with frequent stirring, and then centrifuged at 3000 × g for
10 min. Aliquots of alkalinized urine were applied to an LC- SAX column and subsequently washed with 2 ml H2O and 1 ml 1% (v/v) acetic acid. The t,t-muconic acid was eluted with 1 ml 10% (v/v) aqueous acetic acid and then analyzed by HPLC equipped with a UV detector as previously described (Ruchirawat et al., 2005). Urinary creatinine was analyzed using a Sigma Diagnostic creatinine kit (555-A, St. Louis, MO, USA).