Erratum to: Forensic Toxicol (2015) 33:195–201 DOI 10.1007/s11419-015-0271-z

Unfortunately, there was a mistake in Fig. 1 (the position of the dimethylamine residue of AH-7921). The correct Fig. 1 is placed below.

Fig. 1
figure 1

Chemical structures of AH-7921, fentanyl, doxylamine and phencyclidine