Selectivity analysis HRMS

The use of GC-MS in polymer/additive analysis is now well established. Various GC-based polymer/additive protocols have been developed, embracing HTGC-MS, GC-HRMS and fast GC-MS with a wide variety of front-end devices (SHS, DHS, TD, DSI, LD, Py, SPE, SPME, PTV, etc.). Ionisation modes employed are mainly El, Cl (for gases) and ICPI (for liquid and solid samples). Useful instrumental developments are noticed for TD-GC-MS. GC-SMB-MS is a fast analytical tool as opposed to fast chromatography only [104]. GC-ToFMS is now about to take off. GC-REMPI-MS represents a 3D analytical technique based on compound-selective parameters of retention time, resonance ionisation wavelength and molecular mass [105]. 

The analytes are typically extracted from the biological matrix using solvent extraction or solid phase extraction (SPE). Most analytes require some form of chemical derivatization prior to analysis by GC-MS techniques, whereas with LC-MS-MS no further treatment of the extract is required. The extracts obtained from urine are relatively dirty because of the many endogenous compounds that are present. It is for this reason that the very selective techniques of GC-MS-MS, GC-HRMS, or LC-MS-MS are required to detect some of the prohibited substances that have low detection levels. 

Selected examples of analytical methods used for the determination of global profiling of lipids are listed in Table 5. Extraction is usually based on simple liquid extraction, using modified Folch or Blight and Dyer extraction (4,5). For more acidic lipids, such as PSs and phosphatidic acids, adjustment of the pH in the aqueous phase is required. The analysis is most typically performed with LC-MS in RPLC mode, with the UHPLC methods gradually replacing the conventional HPLC methods. HRMS systems, such... 

Two different sensitive and selective HS-SPME-GC/MS approaches for simultaneous analysis of TCA and TBA in wine using negative chemical ionization MS (GC/NCI-MS) and high-resolution mass spectrometry (GC-HRMS), were developed (Jonsson et al., 2006). Experimental conditions and performance of the methods are summarized in the Table 8.1. 

Selected ion chromatograms from an analysis of a sediment sample by gaoehromatography/high resolution mass spectrometry GC/HRMS... 

The aim of this chapter is to present the state of the art on UHPLC-MS(/MS) analysis of pesticides in food. It includes a selection of the most relevant papers recently published regarding instrumental and column technology focusing on UHPLC analysis with sub-2 pm and novel porous shell particle-packed columns. Sample treatment procedures such as QuEChERS, MIPs, and online SPE will also be addressed. MS strategies for the analysis of pesticide residues as well as to guarantee confirmation and identification such as the use of HRMS or alternative confirmation strategies will be discussed with relevant application examples. 

Purification of the raw extract is always necessary in order to remove interfering compounds and prepare the sample for the chromatographic separation and final instrumental assessment. In many of the cleanup procedures, extracts are treated with concentrated sulfuric acid the planarity and aromaticity of PCDDs and PCDFs are often used to selectively adsorb them on the surface of carbonaceous materials such as activated or graphitized carbon. The raw extract may be spiked with a cleanup standard in order to check the efficiency of purification steps. The instrumental analysis is carried out by HRGC/HRMS. 

Decision 2002/657/EC introduces criteria for confirmatory analysis, based on the so called identification points (IPs). Then, for confirmation of Group A substances, a minimum of four IPs are required, whereas for compounds listed in Group B the minimum number of IPs is set to three for a satisfactory confirmation of a compounds identity. Although the cited document still accepts detection techniques like diode-array (DAD) and fluorimetric detection (ELD) as possible confirmatory techniques, the confirmation of veterinary residues in food is performed nowadays by LC coupled to different MS detection systems. The system of IPs relies on the identification power of the different mass analyzers. For instance, a low resolution mass spectrometer (e.g., triple quadru-pole, QqQ or ion trap IT), provides 1.0 IP for the precursor ion and 1.5 IPs for each product ion. By contrast, high resolution mass spectrometers (HRMS resolution >20,000 fwhm, full width at half maximum) provide 2.0 IPs for the precursor ion and 2.5 IPs for each product ion, which means that (2 + 2.5n) IPs can be acquired when working in the product ion scan mode. In addition to IPs, the retention time of the suspected peak has to correspond to the measured retention time of the relative standard, and the area ratio between the selected ion traces has to be equal in the sample and in the standard [12]. 

Several advanced PyMS configurations have been described. Boon et al. [712] have presented a multi-purpose external ion source FTICR mass spectrometer for rapid microscale analysis of complex mixtures. External source DT-FTlCR-MS allows obtaining nominal mass spectra, temperature windows, HRMS data and exact elemental composition and MS/MS data on selected ions. For more detailed structural analysis of the more volatile part of the pyrolysate PyGC-MS and PyGC-HRMS are frequently applied. Laser pyrolysis experiments benefit... 

Finally, a third method has been proposed for the analysis of toxaphene using EI-HRMS in SIM mode [98,99], This method is based on the congener-specific analysis for Parlar No. 26, 50, and 62, which are considered as indicators of toxaphene contamination. Selective ion monitoring at a resolving power of 10,000 of mass fragments at m/z 340.8806 ([M — Cl — HCl] cluster ion) for Parlar No. 26 and at m/z 338.8649 and 340.8620 ([M — Cl — 2HC1] cluster... 

In general, ECNI-HRMS can provide higher sensitivity, whereas higher selectivity can be achieved using the EI-HRMS mode. This can be explained by the broad fragmentation pattern obtained with El, which allows one to chose a more specific ion to be monitored. Thus, both HRMS techniques may offer greater possibilities than LRMS for the analysis of toxaphene. 

Future development in GC-MS analysis will require the use of more stable GC capillary columns or multidimensional GG coupled to advanced MS techniques such as HRMS and MS-MS with El and EGNI ionization. The availability of further individual congeners for specific analysis and isotopically labeled standards will assure an accurate quantitative analysis. In addition, the development of more selective analytical methods for the isolation of these compounds from environmental and biological matrices can help to enhance the selectivity of the LRMS techniques. Further research and collaborative studies still need to be done to solve the problems associated with the analysis of PGTs and toxaphene. 

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