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Mulls

المؤلف:  Sue Jickells , Adam Negrusz (Editors)

المصدر:  Clarkes Analytical Forensic Toxicology

الجزء والصفحة:  p434-435

2026-11-14

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Mulls

Solid compounds are dispersed in a liquid, such as liquid paraffin (Nujol). The finely powdered compound (about 1–10 mg) is mixed with one drop of the liquid and ground in an agate mortar. The test sample must have the constituency of a smooth thin cream. The mull is spread onto an alkali halide plate, usually NaCl or KBr, and another plate is placed on top, taking care to exclude air bubbles. The plates are pressed together strongly. A disadvantage of this method is that the spectrum of the mulling agent is superimposed upon that of the sample. Consequently, liquid paraffin cannot be used if the C-H stretching vibrations are to be examined, and a halogenated liquid, such as ‘Fluorolube’ (a fluorinated hydrocarbon) or hexachlorobutadiene, must be employed.

Although widely used in the past, mulls have been superseded by techniques such as attenuated total reflectance and diffuse reflectance which offer simpler sampling techniques and avoid the need for spectral subtraction.