Stability of Synthetic Cathinones in Urine

Abstract

In this report, we evaluate the concentration, pH, temperature and analyte-dependent effects on cathinone stability in preserved human urine. A total of 22 synthetic cathinones were evaluated at 100 ng/mL and 1,000 ng/mL in pH 4 and pH 8 urine over 6 months. Specimens were stored at -20°C, 4°C, 20°C and 32°C. The stability of synthetic cathinones was highly dependent on urine pH and storage temperature. Cathinones were considerably more stable in acidic urine (pH 4) at low temperature. In alkaline urine (pH 8) at 32°C, significant losses (>20%) were observed within hours for the majority of drugs. In contrast, all drugs were stable in frozen and refrigerated urine at pH 4 for the duration of the study. These results highlight the importance of sample storage and the potential for pre-analytical changes in concentration during routine shipping and handling of specimens. Significant structural influence was also observed. Cathinones bearing a tertiary amine (pyrrolidine group) were significantly more stable than their secondary amine counterparts. The methylenedioxy group also exerted a significant stabilizing effect on both the tertiary and secondary amines. In the absence of the methylenedioxy group, no significant differences in stability were observed between the unsubstituted and ring substituted secondary amines. Half-lives at ambient temperature in pH 8 urine ranged from 9 h (3-fluoromethcathinone) to 4.3 months (methylenedioxypyrovalerone and 3,4-methylenedioxy-α-pyrrolidinobutiophenone), demonstrating the importance of analyte dependence, and the dual stabilizing effect of both the pyrollidine and methylenedioxy groups. Biological evidence may be subjected to a variety of environmental conditions prior to, and during transport to the forensic laboratory. These findings demonstrate the inherent instability of certain cathinone species in biological evidence under some conditions. Moreover, this study highlights the need for quantitative drug findings in toxicological investigations to be interpreted cautiously, and within the context of specimen storage and integrity.

Stability of synthetic cathinones in clinical and forensic toxicological analysis—Where are we now?

“…A comprehensive and systematic study on the stability of SCs displaying secondary amines (methcathinone, ethcathinone, pentedrone, and buphedrone), secondary amines with ring substituents (3‐FMC, 4‐FMC, methylone, 4‐ethylmethcathinone [4‐EMC], ethylone, methedrone, butylone, mephedrone, eutylone, 4‐MEC, pentylone, and 3,4‐DMMC), and tertiary amines (α‐PVP, MDPBP, 4‐MPBP, MDPV, pyrovalerone, and naphyrone) in whole blood and urine was reported by Glicksberg and Kerrigan 1,12 . Unpreserved whole blood and preserved urine (1% NaF) were assessed under various conditions.…”

“…In clinical and forensic toxicology investigations, instability of analytes under the influence of various conditions may occur in biological samples 1 . The loss of analytes may take place owing to chemical degradation, enzymatic metabolism, or the existence of interfering substances due to matrix degradation, involving (but not limited to) improper sample storage conditions, handling, and/or transportation 2 …”

The Stability of 4‐Chloromethcathinone in Blood and Vitreous Humor

“…They observed a 20% decrease in concentration after 76 days, 19 days, 2 days, and 1 day for 4‐FMC and after 14 days, 4 days, 1 day, and 5.5 h for 3‐FMC (at the respective temperatures of –20°C, +4°C, +20°C, and +32°C). In additional study performed by Glicksberg and Kerrigan (16) on the stability of methanol solution containing 22 cathinones in urine at concentrations of 100 and 1000 ng/mL, the researchers observed a decrease in 4‐FMC concentration by 20% (for the concentration of 1000 ng/mL) after 9 days, 1 day, 6 h, and 4 h at the respective temperatures of –20°C, +4°C, +20°C, and + 32°C (urine pH 8), and after 63 days and 28 days at +20°C and +32°C, respectively (urine pH 4). In urine with pH 8, the concentration of 3‐FMC (1000 ng/mL) decreased by 20% after 5 days (–20°C), <1 day (+4°C), 4 h (+20°C), and 2 h (+32°C); in urine with pH 4, such decrease occurred after 21 days (+20°C) and 9 days (+32°C) (16).…”

“…In additional study performed by Glicksberg and Kerrigan (16) on the stability of methanol solution containing 22 cathinones in urine at concentrations of 100 and 1000 ng/mL, the researchers observed a decrease in 4‐FMC concentration by 20% (for the concentration of 1000 ng/mL) after 9 days, 1 day, 6 h, and 4 h at the respective temperatures of –20°C, +4°C, +20°C, and + 32°C (urine pH 8), and after 63 days and 28 days at +20°C and +32°C, respectively (urine pH 4). In urine with pH 8, the concentration of 3‐FMC (1000 ng/mL) decreased by 20% after 5 days (–20°C), <1 day (+4°C), 4 h (+20°C), and 2 h (+32°C); in urine with pH 4, such decrease occurred after 21 days (+20°C) and 9 days (+32°C) (16). Table 4 shows estimated half‐lives and total degradation times of 4‐FMC and 3‐FMC in biological material based on the obtained results (15,16).…”

Unstability of 4-CMC in human serum specimen

“…Researchers [ 10 , 11 ] also pay attention to the significant effect of pH on the stability of synthetic cathinones. Glicksberg and Kerrigan [ 10 ] showed a high dependence between cathinone stability and urine pH. Synthetic cathinones were more stable in acidic urine (pH 4) in comparison to alkaline urine (pH 8).…”