Microwave-assisted extraction and differential scanning calorimetry in the chemical identification of sliming agents apprehended in the south region of Brazil

Abstract

Over the past decades, consume of slimming agents considerably increased in several countries, including Brazil, due to weight-loss and stimulant properties. Since these drugs are controlled to prevent illicit and indiscriminate use, there is a parallel illegal market that uses the Internet and irregular pharmacies in order to distribute these formulations. Slimming agents produced by these illegal sources are known for being manufactured with little or none quality control resulting in uncertain and unknown formulations. For forensic purposes, apprehended pharmaceuticals have to undergo a process of chemical identification that can be difficult due to its complex matrix. In this sense, application of assisted energies in the extraction step such as microwave irradiation can be a promising method to increase the recuperation of the target molecules of the sample. Therefore, the aim of this research was to identify four slimming agents apprehended in Brazil by means of visual inspection, Fourier Transform Infrared Spectroscopy, Differential Scanning Calorimetry and Gas Chromatography – Mass Spectrometry. Moreover, the efficiency of solid-liquid extraction and microwave-assisted extraction was compared. It should be noted that our work was one of the few to use Differential Scanning Calorimetry and the application of microwave irradiation in the analysis of apprehended materials. Results showed that the majority of the samples was counterfeit being composed of one or several adulterants or contaminants. Initially, visual inspection resourcefully screened the slimming agents for possible signs of falsification, however it failed to detect fraudulent products that were very similar to veridical medicines. Sequentially, Fourier Transform Infrared Spectroscopy detected functional groups present in the samples while the presence or absence of the alleged active ingredients were successfully measured with Differential Scanning Calorimetry and, thus, providing a full chemical screening of the apprehended materials. Gas Chromatography- Mass Spectrometry confirmed the presence of adulterants such as caffeine, fluoxetine and phenolphthalein as well as contaminants such as sulfurol in the falsified samples. Finally, comparison of extraction procedures indicated that microwave-assisted extraction increased the recovery of compounds detected in chromatographic analysis to a greater extent than solid-liquid extraction.