Thin layer chromatography/mass spectroscopy

Supercritical fluid chromatography Thin-layer chromatography Atomic absorption spectroscopy Nuclear magnetic resonance spectroscopy Mass spectrometry Fourier transform infrared spectrometry... 

The conventional approach to solvent extraction is the batch method. Early work with this method was hampered by the low concentration of the compounds present and the relative insensitivity of the methods of characterization. Thus lipids and hydrocarbons have been separated from seawater by extraction with petroleum ether and ethyl acetate. The fractionation techniques include column and thin-layer chromatography with final characterisation by thin-layer chromatography, infrared, and ultra-violet spectroscopy and gas chromatography. Of these techniques, only gas chromatography is really useful at levels of organic matter present in seawater. With techniques available today such as glass capillary gas chromatography and mass spectrometry, much more information could be extracted from such samples [20]. 

From the analytical point of view, reactions were efficiendy monitored using a combination of FTIR (Fourier transform infrared), TLC (thin-layer chromatography), and MALDI-TOF mass spectroscopy analysis of crudes resulting from the cleavage of small resin samples. 

AHLs can be tentatively identified by comparison of the unknown with synthetic AHL standards after Thin Layer Chromatography (TLC) in which the plates are overlaid with agar containing one of the AHL biosensors described above [37,39,44,45]. However, for the unequivocal identification of AHLs the use of more powerful methods such as LC-mass spectrometry, nuclear magnetic resonance and infrared spectroscopy as described below are required. 

Although the metabolism of several phthalate esters has been studied in vitro, essentially all of the in vivo studies have involved DEHP. A summary of these experiments which involved exposure offish to aqueous - C-DEHP is presented in Table IV (11,12). Tissue C was isolated and separated into parent and the various metabolites by preparative thin layer chromatography on silica gel. Metabolites were hydrolyzed where appropriate and identified by gas chromatography-mass spectroscopy. In whole catfish, whole fathead minnow and trout muscle, the major metabolite was the monoester while in trout bile the major metabolite was the monoester glucuronide. The fact that in all cases the major metabolite was monoester or monoester glucuronide despite the differences in species, exposure level and duration, etc. represented by these data, suggests that hydrolysis of DEHP to monoester is important in the biotransformation of DEHP by fish. 

Schulten, H.-R., and Soldati, F. (1981). Identification of ginsenosides from Panax ginseng in fractions obtained by high-performance liquid chromatography by field desorption mass spectrometry, multiple internal reflection infrared spectroscopy and thin layer chromatography. J. Chromatogr. 212, 37-i9. 

Monitoring reaction progress throughout a multistep synthesis is a relatively difficult task.22 Typical methods used for solution-phase synthesis, including thin-layer chromatography (TLC), GC, and most types of mass spectrometry (MS), are less informative for solid-phase methods. However, Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) are particularly useful in solid-phase strategies. 

Additional methods which so far have been of only limited interest for the quantitative study of redistribution equilibria are mass spectrometry (313), Raman (68), and infrared (110) spectroscopy. It can be visualized that methods such as microwave spectroscopy, thin-layer chromatography, or Mdssbauer spectroscopy may be of interest in the near future. 

About 10 g of VLB (vincaleucoblastine or simply vinblastine) sulfate were converted by standard procedures to VLB free base. The free base, obtained as a residue after evaporation of the dried ethereal solvent, was dissolved in about 200 ml of anhydrous methanol. Anhydrous liquid ammonia (300 ml) was added, and the reaction mixture sealed and maintained at about 100°C for 60 hours. The reaction vessel was opened, and the contents removed and evaporated to dryness in vacuo. The resulting residue, containing 4-desacetyI VLB C-3 carboxamide, as shown by thin layer chromatography, were combined and the solvent evaporated therefrom in vacuo, yielding asa residue purified 4-desacetyl VLB C-3 carboxamide free base. The NMR and IR spectra of the solid free base confirmed the structure indicated. The free base showed a band in the infrared at 1,687 cm-1, characteristic of the amide function. The molecular weight of the free base determined by mass spectroscopy was 753 which is in agreement with theoretical value calculated for C43H55N5O7. 

Chapter 14 discusses the very useful technique of thin layer chromatography. It has extensive applications in the analysis of complex mixtures of organic compounds and also has found limited applications in the analysis of organometallic compounds. No applications to anions and cations have been reported to date. The technique can also be used to prepare extracts suitable for subsequent examination by infrared spectroscopy or mass spectrometry. 

Separation is carried out using various techniques, depending on the nature of the compounds. For nonionic species the solubilities of the compounds are generally low and similar, and it has been necessary to use either fractionation by continuous extraction with low boiling solvents (36) or thin-layer chromatography (58, 60). The first method has been used with air-sensitive compounds, whereas the second has been applied only to air-stable substances. In both cases, it is possible to separate only limited amounts of compounds, whose characterization is, therefore, carried out using particular techniques such as mass spectroscopy (58-60). 

Pyrolysis at 200°C of Os3(CO)j2 in a scaled, evacuated tube afforded a mixture of at least seven different carbonyl clusters which could be separated by thin-layer chromatography. In addition to some unreacted Os3(CO)i2, the new compounds, Os.i(CO)i3, Os5(CO)i6, Os6(CO)i8, Os8(CO)23, and Os8(CO)2iC, were identified by mass spectroscopy (58) the last compound was originally formulated as Oss(CO)i5C4 (61). Further pyrolysis of Os6(CO)i8 at 255°C gives the pentanuclear carbide derivative, Os5(CO)I5C, in 40% yield (59). 

We have recently been able to show (34) the presence of a minor component in extracts of many -cultivars of pepper grown in India and Ceylon by the reversed phase, argentation thin-layer chromatography of the isolated total pungent components. This component has the typical 360 nm maximum attributed to piperettine and has shown very little pungency. We are still working on further isolation and purification for study by mass and nuclear magnetic resonance spectroscopy. 

Whichever technique is used - paper chromatography, thin layer chromatography, a column of material - separation will be achieved, but different rates of flow or i f value will be recorded. Different powders are used to achieve different separations. Research in the area of analytical chemistry means that different variations of the techniques are being developed periodically. The products can be separated using chromatography then the separated components characterized using mass spectrometry or various types of spectroscopy. 

Fluorophilic CD derivatives have been obtained as a result of combinations of CDs and a linear perlluorocarbon [73]. 2,3-Di-O-decafluorooctanoyl-y-CD was obtained with a protection-deprotection synthetic method and characterized further by thin-layer chromatography (TLC), Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), elemental analysis, and time-of-flight mass spectrometry (OF-MS). 

A suite of shards of transport amphoras excavated by the Oriental Institute of the University of Chicago, under the direction of L. E. Stager, provided an opportunity to test infrared (IR) spectroscopy and thin-layer chromatography (TLC) as quick and easy methods of identifying the botanical sources of resins and to compare the results obtained with these methods with those obtained by GC and GC-mass spectrometry (GC-MS),... 

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