Peer Reviewed: Forced-Flow Techniques in Planar Chromatography

Basic TLC Techniques, Materials, and Apparatus

“…With this OPLC apparatus, minimum values of reduced plate height are 2.1-3.5, depending on the operating conditions and layer properties. The corresponding range for a good HPLC column is 2.0-2.5, so efficiencies are comparable under optimum conditions (39).…”

“…11), whereas many applications of OPLC for analytical separations have been reported. RPC never reaches an overall mobile-phase velocity that would give the highest separation efficiency, because the radial velocity of solvent migration diminishes from the center to the circumference of the plate (39). In OPLC, mobile-phase velocity can be controlled at a predetermined constant close to optimal value so that solvent front migration is a linear function of time (30).…”

“…The time required for the mobile phase to cover the same distance in OPLC is typically five-to tenfold shorter than in TLC, depending on the surface tension, viscosity, and the ability to wet the layer. Separation time is further reduced because the number of theoretical plates needed to achieve a separation is generated in a shorter time because of the near-optimal mobile-phase flow rate (39). Poole (13) showed that for a development distance of 18 cm, forced-flow development can produce 8000 theoretical plates in 9 min.…”

“…Nurok (39) reported that separation of six pyrimidines on silica gel with acetonitrile mobile phase was 12 times faster than with conventional TLC and that separation in the RP mode is two to three times faster depending on the mobile phase. Only preliminary studies of this approach have been carried out to date, and Poole (13) reports that the mobile-phase velocity declined with migration distance and showed only moderate increase compared to capillary flow, and that the demonstrated improved performance with electro-osmotic flow has been below that predicted by theory.…”

Rotation Planar Chromatography Coupled On-Line with Atmospheric Pressure Chemical Ionization Mass Spectrometry

“…The CycloGraph is a commercially available centrifugally accelerated preparative thin-layer chromatography (TLC) system (Figure ) . This rotation planar chromatography system is used to carry out one type of forced-flow planar chromatography. , Such systems allow establishment of a relatively constant and optimum mobile-phase velocity. These features result in faster separations and higher zone capacities than are possible with capillary flow TLC systems.…”