Determination of Benzoic and Sorbic Acids in Labaneh by High-Performance Liquid Chromatography

A paired-ion, reversed-phase high-performance liquid chromatographic method was developed for the simultaneous determination of sweeteners (dulcin, saccharin-Na and acesulfame-K), preservatives (sodium dehydroacetate, sorbic acid, salicyclic acid, benzoic acid, succinic acid, methyl-para-hydroxybenzoic acid, ethylpara-hydroxybenzoic acid, n-propyl-para-hydroxybenzoic acid, isopropyl-para-hydroxybenzoic acid, n-butyl-para-hydroxybenzoic acid, and isobutyl-para-hydroxybenzoic acid), and antioxidants (3-tertiary-butyl-4-hydroxyanisole and tertiary-butyl-hydroquinone). A mobile phase of acetonitrile-50 mM aqueous α-hydroxy-isobutyric acid solution (pH 4.5) (2.2 ∶ 3.4 or 2.4 ∶ 3.6, v/v) containing 2.5 mM hexadecyltrimethylammonium bromide and a C18 column with a flow rate at 1.0 mL/min and detection at 233 nm were used. This method was found to be very reproducible with detection limits ranged from 0.15 to 3.00 μg. The retention factor (k) of each additive could be affected by concentrations of hexadecyltrimethylammonium bromide and α-hydroxyisobutyric acid, and pH and ratio of mobile phase. The presence of additives in some food samples was determined.

Simultaneous determination of preservatives, sweeteners and antioxidants in foods by paired-ion liquid chromatography

A procedure has been developed using anion exchange high pressure liquid chromatography (HPLC) which is capable of determining microgram quantities of two common food preservatives, sodium benzoate and sorbic acid, in citrus juices. The compounds are eluted from the column with a simple buffer system and detected with a variable wavelength spectrophotometer. Simultaneous determination is possible. Centrifugation and filtration are the only sample preparations required and HPLC analysis time is less than 10 min. Results, confirmed by ultraviolet absorption and phosphorimetric analyses, are accurate and reproducible. Analysis of fortified juice samples in the common ranges yields values within 5% of the prepared concentration.

Quantitative determination of sorbic acid and sodium benzoate in citrus juice

A series of ruthenium substituted polyoxotungstates were used to catalyze the cleavage oxidation of styrene. Under all experimental conditions investigated, reaction products were benzaldehyde and benzoic acid. Kinetic studies showed that these reactions were consecutive reactions consisting of first oxidizing styrene into benzaldehyde and then oxidizing the benzaldehyde into benzoic acid. In this work, the first oxidation step was carefully studied. It has been shown to be first order with respect to substrate and catalysts but zero order with respect to NaIO4 under the conditions studied. The activation energies of the first oxidation catalyzed by different polyanions are closely similar to one another, but the value of pre-exponential factors, differed by orders of magnitudes. Such differences could possibly be accounted for by the phase transfer effect as experiments showed that lowering the concentration of phase transfer reagent for low distribution ratio (Caq/Corg) catalysts would enhance the pre-exponential factor value and selectivity of the reaction.

Studies on styrene oxidation reaction catalyzed by ruthenium substituted polyoxotungstates: kinetics and phase transfer effect

Sodium Benzoate as a Green, Efficient, and Recyclable Catalyst for Knoevenagel Condensation

A procedure has been devised for the separate determination of benzoic and sorbic acids in orange juice. It is based on the steam distillation of these preservatives from an acidified juice into an alkaline trap. The distillate is divided into two portions, each of which is treated with potassium dichromate and sulphuric acid, but under different conditions. Drastic oxidation leads to the destruction of sorbic acid and, after re-distillation, allows the determination of benzoic acid at 225 nm (with no interference from sorbic acid). Milder oxidation selectively converts sorbic acid into malonaldehyde, and the latter is subsequently converted into a coloured compound and determined at 532 nm (with no interference from benzoic acid).Recoveries of both preservatives from orange juice were satisfactory.

Rina Ashkenazy

Papers

Determination of benzoic and sorbic acids in orange juice.