ISO/TS 21310:2025
(Main)Traditional Chinese medicine — Microscopic examination of medicinal herbs
Traditional Chinese medicine — Microscopic examination of medicinal herbs
This document specifies the methods for microscopic examination of medicinal herbs. It covers the equipment, sampling, preparation and observation methods. This document is applicable to medicinal herbs used in traditional Chinese medicine, including Chinese materia medica (whole medicinal materials) and decoction pieces derived from plants. It is not applicable to medicinal materials derived from animals or minerals.
Médecine traditionnelle chinoise — Examen microscopique des herbes médicinales
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Technical
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ISO/TS 21310
Second edition
Traditional Chinese medicine —
2025-06
Microscopic examination of
medicinal herbs
Médecine traditionnelle chinoise — Examen microscopique des
herbes médicinales
Reference number
© ISO 2025
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ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Sampling . 2
5 Apparatus . 2
6 Preparation for microscopic examination . 2
6.1 Cross-section or longitudinal-section slides .2
6.2 Powder slides .2
6.3 Mounting and swelling agents .3
7 Observation of components . 3
8 Test report . 3
Annex A (informative) Preparation methods for microscopy. 4
Bibliography .10
iii
Foreword
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This document was prepared by Technical Committee ISO/TC 249, Traditional medicine, Subcommittee SC 1,
Traditional Chinese medicine.
This second edition cancels and replaces the first edition (ISO/TS 21310:2020), which has been technically
revised.
The main changes are as follows:
— the sampling method has been revised to refer to ISO 23723;
— improvements in sentence expressions and corrections of typographical errors.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
Technical Specification ISO/TS 21310:2025(en)
Traditional Chinese medicine — Microscopic examination of
medicinal herbs
1 Scope
This document specifies the methods for microscopic examination of medicinal herbs. It covers the
equipment, sampling, preparation and observation methods. This document is applicable to medicinal herbs
used in traditional Chinese medicine, including Chinese materia medica (whole medicinal materials) and
decoction pieces derived from plants. It is not applicable to medicinal materials derived from animals or
minerals.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 23723, Traditional Chinese medicine — General requirements for herbal raw material and materia medica
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
microscopic examination
examination of a test specimen by microscope with a magnification of generally ×50 to ×500
[SOURCE: ISO 17639:2022, 3.2, modified — “with or without etching” was removed from the definition.]
3.2
medicinal herbs
raw materials derived from various parts of plants for drugs used in herbal medicine
Note 1 to entry: Herbal medicine includes traditional Chinese medicine, Korean medicine and Kampo.
3.3
slide
flat rectangular plate of glass on which an object is mounted for microscopic examination
[SOURCE: ISO 10934:2020, 3.1.134, modified — Note 1 to entry was removed.]
3.4
cover glass
rectangular or circular piece of thin glass used to cover a microscopical preparation
[SOURCE: ISO 10934:2020, 3.1.34, modified — Note 1 to entry was removed.]
3.5
micrometer
device for measuring small lengths
[SOURCE: ISO 10934:2020, 3.1.96]
4 Sampling
The sampling method specified in ISO 23723 shall apply. After that, select a representative sample of the
material. If necessary, the samples should be preserved in airtight containers.
5 Apparatus
Use the usual laboratory apparatus and, in particular, the following.
5.1 Optical microscope or slide scanner.
5.2 Optical or in-software micrometer.
5.3 Imaging devices such as drawing attachments, embedded camera or digital imaging sensor for the
microscope.
5.4 Slides and cover glasses.
5.5 Botanical dissecting instruments such as tweezers, surgical knife, razor blade, microtome.
6 Preparation for microscopic examination
6.1 Cross-section or longitudinal-section slides
a) According to the sample condition, moisturizing, fixation or maceration process can be added. See
Clauses A.1 to A.3 for additional information.
b) Select representative pieces of the material being examined and cut into suitable lengths.
c) After softening, cut the material with a razor blade or a microtome to a thickness of 10 μm to 20 μm
generally.
d) Place a section on a slide glass, add two or three drops of a mounting agent or chloral hydrate solution
and place a cover glass over it, taking precautions against the inclusion of bubbles.
e) Embed the material in hard paraffin for cutting, if necessary. See Clause A.4.
