Spectrophotometric- determination of morphine and of codeine

Morphine can be distinguished from codeine by the shift of the maximum absorption value of morphine in alkaline medium from that in acid medium. Two spectrophotometric methods, the absolute and the relative methods, are presented for the determination of morphine and of codeine. Equations are given for the calculation of the concentrations of alkaloids in unknown samples. The relative method required a standard each time a sample was assayed while the absolute method did not require a standard. Samples of morphine and codeine were assayed by each of these methods. The percentages of error ranged from 0.4 per cent to 2.46 per cent, using the relative method, and from 0.85 per cent to 2.34 per cent, using the absolute method. No significant difference in precision was found between the two methods.