ASTM D8493-23

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D8493 − 23
Standard Guide for
Sample Preparation of Cannabis and Hemp Inflorescence
for Laboratory Analysis
This standard is issued under the fixed designation D8493; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 In this guide, the basic steps in obtaining a test portion
D1193 Specification for Reagent Water
sample of either dried cannabis/hemp inflorescence are out-
D8197 Specification for Maintaining Acceptable Water Ac-
lined.
tivity (a ) Range (0.55 to 0.65) for Dry Cannabis Flower
w
1.2 Sample preparation depends on many factors including
Intended for Human/Animal Use
moisture (dryness) of the sample, the analyte to be measured,
D8270 Terminology Relating to Cannabis
the concentrations/amounts, and the test method’s precision D8282 Practice for Laboratory Test Method Validation and
and accuracy requirements. In this case, dried cannabis or Method Development
D8334/D8334M Practice for Sampling of Cannabis/Hemp
hemp plant material require particle size reduction-
Post-Harvest Batches for Laboratory Analyses
comminution from a representative sample of which the final
E11 Specification for Woven Wire Test Sieve Cloth and Test
analytical testing portion is determined by the employed testing
Sieves
method. Local regulatory guidelines often dictate both the
2.2 Other Standards:
representative sample that is taken from the bulk material
ASTA Analytical Methods, Preparation of Samples, Method
(harvest batch) and the final mass of the test portion (for
example <1 g) for chemical analyses.
FDA Guide to Inspections Validation of Cleaning Processes
1.3 This guide will not purport to meet every local and state
3. Terminology
jurisdiction since different regulatory requirements vary; the
local/state requirements are at the discretion of the user to
3.1 Definitions:
follow and interpret.
3.2 General definitions are in accordance with Terminology
D8270 unless otherwise indicated.
1.4 Units—The values stated in SI units are to be regarded
3.3 Definitions of Terms Specific to This Standard:
as the standard. No other units of measurement are included in
3.3.1 analytical sample, n—prepared from the laboratory
this standard.
sample; the material from which the test portion is selected.
1.5 This standard does not purport to address all of the
3.3.2 ball mills, n—ball mills pulverize by impact using
safety concerns, if any, associated with its use. It is the
hard balls inside an enclosed grinding jar, sample containers
responsibility of the user of this standard to establish appro-
such as falcon tube (centrifuge tubes-high-clarity
priate safety, health, and environmental practices and deter-
polypropylene), or a bowl with a secure lid.
mine the applicability of regulatory limitations prior to use.
3.3.2.1 Discussion—Types of ball mills include drum ball
1.6 This international standard was developed in accor-
mills, jet mills, bead-mills, horizontal rotary ball mills, vibra-
dance with internationally recognized principles on standard-
tion ball mills, planetary ball mills. Feed material: soft, hard,
ization established in the Decision on Principles for the
brittle, fibrous (dry or wet); material feed size: <8 mm to 10
Development of International Standards, Guides and Recom-
mm. Also referred to as an impact mill and rod, jar, or pebble
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
This test method is under the jurisdiction of ASTM Committee D37 on the ASTM website.
Cannabis and is the direct responsibility of Subcommittee D37.03 on Laboratory. Available from the American Spice Trade Association (ASTA), 1101 17th St.
Current edition approved Jan. 15, 2023. Published February 2023. DOI: NW, Suite 700, Washington, DC 20036, www.astaspice.org.
10.1520/D8493-23. Available from the U.S. Food & Drug Administration, www.FDA.gov.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D8493 − 23
mills. Use high-energy impact and frictional forces created by particle size reduction by cryogenic milling on a laboratory
oscillating, rotational, and/or three-dimensional (3D) move- scale results in a higher surface area quickly homogenizing
ment of vessels containing both the sample and one or more samples into a fine powder.
impactors. Material is placed in a bowl (or jar) with grinding
3.3.9 cutting/shearing mills, n—use blades or rotors to shear
balls and rotated. Throughput and milling efficiency can be
or cut the material and cutting mills can be subcategorized by:
affected by the sizes and shapes of grinding jars; the rotation
(1) rotating blades and stationary blades or (2) rotating blades
speeds (r/min); the cycle time; and the number, weight, and
and either a sieve screen or an abrasive grinding ring.
size of balls added to the grinding jar.
