Then,
a 9.0mL aliquot of the pretreated sample was mixed with
0.5mL 1M tris solution containing 1M potassium chloride
and 0.2mL 1M sodium hydroxide were added into a 10mL
volumetric flask, diluted to the mark using Milli-Q water and
filtered. The pH of the prepared sample was caused to be 8.5
because in more acidic conditions, sulfite is not stable and in
a open beer will be converted to sulfur dioxide and lost.