When our laboratory was in need of a microplate washer a couple years ago, I spent some time questioning colleagues for their experiences with various makes and models. After weeks of research, I settled on the Columbus Washer from TECAN. The reasons were many but can be condensed into 2 words: economy and reliability. We didn’t have a lot of equipment money available at the time but also didn’t want to buy a brand with no reputation. Since its purchase, the Columbus Washer has performed exceptionally well; we are very pleased it.
The Columbus Washer is technically a strip washer rather than a plate washer since plates are washed one strip (i.e. one row or column of wells) at a time. Although this method is somewhat slower than models that wash all wells at once, it allows the flexibility to wash selected strips without washing the whole plate. This feature comes in handy with time-course experiments or in small experiments when only parts of plates are used. Other controllable features are aspiration rates, dispense rates (including a drip dispense for assays involving intact cells), plate type, and number of wells per strip (8, 12, or 16 were available at the time of purchase). The instrument can store up to 30 different user-definable washing programs, with each program having up to 60 steps.
The instrument is controlled and programs are defined either through a computer interface or directly from the 4-button keypad on the front of the washer. We have only used the keypad, which has been adequate for our purposes. The method of defining the wash programs is somewhat less than intuitive but easily learnable. The manual provides decent instructions but learning the language really requires attempting to make a few programs yourself. Once the various washing programs are designed and stored, any one can be called up in just a few keystrokes.
Although the Columbus Washer has been extremely reliable, I believe a major factor is scrupulous attention to a few easy maintenance procedures. One is to avoid letting buffers and wash solutions dry in the lines. After use and before shutdown, we always flush the lines with pure water and then perform a “Night Rinse” as recommended. Although we haven’t allowed this to happen, I imagine it would be fairly difficult to clean the lines of dried PBS/Tween. Another crucial maintenance procedure involves the tray on which the plate sits and also which moves the plate back and forth under the wash manifold. The tray has a movable metal piece that automatically centers the plate correctly under the manifold. Dried salt and detergent residue from wash solutions can prevent the centering device from operating, resulting in an error message. Dried deposits can also compromise the movement of the entire tray. Fortunately, the tray can be removed easily and cleaned.
In short, the Columbus Washer is a relatively inexpensive, reliable, and flexible plate washer. I would recommend it highly for labs with low-to-moderate microplate washing needs. Labs with high microplate usage may want to invest in a plate washer with a faster turnover rate.
Michael Campa, Ph.D.
Asst. Research Professor of Radiology
Duke University Medical Center