Low-Cost Liquid Chromatography. I. Weak-Eluent Sample-Loading, A Novel Technique for Injecting Sub-Microliter Samples

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Abstract
A goal of creating a system for very “low-cost liquid-chromatography” “LC-LC”, is to eliminate most of the conventional components for gradient LC or to use the components in a more productive manner (e.g. a single autosampler can be used with many LC instrument off-line). This paper describes how an on-line robotic autosampler, required to change samples conventionally, can be used to eliminate the injector. Future work will show how the a single robotic autosampler can be used to supply many liquid chromatographys with sample, eliminating injector valves in all of them. Except for the most polar materials, most compounds in a weak eluent are generally accumulated on a reversed-phase column. Later these “focussed” peaks are eluted by a gradient or by an isocratic eluent of higher organic content. This is the basis for injection by loading sample in “non-eluting solvents”, but, still the injection is made with a conventional high-pressure valve. Also, this sample focussing effect is used to evaluate the purity of “LC-grade” water.