Quantitative Study Of Oxalic Acid And Its Esters And Alkaline Salts, Undecylenic Acid And Its Salts, Etidronic Acid And Its Salts In Cosmetics

Three kinds of organic acids and their derivatives are restricted substances incosmetics, which contains undecylenic acid and its salts, oxalic acid and its esters andalkaline salts, and etidronic acid and its salts. Currently, there are no standardanalytical methods for them in cosmetics. The physical and chemical properties ofthem were studied in this paper and their determination methods in cosmetics wereestablished.The main research findings are as follows:(1) Established methyl esterification-GC-FID methods for the determination of undecylenic acid and zinc undecylenate incosmetics. Undecylenic acid and zinc undecylenate were extracted from cosmetics bysocination, and esterified in5%sulfuric acid-methanol at65℃for an hour. Aftercooling,2.5mL n-hexane were added as extraction solvent. Methyl undecenoate wasseparated on HP-5capillary column with temperature programming. The temperaturesof inlet and FID were250℃and260℃.(2) The derivatization HPLC andreversed-phase HPLC method of oxalic acid and its alkaline salts were establishedseparately. In derivatization HPLC method,1,2-diaminobenzene was chose asderivative reagent and the product2,3-quinoxalinediol has a high absorption. In thereversed-phase HPLC method, Agilent Zorbax SB-Aq column was used as stationaryphases, and the mobile phase was aqueous contenting2.5mmol/L tetrabutylammonium hydroxide,50mmol/L potassium dihydrogen phosphate and2.69×10-5mol/L EDTA(pH2.20). The samples were extracted in water by socination.(3) GCmethod for the determination of three kinds of oxalic esters in cosmetics wasestablished. The determinands were extracted in ethanol by socination. This methodused DB-1701capillary column with temperature programming. The temperatures ofinlet and FID were240℃and250℃.(4) HPLC method with post columnCu2+coordination and reversed-phase HPLC method were established for etidronicacid in cosmetics. In the post column Cu2+coordination method, the complex betweenetidronic acid has a higher absorption. In the reversed-phase HPLC method,KromasilC18column was used as stationary phases. The mobile phase was made up of acetonitrile and aqueous which contented0.25mmol/L Tetrabutyl ammonium bromide,50mmol/L boric acid (pH8.0)(v/v=10:90).These methods all had good linearities and recoveries, except derivatizationHPLC of oxalic acid and its alkaline salts and post column Cu2+coordination methodof etidronic acid. In the detection of real samples, the content of three kind organicsand their derivatives were all below the maximum allowable concentration. Thedetermination for cosmetics could be satisfied using these detection methods.