Abstract
Fabrication of a test strip for detection of benzoic acid was successfully implemented by immobilizing tyrosinase, phenol and 3-methyl-2-benzothiazolinone hydrazone (MBTH) onto filter paper using polystyrene as polymeric support. The sensing scheme was based on the decreasing intensity of the maroon colour of the test strip when introduced into benzoic acid solution. The test strip was characterized using optical fiber reflectance and has maximum reflectance at 375 nm. It has shown a highly reproducible measurement of benzoic acid with a calculated RSD of 0.47% (n = 10). The detection was optimized at pH 7. A linear response of the biosensor was obtained in 100 to 700 ppm of benzoic acid with a detection limit (LOD) of 73.6 ppm. At 1:1 ratio of benzoic acid to interfering substances, the main interfering substance is boric acid. The kinetic analyses show that, the inhibition of benzoic is competitive inhibitor and the inhibition constant (Ki) is 52.9 ppm. The activity of immobilized tyrosinase, phenol, and MBTH in the test strip was fairly sustained during 20 days when stored at 3 °C. The developed test strip was used for detection of benzoic acid in food samples and was observed to have comparable results to the HPLC method, hence the developed test strip can be used as an alternative to HPLC in detecting benzoic acid in food products.
Highlights
Benzoic acid is a white solid that is slightly soluble in water and is an extensively used preservative.It is generally effective in controlling mould and inhibiting yeast growth and in preventing a wide range of bacterial attacks
In this paper we describe the use of a phenol biosensor for the development of an optical biosensor for benzoic acid based on immobilized tyrosinase, phenol, and methyl-2-benzothiazolinone hydrazone (MBTH) into filter paper using polystyrene as a polymeric support
Many biosensors based on the inhibition effect of tyrosinase for detecting benzoic acid have been reported [1,12,13,14]
Summary
Benzoic acid is a white solid that is slightly soluble in water and is an extensively used preservative It is generally effective in controlling mould and inhibiting yeast growth and in preventing a wide range of bacterial attacks. Biosensor devices incorporate a biological sensing element and an electrical transducer to produce an electrochemical, optical, or mass signal in proportion to the concentration of analyte in a sample. The use of an amperometric biosensor to detect benzoic acid in food products based on the inhibition mechanism of PPO using a novel phenol biosensor has been reported [1,4,12,13,14]. The use of an optical biosensor to detect benzoic acid based on the inhibition mechanism of tyrosinase using a novel phenol biosensor has not yet been reported. The effect of pH, volume of tyrosinase, interference substances and kinetic study of the inhibition are described in detail
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