The characterization of material at the molecular and atomic level has been important to the advancement of a multitude of applications, scientific and otherwise. For example, identifying the composition of a variety of structures has been important for developing new technologies, developing new medical treatments and for learning more about the world around us.
Mass spectrometry is one approach to characterizing material, with the mass of one or more components in the material used in identifying the composition of the material and/or the quantity of a particular component in the material. In this regard, mass spectrometry has been used to identify materials, quantify known materials and to provide information about the structure, composition and properties of a variety of structures such as molecules.
Generally, mass spectrometry works by identifying the mass of different components in a material (e.g., of different molecules in a compound) as a function of the mass-to-charge ratio of ions of the component. A variety of approaches to mass spectrometry have evolved over the years, the use of which has become particularly extensive in organic applications.
One approach to mass spectrometry is matrix-assisted laser desorption/ionization, or “MALDI.” In MALDI mass spectrometry, a laser is used to impart energy to a sample by directing high energy photons to the sample embedded in a matrix. The energy from the photons facilitates the release of ions from the sample. The released ions are in turn detected and used along with a time-of-flight of the ions (i.e., the time from which the laser is activated until the ions are detected) to determine the composition of the sample.
Another approach to mass spectrometry is electrospray ionization (ESI) mass spectrometry. Charged liquid droplets are formed from a sample, and ions are desolvated or desorbed from the charged liquid droplets. These ions are directed to a detector where they are detected and used to characterize the sample.
Ions detected in mass spectrometry approaches are generally plotted to a visible graph, which depicts peaks related to the quantity of ions received at a particular time. The peaks can then be used to identify components in the sample, thereby facilitating the identification of the type and quantity of material in the sample. For example, by identifying and analyzing a C12 (carbon) peak, the carbon content (e.g., C+) of the sample can be identified. By identifying the type and quantity of molecules in a sample, the sample is readily quantified.
While mass spectrometry has been useful, it is often challenging to accurately and efficiently identify samples, particularly those having a complex variety of materials. For instance, in many applications, multiple plotted peaks are located in a cluster, making it challenging to distinguish the peaks. In addition, data for a particular peak is sometimes spread out over a small range, making it challenging to identify the precise location of the peak (and thus challenging to identify the type of material to which the peak corresponds). Furthermore, analysis of spectra generated using mass spectrometry is somewhat subjective, leading to potential human error. Such analysis can also be time consuming and is generally not useful for analyzing a multitude of samples over a short period of time. These challenges have inhibited the implementation and usefulness of mass spectrometry for a variety of applications.