The commonly used sample preparation methods are tablet method and slice method. The conventional sample should be dehydrated. If the sample does not meet the abovementioned conditions, please refer to the relevant literature for specific preparation.

i. Tablet method. Suitable for powder and other samples, using analytical balance to weigh solid powder sample and potassium bromide powder respectively, the mass ratio of the two is 1:150. After drying the potassium bromide powder under an infrared lamp, use an agate mortar to carefully mix and grind, requiring that the size of the grinding particle is less than 2.5 μm, otherwise it will cause the scattering of mid-infrared light, resulting in the tilt of the baseline.

ii. Slice method. Conventional sample sections can be frozen or paraffin sections, the thickness is recommended to be 2~20 microns, the sections should be placed on the infrared light transmittance substrate (such as barium fluoride, calcium fluoride) in the transmission microscopy experiment, while the sections should be placed on the Low-E substrate in the reflection microscopy experiment. Barium fluoride substrate can be customized according to needs, e.g. a round substrate with a diameter of 30 mm or a square one around 25 mm, with thickness of 1 mm, and double-sided polished.