Separation of dithiothreitol and dithioerythritol by an open tubular capillary electrochromatographic column with an MOF modified by histidine as the stationary phase†

A separation and determination method for dithiothreitol (DTT), as an important small molecule reducing agent, and dithioerythritol (DTE), as a C3-epimer of DTT, was developed via capillary electrochromatography. A functional MOF (His-ZIF-93) was first prepared using ZIF-93 (synthesized via coordination between 4-methylimidazole-5-carbaldehyde and Zn²⁺) as the framework and D-histidine (D-His) as the modifier, and then it was bonded to the inner wall of the capillary column to obtain a His-ZIF-93 column via the Schiff base reaction. Results showed that the baseline separation of DTT and DTE was easily achieved under wide experimental conditions with an extremely short analysis time of less than 3 min. The success of the separation mechanism was proved through binding constant experiments. There was a good linearity between the concentration (0.10–5.0 mg mL⁻¹) and peak area of DTT and DTE (R² ≥ 0.996), and the relative standard deviations for the peak area and retention time were less than 0.93%. The average impurity content of DTE in 5.0 mg per mL DTT was 0.79%. Thus, the method was able to realize simple and fast separation of DTT and DTE and their precise quantification.