A screening method for the quantitative determination of selective androgen receptor modulators (SARMs) in capsules by high resolution ¹⁹F- and ¹H-NMR spectroscopy

A new method for rapid determination of the content of selective androgenic receptor modulators (SARMs) andarine, cardarine, ligandrol, ostarine and S-23 in capsules by H-1- and F-19-high resolution nuclear magnetic resonance spectroscopy was described and validated. Specificity, linearity, accuracy, precision, detection and quantification limits were considered as validation parameters. Full H-1-, C-13- and F-19-NMR structural assignment of the SARMs is provided as a tool for self-standing identification without a reference standard. Amounts of 7-15 mg of SARMs/capsule were detected in different products with an intermediate precision of 0.8-1.7% in 4 to 20 minutes of analysis time. The validation results and rapidity of analysis confirm the applicability of the method for large-scale screening. The statistical analysis of the results from F-19- and H-1-quantitative NMR showed that both approaches were equally effective, thus expanding the potential use of the methodology to non-fluorinated SARMs. At present, no SARM has been approved for human consumption; however, SARMs are actually used by bodybuilders and recreational athletes, who purchase them even though the risk-benefit ratio of these molecules has not been definitively established.