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DEVELOPMENT AND EVALUATION OF AN HPLC-DAD METHOD FOR DETERMINATION OF BENZOIC ACID IN TOMATO SAUCE AND KETCHUP

According to Directive 95/2/EC dated on 20.02.1995 of the European Union (EU), the benzoic acid belongs to the preservatives allowed conditionally, and the quantity of benzoic acid added to foods is restricted by upper limits. There are many methods available for the analysis of benzoic acid in foods and the decision as to what method should be used depends on the matrix to be analyzed. Most of the methods are for liquids and further method development may be required to adapt these methods to be applicable for all matrices. 
As all tomato sauce and ketchup available on our market are made with benzoic acid addition and their consumption is high, the operational parameters leading to the development of a method for the analysis of benzoic acid within tomato sauce and ketchup have been studied, the technique used is the high performance liquid chromatography together with diode array detection (DAD). It has been tried to validate the analysis method settled, in terms of sensitivity, linearity range, reproducibility, repeatability and recovery. The method provides a stable retention time and a limit of detection of 0.8 mg/kg in the sample at a signal to noise ratio of 3. 
For analysis, the sample is extracted or diluted with water, and the solution of the sample with the benzoic acid is purified by an extraction with Carrez reagents. The benzoic acid in the sample test solution is separated on a C18 chromatography column in a reversed phase, detected by absorbance at the wavelength of 217 nm and quantified with a calibration graph.