β-环糊精增敏亚甲基蓝测定抗坏血酸

Fluorescence quenching method for the determination of ascorbic acid with methylene blue by sensitizing effect of β-cyclodextrin

在酸性条件下,抗坏血酸(AA)与亚甲基蓝(MB)形成不发荧光的离子缔合物。在pH 4.0时,加入适量β-环糊精(β-CD),MB由于和β-CD形成包合物而使其荧光强度大大增强,导致荧光猝灭值ΔF随抗坏血酸的加入上升为原来的近3倍,从而提出了一种增敏亚甲蓝荧光猝灭法测定抗坏血酸的新方法。该体系最大激发波长为λex=660 nm,最大发射波长为λem=678 nm,线性范围为0.05～24 mg/L,检出限为0.9688 mg/L,相对标准偏差为3.9%。方法已用于实际样品中抗坏血酸的测定,常见共存离子不干扰。

In acidic medium, methylene blue （MB） can directly react with ascorbic acid （AA） to form an ion association complex with no fluorescence intensity. At pH 4, after adding fight amount of β-cyclodextrin, the fluorescence intensity of MB is largely enhanced because of the inclusion complexation. The value of the fluorescence quenching is nearly tripled. A new fluorescent speetrophotometry based on this principle has been developed to determine AA. Its maximum excitation wavelength is 660 nm, and the maximum emission wavelength is 678 nm. The linear range, detection limit and relative standard deviation are 0. 05 - 24 mg/L, 0. 9688 mg/L and 3.9%, respectively. The common coexisting ions do not interfere in the determination. This method was used to determine AA in samples with satisfactory results.