Analytical Sciences

Abstract − Analytical Sciences, 25(6), 743 (2009).

An Interpretation of Alternative Plugs Flow Liquid Chromatography in a Slightly Modified GC/MS System
Isao TANIKAWA,* Miwako KONUMA,** Hiroko HOSONO,** and Hiroshi NAKAMURA***
*Infra-red Spectroscopy Analytical Laboratory, 3-3-13 Chuo, Ebina, Kanagawa 243-0432, Japan
**Corporate Research & Development Toyo Seikan Group, 22-4 Okazawa, Hodogaya, Yokohama 240-0062, Japan
***Department of Analytical Chemistry, Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
Alternative plugs flow liquid chromatography (APFLC), a type of gas-liquid two-phase flow chromatography (2PFC) is achieved by the agglomeration of unformed condensates in an open tubular capillary column with intermittently alternating condensates in which the supply of the liquid is maintained at a level that provides a hypothetical homogeneous film, 25 to 150 nm thick, on the inner surface. To support stable plugs, the flow mode should normally be maintained at a liquid-to-gas volume ratio (β) of between 0.0006 and 0.004 and below 70°C. Alternative plugs flow is formed as a result of the hydrophobic property of the stationary phase, which is induced at a water contact angle above 75°, as derived from the solubility parameter (δ) of a coated resin of less than 18.3 MPa1/2. Diffusion and mixing between the vicinal partition fields is substantially avoided in alternating disconnected nano-volume plugs, which makes it possible to obtain a very large number of theoretical plates of separation. The plugs flow as a mobile phase can be enhanced by applying sonic vibrations to the column. Since the liquid/gas phases ratio (β) is maintained in the range of 10−4 to 10−3, the extremely small volumes of solvent offer the advantages of compatibility with an EI-ionizing mass spectrometer and the use of commercially available mass search systems. The APFLC/EI-MS system, which employs commercially-available GC/MS equipment, is potentially applicable to both GC and LC analysis containing sparingly volatile components, giving close to the theoretical resolution and eliminating the need for numerous derivatization procedures.