Office of Science

Mass Spectrometer: Single Particle (SPLAT II)

Quick Specs

  • Simultaenous Measurements
  • Yields quantitative information about all particle types
  • Detects particles from 50 nm to 3 μm in size
  • Measures up to 50 particles/second


SPLAT II is a second-generation Single Particle Laser Ablation Time-of-Flight mass spectrometer. A high-precision and unique instrument, it allows users to study the fundamental processes that govern the chemistry and physics of particles on the nano- and micro-scales. SPLAT II's applications include but are not limited to climate, air pollution, human health, bioterrorism, and emerging nanotechnologies.

Portability is a hallmark of SPLAT II—it is the first field-deployable instrument that provides, in real time, the size, density, shape, fractal dimension, and composition of individual particles down to 50 nm in diameter. It is also the first instrument operated in the field in an IR-UV mode; this operation mode yields reproducible and quantitative particle mass spectra.

SPLAT II's high measurement rate permits rapid characterization of quickly changing samples, for example, fast chemical reactions, and its high sensitivity allows characterization of particles with low number concentrations. Its versatility allows characterization of any particle type, including volatile and non-volatile fractions of internally mixed aerosol particles commonly encountered in the atmosphere and engine exhaust. Its wide size range and low size limit are essential for characterizing nanoparticles, atmospheric aerosol, and engine emissions. In addition, its sizing precision allows researchers to follow physical and chemical transformation of the particles with submonolayer resolution. Under normal operating conditions millions of particles are detected and characterized, using dedicated data visualization software called SpectraMiner.

Instrument Description

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SPLAT II uses an extremely efficient aerodynamic lens inlet to produce a narrow (250 μm) low divergent particle beam. Two stages of differential pumping separate particles and gas. Two stages of optical detection use light scattering to detect each particle twice and to measure its velocity, from which the particle aerodynamic diameter is obtained. Pulsed, synchronized IR evaporation followed by UV ionization of semi-volatile fractions and ablation of non-volatile fractions creates ions. From these ions, time-of-flight mass spectra are generated for compositional analysis.

SPLAT II is Designed for Field Research

The compact, portable, and aircraft-compatible SPLAT II is designed for bench and field use. It has been used to characterize the unique properties and behavior of nanoparticles in the laboratory and to characterize atmospheric particles and exhaust particulate emissions in the field.

SPLAT technique has been applied to aerosol studies in Houston, Texas; Cheju Island, South Korea; New York City; National Transportation Research Center, Oak Ridge, Tennessee; and Cummins Inc., Columbus, Indiana.

SpectraMiner for High-Throughput Data Analysis

SpectraMiner presents a multitude of views to the scientist.
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SpectraMiner, a dedicated data mining and visualization software is specifically designed to explore single-particle mass spectra. It helps researchers make use of the vast amounts of detailed data generated by SPLAT II. SpectraMiner puts the scientist at the center of the data mining process, providing intuitive controls that connect the particle data with any other relevant events pushing the knowledge beyond simple statistical analysis.


  1. Spatially resolved chemical imaging of individual atmospheric particles using nanoscale imaging mass spectrometry: Insighs into particle origin and chemistry.
  2. Hygroscopic Properties of Internally Mixed Particles Composed of NaCl and Water-Soluble Organic Acids.
  3. Reactions Between Water Soluble Organic Acids and Nitrates in Atmospheric Aerosols: Recycling of Nitric Acid and Formation of Organic Salts.
  4. Experimental Determination of Chemical Diffusion within Secondary Organic Aerosol Particles.
  5. New Mass Spectrometry Techniques for Studying Physical Chemistry of Atmospheric Heterogeneous Processes.
  1. New data may explain why models underestimate organic aerosols (Sticking Around)
  2. Chemical imaging of individual salt particles advances aerosol research (Inside Sea Salt )