Kushch A. V., Matorina K. V., Posudievska O. R.

Oles Honchar Dnipropetrovsk National University

POTENTIOMETRIC DETERMINATION OF CITRIC ACID IN NON-ALCOHOL DRINKS

Citric acid (CA, E-330) is uses as an acidity regulator, conserving agent and food additive. In the food industry, medicine, cosmetology, as well as in the of productiondetergents and cleansers. Food additive E-330 participates vital metabolic processes, which are important for human life. However, in large doses the E-330 can be the reason of sight loss, chemical burns, dental caries and respiratory tract irritation. All this necessitates control of its amount, particularly in food products. The permitted amount of the E-330 is 10–20 g/kg of the product.

We have proposed a sensitive electrode with an electrode-active substance (EAS) based on triple metal-polymeric complex (TMPC): brompyrogallol red (BPR) –polyvinylpyrrolidone (PVP, Mr≈8·103) – ammonium heptamolybdate. As it was found out, the PVC membrane synthesized on the base of TMPC is sensitive to the presence of citric acid in the water solution. The proposed electrode has the following electroanalytical characteristics: the slope of the electrode function S = 19 mV/pC, operational range pC = 2–8, response time is no more than 4 min). The constructed electrode had been tested on real objects – non-alcohol drinks (the results of determination, C·102 M): juice «Sadochok» (6.98), strongly sparkling drink «Zhyvchyk» (9.66), cold tea «Nestea» (5,55). As the inner solution we have used a water solution of ammonium heptamolybdate (C=1·10-4 M), the volume of the sample is V = 2,5 ml.

We have developed a sensitive potentiometric technique for determination of the food additive E-330 (citric acid) using a plasticized membrane. The proposed electrode shows rather reproducible results at the determination of the additive E-330 in non-alcohol drinks: juice «Sadochok», strongly sparkling drink «Zhyvchyk» and cold tea «Nestea».