2.2. HGA Stability Studies
Solutions of homogentisic acid were prepared in PBS adjusted to pH 4, pH 5, pH 6, pH 7, pH 8 or pH 9. Solutions were incubated at 37 °C for 24 h and optical density measured at regular intervals using a FLUOstar Omega plate reader (BMG Labtech, Aylesbury, UK). The presence of HGA and BQA was detected at their absorbance maxima. Extinction coefficients were determined using known concentrations of HGA and BQA in PBS, and the Beer–Lambert law was used to calculate the concentration of compound present in solution over time [