How’s your flower/edible grinding protocol?
As a cannabis testing lab, you know that in order to analyze your sample you first need to get it into a form that you are able to work with. That typically requires grinding or homogenizing, both terms seem to be used interchangeably. I suppose if you’re a coffee drinker you’ll call it grinding. If on the other hand, you come from the food industry, you’ll call it homogenizing.
Get your grind on.
How do you do it? What type of device do you use? One of the issues that you will see me discuss (and repeat) is a lack thus far of any kind of generally-accepted, industry-wide protocol. Not judging; this industry is just starting to get its act together and so it’s to be expected that different labs will approach the grind in their own way.
The range of grinding instruments used in your labs goes from the most basic to the sophisticated. And, the prices go from inexpensive to thousands of dollars.
This particular blog sesh isn’t going to go into specific sample prep protocols…but will in future posts. This post is about what’s used to get the job done.
The good old standby – The Sieve
It’s pretty straightforward: Simply hold your flower or edible and rub it over the screen, catching the ground sample below. Sieves come in various screen/mesh openings from 4 mm to as small as 30 microns. While it may be stating the obvious, this is clearly a labor-intensive approach to grinding.
Moving up in the world – The Magic Bullet (or similar small grinders)
Inexpensive, readily available from many stores ranging from Target to Amazon, this is basically a mini food processor with different speeds. For edibles, it does a better job than a sieve and it’s a machine as opposed to good old-fashioned elbow grease. It uses a rotating cutting unit in the base…typical of food processors or blenders. As with all devices, it must be cleaned between samples….one of the challenges of the whole grinding experience no matter what type of device you use.
Getting a bit more technical, entering the laboratory device space: The GenoGrinder® and/or Freezer/Mill®.
The GenoGrinder from Spex SamplePrep is a widely-used device in the lab and has found acceptance in the cannabis space for grinding/homogenizing samples into a fine powder prior to further sample clean-up work. You’ve now moved up to more sophisticated devices that are programmable. These types of grinders use a metal ball or rod dropped into the sample container which is then shaken vigorously to homogenize the sample.
If low-temperature work is required a Freezer/Mill from SPEX often is as useful as it is able to grind/homogenize samples cooled down to a cryogenic level.
Another homogenizer used in the cannabis industry and gaining much interest is the BeadRuptor® from Omni International.
The BeadRuptor design allows for varying sizes of sample tubes to be used by switching out the rotor that holds them within the unit. As opposed to rods or metal balls that are required to be cleaned and re-used, the BeadRuptor uses small beads (various materials such as ceramic, stainless steel) that are placed within disposable sample tubes (tubes can be purchased from Omni International with the same mass of beads in each tube as opposed to measuring them out yourself). Shown above is the BeadRuptor homogenizer as well as a setup where the BeadRuptor is attached to its optional cooling unit, maintaining an average temperature of 4C within the homogenizing chamber.
A unique approach to grinding using the BeadRuptor is to wet grind. By adding a homogenizing liquid/solvent, it is possible to have your homogenized sample end up as a slurry or suspension. Here is an example of what a brownie looks like after wet grinding in a BeadRuptor with water:
As you can see, this suspension is capable of being pipetted. Such a homogenization protocol allows for pipetting equivalent volumes of ground material as opposed to having to weigh out after grinding. We will cover novel approaches such as this in future blog posts.
In summary, there are various approaches to how you grind/homogenize all with their own unique pros/cons/price points. We look forward to continuing to hear back from you with your own unique solutions for “The Daily Grind!”
Variability: The Achilles Heel of Sample Preparation
In this blog series, we’ll review what’s being done in labs around the country and the world in terms of their sample prep. We’ll review the different instruments, consumables and techniques that are being adopted. We’ll interview different people to get their take on how they minimize variability and maximize throughput while working to keep precision and accuracy within acceptable limits. We’ll talk about what’s new out there to help you achieve the best results possible.