Improved detection sensitivity of elements in solids via laser postionization in laser desorption time‐of‐flight mass spectrometry

Abstract

A newly constructed laser desorption (532 nm, 5 ns) and laser postionization (266 nm, 5 ns) time-of-flight mass spectrometer (LD-LPI-TOFMS) has been applied for improving the detection sensitivity of elements in solid samples. This method affords to acquire the information of the elemental impurities in solid standards as well as limit of detection (LOD) down to 10 g/g for some elements. Neutral atoms of solids are generated by low-irradiance laser desorption (< 10 W/cm ), followed by high-irradiance laser postionization (~ 10 W/cm ) of the desorbed atoms, facilitating to decouple the desorption and ionization processes in spatial and temporal domain. This non-interacting feature overcomes the discrimination between deteriorating spectral resolution at high irradiance (10 -10 W/cm ) and limited detectable elemental species and high LOD at low or medium irradiance (below 10 W/cm ). The utilization of originally "wasted" neutral atoms by laser postionization will help improve atom utilization and instrumental sensitivity. In this work, getting the utmost out of the consumed neutral atoms instead of an increment in sampling amounts is given attention with high priority for achieving high sensitivity and low LOD, which is especially useful on the occasions where very low sample consumption is desired.

Nanoparticle-immersed paper imprinting mass spectrometry imaging reveals uptake and translocation mechanism of pesticides in plants

“…The irradiance laser energy was set at 5 μJ for the comparison of the two ionization methods on the stainless steel plate, whereas the optimized laser energy of 20 μJ was adopted on the AuNPimmersed filter paper for all mass spectrometry imaging experiments unless otherwise stated. In theory, higher irradiance affords more species to be detected; however, a degraded mass spectral resolution can be foreseen due to high kinetic energy dispersal (KED) [41]. In this study, the KED of the ions were compensated for by a time-lag focusing technique for improved spectral resolution [42].…”

Determination of the microscopic mineralogy of inclusion in an amygdaloidal pillow basalt by fs-LIMS

“…It delivers improved quantitative chemical composition information with considerably reduced element fractionation [18][19][20] . Several recent studies show that LIMS can be considered as a standardless technique delivering semi-quantitative results [18][19][20][21][22] . Further improvements to the quantitative analysis can be achieved by adding to atomic abundance derived from the single-charged atomic mass peaks also multiple ionised atomic mass peaks 23 .…”

Perspective on Advances in Laser-Based High-Resolution Mass Spectrometry Imaging

“…Researchers on MSI have been pursuing the high spatial resolution to resolve more structural details. With plenty of advantages such as direct solid analysis, little or no sample preparation procedures, reduced risk of contamination, low sample consumption, rapid analysis, and sampling in microzones, laser-based sampling is regarded as one of the most versatile sampling techniques for HR-MSI. , As mentioned above, there have been a great amount of progress through modifying the laser optics, utilizing different geometries of the source, as well as reducing the laser wavelength to minimize the laser spot size. However, the diffraction limit is still the main obstacle for the further development of HR-MSI.…”

“…At present, several effective postionization methods have been developed. As the ions only make up a small fraction of the ablated material relative to the ratio of neutral atoms/molecules, ionizing these original “waste” neutral atoms/molecules has shown a great potential to increase utilization and sensitivity. ,,,− Furthermore, the postionization can separate desorption and ionization processes spatially and temporally, ,, which makes it possible to control and optimize both events, respectively. Some postionization techniques have been applied including EI, ,, ESI, and APCI. − As another postionization technique of great potential, the laser has been a prominent candidate with versatile and competent abilities for postionization processes.…”