Development of an Efficient and Sensitive Magnetic Dispersive Solid-phase Extraction Technique for Preconcentration of Amphetamine and Methamphetamine Determined by High-performance Liquid Chromatography and Liquid Chromatography-Tandem Mass Spectrometry in Sports Supplements

Sports and weight control supplements are tempting targets for adulteration. Amphetamines have been mainly prescribed as weight-loss drugs in the past decades. Amphetamines are also abused by athletes to improve their performance. To ensure the content of sports supplements, we propose a simple and straightforward magnetic dispersive solid-phase extraction method to extract amphetamine (AM) and methamphetamine (MET) from sports supplements. A few milligrams of magnetic graphene oxide (GO@Fe3O4) were added to the sample solution for microextraction assisted by shaking. Due to the benefit of dispersion and the high mass transfer rate of the sub-microscale adsorbent, the extraction equilibrium was achieved in a very short time (3 min). Moreover, thanks to the magnetic properties of adsorbent, the separation of the adsorbent from sample solution was easily achieved by an external magnetic field, which therefore simplified the sample pretreatment procedure. A high-performance liquid chromatography-ultraviolet (HPLC-UV) method with precision and accuracy better than 10% was proposed to detect AM and MET in the range of 300-1500 ng ml-1 and 500-2000 ng ml-1, respectively. As a confirmatory analysis of determined AM and MET, an ion-spray LC-MS/MS method using multiple reaction monitoring (MRM) mode was applied. The LC-MS/MS method was linear in the range of 5-100 ng ml-1 and 1-200 ng ml-1 for AM and MET, respectively. Sixteen sports supplements; were scanned using the proposed method and AM and MET were confirmed in four out of sixteen samples.