3.3.9.1 Discussion—Size reduction in cutting mills is af-
3.3.3 blenders, n—use fixed blades rotating at high speeds
fected by cutting and shearing forces. The sample passes
inside a container to comminute materials and can be classified
through the hopper into the grinding chamber where it is seized
into two types: stationary and immersion.
by the rotor and is comminuted between the rotor blades and
3.3.3.1 Discussion—Devices labeled “blenders” or “homog-
the stationary cutting bars inserted in the housing.
enizers” usually include blades that are capable of high-speed
3.3.10 decision unit, n—material from which a primary
movement but are small relative to the total volume of the
sample is collected and to which an inference is made.
container. The container (“blender jar”) is designed to propel
3.3.11 distribution heterogeneity, n—refers to the differ-
the material being mixed into a vortex so that it repeatedly
ences in how the pieces (fragments, particles, or molecules) are
comes into contact with the blades.
distributed spatially, that is, how well mixed or segregated the
3.3.4 bulk, n—large sample that is representative of the lot
material is due to density, particle size, or other factors.
and is prepared in some way (ground up, mixed, and so forth)
3.3.12 food processor, n—similar to a blender, with the
to form the laboratory sample.
exception that blades and disks (attachments) are interchange-
3.3.4.1 Discussion—Bulk material or gross sample or both
able.
aggregation of two or more increments taken from a lot. The
3.3.12.1 Discussion—Modern food processors, in commer-
portions may be either combined (composited or bulked
cial sizes, are also capable of chopping commodities into
sample) or kept separate (gross sample). If combined and
sufficiently fine pieces to provide homogeneity. Commercial-
mixed to homogeneity, it is a blended bulk sample.
size food processors are smaller than the 20 qt cutter-mixers,
3.3.5 cannabis inflorescence, n—fruiting tops of a cannabis
processing of several batches, followed by thorough mixing,
plant (excluding the seeds and leaves when not accompanied
may be necessary.
by the tops) from which the resin has not been extracted by
3.3.13 fundamental error, FE/fundamental sampling error,
whatever name they may be designated by the authority having
jurisdiction (AHJ). FSE, n—error that results from compositional heterogeneity.
3.3.6 comminution, n—reduction of solid material particle
3.3.13.1 Discussion—FSE random error is caused by com-
size by fracture via grinding, milling, or similar processes.
putational heterogeneity (CH) and controlled through the
selection of an adequate mass.
3.3.6.1 Discussion—Such mechanical methods are aimed at
3.3.14 fundamental sample size (sample mass), n—mass of
increasing the accessible surface area.
the sample intended to represent the entire population some-
3.3.7 compositional heterogeneity, n—arising from differing
times termed the composite sample.
composition among individual elements (that is, particles) in a
decision unit.
3.3.14.1 Discussion—Number of samples taken with a mass
3.3.8 cryogenic milling, n—mechanical milling process (of-
sufficient to evaluate, compare, or provide independently
ten of the impact type) in which temperature-sensitive samples
confidence to ensure reproducibility of the composite or the
and samples with volatile components are milled in a cryogen
uniformity of the population.
[liquid nitrogen (LN ), liquid carbon dioxide (CO ) dry ice-
2 2 3.3.15 homogenous, adj—ingredients appear in the same
solidified carbon dioxide].
proportions in any sample taken at any point of a mixture.
