FORWARD-SCATTERING DEGENERATE 4-WAVE-MIXING AS A POTENTIAL LASER-BASED ABSORPTION DETECTION METHOD IN LIQUID SEPARATION SYSTEMS - COUPLING TO CONVENTIONAL-SIZE LIQUID-CHROMATOGRAPHY

An explorative study on the compatibility of liquid separation systems , such as (micro) liquid chromatography (LC) and capillary electrophor esis (CE), and forward-scattering degenerate four-wave mixing (F-D4WM) as a detection method is presented. F-D4WM is a laser-based technique showing some analogy with holographic spectroscopy: a signal on a the oretical dark background is observed as a result of light absorption b y an analyte. Parameters considered are solvent composition (focussing on acetonitrile, methanol and water; mobile phases in LC and CE), det ector cell construction, and influences of laser beam powers. A specia lly designed detector cell has been developed to meet the Brewster con dition, both at the air-quartz and the quartz-liquid boundaries. For p ractical reasons, the tested cell has an optical pathlength of 1 mm; r eduction to 100 mu m is required to apply the cell in microseparations . The F-D4WM technique has been involved for detection in a convention al-size, reversed-phase LC separation of 1- and 2-aminoanthraquinones. The detection limit obtained (for the 1 mm cell) is 2x10(-5) absorban ce units. The experiments indicate that further reduction of backgroun d deserves explicit attention.