Systematic approach to generic matrix elimination via ''heart-cut'' column-switching techniques

Liquid chromatography matrix elimination employing ''heart-cut'' column-switching techniques has been demonstrated previously to be a powerful analytical tool. In some instances this approach affords results that would otherwise be impossible to attain with conventional liquid chromatography, or other analytical techniques. This paper describes a detailed systematic approach to developing the requisite ''heart-cut'' analysis parameters. The analyses investigated were sulfite determination in analgesic formulations and sulfate determination in sodium phosphate. These analyses represent extremes in terms of matrix elimination complexity, i.e., the former was the simplest case, involving low-level anion determination in an organic matrix, while the latter was the most complicated, involving low-level anion determination in an inorganic matrix. The six-step procedure described to develop the requisite ''heart-cut'' parameters is the same for either case. In addition, this approach to matrix elimination has evolved from a research tool into an extremely rugged and practical routine procedure. The ruggedness of this technique was demonstrated by performing analyses continuously, 24 h per day, for several weeks. An on-line system clean-up procedure was developed to maintain optimum performance with maximum sample throughput.