Off-line automated sample preparation--experience in a clinical drug investigation unit

The authors describe an evaluation of the Du Pont Prep. off-line automatic centrifugal sample processing system, used in the authors' Drug Investigation Unit over the past two years. In comparison to liquid-liquid extraction, the authors found that assay precision has generally been improved, absolute recovery was quantitative, reliability has been good and the use of the system has resulted in notable labour saving. However, the cost per test based on a seven-year amortization of capital cost shows that the system is more expensive. Assays for urinary opiates, serum tricyclic antidepressants, serum isoxicam, serum valproate, serum metoclopramide and serum pindolol are presented and the merits of the method are compared with those for manual liquid-liquid extraction procedures.