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偶合滴定法是1949年R.M.Elofsen及P.A.Mecherly [Anal.Chem.,21,565(1949).]首先提出的,后在药物及工业分析上获得广泛应用。此法的原理基于重氮盐与芳胺及芳酚反应,从而定量测定芳胺及芳酚含量。反应为: Ar—N_2~++A′_r—X(OH或NH_2)→ArN=N—A′_r—X+H~+。利用极谱,使重氮盐在滴汞电极上还原,形成Ar—N≡N:或Ar—NH—NH_2。前一反应的半波电位(Ar—N≡N:+e→ArN≡M:)为—0.2～—0.3伏,而后一反应的半波电位(Ar—N≡N:+4e+3H~+→ArNH—
Coupling titration was first proposed by R.M. Elofsen and P.A. Mecherly [Anal. Chem., 21, 565 (1949)] in 1949 and is widely used in pharmaceutical and industrial analysis. The principle of this method is based on the reaction of diazonium salts with aromatic amines and aromatic phenols to quantitatively determine the content of aromatic amines and aromatic phenols. The reaction is: Ar-N_2 ~ ++ A’_r-X (OH or NH_2) → ArN = N-A’_r-X + H ~ +. Using polarography, the diazonium salt is reduced on the drop mercury electrode to form Ar-N≡N: or Ar-NH-NH_2. The half-wave potential (Ar-N≡N: + e → ArN≡M :) of the previous reaction is -0.2 to -0.3 volts and the half-wave potential of the latter reaction (Ar-N≡N: + 4e + 3H + → ArNH-