Detection, identification and quantification

Use of an MS does not automatically lead to a reliable identification of the compound to be analysed. A certain number of conditions have to be fulfilled. Again a contradiction is present. The highest degree in identification is achieved if the complete mass spectrum is identical to the complete mass spectrum of the standard. A lot of MS systems however are most sensitive if only one mass is measured, but one mass is not very selective. 

Are there a number of limited conditions to have a proper identification The procedure to qualify a component consists of two steps (ISO/DIS 22892)  

The relative retention time should fulfil the criteria. Only if step 1 is positive can step 2 be made. For GC-analyses these criteria can be very strict. For instance, the relative or absolute retention time measured in the sample should not differ by more than 0.2% (from the relative retention time in the last measured external standard solution). In HPLC analyses, a higher deviation has to be accepted. 

Firstly the MS results are evaluated by comparing the relative intensities of the selected ion peaks. For every ion peak an identification point is obtained, when its relative intensity (compared to the base peak in %) measured in the sample does not deviate more than ((0.1 x Istd) +10)% from the relative intensity of the diagnostic ion in the external standard solution. Three identification points give a positive identification. If less than three ion peaks are available (due to sensitivity (S/N 3) or absence of fragments (PAH)), additional identification points should be gathered using additional analytical evidence. The possibilities are given in Table 8.3. 

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For analysis of surfactants, i.e. detection, identification and quantification, LC-TSP-MS and MS/MS are also qualified methods for substance-specific information [600-602]. A mixture of non-ionic surfactants, comprising nonylphenol ethoxylates [C9Hi9-(CeH4)-0-(CH2-CH2-0)m-H], anionic surfactants and PEG, was... 

Detection, identification and quantification of these compounds in aqueous solutions, even in the form of matrix-free standards, present the analyst with considerable challenges. Even today, the standardised analysis of surfactants is not performed by substance-specific methods, but by sum parameter analysis on spectrophotometric and titrimetric bases. These substance-class-specific determination methods are not only very insensitive, but also very unspecific and therefore can be influenced by interference from other compounds of similar structure. Additionally, these determination methods also often fail to provide information regarding primary degradation products, including those with only marginal modifications in the molecule, and strongly modified metabolites. 

Surfactants are surface-active compounds, which are used in industrial processes as well as in trade and household products. They have one of the highest production rates of all organic chemicals. Commercial mixtures of surfactants consist of several tens to hundreds of homologues, oligomers and isomers of anionic, non-ionic, cationic and amphoteric compounds. Therefore, their identification and quantification in the environment is complicated and cumbersome. Detection, identification and quantification of these compounds in aqueous solutions, even in the form of matrix-free standards, still poses the analyst considerable problems. 

The prediction that LC-MS will become a powerful tool in the detection, identification and quantification of polar compounds such as surfactants in environmental analysis as well as in industrial blends and household formulations has proven to be true. This technique is increasingly applied in substance-specific determination of surfactants performed as routine methods. From this it becomes obvious that no other analytical approach at that time was able to provide as much information about surfactants in blends and environmental samples as that obtainable with MS and MS-MS coupled with liquid insertion interfaces. 

Continuing developments in analytical chemistry enable the detection, identification and quantification of ever smaller masses of substances of potential interest. Three questions need to be answered about every analytical result ... 

Sample preparation includes all techniques that involve handling the sample before detection begins. The intent of sample preparation is to extract efficiently the analytes and isolate them relatively free of interfering matrix components that could obscure the final detection, identification, and quantification process. 

Crimes involving the use of firearms are particularly serious and demand the fullest investigative effort. Thus it can be seen that the detection, identification, and quantification of FDR provide significant evidence in several areas associated with incidents involving the use of firearms. 

