Application of Dual Wavelength Spectrophotometry and Absorbance Ratio Method in Analysis of Compound Preparations Ⅱ.Determination of Caffeine and Sodium Benzoate in Caffeine and Sodium Benzoate Injection

The dual wavelength spectrophotometry and the absorbance ratio method have been used for determination of caffeine and sodium benzoate in caffeine ard sodium benzoate injection without any preliminary separation.In the dual wavelength spectrophotometry both single ard dual wavelength spectrophotometers have been used.The methods are simple and rapid.Good results have been obtained. The averagerecovery of caffeine is 98.81-100.3% with coefficient of variation below 0.59%; the average recovery of sodium henzoate is 98.44-100.7% with coefficient of variation below 0.6O%. Five batches of sample from different factories have been determined with these methods. The results hare been compared with those obtained by the method of Chinese Pharmacopoeia ( 1977 ). The accuracy and precision meet the requiremrnt of analysis of the pharmaceutical preparations.