High-throughput determination of identity, purity, and quantity of combinatorial library members using LC/MS/UV/ELSD

We have used a high-throughput LC/MS/UV/ELSD method to rapidly determine the absolute quantity and purity of 42 organic compounds from seven lead discovery libraries. A general calibration curve generated from a different set of 42 compounds with seven different scaffolds was used in this analysis. We have also studied 33 organic compounds with different molecular weight (MW) by LC/MS/UV/ELSD to investigate the effect of MW on ELSD response and the accuracy for purity and quantity measurement using UV(214) and ELSD. A general ELSD calibration curve from these compounds was also generated to quantify 42 library compounds. Purity measurement by ELSD underestimates the amounts of impurities due to a reduced ELSD response from smaller molecular weight impurities often produced in library synthesis. Absolute quantity determination by ELSD is more accurate (RSD 28%) than that by UV(214) (48%) using a calibration curve generated from the same set of compounds with diverse MWs. Error assessment for the measurement of absolute quantity of a class of commercial compounds and a class of representing reference compounds from seven diverse lead discovery libraries shows that structurally related compounds should be used to generate calibration curves to sustain smaller deviation.