Considerable advances in methods for the detection, identification and quantification of anthocyanins have been made recently, particularly with the advent of UPLC and improved mass spectroscopy methods. Additional work is needed, particularly with quantitation using MS. However, the biggest limitation in the quantitation of anthocyanins is the commercial availability of anthocyanin standards, which are nonexistent for most anthocyanins, and those that are available are fairly expensive. Some laboratories have been able to isolate and purify the particular anthocyanins of interest (Ling et ah, 2009 Nakamura et al., 2010), but most laboratories do not have the equipment, time, and/or expertise to fully validate the anthocyanin standards. 

Plant toxins represent one of the most important areas of analytical development and the few techniques related herein should only be considered as mere examples of the numerous possibihties of TLC in this field. With the development of densitometry and multiple development systems, the separation power of TLC and its quantitative potential are increasing as well. Considering the usual thermal instability of many plant toxins and their high polarity, HPTLC certainly offers one of the most powerful technologies for the detection, identification, and quantification of plant toxins. 

Martino, R., Gilard, V., Desmoulin, F. and Malet-Martino, M. (2006) Interest of fluorine-19 nuclear magnetic resonance spectroscopy in the detection, identification and quantification of metabolites of anticancer and antifungal fluoropyrimidine drugs in human biofluids. Chemotherapy, 52(5), 215-219. 

Quantitative data are essential components of virtually all environmental investigations, but the range of chemical compounds involved and the different matrices in which xenobiotics may be encountered makes generalizations on analytical procedures extremely hazardous. Whereas it is relatively straightforward to take advantage of modern instrumentation and methodology, and to apply widely accepted procedures for detection, identification, and quantification, there are several fundamental difficulties to which specific attention should be directed and possible solutions sought ... 

A prerequisite for detection, identification, and quantification of any species by MS is that all analytes must be converted into gas-phase ions before they enter the mass analyzer. API techniques are most widely used for metabolite identification, mainly due to their ability to couple to liquid chromatography and generate intact gas-phase molecular ions at very high sensitivity (Rossi, 2002 Voyksner, 1997). 

V HEMICAL MEASUREMENTS ARE CHARACTERIZED by three fundamental processes detection, identification, and quantification. The first of these relates to the ultimate measurement capability as expressed in the detection limit. The invitation to organize a symposium on this topic carried the suggestion that we address the true meaning of detection limits. That charge, in fact, influenced the structure of the symposium and the content of this volume. The objective of this book, therefore, is primarily to explore, from both fundamental and practical perspectives, the meaning of detection in chemical measurement science. It is not intended to serve as a compendium of the current detection limits for a broad range of analytical methods. 

The following sections summarize the extraction, analysis, instrumental detection, identification, and quantification of MM. 

The considerable and increasing number of appHcations where this interface operated in parallel to theTSP interface was the beginning of a fruitful development in LC-MS analysis. The method in general was reviewed in several papers and was also partly compared to results obtained by other interface types [6, 29, 32, 71]. In the field of environmental analysis, that is, predominantly in the detection, identification and quantification as weU as in the confirmation after UV-DAD [72] of pesticides, herbicides and their biochemical or physicochemical degradation products, PBI-MS was appHed. These results can be found in the Hterature together with a few results on surfactants and dyes. 

TLC and GC/MS can be used to determine the age of writing inks on questioned documents. Dating techniques that use TLC are based on analysis of ink dye components, while GC/MS can date inks based on detection, identification, and quantification of the residues of the vehicle solvents in ink hnes. Capabihty to date most ballpoint, porous tip, roller pen, stamp pad, and jet printer inks by analyzing the single ink entry, stamp impression, or printed test in question was shown by testing in the Division of Identification and Forensic Science, Israel Police Headquarters. 

ROLE OF COMPUTERS IN GAS CHROMATOGRAPHY-MASS SPECTROMETRY DETECTION, IDENTIFICATION, AND QUANTIFICATION IN DRUG METABOLISM RESEARCH... 

SERS sensitive detection, identification and quantification of trace amounts of drugs and their uptake in the human body have importance in medical, forensic and criminal investigations. SERS analysis is fast, nondestructive and can be done in situ using a portable Raman spectrometer which is a big advantage when compared with separation and chemical analytical procedures. 

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