Significant Waste Reduction in Liquid Chromatography by a Reusable Large-Volume Monolithic Silica Column

Abstract

The highly efficient separation of product mixtures in chemical synthesis is increasingly crucial for realizing sustainable chemical processes. Here, we report that large-volume monolithic silica with a well-defined cocontinuous porous structure brings significant benefits to liquid chromatography, satisfying both the enhanced efficiency and remarkable reduction of chromatographic wastes of solvent and solid separation media. Reusability of the monolithic silica column has been demonstrated by regeneration with an acid-flow washing, in which the cocontinuous porous structure of monolithic silica is well retained even in aqua regia in the regeneration process. The resolution of separation is comparable to preparative high-performance liquid chromatography, and the extremely low column back-pressure is suitable for open and flash columns. Moreover, a good correlation of the retention with conventional thin-layer chromatography and the high loading capacity up to 10 wt % are advantageous in overloading purification. Improved productivity with the large-volume monolithic silica has been confirmed in the practical purification of a low-solubility compound, 9-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)­phenyl]-N,N,N′,N′-tetraphenyl-9H-carbazole-3,6-diamine (DACT-II), for a highly efficient organic light-emitting diode. Reduction of solvent and solid consumption by 60 and 90%, respectively, with increased purities in each step of the total synthesis of DACT-II, has been demonstrated in comparison with purification with standard silica particles.

Halogen-Free Purification of Low-Solubility Compounds in Supersaturated Liquid Chromatography Using Monolithic Silica

“… a Used monolithic silica column ⌀ 23 × 100 mm; HEX:DCM = 7:3. The data of chromatographic purification were referenced from ref . b Yield, recovery, and HPLC purity values in total. c As microcrystalline powders. …”

“…The column of monolithic silica and DACT-II (Figure a) were prepared according to the literature. , The procedure for halogen-free purification using a monolithic column is shown in Figure b. First, dichloromethane (DCM, 15 mL) was used to achieve the initial dissolution of the reaction mixture of DACT-II (1.50 g, 84.0% purity), and then toluene (20 mL) was added.…”

“… a Used monolithic silica column ⌀ 23 × 100 mm; HEX:DCM = 7:3. The data of chromatographic purification were referenced from ref . …”

“…We previously demonstrated environmentally friendly LC purification by a monolithic silica column for an OLED material of 9-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)­phenyl]- N , N , N ′, N ′-tetraphenyl-9 H -carbazole-3,6-diamine (DACT-II), a highly efficient thermally activated delayed fluorescence emitter with an internal quantum efficiency of almost 100%. , The large-volume monolithic silica for glass columns showed high durability and high tolerance against column regeneration. We showed that the column offers rapid separation and lower costs by high-loading purification, reuse of the whole column, recycling of solvents, and the drastic reduction of solid and liquid waste for 90% and 60%, respectively, in DACT-II purification.…”

Sodium-Mediated Reductive anti-Dimagnesiation of Diarylacetyl­enes with Magnesium Bromide

“…Purification was done by column chromatography using silica gel (KANTO CHEMICAL CO., INC., Silica gel 60 N, spherical neutral, particle size 100-210 µm) or monolithic silica column. 18 Preparative recycling gel permeation chromatography (GPC) was done on a JAI LC-9260 II NEXT system using CHCl3 as the eluent. FID-GC analysis was carried out using a Shimadzu GC-2025 system equipped with a Shimadzu GC column SH-Rtx-5 (30 m x 0.25 mm x 0.25 μm).…”