**3.1.1 Methodology**

Reagents: phenol solution 5% (w/v) and concentrate sulphuric acid (95%, p/v).

Get an aliquot of 100µg.mL-1 from the sample, add 0.5mL of phenol solution 5%, shake in vortex, add 2.5mL, shake again and keep in water-bath 25°C for 15 minutes. After this period, read the absorbance in spectrophotometer at 490nm.