#1. Define your needs. What are the applications you will run on this system? How many parameters (realistically) do you run on average? How many parameters will you run in the near-future? Are there any specialty dyes you run? Do you prepare samples in tubes or plates? At what event rate do you run your samples?
Example: I have some projects in mind which require 8 - 10 fluorescence parameters. At 3 parameters per laser, I probably need a 3-laser system minimally. I like to stain/run my cells in a 96 well plate, so a plate sampler option is needed. My experiments typically involve immunophenotyping rare subsets, so I collect 10^6 cells at rates of about 15,000/second. I don't need to sort.
#2. Query the end-users. If others in the lab or core facility will use the instrument, ask them the same questions as in #1.
Example: Another user in the lab does a lot of screening of her mCherry transfected cell lines. She doesn't collect a lot of cells, but screens many samples. She would require a yellow/green laser for excitation, and fast 96-well sampling capabilities.
#3. Refine your needs. Combining the information you learn from steps 1 and 2, you should be able to refine the needs for this instrument. Annotating this list, and possibly triaging needs and wants will be very helpful at this point. Of course you are working within a budget, so you'll certainly want to keep that in mind as you survey the market.
#4. Survey the market. You probably already have an idea of the "big" players in the market, but even if you didn't, simply typing the query "flow cytometer" in your browser brings up 9 different instrument manufacturers within the first two pages of a Google search. You can follow these links, collecting information on the various instruments. For something like this, I like to use an electronic note taking application like Evernote to keep everything together, and make notes as I go through the process. For those web sites where information and materials are not easily accessible, sending an email to a local sales representative will get you all the marketing materials you could ever ask for.
#5. Learn how to read marketing materials. Speaking of marketing materials, there are a few things you should be aware of. Beyond the very basics (lasers available, number of detectors, etc...), much of what you see in your average cytometer specification sheet is useless information. It's basically a list of values for meaningless metrics that MUST be put into the materials to match what the competition is stating. For example, the ever-present detection threshold of FITC and PE. Most all spec sheets will include something like an MESF Detection Threshold of <150 for FITC and <100 for PE. This means absolutely nothing in terms of how well the system will work for your applications let alone how other colors will fair. You'll also see outrageous specifications for event rates, like 100,000 events per second! Lastly, and probably my favorite, is the panel of histograms showing the resolution of multi-intensity hard-dyed beads (e.g. 8-peak Spherotech beads). You can pretty much ignore all this information, and focus on the things that matter. How many lasers? How many detectors? Can you upgrade the system in the field with more lasers/detectors? Is there a multi-well sampler? etc...
#6. Create the matrix. By now, you have a list of needs/wants, and you have a bunch of marketing materials. Put it all together in tabular format.
|Fictitious Instrument Comparison Chart, with the 3 contenders.|
#7. Gain hands-on experience for the top 3 contenders - make sure the OEM knows the fate of the sale hinges on the success of the hands-on demo. Run your battery of tests that matter to you, evaluating the results, as well as ease-of-use, software, UI, hardware. Simply staining your favorite panel of antibodies and running it on the instrument will give you a TON of information as to how these cytometers stack up. Running real samples (not just beads) is an absolute must.
#8. Take to the social network (and take everyone's opinion with a grain of salt). Useful things that can come back from the community include; recurring hardware/software failures, maintenance issues, service issues, responsiveness, etc... For any negative responses that come up, make sure to bring these to the attention of the manufacturer (respecting people's confidentiality, of course) and ask for a response. Get everything in writing. No phone conversations!
#9. Negotiate the purchasing terms with multiple companies. Make sure the sales representative is aware of their competition. Aside from asking for the best possible price, discuss other value added options. For example, an extension of the warranty, free training slots, discounted multi-year service agreement, free shipping, free upgrades (higher powered lasers, multiwell samplers, extra emission filters, next version of software). Get everything in writing, no phone conversations (did I mention that already)!
#10. Take advantage of year-end discounts. If possible, time your negotiations and purchase with the end of the company's fiscal year. You'd be surprised what sort of deal you can get if the company is close to reaching their target for the year.
BONUS Tip: Don't be afraid of venturing away from the "big companies." When dealing with newer companies and newer technologies, getting cutting-edge hardware can be a double-edged sword. Although you may be able to get a deal on price, make sure there are some protections in place that allow you to get future upgrades or revisions to problematic hardware for free. At the very least, you should be able to get a percentage of your money back if it's a total failure. Again, get it in writing up front.
So there you have it. I think if you keep these common sense tips in mind when purchasing your next cytometer you won't be disappointed. Got any other tips that have helped you make the right purchasing decision? Why not leave a comment below.