3.3.16 increment, n—randomly chosen portion from the
3.3.8.1 Discussion—Cryogenic milling takes advantage of
both cryogenic temperatures and conventional mechanical bulk material from which the primary sample is assembled.
milling. Cryogenic or cold grinding involves grinding aids
3.3.16.1 Discussion—An increment is a correctly
such as dry ice and liquid CO (–78 °C) or liquid nitrogen
delineated, materialized unit of the lot that, when combined
(–196 °C) that are capable of embrittling the sample by cooling
with other increments, provides a multi-increment sample and
and making it break more easily. Low-temperature freezing
a group of elements collected by a single operation of a
also promotes the formation of much smaller ice crystals,
sampling device and combined with other increments to form
which causes less damage to a plant’s cellular structure. In
a sample. For some finite element materials, an increment may
addition, the lower temperature of dry ice or liquid nitrogen or
consist of a single element.
both significantly lowers the high vapor pressure of the
3.3.17 knife mill, n—laboratory purpose design similar to
components and embrittles the sample matrix in which the
food processors designed with more matrix-tolerant materials.
volatile components (that is, terpenes and pesticide residues)
are not largely affected by the relative temperature increase that 3.3.18 laboratory sample, n—original test sample as re-
occurs during the mechanical grinding process. The extensive ceived by the laboratory.
D8493 − 23
3.3.18.1 Discussion—When the laboratory sample is further forming quartering in which the withdrawn portion remains as
prepared (reduced) by subdividing, quartering, mixing, representative as possible.
grinding, or by combinations of these operations, the result is
3.3.26.1 Discussion—Also known as the analytical portion.
the test sample. When no preparation of the laboratory sample
The part of the sample that is actually tested by the laboratory.
is required, the laboratory sample is the test sample. A test
3.3.27 theory of sampling, TOS, n—sampling errors includ-
portion is removed from the test sample for the performance of
ing incorrect sampling errors (ISEs) not included in the
the test or analysis.
measurement uncertainty framework.
3.3.19 mass reduction, n—subdivision of the bulk material
to obtain a sample size suitable for analysis.
3.3.27.1 Discussion—TOS deals comprehensively with
sampling, defines representativity, defines material
3.3.20 measurement uncertainty, n—parameter, associated
heterogeneity, and furthers all practical approaches needed in
with the result of a measurement, that characterizes the
achieving the required representative test portion.
dispersion of the values that could reasonably be attributed to
the measurand.
4. Summary of Guide
3.3.21 mortar and pestle, n—used to grind up solids into a
4.1 The measurement process begins with a primary lot
fine powder and crush solids into smaller pieces.
(decision unit) that is typically characterized by extensive
3.3.21.1 Discussion—The mortar’s interior if unglazed is
material heterogeneity and is the main source of all sampling
more effective for grinding. The substance is ground between
errors, a concept that is fully defined by the theory of sampling
the pestle and mortar by rubbing or pounding the substance
(TOS) as shown in Fig. 1. The following relationships are also
with the pestle against the wall of the mortar, which creates a
defined in TOS: error to mass, error to increments, and error to
fine powder. Friction and pressure grinding is the impact of two
sample correctness, with the ultimate goal of mitigating and
hard surfaces, “mortar grinder.”
estimating the total error in sampling. Heterogeneity contrib-
3.3.22 planetary mills, n—use a two-way planetary action to
utes on all scales from constituent particles to full lot scale and,
comminute rapidly using high impact resulting in a very
thus, securing a representative primary sample is often a
narrow particle size range.
challenging first step. The heterogeneity of a primary lot
material can be split into constitutional or compositional (CH)
3.3.22.1 Discussion—Material to be comminuted is placed
and distributional heterogeneity (DH) or spatial heterogeneity.
in a bowl (or jar) with grinding balls and placed on a rotating
The chemical or physical differences or both between indi-
platform. In planetary action, balls rotate opposite to the
vidual “constituent units” are known as fragments in which
direction of the bowl platform rotation and centrifugal forces
each fragment can exhibit any analyte concentration between
alternately add or subtract.
