user inputting, either manually or via a spreadsheet file, a schedule for the order in which data will be collected for all of the wells in the wellplate. We typically randomize the acquisition order to avoid a systematic bias in the data. Below is the sample order for a titration done at BioCAT. The user can specify if a wash is done after the sample and/or the blank. A separate flow sequence is specified for acquisition and for the wash.
Acquisition sequence: Here is the acquisition flow sequence for the above titration. The user has complete control of the acquisition flow sequence and how to synchronize the Hamilton pump with the data acquisition. The user can decide the valve orientations and flow speeds. Note that it also allows the user to Cycle with provisions for separate valve orientations for the Pick-up and Dispense portions of the Cycle. This is very handy if one wants to flow the sample (to avoid radiation damage or photodamage) during acquisition of multiple frames in SAXS or in fluorescence lifetime experiments.
All of the Hamilton commands are logged with a time stamp to give the user a complete log of exactly what the software did. The log is saved to a file and shown in the status window:
Schematic and parts: Here is a schematic of our autosampler layout if you’re interested in putting one together yourself. Enjoy!
(Update: Although the 75 mm Zaber stage works well, we’ve switched to using the 150 mm stages for both the x- and y- axes. For faster motion in the z-direction we’ve also replaced the LA28 with the NA08B30).