Electron supercritical fluid chromatography

One of the most commonly used detection systems in a gas chromatography laboratory is the electron capture detector. The first paper [25] to be published demonstrating the use of an electron capture detector with supercritical fluid chromatography showed that with supercritical fluid chromatography sensitivity to about 50pg minimum detection limit on column was obtainable. 

McNally and Wheeler [364] used supercritical fluid extraction coupled to supercritical fluid chromatography to determine sulfonylurea herbicides in soil. Klatterback et al. [365,366] used supercritical fluid extraction with methanol-modified carbon dioxide followed by high-performance liquid chromatography with UV detection to determine sulfonylurea herbicides obtained on a Cis solid-phase extraction disc. Alternatively the determination was carried out by gas chromatography of the dimethyl derivatives of the sulfonylurea herbicides, employing an electron capture or a NP detector on the gas chromatograph. 

Detectors used in supercritical fluid chromatography include electron capture, photoionisation and sulphur chemiluminescence. 

The choice of the most suitable instrumental technique depends on several factors, such as the physical-chemical characteristics of analytes, the detection limits required, the level and type of interferences, the resolution needed, the identification power required, the accuracy and the precision of the quantitative determination, the availability of instrumentation and finally the cost and the time necessary per each determination. Moreover, extraction and clean-up procedures have to be suitably matched with instrumental analysis. GC coupled with Electron Capture Detection (ECD) or Mass Spectrometry (MS) has been widely applied for the determination of PCBs in organic extracts of environmental samples. In few cases the instrumentation includes the extraction step, such as an SEE system coupled with Supercritical Fluid Chromatography (SFC) or with GC (40). 

Aside from the work of Randall and Wahrhaftig, the only other early attempt to interface supercritical fluid chromatography was the direct introduction work of Gouw et al (34). Although no details were provided, and additional information has not been published, this approach apparently required compound volatility for transfer to a conventional mass spectrometer electron impact ion source. Application appeared limited by compound volatility and poor sensitivity. 

CE capillary electrophoresis SFC supercritical-fluid chromatography El electron ionization PB particle beam. 

The most convenient way to prepare thermosetting gel is to add reactive monomers such as acrylate and metacrylate of the alkylene oxide to the liquid electrolyte and cross-link by irradiating heat, ultraviolet, or electron beam. The residual monomer can be detected by methods of infrared absorption measurement (on basis the peak of 1638 cm ), supercritical fluid chromatography, and photo-DSC (optical difference scanning thermal analysis). 

Ramsey, E.D. and M.W. Raynor, 1996. Electron ionization and chemical ionization sensitivity studies involving capillary supercritical fluid chromatography combined with benchtop mass spectrometry. Anal. Commun., 33 95-91. 

Since NIV occurs as a co-contaminant with other trichothecene mycotoxins, it is often analyzed simultaneously with the co-contaminants rather than alone. Analytical methods developed so far include thin layer chromatography (TLC) capillary gas chromatography (GC) with electron-capture detection (BCD), flame ionization detection (FID), or mass spectrometric detection (GC/MS) high-performance liquid chromatography (HPLC) with ultraviolet (UV), fluorescence, or mass spectrometric detection supercritical fluid chromatography (SFC) and time-of-flight mass spectrometry (LC/TOF-MS). 

GC-gas chromatography, HPLC-high performance liquid chromatography, SFC-supercritical fluid chromatography, TLC-thin layer chromatography, MS-mass spectrometry, MF-mass fragmentography, Cl-chemical ionization, El-electron ionization, ECI-electron capture ionization, IS-ionspray, FAB-fast atom bombardment, ESI-electrospray, SIMS-secondary ion mass spectrometry. 

In addition, especially in the processed urushi samples, peaks with masses [M]K" =665 daltons and [M]K" =667 daltons which are the expected products of the dimerization reaction by oxidation of the phenol part of the catechol derivatives of urushiol. Supercritical fluid chromatography in combination with electron bombardment mass spectrometry was then used for the identification of some of the major components of the urushiol samples. Most prominently were found the trienes with [M]=314 daltons, and [M]=317 daltons and the monoenes. Again the compound with the mass of [M]=332 daltons was noticed which was the water adduct of the triene [M]=314 daltons. 

GC = gas chromatography GPC = gel permeation chromatography ECD = electron capture detector MS = mass spectrometry MSD = mass selective detector SFE = supercritical fluid extraction TLC = thin layer chromatography... 

Steady-State Solvatochromism. The majority of the reports on supercritical fluid solvation have used steady-state solvatochromic absorbance measurements (21-28). The original aim of these experiments was to determine the solvating power of supercritical fluids for chromatography and extraction (SFC and SFE) (26,28). To quantify solvent strength, researchers (21-28) adopted the Kamlet-Taft x solvent polarity scale (50-55). This scale best correlates solvatochromic effects on a- x and x- x electronic absorption transitions. 

GC gas chromatography, ECD electron capture detection, SCFE supercritical fluid extraction... 

Figure 6.1 Bar-graph of MeHg in CRM 580. The results correspond to six replicate determinations as performed by different laboratories using various methods. MEANS indicates the mean of laboratory means with 95% confidence interval. Abbreviations-. CVAAS, cold vapour atomic absorption spectrometry CVAFS, cold vapour atomic fluorescence spectrometry ECD, electron capture detection GC, gas chromatography HPLC, high-performance liquid chromatography ICPMS, inductively coupled plasma mass spectrometry MIP, microwave induced plasma atomic emission spectrometry QFAAS, quartz furnace atomic absorption spectrometry SFE, supercritical fluid extraction.

ECD = electron capture detector FID = flame ionization detector GC = gas chromatography HRGC = high resolution gas chromatography LC-APCI-MS = liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry LSE = liquid-solid extraction MS = mass spectrometry PVC = polyvinyl chloride SFE = supercritical fluid extraction... 

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