0 % to 100 %. DH is the irregular spatial distribution of the
3.3.23 primary sample, n—initial or gross sample.
constituents (stratification or layering). The greater the differ-
3.3.23.1 Discussion—The collection of one or more incre-
ence in composition of each fragment CH, the greater the
ments or units initially taken from a population. The portions
possible DH. The random error in the overall selection process
may be combined (composited or bulked sample).
includes: FE or FSE because of the CH and grouping or
3.3.24 representative sample, n—correctly extracted mate- 5
segregation error (GSE) because of DH (1, 2) . Since the CH
rial from the lot or batch, which can only originate from an
of a primary lot increases when the difference between indi-
unbiased, representative sampling process.
vidual fragments increases, only comminution, grinding/
3.3.25 rotor mills, n—multi-toothed blade rotating at high
milling of the material reduces the CH of the primary lot. The
speed (3000 r ⁄min to 28 000 r ⁄min) near an enclosing screen
FE is the minimum error generated when a sample is collected
that combines impact, pressure, friction, cutting, shearing, and
sieving forces to reduce particle size.
3.3.26 test portion/sample, n—quantity of material taken for 5
The boldface numbers in parentheses refer to a list of references at the end of
measurement (from the analytical sample) typically by per- this standard.
FIG. 1 Overview of TOS
D8493 − 23
of a given weight and is influenced by particle size. FE analyzed is only a small fraction of the original material. There
expressed as variance (3): is no definitive particle size that a sample shall have to be
3 homogeneous; however, in practice, sizes of 500 μm has been
c × d
max
s 5 (1)
previously reported, which is also dependent on the extraction
FE
mass
method (6-8).
where:
4.6 Cryogenic milling of other commodities such as food
d = Diameter of the maximum-sized particles (cm),
and feed is well documented. The cooling of samples preserves
m = Mass (in g) of the sample collected (or comminuted),
the sample in its entirety by shrinking the crystal lattice of the
and
solids to be ground. Shrinking can cause “microscopic” crack-
c = Constant (g/cm ) related to compositional characteris-
ing and, in turn, reduce the amount of energy required for
tics that are specific to the nature of the analyte/matrix
fracturing (9). When using cryogenic milling for particle size
in the lot.
reduction of solids-fibrous materials such as cannabis/hemp,
4.2 As shown in Table 1, the FSE is controlled by adequate
particle size reduction occurs in multiple stages starting with
mass selection. The larger the mass, the smaller the variance of
the accumulation of defects or stresses in a concentrated
the FSE.
location, which increases strain and eventual divide of the
4.3 A representative sample (primary sample) is often se-
material into pieces. The most efficient particle size reduction
lected randomly with a set number of increments, which when
system is one that applies the minimum amount of energy to
combined makes up a composite sample. A larger number of
rupture the material without adding excess energy or heat.
increments is more representative but often not practical, as
Low-temperature homogenization, therefore, can prevent the
well the number of increments is often dictated by the local
degradation of volatile analytes and product uniform particle
jurisdiction. Once the primary sample is collected, the labora-
size with decomposition of less stable analytes and improves
tory receives the sample (laboratory sample) and further
retention of volatile components.
processes the “analytical sample” from which the final test
4.7 Consistency in the mean diameter of cryogenically
portion is taken, see Fig. 2 (4, 5). The main goal of the sample
milled samples has been reported for other commodities
comminution process and selection of the final test portion is to
compared to ambient milling. During grinding, the temperature
reduce the FE (sample test portions of smaller particle size) and
of the material may rise to a level in the range of 42 °C to
provide a test portion that accurately represents the original
95 °C dependent on the oil and moisture content of the material
sampled primary lot.
