An aliquot of juice (2 mL) was diluted up to 25 mL with a pH 1 solution (125 mL of 0.2 M KCl and 375 mL of 0.2 M HCl). A second aliquot (2 mL) was diluted up to 25 mL with a pH 4.5 buffered solution (400 mLof1M CH3 CO Na, 240 mL of 1 M HCl, and 360 mL of H2O).