Chromatography HPLC mass spectrometric

Schroder [20b] used high-performance liquid chromatography (HPLC)/ mass spectrometric (MS)/MS with a thermospray interface [20c] to detect, identify, and quantify metabolites of Fluowet OTN, a nonionic fluorinated surfactant with the structure R F2,i+iCH2CH2(OCH2CH2)wOH. The biodegradation was limited to the poly(oxyethylene) hydrophile [20b]. The absence of fluoride ions indicated that the perfluorocarbon chain was not degraded. 

HPLC with fluorescence detection gave results for polycyclic aromatic hydrocarbons which were comparable to those obtained by gas chromatography with mass spectrometric detection. 

Analysis methods for the determination of hydroperoxides and hydroxyhydro-peroxides in reaction mixtures were developed and applied to photolysis mixtures of aliphatic and aromatic hydrocarbons, carbonyls, alcohols and halogenated hydrocarbons. HPLC with chemiluminescence, electrochemical and fluorescence detection was used for selective detection of hydroperoxides and hydroxohydro-peroxides and gas chromatography with mass spectrometric and flame ionisation detection for the analysis of all reaction products. 

For off-bead analysis, coupling between chromatographic separation and mass spectrometric detection has proven especially powerful. The combination between high performance liquid chromatography (HPLC) and electrospray ionisation mass spectrometry has the advantage that purity of product mixtures can be coupled on-line with the product identification. 

A number of analytical techniques such as FTIR spectroscopy,65-66 13C NMR,67,68 solid-state 13 C NMR,69 GPC or size exclusion chromatography (SEC),67-72 HPLC,73 mass spectrometric analysis,74 differential scanning calorimetry (DSC),67 75 76 and dynamic mechanical analysis (DMA)77 78 have been utilized to characterize resole syntheses and crosslinking reactions. Packed-column supercritical fluid chromatography with a negative-ion atmospheric pressure chemical ionization mass spectrometric detector has also been used to separate and characterize resoles resins.79 This section provides some examples of how these techniques are used in practical applications. 

Paganga, G. et al.. The polyphenolic content of fruit and vegetables and their antioxidant activities what does a serving constitute Free Radical Res., 30, 153, 1999. Maatta, K.R. et al.. High-performance liquid chromatography (HPLC) analysis of phenolic compounds in berries with diode array and electrospray ionization mass spectrometric (MS) detection Rihes species, J. Agric. Food Chem., 51, 6736, 2003. 

Parallel to the development of mass spectrometric instrumentation and methodologies, the improvements of separation techniques, such as gas chromatography (GC), high performance liquid chromatography (HPLC) and capillary electrophoresis (CE), and of their coupling with MS allowed the study of complex mixtures, that are generally encountered in most studies. 

Figure 2.1 Mass spectrometric approach. Dl, direct inlet GC, gas chromatography HPLC, high performance liquid chromatography CZE, capillary zone electrophoresis El, electron ionization Cl, chemical ionization ESI, electrospray ionization DESI, desorption electrospray ionization APCI, atmospheric pressure chemical ionization MALDI, matrix assisted laser desorption ionization B, magnetic analyzer E, electrostatic analyzer...

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. 

Alternative approaches to improve chromatography and thereby enhance signal-to-noise ratio include the use of ultrapressure liquid chromatography (UPLC) (Dear et al., 2006), where chromatographic resolution can be dramatically increased (Castro-Perez et al., 2004, 2005 Plumb et al., 2004), or nano-HPLC (Schmidt et al., 2003), which may serve to reduce ion suppression effects. For offline use, the 96-well plate approach (typically the Scintiplate) will normally be used in combination with direct mass spectrometric infusion at conventional flow rates (5-10 xL/min). This approach enables multiple experiments to be performed in order to... 

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