(10). The use of cryogenic grinding with cryogens such as
4.4 Sample processing begins with a sufficient collected
liquid nitrogen (LN ), liquid carbon dioxide (LCO ), and solid
2 2
sample mass before comminution and is further subsampled for
carbon dioxide (CO /dry ice) reduces the loss of volatile
analysis to represent the varying composition of the analytes of
analytes (pesticides, terpenes/terpenoids) (11-14).
interest in the sample. In addition, all pre-analysis sampling
steps (primary sample selection, laboratory mass reduction
4.8 Liquid nitrogen, for example, provides a “refrigerated”
(with subsampling steps), sample splitting, and sample prepa-
environment that prechills the cannabis/hemp inflorescence
ration procedures that lead to the final test portion are the
and maintains a lower temperature by absorbing the heat
primary contributors to the total uncertainty budget, which will
generated during the milling operation. Additionally, a precool-
need to be included to ensure the validity of measurement
ing step is often recommended before feeding the material into
uncertainty estimates as shown in Fig. 3.
the milling equipment, which ensures that the material is at or
below its brittle point. As the liquid nitrogen vaporizes into the
4.5 Particle size reduction is the mechanical process of
gas state, an inert and dry atmosphere is created that addition-
grinding (also referred to as milling, cutting, shearing,
ally protects the milled material preventing further loss of both
granulating, comminuting, and so forth) to obtain particles in a
volatiles and moisture.
material, reduce their average size, reduce the FE, and increase
overall sample surface area as to improve extraction efficiency
4.9 If liquid nitrogen is not available, dry ice can be used to
before sample analysis. Dried plant material requires commi-
improve sample homogeneity and the prevention of labile
nution to reduce the particle size to between 250 μm to
analyte loss such as pesticides. One major disadvantage of
5000 μm (see Table 2). Homogeneity and analytical fineness
using dry ice, particularly for bulk samples, is the need to chop
are often dictated by the analysis method in which the amount
and pre-freeze the cannabis/hemp before the addition of dry ice
or CO fog along with small pieces of the sample that will be
generated in the milling equipment (14). In addition, the CO
TABLE 1 Sample Mass Requirements: Fundamental Sampling
Error Versus Particle Size (4) takes several minutes to sublime after it mixes with the sample,
which adds additional time before a test portion can be taken.
Minimum Mass: Relative Standard Deviation (RSD)
from Laboratory Subsampling
In humid climates, condensation of water may occur on the dry
FSE (expected RSD)
15 % 10 % 5 % 2 % 1 %
ice itself, that is, from the laboratory room air, and reduce the
maximum particle size
purity of dry ice. The addition of water to dry ice can form
0.5 mm 0.06 g 0.13 g 0.5 g 3 g 12.5 g
1 mm 0.4 g 1 g 4 g 25 g 100 g
carbonic acid and change the pH of the sample that may have
2 mm 4 g 8 g 32 g 200 g 400 g
downstream implications on the analytical test method versus
5 mm 56 g 125 g 500 g 3130 g 12 500 g
liquid nitrogen, which is inert.
D8493 − 23
FIG. 2 Sampling Stages to get to the Final Test Portion
FIG. 3 Error Contributions Sampling, Sample Preparation, and Analytical Test Sample
D8493 − 23
TABLE 2 Sieve Sizing Specification E11 TABLE 3 Classification of Milling Equipment
and Description (16, 17)
Sieve No. (U.S Standard Number) Size, μm
A
N/A 5000 (ISO)
Classification of Milling Equipment Description
No. 4 4750
Rotor mills (ultra-centrifugal mills, Rotor mills have a multi-toothed blade
No. 6 3350
cyclone mills, rotor beater mills) rotating at high speed ~3000 r ⁄min to
No. 10 2000
28 000 r/min in close proximity to an
No. 18 1000 enclosing screen that combines
No. 20 850
impact, pressure, friction, cutting,
No. 25 710 shearing, and sieving forces.
No. 30 600
Knife mills Similar to food processors, designed
No. 35 500 with more matrix tolerant materials,
No. 40 425
accessories—different knives, types
No. 45 355 of containers (stainless steel,
No. 50 300 polycarbonate), reduction lid.
