Green Analytical Methods for the Separation of Seven Antihistamines: Application in Separation of Azelastine and Related Impurities in Nasal Solution

Table 1

The chemical names, molecular structures, and dissociation constants of azelastine HCl, desloratadine, ebastine, fexofenadine HCl, ketotifen, loratadine, and olopatadine HCl [17].

Antihistamines	Chemical name	pKa	Chemical structure
Azelastine HCl	4-[(-chlorophenyl)methyl]-2-(1-methylazepan-4-yl)phthalazin-1-one hydrochloride	8.88
Desloratadine	8-Chloro-6,11-dihydro-11-(4-piperidinylidene)-5H- benzo[,6]cyclohepta[,2,b]pyridine	4.33 and 9.73
Ebastine	1-[-(1,1-Dimethylethyl)phenyl]-4-[-(diphenylmethoxy)-1-piperidinyl]-1-butanone	8.43
Fexofenidine HCl	2-[-[1-hydroxy-4-[-[hydroxy(diphenyl)methyl]-1-piperidyl]butyl]phenyl]-2-methyl-propionic acid hydrochloride	4.04 and 9.01
Ketotifen	4-(1-Methyl-4-piperidinylidene)-4,9-dihydro-10H-benzo[,5]cyclohepta[1,2-b]thiophen-10-one	7.18 and 8.11
Loratadine	Ethyl 4-(8-chloro-5,6-dihydro-11H-benzo[,6]cyclohepta[,2-b]pyridin-11-ylidene)-1-piperidinecarboxylate	4.33
Olopatadine HCl	(11Z)-11-[-(Dimethylamino)propylidene]-6,11-dihydrodibenz[b,e]oxepin-2-acetic acid hydrochloride	3.78 and 9.76