The influence of electrospray deposition in matrix‐assisted laser desorption/ionization mass spectrometry sample preparation for synthetic polymers

Abstract

Although electrospray sample deposition in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) sample preparation increases the repeatability of both the MALDI signal intensity and the measured molecular mass distribution (MMD), the electrospray sample deposition method may influence the apparent MMD of a synthetic polymer. The MMDs of three polymers of differing thermal stability, polystyrene (PS), poly(ethylene glycol) (PEG), and poly(propylene glycol) (PPG), were studied by MALDI time-of-flight (TOF) MS as the electrospray deposition voltage was varied. The MMDs obtained using the electrospray deposition method were compared with those obtained for hand-spotted samples. No change was observed in the measured polymer MMD when the electrospray deposition voltage was varied in the analysis of PS, but those of PEG and PPG changed at higher electrospray voltages due to increased ion fragmentation. It was also shown that the fragmentation in the hand-spotted samples is dependent on the matrix used in sample preparation.

Electric field enhanced sample preparation for synthetic polymer MALDI-TOF mass spectrometry via Induction Based Fluidics (IBF)

“…Two trends appear when looking at the depositions made with amorphous polymers: (1) IBF depositions yielded larger crystal depositions; (2) IBF depositions having the same volume and concentration when compared to their MP counterparts were more compact, occupying less physical surface area on both the steel AB MALDI plate and glass slides. As previously mentioned, studies have shown and promoted that smaller homogenous crystallization as the preferred and most productive morphology that renders quality MALDI signals [31][32][33]. In this study, we present evidence from cross-polarization microscopy that directly contradicts the commonly held belief that only smaller homogenous crystals produce quality signal.…”

“…It has been reported that micropipette 'dried droplet' polymer depositions have high local deposition variability and this variability leads to less reproducible signals [31,32]. A consequence of this heterogeneity of deposition is that characteristic data (M N and M W ) have high degrees of variance and are not accurate enough for polymer classification.…”

Tissue protein imaging at 1 μm laser spot diameter for high spatial resolution and high imaging speed using transmission geometry MALDI TOF MS

“…Although playing important role in establishing the transmission geometry LDI sources, this setup was not readily applicable for imaging applications. There were also several reports of using the laser focusing optics inside the vacuum chamber by employing reflective optics in a Cassegrain scheme, providing a longer working distance, for example LIMA instrument (Cambridge Mass Spectrometry, Cambridge, UK) [5]. The reflective objectives however introduce additional diffraction limits and aberrations and the minimum laser spot sizes are larger, for example 1–3 μm at 266 nm wavelength in LIMA-2A [6] and were useful only for profiling applications.…”

Significant parameters in the optimization of MALDI-TOF-MS for synthetic polymers

“…These parameters, as well as laser energy, were most influential for the polystyrene with dithranol as the matrix. any factors influence the quality of matrixassisted laser desorption/ionization (MALDI) time-of flight (TOF) mass spectra of synthetic polymers [1][2][3][4][5][6][7][8][9][10][11]. Foremost is the nature of the sample itself.…”

“…The detector voltage influences the sensitivity of the detector, but if the detector voltage is too high, a loss in the signal-to-noise may result because of the increase in background noise. To keep the design relatively simple and the amount of data to a minimum, we chose to concentrate on only two sample preparation parameters: matrix type and polymer concentration [6,8,10,21].…”