Liquid chromatography - mass spectrometry (LC-MS) is an extremely powerful technique for analysis of mixtures. Usually, 20 uL of a sample is injected onto a HPLC column for separation. It is recommend that the submitted sample contains 200 pmoles/uL of sample with a total volume of 40 uL. The extra 20 uL is held in reserve for a second run if needed.

As the eluant comes off of the HPLC column, it goes into a UV detector that monitors one wave length. Unless otherwise requested, the lab monitors 214 nm.

After detection by UV, the sample flows into the mass spectrometer where the eluant is continually monitored. By the end of the analysis hundreds if not thousands of electrospray mass spectra are recorded.

The mass spectra can then be correlated to the UV trace. Below is the mass spectrum of the UV peak marked insulin.

The above pictures demonstrate what the UV intensity and peak intensities are of a sample containing 376 pmoles of protein (insulin). The reconstructed mass spectrum is shown below.

For an explanation of the mass spectrum and reconstructed mass spectrum see ESI analysis.