Disadvantages:
(1) It takes several weeks for newly formed nail matrix to advance.
(2) It cannot be used to evaluate a terminal event.
(3) A drug of abuse may be present or absent but it may be hard to correlate with a plasma level.
Advantages:
(1) It gives a look-back of weeks and months.
(2) It may be available when hair or body fluids are not.
(3) Nails may be better preserved if the body is decomposed.
Procedure of Engelhart et al:
(1) Wash the nail clippings in methanol.
(2) Solubilize the nail in 0.1 M potassium phosphate at pH 5.0.
(3) Isolate the drugs by solid-phase extraction.
(4) Derivatize with N-methyl-N-trimethylsilyl-trifluoroacetamide.
(5) Analyze the extract in a GC-MS in the selective ion monitoring mode.
Drugs that can be detected include:
(1) cocaine and benzoylecgonine
(2) norcocaine and cocaethylene
(3) morphine and 6-monoacetylmorphine (6-MAM)
(4) codeine and hydrocodone
