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The weak UV absorbing ephedrine alkaloids such as ephedrine, pseudoephedrine, methylephedrine and norephedrine could be analyzed by charge-transfer spectrophotometric method. The results obtained are summarized as follows: (1) It was possible to determine a weak UV absorbing ephedrine alkaloids using the intense charge-transfer UV bands in chloroform. (2) This method was suitable for the spectrophotometric determination of ephedrine alkaloids in mixed pharmaceutical preparation. (3) Linear relationship was found between absorbance and concentration in the range of 1.0 X 10-5M-5 X 10-5M of ephedrine (epsilon=2.72 X 104LM-1cm-1) and pseudoephedrine (epsilon=2.84 X 104LM-1cm-1), 1.O X 10-5M-5 X 10-5M of methylephdrine (epsilon=1.68 X 104LM-1cm-1) and 1/3 X 1O-4M-4/3 X 10-4M of norephedrine (epsilon=0.74 X 104LM-1cm-1). (4) CT-complex of ephedrine, pseudoephedrine and methylephedrine has absorption maximum at 293nm and norephedrine have absorption maximum at 253nm. (5) CT-complexes were formed in a 1 : 1 ratio between ephedrine alkaloids and iodine in chloroform. (6) By UV, IR, and 1H-NMR spectra, it could be inferred that CT-complexes were formed by interaction between the basic nitrogen of ephedrine alkaloids as electron (n) donor and iodine as electron (sigma) acceptor.
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