Liquid chromatography-mass spectrometry high polarity

While the alkyl chain distribution is determined on a non-polar RP8 and RP18, EO homologue distribution is determined using a polar phase. AEOs are not UV-absorbing species, so they cannot be directly determined by HPLC followed by standard optical detection systems (UV and FL), unless suitable derivatives are prepared [2], Because of this, methods based on liquid chromatography-mass spectrometry [77-79] are currently considered as the benchmark procedure that gives sufficiently high selectivity and sensitivity. 

Wu, J., Tragas, C., Lord, H., and Pawliszyn, J. (2002). Analysis of polar pesticides in water and wine samples by automated in-tube solid-phase microextraction coupled with high-performance liquid chromatography-mass spectrometry, J. Chromatogr. A, 976,357-367. 

Analysis of intact polar lipids by high-pressure liquid chromatography-mass spectrometry/tandem mass spectrometry with use of thermospray or atmospheric pressure ionization... 

When less thermally labile compounds require separation prior to analysis, in-line liquid chromatography-mass spectrometry (LC-MS) can be used. Even where liquid chromatographic separation is not required LC-MS interfaces may be used as a convenient method of sample introduction, e.g. for polar, ionic, thermally labile, involatile or high-molecular-weight species. There are several different types of LC-MS interface each with its own characteristics in terms of the solvent systems and sample types that it can handle and the appropriate solvent flow rates no one interface is applicable to all solvent-solute combinations. 

Tolonen, A. and Uusitalo, L, Fast screening method for the analysis of total flavonoid content in plants and foodstuffs by high-performance liquid chromatography/electrospray ionization time-of-flight mass spectrometry with polarity switching. Rapid Commun. Mass Spectrom., 18, 3113, 2004. 

T Rezanka, M Podojil. Preparative separation of algal polar lipids and of individual molecular species by high performance liquid chromatography and their identification by gas chromatography-mass spectrometry. J Chromatogr 463 397-408, 1989. 

Modern tHcy methods include enzyme immunoassays and chromatographic-based methods. In practice, immunoassays " are most often used for routine purposes (e.g., fluorescence polarization immunoassay IFPIA] as run on Abbott s IMx and AxSYM platforms) Chromatographic assays include amino acid analysis high-performance liquid chromatography (HPLC) with ultraviolet, fluorescence, or electrochemical detection ° " capillary electrophoresis with fluorescence detection gas chromatography-mass spectrometry (GC-MS) and liquid chromatography with tandem MS (MS-MS). 

Lytle, C.A., Fuller, M.E., Can, Y.D.M., Peacock, A., DeFlaun, M.F., Onstott, T.C. and White, D.C. (2001) Utility of high-performance liquid chromatography/electrospray/mass spectrometry of polar lipids in specifically Per-C-13 labeled Cram-negative bacteria DA001 as a tracer for acceleration of bioremediation in the subsurface, yourna/of Microbiological Methods 44, 271-281. 

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. 

Moder M, Popp P, Eisert R, Pawliszyn J. Determination of polar pesticides in soil by solid phase microextraction coupled to high-performance liquid chromatography-electrospray/mass spectrometry. Fresenius. J. Anal. Chem. 1999 363 680-685. 

Whilst these methods are informative for the characterisation of synthetic mixtures, the information gained and the nature of these techniques precludes their use in routine quantitative analysis of environmental samples, which requires methods amenable to the direct introduction of aqueous samples and in particular selective and sensitive detection. Conventionally, online separation techniques coupled to mass spectrometric detection are used for this, namely gas (GC) and liquid chromatography (LC). As a technique for agrochemical and environmental analyses, high performance liquid chromatography (HPLC) coupled to atmospheric pressure ionisation-mass spectrometry (API-MS) is extremely attractive, with the ability to analyse relatively polar compounds and provide detection to very low levels. 

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