title: Determination of penicillin G in milk samples using its effect on cloud point extraction of triiodide ion.
abstract: A cloud point extraction (CPE) method for determination of trace amounts of penicillin G by spectrophotometry based on its effect on the triiodide ion (I3(-)) has been developed. Penicillin G is converted to the corresponding penicilloic acid by carrying out hydrolysis with sodium hydroxide solution, and treatment with acid yields D-penicillamine that is oxidized quantitatively by iodine to give rise to a disulfide. The 13- remaining in the solution is extracted into the surfactant Triton X-100, and the difference between absorbance of the working solution in the presence and absence of penicillin G is proportional to the amount of penicillin G. The effects of different variables, such as concentrations of sodium hydroxide, hydrochloric acid, surfactant, and I3(-) and the temperature and incubation time on the CPE were studied. The calibration graph was linear in the range of 50-1250 microg/L, and the LOD was 38 microg/L (n = 10). The RSD for 10 replicate determinations of 1000 microg/L of penicillin G was 1.0%. The method was applied to the determination of penicillin G in milk samples.
authors.forename: Nahid
authors.initials: N
authors.lastname: Pourreza
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Fat'hi
authors.forename: Ali
authors.initials: A
authors.lastname: Hatami
mesh_terms: D000818:Animals; D005591:Chemical Fractionation / Q000379:methods*; D007454:Iodides / Q000737:chemistry*; D007477:Ions / Q000737:chemistry; D008892:Milk / Q000737:chemistry*; D010400:Penicillin G / Q000032:analysis*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D007454:Iodides; D007477:Ions; D010400:Penicillin G