Enzyme-linked Immunosorbent Assay (ELISA) or Enzyme Multiplied Immunoassay Technique (EMIT) for semiquantitative measurement; and GC/MS or LC/MS for confirmation.
Immunoassays (EMIT, CEDIA, KIMS, ELISA) for cocaine (benzoylecgonine) are quite robust for presumptive analysis. If you need confirmation GC/MS or LC/MS/MS are need.