MATRIX ELIMINATION IN LIQUID-CHROMATOGRAPHY USING HEART-CUT COLUMN SWITCHING TECHNIQUES

A generic approach to matrix elimination in liquid chromatography has been developed. A physical rather than chemical means of matrix elimination, i.e., an on-line sample preparation scheme, using column switching techniques, is described herein. The bulk of the sample matrix is diverted to waste and only a "heat-cut" of the chromatogram completely analyzed. The technique has universal applicability, does not suffer the limitations associated with classical matrix elimination, and significantly reduces system abuse. Dramatic improvements in chromatography were realized for sulfite determinations in bulk analgesic formulations. Accuracy, based on spike recovery data, was 91%, precision was within 20% RSD throughout, and the quantitation limit was 2 ppm. It was postulated that the method should be able to accommodate a broad diversity of sample types with little or no matrix interference, since the majority of the matrix has been eliminated from the analysis. Therefore, the method was extended to OTC analgesics, beer, wine, and various food items. The heart-cut technique has also been used in a multidimensional analysis of an organic sample with electrochemical detection and in brine analysis. Advantages realized include superior chromatography, a reduction in system abuse, economic advantages, and greater sample throughput, i.e., shorter analysis time.