盐酸普鲁卡因注射液在制备和存放过程中要发生微量水解,中国药典采用TLC法检测水解产物对氨基苯甲酸(PABA)的限量。应用双波长法比色法检测PABA的限量已有报道,但以上均是半定量的方法。本文应用差示正交函数分光光度法(简称△P_2法)不经分离直接测定水解产物PABA的含量。当PABA的浓度在0.2～0.8 ppm时,△P_2系数与 Procaine Hydrochloride Injection in the process of preparation and storage to the occurrence of micro-hydrolysis, Chinese Pharmacopoeia TLC method for the determination of hydrolyzate para-aminobenzoic acid (PABA) limits. The use of dual wavelength colorimetric detection of PABA limit has been reported, but the above are semi-quantitative method. In this paper, differential orthogonal function spectrophotometry (referred to as △ P_2 method) without direct determination of the hydrolysis product PABA content. When PABA concentration of 0.2 ~ 0.8 ppm, △ P_2 coefficient and