Nuclear magnetic resonance forensic

LeBelle MJ, Savard C, Dawson BA, Black DB, Katyal LK, Zrcek F, By AW. Chiral identification and determination of ephedrine, pseudoephedrine, methamphetamine and meteca-thinone by gas chromatography and nuclear magnetic resonance. Forensic Sci. Int. 1995 71 215-223. 

Forensic scientists make use of both these techniques because they are very accurate but they only require tiny amounts of sample - often only small amounts of sample are found at crime scenes. Other techniques utilised are nuclear magnetic resonance spectroscopy and ultraviolet/visible spectroscopy... 

Nuclear magnetic resonance spectrophotometry (NMR) makes use of the fact that nuclei of some molecules absorb radio frequency radiation in strong magnetic fields. Nuclei in certain molecules absorb radiation at characteristic frequencies, making the identification of even tiny or impure samples possible. X-ray analysis allows the forensic investigator to visualize foreign objects within the body. 

Most of the development work on molecular markers (MMs) has resulted from the use of GC-MS, but with advances in other techniques it is clear that this field will benefit from making greater use of alternative identification methods, such as Fourier transform infrared spectroscopy and nuclear magnetic resonance techniques. Isotopic measurements can now be used to obtain complimentary information on the history and origin of a sample. It is now possible to perform a forensic investigation using stable carbon isotopic analyses on individual MMs by GC-Isotope Ratio MS without prior isolation of com-... 

A glance at the table of contents, in volume 10, will show that some topics merit a large number of articles, a reflection of their importance in current analytical science. Several techniques, for example, mass spectrometry, nuclear magnetic resonance spectroscopy, atomic emission spectrometry, microscopy, the various chromatographic techniques (e.g., gas, liquid and thin-layer), and electrophoresis, merit a series of articles, as do areas such as food and nutritional analysis, forensic sciences, archaeometry, pharmaceutical analysis, sensors, and surface analysis. Each of these collections of articles, written by experts in their fields, provides at least as much up-to-date information on that particular subject as a complete textbook. 

Since conclusions reached in forensic laboratories are used in the criminal justice system, they must leave no room for doubt. Thus, analytical methods must meet strict criteria. They must be extremely selective, reproducible, sufficiently sensitive, and suitable for qualitative and quantitative analysis. It is also highly desirable for the method to call for the minimum number of pretreatment steps and to be applicable to compound mixtures without preliminary separation of their components. Nuclear magnetic resonance (NMR) spectroscopy meets these criteria. It is well... 

Sample Handling. Forensic Sciences Blood Analysis Explosives Systematic Drug Identification. Nuclear Magnetic Resonance Spectroscopy Techniques Nuclear Overhauser Effect. Pharmaceutical Analysis Drug Purity Determination Sample Preparation. 

Elements and compounds can be detected by a variety of instrumental methods (see Chapter 21, and Chapter 22 on the accompanying website), for example mass spectrometry (MS), nuclear magnetic resonance (NMR), various forms of chromatography, inductive coupled plasma spectroscopy (ICP) and infrared spectroscopy (IR). These instruments allow chemists to probe and discover which elements are present in the substance, their quantities and, in some cases, give information about the structure of the substance. Forensic scientists also make use of these techniques because they are very accurate and sensitive they only require tiny amounts of sample. 

Chew, S. L., and J. A. Meyers. "Indentification and Quantitation of Gamma Hydroxybutyrate (NaGHB) by Nuclear Magnetic Resonance Spectroscopy." Journal cf Forensic Sciences, 48 2003,291- 297. 

Dawson, B. A., et aL "Nuclear Magnetic Resonance Identification of the Fhenylalkylamine Alkaloids of Khat U g a Chiral Solvating Agent." Journal if Forensic Sciences, 39, no. 4,1994,1026. 

If you have wondered about any of these things, then some of your curiosity will be satisfied by learning about spectroscopic methods such as nuclear magnetic resonance (NMR) spectrometry, which involves the same physical principles as MRI imaging, and MS (mass spectrometry), which is used in some airport screening processes as well as many forensic applications. NMR and MS are workhorse techniques for the study of both biological and nonbiological molecular structure. 

An important issue in forensic science is the criteria required for a positive identification of a single organic compound. An opinion held by some forensic scientists is that such identification cannot be based on chromatographic methods only, even when several such methods are applied. It is argued that other methods, such as infrared (IR) spectrometry, nuclear magnetic resonance (NMR) spectrometry, or mass spectrometry (MS), should be included. 

UV-visible spectroscopy has proved useful in biochemical analysis, environmental studies, in forensic science, drug kinetics, food quality, identification and quantification of chemical and biological substances but is limited as a tool for the investigation of molecular structure compared with infrared and nuclear magnetic resonance. However, it is quite useful for the study of reaction kinetics and equilibrium. 

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