Ambient Diode Laser Desorption Dielectric Barrier Discharge Ionization Mass Spectrometry of Nonvolatile Chemicals

Abstract

In this work, the combined use of desorption by a continuous wave near-infrared diode laser and ionization by a dielectric barrier discharge-based probe (laser desorption dielectric barrier discharge ionization mass spectrometry (LD-DBDI-MS)) is presented as an ambient ionization method for the mass spectrometric detection of nonvolatile chemicals on surfaces. A separation of desorption and ionization processes could be verified. The use of the diode laser is motivated by its low cost, ease of use, and small size. To achieve an efficient desorption, the glass substrates are coated at the back side with a black point (target point, where the sample is deposited) in order to absorb the energy offered by the diode laser radiation. Subsequent ionization is accomplished by a helium plasmajet generated in the dielectric barrier discharge source. Examples on the application of this approach are shown in both positive and negative ionization modes. A wide variety of multiclass species with low vapor pressure were tested including pesticides, pharmaceuticals and explosives (reserpine, roxithromycin, propazine, prochloraz, spinosad, ampicillin, dicloxacillin, enrofloxacin, tetracycline, oxytetracycline, erythromycin, spinosad, cyclo-1,3,5,7-tetramethylene tetranitrate (HMX), and cyclo-1,3,5-trimethylene trinitramine (RDX)). A comparative evaluation revealed that the use of the laser is advantageous, compared to just heating the substrate surface.

Atmospheric pressure mass spectrometric imaging of live hippocampal tissue slices with subcellular spatial resolution

“…AuNRs are well known to serve as not only a photon energy reservoir but also a thermal energy transfer material to analytes 26 . While most biological analytes do not effectively absorb NIR light 27 , AuNRs absorb NIR light due to their longitudinal resonance given by their aspect ratio and convert the photon energy from laser beam into thermal energy 28 . Even though the tissue slice was treated by AuNRs, uptake of AuNRs is a natural biological behavior mainly caused by endocytosis of live tissues.…”

Plasma‐based ambient ionization mass spectrometry in bioanalytical sciences

“…This technique was applied to analyze some pharmaceuticals containing antibiotics, such as tetracycline, oxytetracycline, erythromycin, and spinosad (insecticide), deposited on a glass slide. A significant advantage of LD‐DBDI‐MS, in comparison to DBDI‐MS with heated substrate, is the opportunity to obtain a higher signal of the analyzed compounds, even when the substrate was heated up to 200°C (Gilbert‐López et al, ). Heating up the sample's surface has also been used to detect compounds from TLC plates (Cegłowski et al, ).…”

Multimodal Vacuum-Assisted Plasma Ion (VaPI) Source with Transmission Mode and Laser Ablation Sampling Capabilities

“…One successful strategy used to improve spatial resolution has been coupling of plasma ionization with laser ablation, wherein high-energy laser pulses desorb neutral material with micron spatial resolution. For example, laser ablation has been paired successfully with dielectric-barrierdischarges (DBD) [32] to examine nonvolatile explosives, and used with DART [33] and FAPA [34] for imaging mass spectrometry of biological tissues, dyes, and drugs. In these approaches, the substrate radiation absorption efficiency and ablation plume expansion remain the limiting factors determining the abundance of aerosolized sample available for ionization, while the plasma ion current and source gas-flow fidelity dictate the ion generation and transmission efficiencies, respectively.…”