A FTIR-BASED METHOD FOR QUALITY ASSESSMENT OF COMERCIAL CREATINE SUPPLEMENTS

Creatine (C₄H₉N₃O, N-(aminoiminomethyl)-N-methylglycine) is a non-proteinogenic amino acid widely used as a dietary supplement due to its well-established benefits in muscular energy metabolism and athletic performance. It acts as a rapid source of ATP by increasing phosphocreatine stores in muscle cells, supporting short bursts of strength. While creatine is especially popular among athletes in explosive sports such as sprinting and weightlifting, its use has expanded to recreational users seeking general health benefits. Despite its proven efficacy and safety, concerns regarding the authenticity and labeling accuracy of commercial creatine products persist, particularly due to past reports of adulteration in dietary supplements. Therefore, the objective of this study was to establish a rapid, affordable and practical analytical workflow to evaluate the authenticity and quality of creatine supplements. This study presents a comprehensive analytical workflow that integrates Fourier-transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) and high-resolution mass spectrometry (HRMS) coupled to chemometric tools to evaluate the authenticity and adulteration of creatine supplements. FTIR-ATR, a non-destructive and rapid technique, was applied to comercial creatine samples spiked with three common adulterants at controlled incremental levels. Spectral data were processed in Python, where descriptive statistics, band–response correlations and Partial Least Squares Regression (PLS Regression) were used to build calibration models for each adulterant individually and jointly. Multivariate analyses, including Principal Component Analysis (PCA) and PLS, were additionally performed to explore spectral variation and classify the creatine samples. The FTIR spectra showed marked differences in the fingerprint region (approximately 990–1100 cm⁻¹) and in characteristic bands of the adulterants, enabling the tracking of peak shifts with increasing adulteration. HRMS analysis confirmed the presence of creatine by detecting the protonated molecular ion at m/z 132.07 and allowed the observation of multimeric species and adducts. This combined approach demonstrates that FTIR-ATR can serve as a practical and efficient tool for the preliminary screening and quantitative assessment of supplement authenticity, providing valuable support for quality control laboratories and regulatory agencies in detecting adulterated or mislabeled products.