Extended 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 ... 

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

In a recent review. Blank and KidweU have questioned the adequacy of the wash procedures used in various hair analysis laboratories. In their review they also extended their earlier criticism23-24 of our wash kinetic approach. 

Correct sample preparation ensures efficient binding and extends the life of a column. Removal of contaminants which may bind non-specifically to the column, such as lipids, is crucial. Stringent washing procedures may damage the ligand of an affinity medium, destroying the binding capacity of the column. Samples must be free from particulate matter (see Chapter 8 for details of sample clarification procedures). 

The resin thus obtained was subjected to two more entire 24-h coupling and washing procedures as described above. The third and final washing sequence was extended as follows ... 

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