Turbidimetric and photometric determination of total tannins in tea using a micro-flow-batch analyzer

MARCELO B. LIMA; STÉFANI I. E. ANDRADE; DAVID P. HARDING; MARCELO F. PISTONESI; FERNÁNDEZ BAND BEATRIZ; MARIO UGULINO DE ARAÚJO

TALANTA

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2012 vol. 88 p. 717 - 723

0039-9140

Both turbidimetric and photometric determinations of total tannins in samples of green and black tea,using a micro-flow-batch analyzer (FBA) were studied. The miniaturized system was formed usingphotocurable urethane-acrylate resin and ultraviolet lithography technique. The turbidimetric methodwas based on the precipitation reaction of Cu (II) with tannins in acetate medium at a pH of 4.5. Thephotometric method was based on the complexation reaction of tannins with ferrous tartrate. The turbidimetricFBA was able to test 200 samples per hour. The photometric FBA allowed 300 analyses perhour, generating 136 L of residue per analysis. The paired t test, at a 95% confidence level, showed nostatistically significant differences between results obtained by both methods and the reference method.The urethane-acrylate FBA maintained satisfactory physical and chemical properties, and representsan improvement over conventional flow-batch analyzer.