Mass spectrometry computer techniques

Erikson and Pellizzari [77] analysed municipal sewage samples in the USA by a gas chromatography-mass spectrometry-computer technique for chlorinated insecticides and polychlorobiphenyls. 

Schulman M. F. and Abramson F P. (1975) Plasma ammo acid analyses by isotope ratio gas chromatography mass spectrometry computer techniques Btomed Mass Sped 2, 9-14 Shank R P. and Aprison M H (1971) Postmortem changes in the content and specific radioactivity of several ammo acids in four areas of the rat brain. J Neurobwl 2, 145-151 Shaw R K. and Heme J D (1965) Nmhydrin positive substances present m different areas of normal rat brain. /. Neurochem, 12,151-155 Sjoquist B (1979) Analysis of tyrosine and deuterium-labelled tyrosine in tissues and body fluids. Btomed Mass Sped 6, 392-395 Spencer H J., Tominez G., and Halpern B. (1981) Mass spectrographic analysis of stimulated release of endogenous amino acids from rat hippocampal slices Brain Res, 212, 194-197... 

Gas Chromatography-Mass Spectrometry-Computer Techniques for the Quantification of Anticonvulsant Drugs Quant. Anal. Stud. Epilepsy 1976 77-94 CA 86 65249h... 

Schulman, M. F., and Abramson, F. P. Plasma Amino Acid Analysis by Isotope Ratio Gas Chromatography-Mass Spectrometry-Computer Techniques... 

Identification of Atypical Bile Acids by Gas Chromatography-Mass Spectrometry-Computer Techniques Report 1978 CONF-7806100-1, 18 pp.,... 

The following is a procedure recommended for elucidating the structure of complex organic molecules. It uses a combination of different NMR and other spectroscopic techniques. It assumes that the molecular formula has been deduced from elemental analysis or high-resolution mass spectrometry. Computer-based automated or interactive versions of similar approaches have also been devised for structural elucidation of complex natural products, such as SESAMI (systematic elucidation of structures by using artificial machine intelligence), but there is no substitute for the hard work, experience, and intuition of the chemist. 

The pyrolysis high resolution mass spectrometry (PyHRMS) technique has been described in detail previously (20). Briefly, the coal sample was placed on a platinum rhodium mesh on the end of a probe as a slurry. After the solvent had evaporated, the probe was inserted into the mass spectrometer and positioned within 5 mm of the source. The probe, which had been previously calibrated with an infra-red thermometer, was computer-controlled to give a temperature profile beginning at 100°C and increasing at 50°C/min to 800 C. The precise masses were matched to their corresponding chemical structures by computer programs developed in-house. This technique results in the relatively slow vacuum pyrolysis of the coal sample. 

Vu, V.T., and Abramson, F.P. (1978) Quantitative analysis of propranolol and metabolites by a gas chromatograph mass spectrometer computer technique. Biomedical Mass Spectrometry, 5,686-691. 

Thermal desorption spectroscopy and temperature programmed reaction experiments have provided significant insight into the chemistry of a wide variety of reactions on well characterized surfaces. In such experiments, characterized, adsorbate covered, surfaces are heated at rates of 10-100 K/sec and molecular species which desorb are monitored by mass spectrometry. Typically, several masses are monitored in each experiment by computer multiplexing techniques. Often, in such experiments, the species desorbed are the result of a surface reaction during the temperature ramp. 

In the end, mass spectrometry and ion techniques will continue to be powerful tools for the investigation of the structure, bonding, energetics, and reactivity of unusual organic molecules. New sophisticated techniques will continue to be developed and applied to interesting problems in physical organic chemistry. These studies, along with the continued improvements in computational methods (Chapter 9), provide means to obtain very detailed and accurate descriptions of chemical reactions. 

Various analytical methods have made quantum leaps in the last decade, not least on account of superior computing facilities which have revolutionised both data acquisition and data evaluation. Major developments have centred around mass spectrometry (as an ensemble of techniques), which now has become a staple tool in polymer/additive analysis, as illustrated in Chapters 6 and 7 and Section 8.5. The impact of mass spectrometry on polymer/additive analysis in 1990 was quite insignificant [100], but meanwhile this situation has changed completely. Initially, mass spectrometrists have driven the application of MS to polymer/additive analysis. With the recent, user-friendly mass spectrometers, additive specialists may do the job and run LC-PB-MS or LC-API-MS. The constant drive in industry to increase speed will undoubtedly continuously stimulate industrial analytical scientists to improve their mass-spectrometric methods. 

Smith [83] classified large sets of hydrocarbon oil infrared spectral data by computer into correlation sets for individual classes of compounds. The correlation sets were then used to determine the class to which an unknown compound belongs from its mass spectral parameters. A correlation set is constructed by use of an ion-source summation, in which a low resolution mass spectrum is expressed as a set of numbers representing the contribution to the total ionisation of each of 14 ion series. The technique is particularly valuable in the examination of results from coupled gas chromatography-mass spectrometry of complex organic mixtures. 

Electron ionization (earlier called electron impact) (see Chapter 2, Section 2.1.6) occupies a special position among ionization techniques. Historically it was the first method of ionization in mass spectrometry. Moreover it remains the most popular in mass spectrometry of organic compounds (not bioorganic). The main advantages of electron ionization are reliability and versatility. Besides that the existing computer libraries of mass spectra (Wiley/NIST, 2008) consist of electron ionization spectra. The fragmentation mles were also developed for the initial formation of a radical-cation as a result of electron ionization. 

---