Phase-shift-free subtraction chromatograms from a dual-channel detector

Compared to single-channel analysis, dual-channel correlational chromatography can dramatically improve selectivity. Yet the extent of improvement is often limited by phase shifts due to the slow conventional electrometer/filter instrumentation used prior to signal deduction. Since fast amplification/correlation circuitry can avoid these phase shifts, a suitable electronic module with a millisecond time constant was constructed. In a demonstration experiment, it improved the linear selectivity of a chromium vs. a ruthenium compound to theoretical limits, i.e. by well over three orders of magnitude.