Abstract

OLIVEIRA, Fabio Santos de; LEITE, Bárbara Cecília O.; ANDRADE, Marta Valeria A. Santana de  and  KORN, Mauro. Determination of total aldehydes in fuel ethanol by MBTH method: sequential injection analysis. J. Braz. Chem. Soc. [online]. 2005, vol.16, n.1, pp. 87-92. ISSN 0103-5053.  http://dx.doi.org/10.1590/S0103-50532005000100013.

A sensitive SIA method was developed for total aldehyde determination in automotive fuel ethanol samples. It was based on the selective reaction of aliphatic aldehydes with 3-methyl-2-benzothiazolone hydrazone (MBTH) with the formation of blue dye in the presence of Fe³⁺. Monosegmentation and binary sampling were employed to increase the sensitivity of the method. In order accelerate reaction rate of MBTH and aldehyde a mixing coil was inserted into a microwave oven cavity were the sample zone was homogeneously heated. The linear range was 0.3-6 mg L^-1 with a precision, expressed as relative standard deviation, lower than 2.5% and detection limit of 60 mg L^-1. The method has been successfully applied to the determination of total aldehydes in fuel ethanol and the results agreed with those obtained with 2,4-DNPH-HPLC. In the optimal condition the system can carry out 10 samples per hour.

Keywords : sequential injection analysis; total aldehyde determination; MBTH; binary sampling; monosegmentation.