Mass Spectrometry is the measuring of individual molecules or atoms that have been converted into ions to determine their molecular weight, identify unknown materials, and study molecular structures. Using a series of steps, Mass Spectrometry can be useful if you would like to identify molecules in a mixture, detect impurities in a sample, and analyze a purified protein. Mass spectrometry is in essence a method used for weighing atoms or molecules. A mass spectrometer determines the mass of a molecule by measuring the mass-to-charge ratio of its ion. Ions are generated by inducing either the loss or gain of a charge from a neutral sample. Once formed, ions are directed into a mass analyzer where they are separated according to the mass-to-charge ration and finally detected.
The results of molecular ionization, ion separation, and ion detection process can provide molecular mass and even physical information, all detected by an ion detector. The analyzer, detector of the mass spectrometer, and the ionization source are maintained under high vacuum to give the ions a coherent chance of travelling from one end of the instrument to the other without any interference from air molecules.
Mass spectrometry can be very precise, depending on the ionization source. Essentially there are eight ionization methods. One of the most commonly used is the electrospray method. During standard electrospray ionization the sample is dissolved in into a fine aerosol. Because the ion formation involves extensive solvent evaporation, the typical solvents for electrospray ionization are prepared by mixing water with unstable organic compounds. The aerosol is sampled into the first vacuum stage of a mass spectrometer through a tube, which can be heated to aid further solvent evaporation from the charged droplets. The solvent evaporates from a charged droplet until it becomes unstable upon reaching its limit. The droplet bends and releases charged jets. During the splitting, the droplet loses a small percentage of its mass along with a large percentage of its charge. The nitrogen helps to direct the spray emerging from the tube tip towards the mass spectrometer. The charged droplets reduce in size by solvent dehydration, helped by a warm flow of nitrogen known which passes across the front of the ionization source. Charged sample ions that are free from solvent, are released from the droplets, some of which pass through a sampling cone into a vacuum region, and from there through a small aperture into the analyzer of the mass spectrometer, which is held under a high vacuum. The lens currents are adjusted individually for each sample.

The advantage of using Mass Spectrometry is that it provides the molecular weights of peptides and proteins with high accuracy. However, Non-covalent complexes are often disrupted and the instrumentation is very expensive. Blood is diagnostic specimen for scientific analysis. Metabolites and Peptides are likely to serve as reliable indicators of progress from a normal to a contaminated state. However, the presence of salts, fats and high concentrations of protein in blood can unhelpfully affect its mass spectrometric reading. Another popular method of mass spectrometry is Fast Atom Bombardment. It provides an efficient means of analyzing polar, ionic, thermally labile and high molecular weight compounds not cooperative to analysis by electron impact or chemical ionization. Fast Atom Bombarding is used for the analysis of detergents and surfactants and natural products such as the analysis of mixed products in industrial and household detergent, detergents in gasoline, residual surfactants in environmental samples of firefighting foams residues in soil and water, as well as monitoring cleaning protocols in the pharmaceutical industry.
An alternative to using a mass spectrometer is atmospheric-pressure thermal desorption ionization, used to ionize various materials, including organic salts, which play vital roles in biological processes. The method works at atmospheric pressure instead of inside a mass spectrometer's vacuum chamber, and it does not require technologies such as electron beams and lasers.
Purdue analytical chemistry professor R. Graham Cooks and his team have created a tool that can determine not only the identity of a suspect but also what that suspect has recently handled, be it cocaine, gunpowder or any other incriminating substance. The process is called desorption electrospray ionization. It involves spritzing a surface with electrically charged droplets, which transfer their charges to the sample’s molecules, ionizing them. The molecules are collected into a standard mass spectrometer, “and after that, it’s really a case of simple mass spectrometry,” Cooks said. The molecules are analyzed, and their chemical makeup is determined.

A typical use of mass spectrometry is the identification of small amounts of materials found at a crime scene. Fabrics, hair, fibers, soil, glass are some of the materials a mass spectrometer can ionize. Mass spectrometry can also be used to determine the purity of urine. The specificity of the mass spectrometer shifts suggests that this method can be expanded to the analysis of a broad range of drugs of abuse in urine that show. This method is useful in detecting very small amounts of fentanyl in urine that arise from either therapeutic or illicit use.