No. 60 250 Impactor mills (bead and ball mills, Impact and frictional forces created
mixer mills, and some cryogenic mills by oscillating, rotational 3D movement
A
5 mm sieve is ISO compliant, no Specification E11 equivalent sieve number.
(specialized vessels) and disc mills) of vessels containing both the sample
and impactors.
Cutting mills parallel section rotor Cutting and shearing forces in which
(axe) sixdisc rotor (shredder) V-rotor the sample passes to a hopper into a
4.10 Other sample processing steps may include mechanical
(scissor) grinder chamber where the rotor
pretreatment such as:
“grabs” and further reduces the
particle size between the rotor blades
4.10.1 Two-step communition (primary bulk sample ho-
and stationary cutting bars.
mogenization followed by fine milling of subsample to get to
Blender Kitchen appliance—top of the vessel
a reasonably sized test portion), and
is a cap (sealing) and a bottom
vessel with a fixed blade assembly
4.10.2 Cleaning, drying, grinding, sieving, vortexing, and
where the base sits on a motor,
filtering before instrumental methods of analysis. This ap-
multiple speed capable.
proach extends to chemical methods, for example, digestion,
Food processor Similar to blender, swappable blades
and discs versus fixed blades.
decomposition, extraction approaches, separation, and enrich-
Mortar grinder (mortar and pestle) Mortar grinders force the samples
ment required for a wet chemical procedure.
against two hard surfaces, grinding
the sample by combining pressure
5. Significance and Use
and friction.
5.1 The sample preparation procedure for comminution
impacts other downstream processes such as extraction and
TABLE 4 Common Types of Cryogenic Mills (18)
sonication, which ultimately affects the total analytical error
Type of Mill Feed Size and Notes
(TAE) and measurement uncertainty.
Maximum Feed Amount
Mixer mill <8 mm Sample is placed into
5.2 Factors that may influence the sample preparation pro-
2 × 20 mL stainless-steel grinding
cess include the prevention of cross-contamination (carryover)
jars tightly sealed and
from a prior sample and an inadequate cleaning procedure immersed into liquid
nitrogen before
between preparation of samples, poor sample handling, storage
grinding.
(sample preservation), and moisture content (drying methods)
Cryogenic (cold) mill <8 mm Continuous feed of LN
of plant material being greater than 15 % (15). Samples with 2 x 20 mL (direct connection to
source), user is never
high moisture content are hard to process completely and may
in contact with the LN .
yield lower analyte (that is, cannabinoid) concentration during
Knife mill <40 mm Dry ice embrittlement,
2000 mL use of full metal knife,
extraction and further processing. Lastly, water activity Speci-
stainless-steel grinding
fication D8197 is recommended, activity (aw) range (0.55 to
container and reducing
0.65) for dry cannabis or hemp flower or both.
lid.
Ultra-centrifugal (rotor) <10 mm Embrittlement with dry
5.3 There are many different types of hardware technologies
mill 4000 mL ice or LN . Dry ice is
that address the comminution of dried cannabis or hemp;
preferred if the sample
material is <1 mm or
however, the list of devices is exhaustive and thus beyond the
has low thermal
scope of this guide. See Table 3 and Table 4 (16-18) for a
capacity.
summary of different milling technologies. Distinctions among Cutting mill <80 mm Cryogenic grinding with
4000 mL dry ice or LN . Use of
various pieces of equipment often relate to the type, mass, and
six-disc rotor or cyclone
size/shape of the sample (dry, fibrous) for which each is most
or both mandatory,
effective. In addition, there may be economic reasons for mill including sieves of
2 mm to 20 mm.
selection, that is, the sample throughput of the testing labora-
tory (number of samples per day), access to cryogenics, and
sample mass requirements.
