Analytical validation of a reversed-phase ion pairing HPLC-DAD method for the simultaneous determination of anthropogenic pollutants

Caffeine, trigonelline, nicotinamide, and hippuric acid are potential organic markers of anthropogenic activities in the environment. In this work, a selective, precise, accurate, and robust reverse phase high performance liquid chromatography with a diode array detection method was developed for their simultaneous determination. Chromatographic analysis was achieved on GraceSmart RP C18 (150 mm x 4.6 mm, 5 µm) column. The mobile phase was 20 mM ammonium acetate buffer (pH 4.5) and methanol in gradient elution mode at a flow rate of 1.0 mL min-1, with 5 mM heptafluorobutyric acid as an ion pairing agent. Detection was performed at 275 nm for caffeine, 265 nm for trigonelline, 261 nm for nicotinamide, and 250 nm for hippuric acid. The method was validated as per the International Conference on Harmonization guidelines. Linear responses were found in the concentration range of 10-200 µg mL-1 with a correlation coefficient of at least 0.999. The percent relative standard deviation of intra-day precision, inter-day precision, and robustness was less than 2 %. The accuracy, expressed as percentage recovery ranged between 93.23 – 99.22%. Values for limits of detection and quantification were between 0.07-0.34 µg mL-1, and 0.21-1.04 µg mL-1, respectively. Lake samples from public parks were collected and subjected to analysis using the validated method.