Automated analysis of benzoic acid in food: colorimetric determination after continuous volatilization.
A method is developed to determine benzoic acid colorimetrically with the Technicon AutoAnalyzer. After a selective hydroxylation of benzoic acid by means of hydrogen peroxide and a catalyzing reagent consisting of a buffered solution of cupric ion, catechol and sorbic acid, a reaction follows with 4-aminoantipyrine. The reddish brown reaction product formed is measured at 505 nm. In a distillation unit benzoic acid is continuously separated from the acidified sample stream by volatilization into a stream of nitrogen. With simple manual treatments solid samples can be analysed. Possible interferences caused by naturally present or added compounds in food were investigated. The precision of the method is very good. The coefficient of variation is 0.6% at 50 mug/ml. For several products the recovery was determined with a mean of 98.4%. The working range covered is 0--100 mug benzoic acid/ml.
D001565:Benzoates / Q000032:analysis*; D003124:Colorimetry; D005504:Food Analysis; D005506:Food Contamination; D005519:Food Preservation
D001565:Benzoates