Analysis of Compounds Dissolved in Nonpolar Solvents by Electrospray Ionization on Conductive Nanomaterials

Abstract

Electrospray ionization mass spectrometry (ESI-MS) technique has limitations in analysis of compounds that are dissolved in nonpolar solvents. In this study, ambient ionization of compounds in solvents that are not "friendly" to electrospray ionization, such as n-hexane, is achieved by conductive nanomaterials spray ionization (CNMSI) on nanomaterial emitters, including carbon nanotubes paper and mesodendritic silver covered metal, which applies high voltages to emitters made of these materials without the assistance of polar solvents. Although the time intensity curves (TIC) commonly vary from 4.5% to 23.7% over analyses, protonated molecular ions were found to be the most abundant species, demonstrating good reproducibility of the technique in terms of ionized species. Higher mass spectrometric responses are observed in analyzing nonpolar systems than polar systems. 2-Methoxyacetophenone, 4-methylacetophenone, benzothiazole, quinolone, and cycloheptanone as low as 2 pg in n-hexane can be directly detected using the developed method. The developed technique expands the analysis capability of ESI-MS for direct, online analysis of nonpolar systems, such as low polarity extracts, normal phase liquid chromatography eluates, and synthetic mixtures. Graphical Abstract.

Does the Red Shift in UV–Vis Spectra Really Provide a Sensing Option for Detection of N-Nitrosamines Using Metalloporphyrins?

“…Since we did not have HR-MS at our disposal, the binding of NNN as representative TSNA to metalloporphyrin CY-B was studied using ESI-MS. Interestingly, the authors claimed that the solutions used for UV–Vis spectroscopy were analyzed subsequently by HR-MS. This is a rather unusual approach due to CH 2 Cl 2 used in UV–Vis measurement being too nonpolar (dielectric constant ε = 9.1) and thus less suitable as MS solvent due to weak stabilization of charged species . Our UV–Vis samples (with red-shifted metalloporphyrin CY-B Soret band due to NNN binding) were thus diluted 10 times with methanol prior to MS analysis.…”

“…This is a rather unusual approach due to CH 2 Cl 2 used in UV–Vis measurement being too nonpolar (dielectric constant ε = 9.1) and thus less suitable as MS solvent due to weak stabilization of charged species. 47 Our UV–Vis samples (with red-shifted metalloporphyrin CY-B Soret band due to NNN binding) were thus diluted 10 times with methanol prior to MS analysis. The formation of 1:1 and 1:2 CY-B/NNN complexes was indeed observed, as evidenced by peaks with m / z 711.0, 888.0, and 1065.2.…”

Selective Enrichment of Phosphopeptides and Phospholipids from Biological Matrixes on TiO2 Nanowire Arrays for Direct Molecular Characterization by Internal Extractive Electrospray Ionization Mass Spectrometry

“…The detection sensitivity and chemical selectivity of direct MS analysis has been significantly improved with the adoption of functional materials. , Various functional materials have been used for the selective chemical extraction of biosamples prior to MS detection. − Also, use of molecularly imprinted membranes, surface modified wooden tips, and octadecyl silica coated blades , allowed MS detection of target compounds at sub-ppb level in complex samples. ,, Recently, titanium dioxide (TiO 2 ) particles were demonstrated for the enrichment of analytes with phosphoryl group based on the Lewis acid–base interactions between the phosphoryl group and Ti ions. − Thus, the development of ambient ionization method combined with the TiO 2 material should be a potential solution for the rapid determination of phosphopeptides or phospholipids in biological matrixes.…”

Controlling morphology in electrosprayed methylcellulose nanowires via nanoparticle addition: coarse-grained modeling and experiments

“…This behavior is consistent with observations in electrospray mass ionization that the sharp vertex of a graphene flake can enable the ionization of otherwise incompatible fluids. 34 We further investigate the effects of particle shape through electrospray experiments. Ti 3 C 2 T x was selected for this study because it is the most studied and best understood MXene material.…”