Abstract: A liquid chromatography-electrospray ionization mass spectrometry method is capable of separating and identifying different prostaglandin isomers, including PGD2 and PGE2. Unlike traditional gas chromatography methods, little sample preparation and no derivatization are required. The chromatography is performed under acidic conditions that are optimal for separating the isomers. A basic sheath flow liquid is added to the chromatographic eluent, resulting in high ionization efficiency when the electrospray ionization is performed in negative ion mode. Additionally, by altering the energy at which the ionization is performed, tandem mass spectra of the two isomers can be made to differ as a result of the different relative energies of the two isomers.

Abstract: High-intensity, spiked noise is reduced in chromatography-mass spectrometry data by applying a nonlinear filter such as a moving median filter to the data. The filter is applied to individual mass chromatograms, plots of ion abundance versus retention time for each detected mass-to-charge ratio, and the filtered chromatograms are combined to form a filtered total ion current chromatogram. Standard linear filters are not effective for reducing noise in liquid chromatography-mass spectrometry (LC-MS) data because they assume a normal distribution of noise. LC-MS noise, however, is not normally distributed.