or thermal stress. The water evaporates and low-volatile compounds like drugs of abuse remain on the skin for a limited time. Sweat samples can be taken from various parts of the body surface. The forehead is a compromise among excretion characteristics, accessibility, and contamination risk. In earlier studies, Drugwipe was used to collect sweat from the armpit, but this sampling location has operational disadvantages.
A laptop-/palmtop-controlled reader is available for recording of the Drugwipe result in an electronic format. Figure 4 is a picture of the reader, which is marketed under the brand name DrugRead® (Securetec). DrugRead is advantageous under poor light conditions or when the Drugwipe result must be obtained independent of a visual interpretation. A further benefit is that all test data are stored on a hard disk and can be further processed (e.g., mathematically interpreted) or printed. Calibration curves for the different target drugs can be implemented and used to correlate the Drugwipe signal with certain drug quantities. An example for a correlation curve is given in Fig. 5.
The individual points in the calibration curve are mean values of 10 single measurements. Drugwipe starts to show positive signals between 20 and 30 ng of A-9-THC per mL of saliva.
2. Drugwipe as a Saliva Test
2.1. Roadside Drug Testing Assessment (ROSITA II): Confirmation of the Drugwipe Cut-Off Values (2,3)
In 2003, the Office of National Drug Control Policy (ONDCP) and the National Highway Traffic Safety Administration (NHTSA) sponsored an initial comparative laboratory evaluation of eight commercially available oral-fluid testing devices. Under supervision of the Walsh Group (TWG), the Center for Human Toxicology (CHT) of the University of Utah conducted the analytical evaluation at their laboratories in Salt Lake City, UT.
Human oral fluid was collected from drug-free individuals, pooled, and purified by freezing, thawing, and centrifugation. Standard solutions were prepared through the addition of known amounts of drugs to the purified saliva. The fortified solutions were assayed by gas chromatography (GC)-mass spec-trometry (MS) or liquid chromatography (LC)-MS for the quantitative levels of spiked drugs. Drug-free saliva was used as negative control.
In the case of Drugwipe, 10 ^L of each drug-saliva solution was added to the wiping fleece and the test was performed as described in the instructions for use (4). The negative control experiments were repeated five times, and spiked
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