title: An improved flow system for phenols determination exploiting multicommutation and long pathlength spectrophotometry.
abstract: A greener and sensitive procedure for spectrophotometric determination of phenols based on a multicommuted flow system with a 100cm optical path flow cell is presented. The method exploited the oxidative coupling of phenolic compounds with 4-aminoantipyrine in alkaline medium containing potassium hexacyanoferrate(III). Sensitivity was 80-fold higher than that achieved with a 1cm flow cell, making feasible the determination of phenols in the 10-100mugl(-1) range with a detection limit estimated as 1mugl(-1) phenol. The sampling rate and the coefficient of variation were estimated as 90 determinations per hour and 0.6% (n=10), respectively. The multicommutation approach allowed a 200-fold reduction of the reagent consumption in comparison with the reference batch method. Moreover, the chloroform extraction for analyte concentration is unnecessary in view of the increase in sensitivity. Recoveries within 93.3 and 106% were achieved for determination of phenol in natural and wastewater samples. Results agreed with the obtained by a reference method at the 95% confidence level.
authors.affiliation: Departamento de Quimica, Universidade Federal de São Carlos, PO Box 676, 13560-970 São Carlos-SP, Brazil.
authors.forename: Karina Omuro
authors.initials: KO
authors.lastname: Lupetti
authors.forename: Fábio R P
authors.initials: FR
authors.lastname: Rocha
authors.forename: Orlando
authors.initials: O
authors.lastname: Fatibello-Filho