Spectrometric techniques identification

Mass Spectrometric Technique Identification Points per Ion Monitored... 

Gibson, B. W. Phillips, N. J. John, C. M. Melaugh, W. Lipooligosaccharides in pathogenic Haemophilus and Neisseria species—Mass spectrometric techniques for identification and characterization. ACS Sympo. Ser. 1994,541,185-202. 

The development of mass spectrometric techniques for nuclide identification using a tandem Van de Graaff accelerator at the University of Rochester Nuclear Structure Laboratory by H. Gove, K. Purser, A. Litherland, and numerous associates has provided an excellent means for the precise measurement of 36C1 concentrations in natural water [43]. Thus far, about 40 groundwater related samples which have been collected and purified chemically by H. Bentley have been analyzed for 36C1 by D. Elmore, H. Bentley, and others using the University of Rochester machine. Some of these samples are listed in Table 2. 

A most widely used technique for quantitative trace analysis. Used as an adjunct to other spectrometric techniques in the identification and structural analysis of organic materials. Relative precision 0.5-5%. 

He, X.-G., On-line identification of phytochemical constituents in botanical extracts by combined high-performance liquid chromatographic-diode array detection-mass spectrometric techniques, J. Chromatogr. A, 880, 203, 2000. 

With respect to sample preparation, it is necessary to develop effective and fast procedures involving only a few steps in order to avoid contamination, reduce analysis time and to improve the quality of analytical work. Microsampling and the use of smaller sample sizes is required and also the further development of analytical techniques. In particular, there is a need for the development of online and/or hyphenated techniques in ICP-MS. Microsampling combined with the separation of small amounts of analytes will be relevant for several chromatographic techniques (such as the development of micro- and nano-HPLC). There is a demand for further development of the combination of LA-ICP-MS as an element analytical technique with a biomolecular mass spectrometric technique such as MALDI- or ESI-MS for molecular identification and quantification of protein phosphorylation as well as of metal concentrations, this also enables the study of post-translational modifications of proteins, e.g. phosphorylation. 

Identification of the different types of ions observed in a mass spectrum through peak-matching and metastable ion analysis allows the determination of molecular structure. Several newer mass spectrometric techniques Mass analysed ion kinetic energy (MIKE) or reversed Nier-Johnson geometry) can also be used in spectral interpretation. These techniques are described in specialised monographs. 

Andrew G. Sharkey, Jr. Positive, negative, and neutral species have been found by probe techniques in flames. Direct mass spectrometric techniques should lead to identification of many of the primary species obtained by heating coal to extreme temperatures. 

As pointed out by Swisher and Prothero (1990) relatively recent advances (1989-1990) in mass spectrometric techniques and the development of laser-fusion 40Ar/39Ar dating techniques have resulted in the ability to date individual volcanic crystals, Multiple analysis and the ability to date single crystals allow the identification of multiplc-agc components due to detrital contamination, and thus permit improved precision and accuracy. To date, studies have been directed to North American chronology, notably minerals (biotite, anor, plag) found in Nebraska and Wyoming. 

The greatest advance in the analysis of peptides has been the coupling with spectrometric techniques, both for identification and for characterization. Their high accuracy, sensitivity, and, in some instances, tolerance to solvents make mass spectrometers ideal detectors for analyses of HPLC-separated peptides. 

The second step in the analysis of CWC-related chemicals involves unambiguous identification of target chemicals that have tentatively been identified during the screening process. Unambiguous identification of CWC-related chemicals is achieved when, at least, two different techniques give consistent results at least one of the identification techniques must be a spectrometric technique (8). 

The main spectrometric identification techniques employed are gas chromatography/mass spectrometry (GC/MS) (13), liquid chromatography/tandem mass spectrometry (LC/MS(/MS)) (14), nuclear magnetic resonance (NMR) (11), and/or gas chromatography/Fourier transform infrared spectroscopy (GC/FL1R) (15). Each of these spectrometric techniques provides a spectrum that is characteristic of a chemical. MS and NMR spectra provide (detailed) structural information (like a fingerprint ), whereas an FUR spectrum provides information on functional groups. 

Retention parameter techniques (such as GC, CE, or LC techniques equipped with selective detectors) are accepted as identification techniques, however, only when used in combination with at least one of the spectrometric techniques listed above, and when compared to the results obtained from a reference standard analyzed under similar conditions as the sample, giving consistent results. 

In general, the chromatographic techniques applying specific detectors and selected spectrometric techniques are used in screening to decrease the number of chemical candidates. The screened chemicals may be relevant and are then analyzed using spectrometric techniques in a complementary manner to obtain their unambiguous identification. 

In addition, analysis using the spectrometric techniques may reveal other chemicals relevant to the test. Unambiguous identification of a chemical is obtained if at least two analytical, preferably spectrometric, techniques give consistent results. Analyses are mostly qualitative (identification). Work is conducted according to the ROPs and other documented procedures of demonstrated performance. In the case of a PT, the testing report... 

In the case of an unknown chemical, or where resonance overlap occurs, it may be necessary to call upon the full arsenal of NMR methods. To confirm a heteronuclear coupling, the normal H NMR spectrum is compared with 1H 19F and/or XH 31 P NMR spectra. After this, and, in particular, where a strong background is present, the various 2-D NMR spectra are recorded. Homonuclear chemical shift correlation experiments such as COSY and TOCSY (or some of their variants) provide information on coupled protons, even networks of protons (1), while the inverse detected heteronuclear correlation experiments such as HMQC and HMQC/TOCSY provide similar information but only for protons coupling to heteronuclei, for example, the pairs 1H-31P and - C. Although interpretation of these data provides abundant information on the molecular structure, the results obtained with other analytical or spectrometric techniques must be taken into account as well. The various methods of MS and gas chromatography/Fourier transform infrared (GC/FTIR) spectroscopy supply complementary information to fully resolve or confirm the structure. Unambiguous identification of an unknown chemical requires consistent results from all spectrometric techniques employed. 

For the purposes of the CWC, results obtained with two spectrometric techniques are required for the identification of a compound. Although very useful as such, the interpretation of infrared spectra does not identify the chemical but may give tentative structures. Interpretation gives excellent results in some cases, but it should be remembered that the accuracy of interpretation depends on the type of the chemical and the experience of the scientist. In a case when an unknown compound is encountered, spectral interpretation (MS, IR, and NMR) is required so that the reference chemical can then be synthesized. 

In an analysis of a complicated sample, GC/FTIR alone cannot fulfill the identification criteria, just like any other analytical technique. Results from one technique can be correct but still for the final proof of the correctness, consistent results from other techniques are required, preferably from two spectrometric techniques. 

Since some form of liquid sample presentation is common to most atomic spectrometric techniques, these may be considered as the method of choice for the identification and quantification of trace metals in liquid foods. In spectrometric techniques, after conversion of the sample into microspray, chemical flames as in flame atomic absorption spectrometry (FAAS) and atomic... 

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