無水酢酸-氷酢酸溶液中における塩基の強酸塩の過塩素酸滴定(<特集>医薬品の分析)  [in Japanese] Titration of bases of strong acid salts with perchloric acid in acetic anhydride and glacial acetic acid.(<Special Issue>Drug Analysis)  [in Japanese]

日本薬局方収載の塩化ベタネコール(I),塩酸ピロカルピン(II),臭化水素酸スコポラミン(III),臭化水素酸ホマトロピン(IV),塩酸キニーネ(V),塩酸ジブカイン(VI),塩酸プロカインアミド(VII),塩酸テトラカイン(VIII)の非水滴定法を検討した.いずれも酢酸第二水銀で前処理しなくても,無水酢酸-氷酢酸(9:1〜7:3)溶液中0.1M過塩素酸で電位差滴定しうる.第一,第二アミン(VII,VIII)は直ちにアセチル化されるが第三アミン塩酸塩を滴定しうる.V,VIは第三アミン塩に相当する第2当量点での電位変化が大きい.指示薬塩化メチルロザニリンより電位差法のほうがよい.

Ten base halides in Japanese Pharmacopoeia were determined by nonaqueous titration after treating with mercuric acetate. Aim of this study was to omit the poisonous reagent. Bethanechol chloride (I), pilocarpine hydrochloride (II), scopolamine hydrobromide (III) and homatropine hydrobromide (IV) could be determined by potentiometric titration with 1 eq. perchloric acid in acetic anhydride-acetic acid (9:1〜7:3). Quinine hydrochloride (V) and dibucaine hydrochloride (VI) were similarly titrated with 2 eq. perchloric acid. Procainamide hydrochloride (VII) and tetracaine hydrochloride (VIII) were also titrated with 1 eq. perchloric acid after acetylation of the aromatic amine. A silver-silver chloride electrode with ceramic junction containing acetic acid saturated with lithium chloride and a reqular glass electrode were preferred as the electrodes. Standard deviation of this method was 0.3%. The potentiometry was more exact than indicator method using methylrosanilinium chloride. It was estimated from the potential of glass electrode at the half equivalent point that the order of acid strength was perchloric acid, hydrobromic acid and hydrochloric acid and that of base strength was quaternary amine (I), tertiary amines (III, VIII), quinolines (V, VI), aromatic amines (VII, VIII) and aromatic amides (VII, VIII).