Читать книгу Fundamentals of Analytical Toxicology - Robin Whelpton - Страница 60

Sweat production is not uniform in either amount, or composition. ‘Insensible sweat’ is moisture that is lost from the body through the skin and does not form droplets. ‘Sensible sweat’, i.e. sweat that can be seen as liquid, arises from two types of gland, apocrine and eccrine. The former, which tend to be located in the axillae, pubic, and mammary areas, are larger and secrete a thicker substance. The surface of the skin is also covered with sebaceous secretions, chiefly lipids, higher concentrations being found on the scalp and forehead. Thus, the fluid collected for analysis by patches applied to the skin is generally a mixture of secretions and can only give an indication of drug exposure over the period when the device was attached to the skin.

Collection of sweat has been suggested as a means of testing for misused drugs. Surface contamination by exposure to drug use by others (e.g. smoking either cocaine, or cannabis) is a potential problem when analysing sweat. There are two methods of collecting and testing sweat. One is the Drugwipe, which may also be used with oral fluid, and has found use for roadside testing (Section 17.3.2.1). The other is a tamper-proof ‘sticking-plaster’ that may be used to collect sweat over several days and is generally used in detoxification clinics and US prisons. The patches are not amenable to point-of-contact testing (POCT).