Iodlne-amine charge-transfer complexes are demonstrated to enhance the UV detectability of N,Ndlmethylbenzylamlne. The complexation reactlon is rapid, reaching equlllbrlum In less than 7 s. The molecular ratio of reactants In the complex Is 1:l 1,:amIne. Maximum charge transfer band Intenshy which reflects the total amount of complex present was observed at a 1 O : l 1odlne:amlne ratio. An HPLC analysls Is described lor N,N-dlmethylbenzylamlne which Includes the direct chromatography of the free amine, the "In line" formatlon of the complex, and the detectlon of the amine in the charge transfer complex form. The use of the complex allows for a 20-fold Increase In peak area over the same concentration of uncomplexed N , N-dlmethylbenzylamlne. This procedure appears to be of general appllcablllty to all types of amines.A charge-transfer complex can be described as a molecular complex formed by the weak interaction of an electron donor and an electron acceptor. Charge-transfer complexes usually involve simple integral ratios of the components and the enthalpy of formation is usually only a few kcal/mol. The rates of formation and decomposition into the components are so high that the reactions appear to be instantaneous by normal techniques. In most cases, the complex has absorption peaks in its electronic absorption spectrum which are not common to either component. Charge-transfer complexes of organic materials with iodine have long been used as a method of visualization of thin-layer and paper chromatography. Iodine has been described as a sacrificial a-acceptor and amines as increvalent n-donor. Yada et al. ( I ) have shown that iodine-aliphatic amine complexes show two characteristic absorption bands in the 430-410 and 280-230 nm regions. Taha and co-workers (2) 2080 ANALYTICAL CHEMISTRY, VOL. 49, NO. 13, NOVEMBER 1977reDorted a considerL,,; increase in the JV bani intensity of many alkaloids via charge transfer complexation with a-acceptors such as iodine. The increase in absorptivity (up to 100 times the value of the uncomplexed alkaloid) was much greater for weak UV absorbers such as the tropine alkaloids, ephedrine, codeine, and spartane. The UV analysis of other pharmaceuticals utilizing iodine charge-transfer complexation has been reported (3).The highly efficient separation powers of high pressure liquid chromatography have been demonstrated in many areas of analytical chemistry. The most common method of detection in HPLC is spectrophotometric; therefore, the detection limits of a compound are directly related to its absorptivity. Molecules having high natural absorptivity can be detected in low concentrations by HPLC. However, compounds with low absorptivity values must be derivatized (4) with a strong chromaphoric group in order to achieve good detectability. The use of derivatizing reagents to produce molecules of high absorptivity has been applied to many classes of compounds (5-7). These derivatization procedures generally link chromaphore to substrate through a covalent bond.The formation of coval...

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