In LC – DAD the ability to collect UV-Vis ‘scan’ data enables peak purity estimations, this combined with a retention time identifier gives an overall 3-dimensional output akin to GC-MS. Thousands of compounds are present in many libraries, covering applications from Environmental, through Pharma, Cosmetics, Pesticides and QC Testing, many of these compounds aren’t amenable to GC analysis.

The theory is based on an absorbance profile over a wavelength range, as shown in Figure 1. Plus, many other parts of a matching algorithm combine to give a ‘peak purity’, as shown in Figure 2, leading to powerful probability-based matching (PBM).

Small differences in the spectra can also differentiate between isomers, as shown in Figure 3, which mass spectrometers aren’t so good at.

LC-DAD is often overlooked as a technique for unknowns analysis, with a preference for using mass spectrometers hyphenated to chromatography instrumentation, however LC-DAD has many advantages in terms of cost and simplicity of instrumentation making it a good choice for many applications.