5.4 In addition to sampling devices, this guide does not 5.5 The sample size for comminution purposes is limited as
include the sample preparation of edibles, tinctures, oils/ the analytical testing portion required is often 500 times
concentrates, beverages, and so forth in which the sample smaller than the bulk sample lot and not every testing labora-
diversity poses significant sample preparation challenges to be tory is equipped to handle large sample sizes (that is, greater
put forward in additional work items. than 100 g of dried cannabis inflorescence/hemp).
D8493 − 23
5.6 The particle size is determined by passing the milled 6.2 Milling Apparatus (See Table 3 and Table 4 for Avail-
cannabis/hemp material through standard sieves, for example, able Types of Technologies)—Select a size-appropriate
starting with #18 (1000 μm) for the optimum particle size is stainless-steel blade grinder, blender, ball mill (jars or sample
further determined by extraction efficiency, where <1 mm for container), and ball-type stainless steel; ball size dependent on
cannabis and hemp has been previously reported. sample mass of test portion and capable of size reduction to a
particle size of <1 mm. Often a single type of reduction
5.7 Preparing multiple analytical samples from one commi-
equipment is not adequate to obtain the desired particle size.
nuted primary sample and their parallel analysis gives infor-
6.3 Examples:
mation about the repeatability of the corresponding analytical
6.3.1 Rotary screen several diameters, 20 cm; screens,
process (including sample preparation, injection, and integra-
3.15 mm and 2 mm mesh size; screen deck; lid; centrifugal
tion) and reflects on the homogeneity of the primary sample.
grinder with 0.5 mm to 1 mm sieve insert with rotor and lid
5.8 Moisture removal is critical before any comminution.
(19).
This step can be accomplished by “drying” at various tempera-
6.3.2 Primary or bulk homogenization equipment: knife
tures ranging from freeze drying to ambient room temperature,
mill or vertical cutter mixer, blender or food processor (ex-
as well as vacuum oven drying and forced air oven drying.
changeable blades, fine serrated s-shaped) for use with large
Some of the active compounds in the product are temperature
sample sizes (for example >100 g) up to 2 L volume, and
sensitive, and thus, freeze drying before primary and secondary
stainless-steel container with size-reduction lid capable of
drying steps is expected to be advantageous in reducing quality
cryogenic milling with the addition of dry ice and or liquid
deterioration.
nitrogen directly to sample container. Secondary or fine milling
5.9 Freeze drying is often a fast approach when a vacuum of subsamples can be conducted with a cryogenic freezer mill,
holds the cannabis plant at temperatures below –40 °C, which ball mill, or other size-reduction equipment.
retains the high-quality phytochemicals, for example, volatile 6.3.3 Ball Mill—Polypropylene (PP) centrifuge tubes
compounds (terpenes/terpenoids) and acidic forms of cannabi- (50 mL) or equivalent for aliquoting sample test portion and
noids. In addition, embrittlement is accomplished before com- stainless-steel 11 mm and 9.5 mm balls or similar active
minution by freezing (–80 °C freezer, for example) for a set grinding media. Polyethylene terephthalate (PET) jars (various
time period or by adding cryogen dry ice or liquid gases, such sizes, 5 oz or 12 oz) and screw-top grinding jars ranging from
as liquid nitrogen. 1.5 mL to 50 mL in materials such as hardened steel, stainless-
steel agate, tungsten carbide, zirconium oxide, and polytet-
5.10 Cryogenic milling may be the preferred way of particle
rafluoroethylene (PTFE).
size reduction because of the fact that cannabis/hemp inflores-
6.3.4 Consideration shall be made to minimize contamina-
cence exhibits many material properties that can be challenging
tion of the sample by reducing the formation of metal shavings
(that is, moisture content, oil/resin content, and fibrosity). In
from the grinder blades. If using a blade-type milling
cannabis milling applications, it is common to add liquid
apparatus, may substitute with ceramic, zirconia, plastic grind-
nitrogen directly into the mill to reduce the heat of grinding.
ing
...