Non-target analysis

Unlike, e.g. in pharmaceutical metabolism studies, where the parent compound is known and thus some preliminary knowledge of the expected structures is available, the composition of a natural products extract is often completely unknown beforehand ( non-target analysis ). In such cases, NMR spectroscopy is especially well suited as a detection system since it does not discriminate any classes of compounds. (Sufficient relaxation delays provided, the NMR signal depends only on the number of nuclei in the active probe volume.)... 

In the case of degradation products and metabolites, the situation is different. Generally, these compounds were not analysed because in most cases they are not regulated and no effective analytical methods exist for their determination. This means that a correct diagnosis of the environmental situation cannot be made and, as a consequence, no appropriate action can be taken. Therefore, in order to improve the risk assessment of a hazardous waste site for example, as many compounds as possible should be analysed at the beginning of the investigations (non-target analysis). 

For aliphatic compounds with longer alkyl chains, such as surfactants, the NMR detector can contribute little to an increased selectivity of the LC-NMR coupling since, in the range of aliphatic protons, the spectra are often complex. Moreover, analyte signals around 2 ppm can be suppressed or influenced by the solvent suppression when acetonitrile is used as the organic component of the eluent. Since surfactants are present in many environmental samples, they pose problems for non-target analysis, not only because of their complex spectra but also because they can influence the separating properties of the analytical column by their surface activity [2]. 

Figure 6.2 demonstrates this in the case of a ground water sample from the former ammunition site in Elsnig (Germany). Many unknown compounds could be identified in the non-target analysis, e.g. 2,4-dinitrobenzoic acid (2,4-DNBA) and 3,5-dinitrophenol (3,5-DNP) which are major components (see Figure 6.2(a) and Table 6.1). 

In the non-target analysis of this sample, carried out by LC-NMR and LC-MS, TNT-typical biodegradation products such as 2-amino-4,6-dinitro-toluene and 4-amino-2,6-dinitrotoluene were detected, although smaller quantities of 2-amino-4,6-dinitrobenzoic acid, trinitrobenzene and 2,2/6,6/-tet-ranitro-4,4/-azoxytoluene could also be identified. The NMR chromatogram further reveals that the soil was also contaminated by PAHs. Several late-eluting compounds could be identified as PAHs. 

Effluents, released from textile companies, may contain dyes and auxiliaries used in the textile industry. The dyes themselves often form complex mixtures that contain considerable quantities of manufacturing precursors and by-products. However, for non-target analysis not only the large variety of compounds but also the large differences in the volatility, solubility and polarity of individual components pose problems. Most of the dyes are nonvolatile or thermally unstable. Thus, in recent years predominantly LC-MS techniques have been used for the analysis of dyes [10]. However, the combined use of LC-NMR and LC-MS offers extended possibilities which are illustrated by the analysis of an untreated waste water sample from a textile company [11],... 

The determination of known organic pollutants in the environment (target analysis) and the identification of all possible organic pollutants, i.e. in hazardous waste sites (non-target analysis), are important tasks in environmental analysis. However, the chemical, photochemical and microbiological... 

Instead of looking for residual contents and/or specific migration which are covered by the previous step, in non-conventional compliance testing a non-target analysis is performed. This follows discrete steps ... 

A Perhaps first data on an illicit drug in the ambient environment non-target analysis revealed cocaine associated with fractions of particulate matter in outdoor air (Los Angeles) Flannigan et al. (1998)... 

Keywords Data mining Deconvolution software Degradation products Emerging contaminants High resolution mass spectrometry system Hybrid mass spectrometry system Metabolites Non-target analysis Screening analysis Transformation products Surface water UHPLC Unknown compounds... 

The applicability of non-target analysis, i.e. full-scan screening, greatly depends on current technical developments. GC-MS methods have greatly contributed to the characterization of (semi)volatile and thermostable contaminants in water, whereas LC-MS methods have been utilized to extend the investigation of water contaminants to non-volatile, (highly) polar, and thermally labile compounds, such as for example pharmaceuticals, pesticides, endocrine disrupting compounds and personal care products (Richardson 2011). 

In non-target analysis, no a priori information is available, as for instance retention time or SRM transitions. The possibility of obtairfing cormnercially available... 

Recent developments in mass spectrometers have created a situation where many different mass spectrometers are suitable for non-target analysis, each with their specific strengths and drawbacks. 

Unlike QqQ, the 3D IT is characterized by high duty cycles because the time to fill an ion trap and generate a mass spectrum is short. Therefore, ion trap instruments can be also used for non-target analysis by virtue of their MS" capability that allows the sequential and multistage isolation, in the same space and as a function of time, of precursor ions, fragmentation, trapping, and mass scanning. 

In addition, in the case of non-target analysis, a further slight differentiation has been done between the suspect screening without reference standards and a genuine non-target screening of unknowns (Kranss et al. 2010). 

LC-MS non-target analysis has been scarcely applied until now, as it presents important limitations mainly due to the absence of wide commercial reproducible libraries (Ibfinez et al. 2005, 2008 Thurman et al. 2006 Hernandez et al. 2008). 

Because matrix effects might exert a detfimental impact on important method parameters (limit of detection (LOD), limit of quantification (LOQ), linearity, accuracy, and precision), sample pre-tteatments, involving isolation of analytes, purification of exttacts and pre-concenttation, are generally required. It must on the other hand underhned that in a genuine non-target analysis, each sample pre-tteatment could result just in a lack of the potential unknowns of interest. 

Keywords emergency toxicology poisoning full scan screening targeted non-targeted analysis liquid-liquid extraction one-point calibration... 

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