Table 2.

Stability of targeted compounds in influent wastewater samples stored over a 48 h (^aexpressed as difference in percentage from time-point 0 ± SD).

Analyte	Stabilitya [%]
	Raw (unfiltered) wastewater, pH 7.4, stored at 17 °C		Raw (unfiltered) wastewater, pH 7.4, stored at 4 °C
	12 h	24 h	12 h	24 h
R-(+)-Mephedrone	−23.4 ± 2.7	−29.3 ± 4.7	−9.5 ± 2.7	−10.9 ± 3.5
S-(−)-Mephedrone	−7.1 ± 4.8	−10.2 ± 7.0	−4.0 ± 4.0	−11.9 ± 17.1
R-(+)-Normephedrone	−19.0 ± 13.6	n.a.b	n.a.b	−19.9 ± 25.7
S-(−)-Normephedrone	−6.9 ± 0.0	1.5 ± 5.1	n.a.b	−11.1 ± 1.0

^bDue to lack of reproducibility and stability of normephedrone in wastewater, values could not be established (for further details see Fig. S6).