Truncated wash procedure

Under mass production conditions, all hair samples are washed in an identical manner by the truncated wash procedure. This consists of one 15-min wash with dry isopropanol and three 1/2-h washes with phosphate buffer. Not aU hair samples will have reached plateau conditions by this procedure. To identify those samples which require further washing, we have defined two additional wash kinetic criteria " the curvature ratio, R, and the extended wash ratio, R w These are defined as follows ... 

Rew and R ratios were used in conjunction with the truncated safety zone ratio, Rj z, to describe the results obtained with populations of known drug users. The percentage distributions of values for these wash kinetic parameters are given in Tables 2, 3, and 4. Based on the data from these populations of known drug users and the wash kinetic values obtained with artificially contaminated hair, the following cutoff levels were set for the truncated wash procedure R< = 1.3, Rew = 10/ Rtsz = 0.33. Samples are judged to be contaminated if any one of the three wash kinetic parameters falls below its cutoff value. 

Percentage Distribution of Extended Wash Ratio Values Using the Truncated Wash Procedure... 

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