To characterize UV-visible absorbance spectral changes caused by catechol browning -and its enhancement by other chemical species -1,000 L reaction mixtures were prepared in 1.5-mL microtubes and incubated at 37 °C in a mini dry bath for 96 h, allowing the browning reaction to proceed to an appreciable extent. Each mixture included 15.6 mM catechol, with i) DMEM, ii) 50 mM Pi buffer (pH 7.8), iii) 50 mM Tris buffer (pH 7.8), iv) 15 mM Gly (unbuffered or buffered with 50 mM Pi, pH 7.8), v) 20 mg/mL BSA (unbuffered or buffered with 50 mM Pi, pH 7.8), or vi) 20 mg/mL skim milk (unbuffered or buffered with 50 mM Pi, pH 7.8). Upon completion of the 96-h incubation, 200 L aliquots were transferred to microplate wells, and a spectral scan was initiated between 300-500 nm at 1 nm increments.