6.2 Powder slides
a) Place approximately 1 mg of powdered sample in a watch glass containing two or three drops of a
swelling agent or chloral hydrate solution, stir well with a small rod to prevent the inclusion of bubbles
and allow to stand for more than 10 min to swell the sample.
b) Using a small glass rod, smear the slide glass with a small amount of the swollen sample, add one drop
of the mounting agent and place a cover glass on it so that the tissue sections spread evenly without
overlap, taking precautions against the inclusion of bubbles.
6.3 Mounting and swelling agents
Mounting and swelling agents may be made of a mixture of glycerine and water (1:1) or a mixture of
glycerine, 95 % ethanol and water (1:1:1). Other agents which have characteristics of mounting and swelling
agents can be used.
7 Observation of components
Observation can be conducted in the order of the outer portion, inner portion and cell contents. In case of a
powdered sample, observation can be made in the order of characteristic component, matter present in large
amounts, rarely existing matter and cell contents. For histochemical detection of the sample, see Clause A.6.
8 Test report
The test report shall include the following information:
a) all information necessary for the complete identification of the sample;
b) the sampling method used;
c) the test method used, with reference to this document, i.e. ISO/TS 21310:2025;
d) the test result(s) obtained;
e) all operating details not specified in this document, or regarded as optional, together with details of any
incidents which can have influenced the test result(s);
f) any unusual features (anomalies) observed during the test;
g) the date of the test.
Annex A
(informative)
Preparation methods for microscopy
A.1 Moisturizing
Dried parts of a plant can require softening before preparation for microscopy, preferably by soaking in
water. Use a desiccator for larger quantities of material, placing water into the lower part instead of the
drying agent.
Bark, wood and other dense and hard materials should be soaked in water or in equal parts of water, ethanol
and glycerol for a few hours or overnight until they are soft enough to be cut. Boiling in water for a few
minutes can sometimes be necessary.
Any water-soluble contents can be removed from the cells by soaking in water. Starch grains can be
gelatinized by heating in water. In certain cases, material can be moistened with water for a few minutes to
soften the surfaces and allow sections to be cut.
A.2 Fixation
Fixation is the process of preserving the tissue by placing the tissue in fixatives. The permeation of fixatives
into the tissue can be dependent upon the size of the sample. Before fixation, it is recommended that samples
be cut smaller than 6 mm ⨯ 6 mm ⨯ 6 mm.
The following water solutions are used as fixatives:
— ethanol: 50 % to 70 %;
— formalin: under 5 %;
— acetic acid: approximately 100 %;
— chromic acid: approximately 1 %;
— F.A.A. solution: formalin 5 ml, acetic acid 5 ml, 50 % to 70 % ethanol 90 ml;
— Craf III solution: 1 % chromic acid 30 ml, 10 % acetic acid 20 ml, formalin 10 ml, water 40 ml.
A.3 Maceration
A.3.1 General
For maceration, cut or slice the sample into small pieces approximately 2 mm in thickness. Depending on the
feature of the material, one of the following three methods can be used. For medicinal herb samples with
only a few or scattered woody tissues or with parenchyma tissues, use the potassium hydroxide method. For
hard materials mainly composed of woody tissues or woody tissues grouped into bundles, use the chromic-
nitric acid or the potassium chlorate method.
A.3.2 Potassium hydroxide method
Place the sample in a test tube, add an adequate quantity of aqueous potassium hydroxide solution (a volume
fraction of 5 %), then heat until the residue can be easily separated when pressed with a glass rod. Decant
the alkaline solution and wash the residue with water. Transfer a small amount of mac
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