Quantitative Analysis Of Alpha-Long Chain Alkyl Betaine

By the analysis of a novel type of amphoteric surfactants alpha-long chain alkyl betaine(α-LAB) prepared through ammonolysis of long chain fatty acid derivative alpha-chlorododecanoic acid with trimethylamine,the chemical methods to determine alpha-capric betaine and free fatty acids were developed.A method for the determination of alpha-capric betaine(α-CB),alpha-hydroxy dodecanoic acid(α-HDA),dodecanoic acid(DA) and alpha-chlorinated dodecanoic acid(α-CDA) by high performance liquid chromatography (HPLC) coupled with evaporative light-scattering detection(ELSD) and refractive index detector(RID) was developed,and the effect was investigated.The main points were as follows:A novel rapid method for the standardization of phosphotungstic acid was developed by titration,the relative standard deviation is lower than 0.3%,and the result was consistent with the gravimetric analysis by Benzidine.A method to determine theα-LAB by back titration with Hamming was developed;the average recovery rate ofα-CB is 100.33%.A method to determine the free fatty acids by in reaction products was developed by two-phase titration with bromocresol green indicator,and the scope of application was the concentration of NaCl andα-CB in sample solution must be lower than 5 g/L and 20 g/L, respectively.The average recovery rate of DA is 98-100%;the relative standard deviation is lower than 0.3%.There is no influence of trim ethyl amine in product for the result,so this method can determine free fatty acids directly.A new method of HPLC-ELSD has been developed for the separation and quantitative analysis of the compose of alpha-capric betaine.This method employs an isocratic elution, mobile phase was composed of acetonitrile,methyl,water(V:V:V=40.9:46.6:12.5) and the flow of mobile phase was maintained at 0.8 mL/min.The separation and quantitative of alpha-capric betaine,alpha-hydroxy dodecanoic acid,alpha-chlorinated dodecanoic acid, dodecanoic acid were performed.This method has a high accuracy and sensitivity,so it can be the standards for other methods.A high-performance liquid chromatography technique with refractive index detector has been developed for the determination ofα-CB by the change of mobile phase.The minimum limit of detection ofα-CB is about 1.2μg and ratio of mass to signal is essentially linear in the range of 1.6 to 32μg.A method for the separation analysis of a mixture ofα-LAB prepared by fatty acid mixed was developed by computer-aided optimize and experimentation.The method provides an analytical condition for quantitative analysis of the mixture ofα-LAB.