Wed May 14, 2014 3:00 pm by mleipold
HI Adeeb,
One reason the samples might be OK on flow but not on CyTOF is the fact that your samples are in MilliQ water for CyTOF rather than PBS/FACS buffer. Some people have reported having some issues with increased stickiness in MilliQ.
Unfortunately, there aren't many options.
1. Continue MilliQ washes and resuspension, and deal with stickiness by running Wash solution after every 2 samples or so. This has worked for some people doing whole blood, for instance.
2. Do all your washes in PBS, then do just the resuspension in MilliQ. This was the original CyTOF workflow, several years ago. This may help with your stickiness, as some buffer salts will remain. Unless you have a barium or other heavy-metal contamination in your buffer, the buffer salts won't make it through the quadrupole mass filter and therefore won't be killing your detector because of their high concentration.
-HOWEVER: the buffer salt *will* build up on the cones rather quickly. This won't harm the cones, per se, but *will* cause your Current peak to shift to higher Current over the course of even one day. I've seen the peak optimum/tip move by as much as 2 Current units (unsure whether it's A, or mA...) over one day of runs. So, if you do this, I would recommend re-checking the tuning halfway through your run. Also, the buffer salts will build up on the spray chamber as well: I have attached a picture of this. So, if you don't mind cleaning the cones every morning, this might be something worth trying (you should already be cleaning the spray chamber every day). Note: buffer salts are white: cell debris and most associated heavy metal debris is yellowish/brownish.
Mike
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