Revisiting the quantitative features of surface-assisted laser desorption/ionization mass spectrometric analysis

Abstract

Surface-assisted laser desorption/ionization (SALDI) coupled with mass spectrometry (MS) is frequently used to analyse small organics owing to its clean background. Inorganic materials can be used as energy absorbers and the transfer medium to facilitate the desorption/ionization of analytes; thus, they are used as SALDI-assisting materials. Many studies have demonstrated the usefulness of SALDI-MS in quantitative analysis of small organics. However, some characteristics occurring in SALDI-MS require certain attention to ensure the reliability of the quantitative analysis results. The appearance of a coffee-ring effect in SALDI sample preparation is the primary factor that can affect quantitative SALDI-MS analysis results. However, to the best of our knowledge, there are no reports relating to quantitative SALDI-MS analysis that discuss or consider this effect. In this study, the coffee-ring effect is discussed using nanoparticles and nanostructured substrates as SALDI-assisting materials to show how this effect influences SALDI-MS analysis results. Potential solutions for overcoming the existing problems are also suggested.This article is part of the themed issue 'Quantitative mass spectrometry'.

Continuous synthesis of BaFe2O4 and BaFe12O19 nanoparticles in a droplet microreactor for efficient detection of antihistamine drugs in oral fluid using surface-assisted laser desorption/ionization mass spectrometry

“…This is not surprising as coffee ring phenomenon was previously observed in SALDI-MS especially upon using dried droplet method. 42,43 Despite the inhomogeneous distribution been observed after the deposition of the analyte-substrate mixture, a reproducible qualitative and quantitative data with satisfactory relative standard deviation (RSD) were obtained.…”

Single-Walled Carbon Nanohorns as Boosting Surface for the Analysis of Low-Molecular-Weight Compounds by SALDI-MS

“…The main issue is related to the presence of background interfering species, generated by the ionization of the matrix itself, which are accounted for the suppression of analytes signals in the low mass region of the spectrum. Furthermore, the co-crystallization process, i.e., the inclusion of analyte molecules in the matrix crystals occurring by solvent evaporation at room temperature, causes inhomogeneity of the resulted crystals, the presence of hot spots, and the unwanted coffee-ring effect [1]. The severity of these effects is matrix-dependent and interferes with the possibility of obtaining accurate quantitative results and good reproducibility by MALDI-MS analysis.…”

Coffee Ring Effect Free TiO2 Nanotube Array for Quantitative Laser Desorption/Ionization Mass Spectrometry

“…In some previous studies, it is reported that the coffee ring effect can be suppressed by fabricating wells on the sample plate through oxygen plasma treatment or additional copper tape. 36,37 In this study, a TiO 2 nanotube array with hydrophilic dot patterns surrounded by hydrophobic areas (HB/HL-patterned TiO 2 NTA) is presented to both distribute analytes uniformly to concentrate them within a sample spot. A vertically aligned one-dimensional (1D) TiO 2 NTA can act as a liquid vessel rather than other nanostructures such as nanoparticles and randomly oriented nanowires.…”

“…Several attempts have been made to suppress the coffee ring effect through sample preparation methods, such as controlling the surface tension, viscosity, pH, and temperature of the sample. − However, these approaches usually require specific additional reagents depending on the samples, which make interference mass peaks from chemical additives in LDI-MS. In some previous studies, it is reported that the coffee ring effect can be suppressed by fabricating wells on the sample plate through oxygen plasma treatment or additional copper tape. , …”