title: Spectrophotometric method for the determination of sorbic acid in various food samples with iron(III) and 2-thiobarbituric acid as reagents.
abstract: A simple, rapid and accurate spectrophotometric method has been developed for the determination of sorbic acid in various food samples based on the oxidation of sorbic acid by iron(III) at 100 degrees C to malonaldehyde, which then reacts with 2-thiobarbituric acid to form a reddish brown product. The optimum experimental conditions for colour development have been assessed. Absorbance measurements were made at 529 nm in the presence of 0.4% m/V citric acid. The calibration graph was linear for 0-6 micrograms ml-1 of sorbic acid with a slope of 0.131 A micrograms-1 ml. The recoveries of sorbic acid at concentrations of 164-557 micrograms ml-1 ranged from 96 to 103%. The relative standard deviations of ten replicate determinations of sorbic acid in a synthetic cream soda sample spiked with 573 micrograms ml-1 of sorbic acid and in an onion juice sample containing 82 micrograms ml-1 of sorbic acid were 1.6 and 1.9%, respectively. Interferences from several common food additives can be minimised by extracting sorbic acid with diethyl ether and then back-extracting the acid with sodium hydrogen carbonate. The method has been applied successfully to the determination of sorbic acid in a wide range of food samples including beverages, cake, cake mate, garlic bread sprinkle, onion juice, oyster flavoured sauce and grenadine syrup.
authors.forename: O W
authors.initials: OW
authors.lastname: Lau
authors.forename: S F
authors.initials: SF
authors.lastname: Luk
authors.forename: R K
authors.initials: RK
authors.lastname: Lam
mesh_terms: D005231:Fatty Acids, Unsaturated / Q000032:analysis*; D005504:Food Analysis; D007202:Indicators and Reagents; D007501:Iron; D013011:Sorbic Acid / Q000032:analysis*; D013056:Spectrophotometry, Ultraviolet; D013858:Thiobarbiturates
chemical_list: D005231:Fatty Acids, Unsaturated; D007202:Indicators and Reagents; D013858:Thiobarbiturates; D007501:Iron; C029684:thiobarbituric acid; D013011:Sorbic Acid