تسجيل الدخول

تسجيل

Specimen preparation and extraction Homogenisation

المؤلف:  Sue Jickells , Adam Negrusz (Editors)

المصدر:  Clarkes Analytical Forensic Toxicology

الجزء والصفحة:  p200-202

2026-10-12

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Specimen preparation and extraction

Homogenisation

Tissues may be homogenised in water or buffer (e.g. Tris buffer). A dilution of one part tissue plus three parts water is common and gives a homogenate sufficiently thin to be pipetted easily, although some laboratories use one part tissue to nine parts water. Use of an efficient homogeniser, such as those that have a ‘probe’ design that blends, shears and cuts, is preferable. Older-style Waring (food-processor style) blenders or ‘stomachers’ are less efficient. Tissue homogenates may be analysed without further treatment if they have been prepared with an efficient homogeniser and the assay uses a good internal standard. Care should be taken to prevent exposure of the operator to aerosols that might be formed during the homogenisation process. A typical procedure is as follows: weigh 5 g liver or other tissue, and cut into small pieces with scissors or a scalpel. Place the tissue in a suitable tube or small beaker and add 15 mL distilled water. Homogenise the tissue to a uniform consistency. For liver and most other tissues, 1–2 mL can subsequently be extracted directly using the protocol in Figure 1 for basic drugs. The protocol will extract basic drugs but leave behind lipids and sterols such as cholesterol. The protocol described in Figure 2 may be applied for acidic and many neutral drugs. For difficult tissues, e.g. those with a large amount of connective tissue, the enzymatic digestion described below may be useful.

Figure 1 Extraction pathway for strong bases.

Figure 2 Extraction pathway for acids and neutrals.