Innovative configuration of multiple MIL-100(Fe) monolithic columns for in-tube solid-phase microextraction of...

In-tube solid-phase microextraction (IT-SPME) is an ideal method for the extraction of non-volatile and heat-sensitive compounds. However, the development of configurations and sorbents of the IT-SPME method has always been of interest to reduce limitations. One type of these modes is monolithic columns that can be easily synthesized in any shape. Considering the previously introduced two monolithic column and fiber configurations, an HPLC guard column can be designed in which MIL-100(Fe) monolithic columns are placed side by side as parallel fibers. Multiple poly(methacrylic acid-ethylene glycol dimethacrylate) monolithic columns were first prepared. Then MIL-100(Fe) was synthesized in situ at room temperature within and throughout the monolith, enhancing the extraction efficiency of five sulfonamides as model analytes.

A multiple MIL-100(Fe) monolithic column-IT-SPME-HPLC-UV method was introduced for the extraction of sulfonamides from human tear fluid and milk samples. The poly(methacrylic acid-ethylene glycol dimethyl acrylate) monolithic columns were prepared separately in glass capillary tubes, and then MIL-100(Fe) was formed in situ at ambient temperature inside the activated monolithic columns. Due to the two-step synthesis method, pore-clogging monolithic columns with crystalline MIL-100(Fe) were not observed. High reusability of the structure was observed because all experiments were performed with a single device. Also, a reduction in back pressure and an increase in extraction efficiency were achieved. The limits of detection were 0.2-0.4 μg L^-1 with RSD% < 7.4 %; the linear dynamic range was 0.6-250.0 μg L^-1, while RR% ranged from 93.4 to 117.6 and 89.2-115.0 for tear and milk samples, respectively.

This work represents the first approach to apply multiple monolithic columns composed of MIL-100(Fe) for IT-SPME of sulfonamides.