Analytical Sciences

The Halogen Bond between Amantadine and Iodine and Its Application in the Determination of Amantadine Hydrochloride in Pharmaceuticals

Xiao Qing YAN, Hui WANG, Wei Di CHEN, and Wei Jun JIN

College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China

It is proposed that molecular iodine as a donor could form halogen bonding complexes with amantadine (AMD) and amantadine hydrochloride (AMD-HCl) in chloroform and the resultant charge transfer bands (CT band) would be located at 259 and 253 nm, respectively. The halogen bonding interaction was explored by UV absorption, Raman and X-ray crystallography, and a new bonding model named N⁺···N^lep bond in crystal was observed. The halogen bonding complexes were utilized in the development of simple and accurate spectrophotometry for the analysis of AMD/AMD-HCl. Compared with the traditional method based on the absorption of I₃⁻ at 290 and 365 nm, the new proposed spectrometry based on the CT band of halogen bonding complex was more sensitive and selective for the detection of AMD/AMD-HCl. Linear relationships with good correlation coefficients (>0.9994) were obtained between the absorbance and the AMD/AMD-HCl concentration in the range of 10 – 180 μg mL⁻¹ for AMD-HCl and 0.2 – 13 μg mL⁻¹ for AMD. The limit of detection (LOD) was 2.23 μg mL⁻¹ and limit of quantification (LOQ) was 7.45 μg mL⁻¹ for AMD-HCl. And because of the stronger bond constant between AMD and iodine than AMD-HCl, the method is more sensitive for AMD; the LOD was 0.02 μg mL⁻¹ and LOQ was 0.08 μg mL⁻¹ which was 100 times lower than that of AMD-HCl.

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