A method and apparatus for high-throughput identity confirmation, quantitation and purity determination of a compound of interest in a mixture of compounds is disclosed. According to the method, a chemical mixture, such as may be obtained from a chemical library, is processed to obtain a stream having a time-varying composition, such as by using a high pressure liquid chromatograph. The stream is split into two portions or streams for substantially contemporaneous detection in a compound-identifying device, such as a mass spectrograph, and in a compound-quantitating device, such as an evaporative light scattering detector. A peak in a chromatogram obtained from the compound-quantitating device is identified as the compound of interest by cross-correlation, via elution time, with chromatographic results obtained from the compound-identifying device. Once the peak is identified as corresponding to the compound of interest, the corresponding peak area is used for quantitation and purity determination.