Tandem mass spectrometry separation techniques

SEC-ESI-FTMS combines the size separation based technique of SEC with one of the most powerful mass spectrometric techniques of FTMS offering high mass accuracy (ppm), ultrahigh resolving power (>10(i) 6) and the capability to perform tandem mass spectrometry. The technique enables generation of oligomer elution profiles, which can be used for accurate calibration of standard SEC data. Coupling of SEC to ESI-MS is further described in ref. [710],... 

Multidimensional or hyphenated instmments employ two or more analytical instmmental techniques, either sequentially, or in parallel. Hence, one can have multidimensional separations, eg, hplc/gc, identifications, ms/ms, or separations/identifications, such as gc/ms (see CHROMATOGRAPHY Mass spectrometry). The purpose of interfacing two or more analytical instmments is to increase the analytical information while reducing data acquisition time. For example, in tandem-mass spectrometry (ms/ms) (17,18), the first mass spectrometer appHes soft ionization to separate the mixture of choice into molecular ions the second mass spectrometer obtains the mass spectmm of each ion. 

A further extension of the DFG S19 method was achieved when polar analytes and those unsuitable for GC were determined by LC/MS or more preferably by liquid chromatography/tandem mass spectrometry (LC/MS/MS). Triple-quadrupole MS/MS and ion trap MS" have become more affordable and acceptable in the recent past. These techniques provide multiple analyte methods by employing modes such as time segments, scan events or multiple injections. By improving the selectivity and sensitivity of detection after HPLC separation, the DFG S19 extraction and cleanup scheme can be applied to polar or high molecular weight analytes, and cleanup steps such as Si02 fractionation or even GPC become unnecessary. 

If we consider only a few of the general requirements for the ideal polymer/additive analysis techniques (e.g. no matrix interferences, quantitative), then it is obvious that the choice is much restricted. Elements of the ideal method might include LD and MS, with reference to CRMs. Laser desorption and REMPI-MS are moving closest to direct selective sampling tandem mass spectrometry is supreme in identification. Direct-probe MS may yield accurate masses and concentrations of the components contained in the polymeric material. Selective sample preparation, efficient separation, selective detection, mass spectrometry and chemometric deconvolution techniques are complementary rather than competitive techniques. For elemental analysis, LA-ICP-ToFMS scores high. 

The analysis of estrogens and progestogens by GC-MS has been carried out with a variety of capillary columns using helium as carrier gas [7,26,36,43, 59, 66]. LODs in the range of 0.1—1.8 ng L 1 have been achieved. In terms of sensitivity, GC- and HPLC-tandem mass spectrometry are comparable techniques. However, the derivatization carried out prior to GC separation is time consuming and can be a source of inaccuracy [7]. 

M. Pelzing and C. NeusiiB. Separation Techniques Hyphenated to Electrospray-Tandem Mass Spectrometry in Proteomics Capillary Electrophoresis versus Nanoliquid Chromatography. Electrophoresis, 26(2005) 2717-2728. 

Even though the MALDI peptide mass mapping technique is very powerful, it has limitations. It requires well-separated proteins, is less sensitive than identifications based on electrospray tandem mass spectrometry, can only identify proteins whose complete sequences are available in databases, and does not produce redundant information. 

Natural products and natural-like compounds, generally coming from microbes, plants, sponges and animals [2, 3] may be fully identified and quantified by means of modem and advanced analytical techniques, such as high-performance liquid chromatography (HPLC) coupled to various detectors - from the most common UV/Vis to mass spectrometry and tandem mass spectrometry (HPLC-MS and HPLC-MS/MS). The role of MS is to provide quantitative and qualitative information about mixtures separated by liquid chromatography [4],... 

Gas chromatography coupled to tandem mass spectrometry (GC-MS/MS [49]) prior to analysis of the three primary active components of cannabis (THC, cannabidiol and cannabinol) by this technique, airborne particulates were extracted in an ultrasonic bath with chloroform. The extracts were combined and concentrated under a stream of nitrogen. The residue was filtered through pre-washed disposable PTFE membranes, dried and finally reconstituted with cyclohexane. After separation and solvent partitioning, the extracts were analysed by GC-MS/MS. 

However, tandem mass spectrometry, as a separation technique, does have limitations. It cannot easily differentiate between isomeric and isobaric species, and, in complex matrices, the presence of components with a high surface activity can suppress the ionization of components with a lower surface activity, leading to the nondetection of analytes (66). Therefore, the combination of MS-MS with a readily available chromatographic separation method such as TLC affords analysts real benefits. 

In recent years the rapid development of high-sensitivity analytical techniques such as mass spectrometry (MS) and liquid chromatography (LC) supported the investigation of the endocannabinoids as part of a complex lipid network. The identification of lipid components of the endocannabinoid system can be achieved in a single analytical step by state-of-the-art platforms such as tandem mass spectrometry (MS/MS), which provides the detailed structural information necessary for characterization of lipids and increases specificity in complex biological matrices. Furthermore, the implementation of ionization techniques such as electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) allow the coupling of LC to MS, and permits the separation and analysis of endocannabinoids with greater speed and accuracy. 

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