Development of an Eco-Friendly Liquid Chromatography Method for the Separation and Trace Determination of Caffeine in Beverages, Pharmaceuticals, and Environmental Water Samples Utilizing High-Temperature and Superheated Water: A Greenness Assessment

The retention behavior of the central nervous system stimulant caffeine (CAF) on the thermally stable Zir-Chrom-PBD column (5 μm, 150 × 4.6 mm) was investigated thermodynamically at various elevated temperatures utilizing high-temperature liquid chromatography (HTLC). The HTLC method was optimized for CAF analysis. The determination was performed using pure water or 20% acetonitrile in water as the mobile phase.The lower limit of detection for CAF was found to be 0.008 mg/mL, whereas the limit of quantification was 0.026 mg/mL. The developed HTLC method is the first HTLC method for this compound and has been used for multiple applications. It was applied for the assay of CAF in tablets and energy drinks, with acceptable mean recoveries ranging from 99.7 ± 0.3 to 100.0 ± 0.2% and 90.9 ± 1.9 to 103.6 ± 2.1%, respectively. Furthermore, the HTLC method was applied for monitoring of CAF in wastewater and groundwater. Multi-walled carbon nanotubes (MWCNTs) were applied for the efficient removal of CAF from water, and a mechanism of interaction between CAF and the MWCNTs was proposed. The method greenness was positively evaluated using two tools: the Analytical GREEnness metric and the Green Analytical Procedure Index.