Boosting the Detection Potential of Liquid Chromatography-Electron Ionization Mass Spectrometry Using a Ceramic Coated Ion Source

Abstract

Abstract. Detection of target and non-target substances and their characterization in complex samples is a challenging task. Here we demonstrate that coating the electron ionization (EI) ion source of an LC-MS system with a sol-gel ceramic film can drastically improve the detection of high-molecular weight and high-boiling analytes. A new ion source coated with a ceramic material was developed and tested with a mixture of polycyclic aromatic hydrocarbons (PAH) with an increasing number of rings. Comparison of the results obtained with those for an uncoated stainless steel (SS) ion source shows a dramatic improvement in the MS signals, with a nearly 40-fold increase of the signal-to-noise ratio. We also demonstrate the ability of the new system to produce excellent chromatographic profiles for hard-to-detect hormones.

Condensed Phase Membrane Introduction Mass Spectrometry with Direct Electron Ionization: On-line Measurement of PAHs in Complex Aqueous Samples

“…It appears that the higher the PAH boiling point, the slower its subsequent release into the gas phase, and this may explain the results obtained with the larger PAHs. Although not available at the time of this study, a ceramic coated DEI ion source improves the DEI measurement of high molecular weight PAHs [33]. It should be noted that PAH isomers with the same m/z (e.g., phenanthrene and anthracene) are not resolved by this method and quantitation requires an aggregated approach.…”

“…Future work includes improving further the detection limits, and expanding the range of possible analytes (e.g., PCBs, dioxins) that can be detected. This will include the development of improved membrane interface designs to accommodate lower acceptor flow rates, the continued use of thinner membranes, incorporation of on-line internal standard infusion strategies [7], as well as the use of EI source modifications to facilitate successful measurements of analytes with very low vapor pressures [33].…”

Current developments in LC-MS for pharmaceutical analysis

“…Adsorption and thermal degradation on the metal surface of the ion source can have a severe impact on the sensitivity and reproducibility of the detection signal, especially for polar, low-volatility and thermally sensitive compounds. It has been demonstrated that ceramic coating of the inner surface of the stainless steel ion source significantly improves the MS signal 28 . Both for the direct flow injection analysis of 16 polyaromatic hydrocarbons (PAHs) and the Direct-EI-LC-MS analysis of four hormones, peaks obtained with a ceramic coated ion source were much sharper and displayed significantly higher signal-to-noise (S/N) ratios (up to a four-fold increase) compared to a stainless-steel ion source.…”

MS-Based Analytical Techniques: Advances in Spray-Based Methods and EI-LC-MS Applications

“…Regarding Direct-EI LC-MS, recent studies have been carried out also to increase the inertness of the electron ionization ion source by developing new materials [ 37 , 38 ].…”

“…As already stated, the vaporization surface of an electron ionization MS source is a key parameter for the detection and characterization of targeted and untargeted analytes: it is known that difficulties in the vaporization process arise when compounds characterized by high molecular weight and/or polarity have to be analyzed, thus requiring both the use of inert ion sources to reduce the interactions of the analytes with the stainless steel ion source and the use of high source temperatures to promote analyte vaporization. In this field, Magrini et al [ 37 ] proved that the use of a commercially available ceramic coating is able to improve the detection of high molecular weight and high boiling compounds like polycyclic aromatic hydrocarbons (PAHs) and hormones. More recently, Riboni et al [ 38 ] were able to increase the inertness of the electron ionization ion source by developing different sol-gel coatings based on silica, titania, and zirconia.…”