Target compounds, analysis

In target-compound analysis, a particular compound, usually present in a complex matrix and at trace levels, needs to be quantified. Here, selectivity and... 

The Use of Target-Compound Analysis and LC-MS-MS for the Identification of Drug Metabolites... 

A well-known method for peak tracking is based on the phase-system switching idea, " which was developed to solve problems of mobile phase incompatibility in LC/MS target compound analysis. An analytical column is usually connected to a trapping column in tandem mode. A switching valve is placed after the UV detector, and the flow of nonvolatile eluents is directed through the trapping column to waste. When the peak of interest elutes from the analytical column it is... 

Flavor chemists have traditionally relied on mass spectrometry in conjunction with gas chromatography (GC/MS) to identify the structures of volatile flavor components in heated food systems. Mass spectrometry provides the molecular weights of fragment ions, which are useful for deducing-molecular structure. The MS detection limit is on the order of 1CT g, however detection limits for target compound analysis or chemical class detection via selected ion monitoring can be much lower. Extensive libraries of mass spectra are available even so, many new flavor compounds can often not be identified from MS data alone. 

Because often only limited resolution is required for adequate LC-MS determination of target compounds, an alternative approach to on-line SPE-LC-MS was explored the single-short-column. A single-short-column is a short (10-20 mm) column, similar to the cartridge columns applied in on-line SPE, but high-pressure packed with 3-5-pm-ID particles instead of manually-packed with 20-60-pm-ID particles. The same column is used for both trace enrichment and separation. The approach was successfully applied in target-compound analysis for enviroiunental analysis in combination with MS and MS-MS, both on quadrapole and ion-trap instraments [27] (see Ch. 7.3.2). 

F.S. Pullen, D.S. Ashton, M.A. Baldwin, Corona-discharge ionization LC-MS interface for target compound analysis, J. Chromatogr., 474 (1989) 335. 

As an example of the type of studies performed in environmental target compound analysis, the optimization and method development for the quantitative LC-MS analysis of quaternary ammonium compounds, especially paraquat and diquat, is briefly reviewed. The type of ions observed for paraquat and diquat strongly depends on the experimental conditions (Ch. 7.2.7). 

In this paper some important aspects of LC/MS in bioanalysis are discussed. In order to achieve best performance in thermospray LC/MS optimization of the various experimental parameters is necessary. As a result of systematic studies on the influence of the various parameters an optimization strategy is developed, which will be discussed. Two recent bioanalytical applications are discussed. The applications are concerned with confirmation and identification of compounds in biological matrices (qualitative aspects) and with target-compound analysis. The examples have been selected in order... 

The two examples discussed show the bioanalytical applicability of LC/MS, both in qualitative analysis and in target compound analysis. Although the moving belt interface owing to its El capabilities is ideally suited for the identification of unknown compounds and is used often for that purpose, identification problems can sometimes also be solved with thermospray LC/MS, for instance by applying repeller-induced fragmentation, and LC/MS/MS. The PSS approach is an example that indicates that LC/MS still can be improved. A more elaborate discussion on the so-called multidimensional approaches in LC/MS is given elsewhere (14). 

Target Compound Analysis with Liquid Chromatogranhy/Particle Beam Mass Spectrometry. 

For more detailed and generally more relevant analysis, individual compounds such as BTEX or individual PAHs can be determined by target compound analysis. This is generally performed by GC-MS. This precise identification and quantification is usually required for risk assessments. 

Although optimization was achieved by largely empirical means, a number of impressive separations of complex mixtures (petroleum products [211,214,233], essential oils [234], polychlorinated biphenyls [235], low-volatility chlorinated compounds [236] and fatty acid esters [212]) have been published. In addition, the possibility of interfacing two-dimensional comprehensive gas chromatography with time-of-flight mass spectrometry has been demonstrated [212,237]. This later combination provides a very powerful tool for target compound analysis by combining retention information on two... 

The higher overall peak capacity of comprehensive 3D chromatography is mainly attractive for target compound analysis and profiling applications of chromatography, as mentioned in the Introduction. The total peak capacity of a comprehensive 3D system is given by... 

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