Quality control methods for

Preparation of specimens 
 
Powdered materials 
Place 1 or 2 drops of water, glycerol/ethanol TS or chloral hydrate TS on a glass 
slide. Moisten the tip of a needle with water and dip into the powder. Transfer a 
small quantity of the material that adheres to the needle tip into the drop of fluid 
on the slide. Stir thoroughly, but carefully, and apply a cover-glass. Press lightly 
on the cover-glass with the handle of the needle, and remove excess fluid from 
the margin of the cover-glass with a strip of filter-paper. Other fluids may be 
used, if necessary, in the same manner. 
If the specimen is to be freed from air bubbles, boil carefully over a small flame 
of a microburner until the air is completely removed. Care should be taken to 
replace the fluid that evaporates so that the space beneath the cover-glass is 
completely filled with fluid at the conclusion of the operation. 

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Quality control methods for medicinal plant materials 
Surface tissues of leaves and flowers 
To render pieces of thin leaves transparent, boil them directly on a slide. Cut a 
piece of leaf into two portions, turn one piece upper side down and add chloral 
hydrate TS. Boil the specimen carefully over a small flame of a microburner and, 
as soon as bubbles escape, remove the slide from the flame. When the bubbles 
have ceased to appear, boil again until the fragments are transparent. 
For slightly thicker but still papery leaves, cut square pieces, about 6 mm from 
the edge of the leaf, if not otherwise specified. The pieces should be taken one-
third to one-half of the way from the leaf-base and should include a midrib or 
large vein. In addition, cut 1 or 2 pieces from the edge including 1 or 2 
indentations, where appropriate. For broken or cut leaves take suitable 
fragments as described above. Place the fragments in a test-tube containing 
chloral hydrate TS and boil for a few minutes until they become transparent. 
Transfer a fragment to a slide and cut it into two equal portions. Turn one piece 
upper side down and align the two pieces so that both upper and lower surfaces 
can be observed under the microscope. Add 1-2 drops of chloral hydrate TS and 
apply a cover-glass. 
For thicker leaves, that do not become transparent enough when prepared by 
the method described above, clarify fragments by boiling with chloral hydrate 
TS in a test-tube. Transfer a fragment onto a slide, cut it into two equal portions 
and turn one portion upper side down. Scrape the surface of the two portions 
using a scalpel until only a single layer of epidermis remains. Wash the 
epidermis with drops of chloral hydrate TS or glycerol /ethanol TS to remove 
any residues. If possible, turn both parts of the epidermis upper side down, and 
add one of the above fluids. 
For very thick or fleshy leaves, pull off the upper and lower parts of epidermis 
by winding the softened leaf around the index finger, pressing with the thumb 
and the middle finger against the index finger and carefully incising, catching 
the incised part with forceps, and bending the epidermis backwards carefully. 
Petals and sepals of flowers may be treated in a similar manner. 
Sections 
Select representative pieces of the material being examined and cut into suitable 
lengths, one end of which is softened and smoothed. Prepare cross or transverse 
sections by cutting with a razor blade or microtome at a right angle to the 
longitudinal axis of the material. Prepare longitudinal sections by cutting in 
parallel with the longitudinal axis, either in a radial direction (radial section) or 
in a tangential direction (tangential section). 
Thick materials, such as wood, woody stems, rhizomes and roots can be cut by 
holding the softened material between the thumb and index finger, supported 
by the middle finger or by holding it in the central hole of a hand microtome. 
Thin materials such as leaves, petals and slender stems should be bound 
between two halves of a piece of elder-pith or other suitable support. If 
necessary, moisten the surface to be cut and the blade with ethanol (∼375 g/l) 
TS. Cut the sections as thinly and evenly as possible. Transfer the sections with a 

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Quality control methods for medicinal plant materials 
brush moistened with ethanol (∼150g/l) TS to a dish containing ethanol 
(∼150g/l) TS. Select satisfactory sections for the preparation of the slides. For 
certain materials a sliding microtome may be used. 
Seeds and fruits that are very flat, or that are small and spherical, and cannot be 
held in the manner described above may be inserted into a notch cut into a small 
rubber stopper or embedded in hard paraffin (paraffin wax) as follows. Prepare 
a hard paraffin block, rectangular in shape, measuring about 7 x 7 x 15 mm, and 
melt a small hole in the centre of one end using a heated needle or thin glass rod. 
Press the material, which should be dry or softened by exposure to moisture, 
into this hole. Then prepare sections with a microtome. 
For the examination of mucilage, aleurone grains or spherical aggregations of 
inulin, cut the material without using water.