Cleaning beads for bead mill

Safety glasses and gloves should be worn through this whole process. Diluted HCL is used to wash the beads, so care must be taken to avoid contact with skin or eyes. Make sure the spill kit is nearby BEFORE STARTING this protocol. The spill kit should have a neutralizing solution for spills of acids. If you spill any acid make sure to clean it up, we do not want dried acid on counters or inside of the hoods.

Beads should be in a small bottle labeled “dirty beads”. They may be soaking in ethanol.

1. First wash the beads lightly in pure water or ethanol to get the big chunks of plant matter off. If using water, then waste can go in the sink. If using ethanol, then put waste in an appropriate waste container for organic solvents. Place the beads into a clean container, or if your current container looks clean enough continue to next step. There should be no visible chunks of plant material present before moving to the next step.

2. Soak beads in diluted HCL. 0.4 M or 0.5 M is a good concentration, though a bit higher concentration is fine as well. Diluted HCL is stored under the fume hoods and should be labeled with the molarity (the big M symbol that was just used stands for molarity). Just use enough diluted HCL to cover the beads, no reason to use too much. If more diluted HCL needs to be made, then you can find HCL underneath the fume hoods with other acids.

3. Agitate beads in HCL for at least one minute. You can simply swish the beads around in the bottle.

4. Dump the HCL into the HCL waste bottle. This is a glass bottle that should be stored under the hood with other acids and is clearly labeled. Be careful not to dump the beads into the waste. It is ok if there is a little HCL residue left in the bottle with the beads.

5. Place pure water or ethanol on the beads and agitate. Pour off this waste. If using water, then this can go in the sink. If ethanol is used, then put into appropriate waste receptacle. If, for some reason, there was a lot of acid left in the bottle (there should not have been) then consider dumping waste into the acid waste.

6. If you are in a hurry to get dry beads, then you can rinse with acetone. Otherwise, dump beads into a clean dry receptacle. Weigh boats work well, so do petri dishes or clean, dry bottles. Let dry under a cleaned laminar flow hood if doing microbial work, otherwise let air dry on the counter. For non-critical work, can press dry with a chem-wipe

7. Beads can then go in a clean plastic bag or bottle for reuse. I try to pick out any beads that have broken and throw them away. Sometimes the beads will crack in half, though this normally takes awhile. If beads are very pitted or rusty consider not using them and adding them to a stash of beads for less critical uses. Make sure the receptacle is clean and load beads into it under the hood, if doing critical microbiome work.