Separations of small molecules and polar analytes can be challenging when sourced from food, natural, or consumer products. Nonetheless, analysis of water-soluble vitamins and other polar compounds including catecholamines is essential in product quality testing or detection for the presence of metabolites.
The new epic polar HPLC columns from Perkin Elmer contain high-density C18 specifically engineered for the retention of polar analytes including small organic acids, water-soluble vitamins, catecholamines, and other polar compounds. A recent application note demonstrates the separation of 11 highly polar organic acids, which is possible even with the use of 100% aqueous mobile phases. This performance is thanks to a novel proprietary binding chemistry which allows bonded chains to remain fully extended in the mobile phase.
Perkin Elmer also recently released a column technology for supercritical fluid chromatography (SFC) separations of complex natural products. The GreenSep NP-II column is specifically designed for isolation of THC and THCV (tetrahydrocannabivarin) from cannabis. Although THC is well-known, THCV is produced in far smaller quantities in the plant. Limiting sources of sample combined with the lack of high-performance isolation techniques has hindered the study of THCV and its potential role in medicine.
SFC is a powerful technique, owing to attributes of both GC and LC separations. It can be limited, however, to the use of “older” normal-phase media such as silica, diol, amino, and cyno beads. Performance impacts of these columns can include low capacity, poor selectivity, and poor peak shape. The GreenSep NP-II uses a bonded-phase that exhibits excellent peak separations in complex cannabinoid mixtures, which include the minor compound THCV. The columns are available with 5 or 10 µm particle sizes and formats ranging from analytical to preparative up to 50 mm ID.
C18 columns and reverse-phase media in general have been widely used for a broad range of applications over the years. Biphenyl stationary phase columns, however, have received growing appeal due to their ability to retain and resolve challenging small molecule analytes. In some cases, biphenyl columns can perform on par with C18. In other scenarios where small compounds, isomers, and metabolites are involved, biphenyl can sometimes outperform C18.
Biphenyl columns excel at being able to be “tuned” simply using different mobile phases. With the use of acetonitrile, the column can function like C18. Switching to methanol, the selectivity and retention is extended beyond that of other separation phases. Restek, a pioneer in the method of biphenyl chromatography offers a host of resources on their website that highlight the performance and utility of these separations. Restek offers a range of columns from SPP to traditional fully porous particles for both HPLC and UHPLC applications.