Nanosecond Pulsed Dielectric Barrier Discharge Ionization Mass Spectrometry

Abstract

Dielectric barrier discharge ionization (DBDI) is an emerging technique for ionizing volatile molecules directly from complex mixtures for sensitive detection by mass spectrometry (MS). In conventional DBDI, a high frequency and high voltage waveform with pulse widths of ∼50 μs (and ∼50 μs between pulses) is applied across a dielectric barrier and a gas to generate “low temperature plasma.” Although such a source has the advantages of being compact, economical, robust, and sensitive, background ions from the ambient environment can be formed in high abundances, which limits performance. Here, we demonstrate that high voltage pulse widths as narrow as 100 ns with a pulse-to-pulse delay of ∼900 μs can significantly reduce background chemical noise and increase ion signal. Compared to microsecond pulses, ∼800 ns pulses can be used to increase the signal-to-noise and signal-to-background chemical noise ratios in DBDI-MS by up to 172% and 1300% for six analytes, including dimethyl methylphosphonate (DMMP), 3-octanone, and perfluorooctanoic acid. Using nanosecond pulses, the detection limit for DMMP and PFOA in human blood plasma can be lowered by more than a factor of 2 in comparison to microsecond pulses. In “nanopulsed” plasma ionization, the extent of internal energy deposition is as low as or lower than in electrospray ionization and micropulsed plasma ionization based on thermometer ion measurements. Overall, nanosecond high-voltage pulsing can be used to significantly improve the performance of DBDI-MS and potentially other ion sources involving high voltage waveforms.

Plasma‐based ambient mass spectrometry: Recent progress and applications

“…Subsequently, they combined dopants, such as methanol, ethanol, acetone, NH 3 , and so on, with Ar‐SDDBDI to analyze the liable compounds and reduce the fragmentation (Zhang et al, 2018), for which the analytes were ionized primarily through proton transfer with dopant ions. Recently, a study introduced a nanosecond high voltage pulses in DBDI‐MS instead of the conventional microsecond pulses (Ahmed et al, 2020). This method highly improved the performances of sensitivity, signal‐to‐noise ratios, and LODs of dimethyl methylphosphonate (DMMP) analysis in blood plasma.…”

Ion Heating in Advanced Dielectric Barrier Discharge Ion Sources for Ambient Mass Spectrometry

“…DBD plasmas can be readily generated at ambient pressures and near room temperature using many different geometric configurations of the electrodes, 8 dielectric material, gases, 9,10 and high voltage pulsing sequences. 11,12 For example, since DBD ionization (DBDI) was first reported in 2007 as an ion source for ion mobility spectrometry by Franzke and co-workers (Figure 1), 13 several additional DBD-based ion sources have been developed, including low-temperature plasma (LTP), 14 active capillary plasma ionization (ACaPI), 15 and most recently flexible microtube plasma (FμTP) (Figure 1). 10 DBD-based ion sources can be used to enhance the sensitivity and detection limits of liquid chromatography mass spectrometry for the detection of both polar and nonpolar compounds (e.g., amino acids and perfluoroalkanes) 16,17 and can be readily integrated with solid-phase microextraction 18 and complementary sprayand laser-based ionization methods.…”

“…In dielectric barrier discharges, a high voltage alternating waveform is applied between two electrodes that are separated by an insulator (usually glass), resulting in a plasma that is highly versatile in terms of operating pressure, geometric configuration, size, and density. DBD plasmas can be readily generated at ambient pressures and near room temperature using many different geometric configurations of the electrodes, dielectric material, gases, , and high voltage pulsing sequences. , For example, since DBD ionization (DBDI) was first reported in 2007 as an ion source for ion mobility spectrometry by Franzke and co-workers (Figure ), several additional DBD-based ion sources have been developed, including low-temperature plasma (LTP), active capillary plasma ionization (ACaPI), and most recently flexible microtube plasma (FμTP) (Figure ). DBD-based ion sources can be used to enhance the sensitivity and detection limits of liquid chromatography mass spectrometry for the detection of both polar and nonpolar compounds (e.g., amino acids and perfluoroalkanes) , and can be readily integrated with solid-phase microextraction and complementary spray- and laser-based ionization methods. , Moreover, DBD-based ion sources can be used to image the chemical profiles on surfaces or to passively sample volatile organic compounds from human breath with very high sensitivity …”

Rapid analysis of fragrance allergens by dielectric barrier discharge ionization mass spectrometry

“…Dielectric barrier discharge ionization (DBDI) has been developed considerably in recent years, 11,12 and features a small size, simple structure, low cost, high efficiency, good reproducibility, and ease of operation. Since DBDI can ionize polar, mid‐polarity, and non‐polar compounds, 13 its application to the analysis of fragrances could make an interesting contribution.…”