Identification and analytical characterization of nine synthetic cathinone derivatives N‐ethylhexedrone, 4‐Cl‐pentedrone, 4‐Cl‐α‐EAPP, propylone, N‐ethylnorpentylone, 6‐MeO‐bk‐MDMA, α‐PiHP, 4‐Cl‐α‐PHP, and 4‐F‐α‐PHP