Dietary Supplements Testing

Yakupova, Zilya, et al. Microchemical Journal 187 (2023): 108373.

Melatonin, a widely used supplement for treating various health conditions, has gained attention for its potential efficacy in reducing the severity of COVID-19. Accurate determination of melatonin content in dietary supplements and pharmaceuticals is essential for quality control and regulatory compliance. This study presents a novel, miniaturized clean-up and preconcentration method utilizing deep eutectic solvent-based solidified floating organic drop microextraction (SFODME), followed by high-performance liquid chromatography with UV detection (HPLC-UV).

A range of hydrophobic deep eutectic solvents (DES), including menthol with medium-chain fatty acids and long-chain alcohols, was explored for the microextraction of melatonin. Among these, the menthol-heptanoic acid DES exhibited the highest extraction efficiency, achieving a 90% recovery rate. The microextraction process, carried out under magnetic stirring, enabled rapid extraction (within 1 minute) with minimal solvent use, requiring only 25 μL of extract for analysis.

The method was validated with limits of detection (LOD) and quantification (LOQ) of 0.003 mg/g and 0.01 mg/g, respectively, ensuring its suitability for sensitive analysis in complex samples. This efficient, environmentally friendly technique provides a reliable approach for the determination of melatonin in dietary supplements, ensuring quality and consistency in pharmaceutical formulations.

Soto, C., et al. Journal of Chromatography A 1664 (2022): 462770.

Caffeine, a widely used stimulant in dietary supplements, requires precise quantification to ensure quality, safety, and effectiveness. This study evaluates three miniaturized liquid chromatography (LC) systems for caffeine analysis in dietary supplements: benchtop capillary LC (capLC), benchtop nano LC (nanoLC), and a portable LC system. These methods were optimized and compared for their sensitivity, precision, and efficiency in caffeine detection.

The results demonstrated that the capLC and nanoLC systems offered superior sensitivity, with limits of detection (LODs) of 0.01 µg/mL and 0.003 µg/mL, respectively. In contrast, the portable LC system, while having a higher LOD of 1 µg/mL, excelled in simplicity and throughput, providing analysis in under 15 minutes. Despite the differences in sensitivity, the portable LC method achieved excellent linearity (1–20 µg/mL) and accurate caffeine quantification, even in decaffeinated green coffee extracts. The caffeine concentrations found in real samples ranged from 1.38 to 7 mg per gram, with relative standard deviations (RSD) between 2-14%, consistent with benchtop systems.

This portable LC-based method provides a simple, rapid, and reliable alternative for caffeine quantification in dietary supplements, offering a valuable tool for quality control and safety assessments in the supplement industry.

Leal, Gabriela Camera, et al. Journal of Food Composition and Analysis 86 (2020): 103360.

Lead (Pb) contamination in dietary supplements is a significant concern due to its toxicity and potential health risks. This study developed a method for accurately determining Pb levels in dietary supplements using direct solid sampling and high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GFAAS). The method employed zirconium-coated platforms and chemical modifiers (Pd(NO3)2 and Mg(NO3)2) to enhance detection. Mass aliquots between 0.8 and 1.0 mg of the samples were directly introduced into the graphite furnace, achieving a detection limit of 2.16 pg and a limit of quantification of 7.2 pg at the 283.306 nm resonance line. The precision of the method was below 5% RSD.

Pb recovery in the standard reference material (Bitter Orange-Containing Solid Oral Form, NIST SRM 3260) was 116%, demonstrating the method's accuracy. The Pb content in the 74 dietary supplement samples varied from 0.04 to 25.3 μg/day. Notably, two samples exceeded the limits set by the American Pharmacopoeia for inorganic contaminants in food supplements. This method provides a reliable and efficient tool for monitoring Pb contamination in dietary supplements, ensuring consumer safety and compliance with regulatory standards.