Universal liquid chromatography methods : IV. Use of 190-mm full gradients by adjustment of eluent ultraviolet absorbance and pH with gases

Abstract

The full-gradient “universal liquid chromatography” methods are extended to 190 nm detection for even greater sensitivity and detection of more components than shown previously at 210 nm. Universal liquid chromatography offer major time/costs savings by increasing problem solving throughout. Further, at 190 nm, simple molecules such as aliphatic alcohols are detected and 254-nm detectable species are quantified to much lower levels. Universal liquid chromatography “elutes-all” in a first wide-polarity, full gradient run and “detects-all” with low wavelength (less than 214 nm) UV and permits easy resolution changes. A single universl method replaces many different tailored isocractic runs for first-run-problem-solving of most mixtures. These methods eliminate method development for each new problem and also permit unattended runs of totally different separation problems. Universal methods permit rapid product, mix, or raw material comparisons of good vs. bad, new vs. old, or starting vs. purified materials while signaling new components that might not be seen in the narrow polarity window of isocratic runs. “Injection loading” of ion-pairing agent is also extended to 190 nm. This allows rapid run-to-run change in selectivity and exploration of ion-pairing effects plus determination of charges of ionic species. A new “gas baseline adjustment” method allows very simple eluent preparation to fix pH and give flat, ghost-peak-free baselines. A new method is given to calibrate detectors at all wavelengths and a simple “linear mixer” eliminates short-term baseline noise.