Matrix assisted laser desorption/ionization (MALDI) has been used to provide the weight average molecular weight (Mw), the number average molecular weight (Mn), and the polydispersity (PD) of synthetic polymers since the late 1980's [1]. The soft ionization technique of MALDI-time of flight mass spectrometry (MALDI-TOF MS) has allowed for the ionization and desorption of macromolecules without fragmentation [2].

This research focuses on improving the intensity and sensitivity of MALDI signals by using nanoliter volume spots [3]. The concentration of the sample spot on the MALDI plate is one factor in the quality of MALDI-TOF MS signals. Using the traditional dried droplet “method” where uL quantities are deposited, analyte sample inhomogenieties are known to result which are known as “hot” or “sweet “spots, plus volumetric deposition can be inaccurate. It was reasoned that by using nanoliter volumes of samples, the spatial concentration of the sample could be increased, as excessive matrix related noise is reduced. Also a confluence of factors, including the use of liquid ionic matrices, were anticipated to improve S/N ratios and MALDI data quality. This was shown by researchers at Washington University in 2007 for proteins [3].

This work examines if precise nanoliter sample deposition can improve MALDI for industrial polymers. Using a nanoliter syringe and induction-based fluidics (IBF), precise volume deposition from 10-300nL were placed on the MALDI target and MALDI spectra were acquired. Observations, a comparison of MALDI signals, Mw, Mn, and PD, on the use of nanoliter and microliter sample spots of polystyrene were reported.