Mass spectrometry LC-NMR

LC-MS/MS Liquid chromatography coupled with tandem mass spectrometry LC-NMR Liquid chromatography coupled with nuclear magnetic resonance TLC Thin-layer chromatography... 

K. I. Burton, J. R. Everett, M. J. Newman, F. S. Pullen, D. S. Richards, and A. G. Swanson, On-line liqnid chromatography conpled with high field NMR and mass spectrometry (LC-NMR-MS) A new techniqne for drug metabolite structure elucidation, J. Pharma. Biomed. Anal. 15 (1997), 1903-1912. 

Burton, K.I. Everett, J.R. Newman, M.J. Pullen, F.S. Richards, D.S. Swanson, A.G. On-line Liquid Chromatography Coupled with High Field NMR and Mass Spectrometry (LC-NMR-MS) A New Technique for Drug Metabolite Structure Elucidation, 7. Pharm. Biomed. Anal. 15(12), 1903-1912 (1997). 

Shockcor PJ, Unger SH, Wilson ID, FoxaU PJD, Nicholson JK, Lindon JC. Combined hyphenation of HPLC, NMR spectroscopy and ion trap mass spectrometry (LC-NMR-MS) with application to the detection and characterization of xenobiotic and endogenous metabolites in human urine. Anal Chem 1996 68 4431-4435. 

The experimental study of steroidal glycosides of echi-noderms is difficult, as noted in many reviews (Burnell and ApSimon, 1983 Quinn, 1988 Minale, Riccio, and Zollo, 1993). The contemporary technique of combined liquid chromatography, nuclear magnetic resonance, and mass spectrometry (LC-NMR-MS) together with solid-phase extraction (MSPD) has been used to characterize all the constituents of a crude mixture of asterosaponins. Use of this technique led to the identification of the 17 constituents of the asterosaponin fraction of Asterias ruhens from 11 mg of crude mixture, itseF obtained from a sample of 5 g of the sea star (Sandvoss et al., 2001). 

Important progress in terms of higher throughput in ADME/PK work was realized recently by wider use of liquid chromatography/mass spectrometry (LC/MS), which has now become a standard analytical tool [26]. Flow NMR spectroscopy has become a routine method to resolve and identify mixtures of compounds and has found applications in drug metabolism and toxicology studies [27]. 

The system relies upon preliminary fractionation of the microbial crude extract by dualmode countercurrent chromatography coupled with photodiode array detection (PDA). The ultraviolet-visible (UV-Vis) spectra and liquid chromatography-mass spectrometry (LC-MS) of biologically active peaks are used for identification. Confirmation of compound identity is accomplished by nuclear magnetic resonance (NMR). Use of an integrated system countercurrent chromatography (CCC) separation, PDA detection, and LC-MS rapidly provided profiles and structural information extremely useful for metabolite identification (dereplication, Figure 14.1). 

We will briefly highlight some examples using NMR methods [14, 19] but the remainder of this chapter will focus on MS and liquid chromatography-mass spectrometry (LC-MS) metabolomics [5, 15, 18]. We should also point out that there are a number of examples of both NMR and MS methods being used in the discovery of medicinally important biomarkers [23, 31] however, this review will focus more on the use of metabolomics to characterize proteins. 

The main spectrometric identification techniques employed are gas chromatography/mass spectrometry (GC/MS) (13), liquid chromatography/tandem mass spectrometry (LC/MS(/MS)) (14), nuclear magnetic resonance (NMR) (11), and/or gas chromatography/Fourier transform infrared spectroscopy (GC/FL1R) (15). Each of these spectrometric techniques provides a spectrum that is characteristic of a chemical. MS and NMR spectra provide (detailed) structural information (like a fingerprint ), whereas an FUR spectrum provides information on functional groups. 

One set of samples is prepared for the analysis techniques relying on GC separation. Samples from water and aqueous extracts can be prepared in straightforward way for analysis by liquid chro-matography/mass spectrometry (LC/MS) and NMR. Samples for NMR are normally prepared so as to obtain 5-10-fold concentration. Aqueous liquids are particularly suitable for NMR. 

For the precise determination of the complex polymer composition including the chemical composition and MMD of the components in most cases a separation step is required. Only after obtaining fractions comprising the different polymer components, can an analysis with regard to chemical composition and MMD be conducted. The present section discusses different options which enable the use of liquid chromatography (SEC, HPLC, LC-CC) in conjunction with FTIR, mass spectrometry and NMR for the separation of complex polymers. 

Methods in the analysis of drug impurities (e.g., ultraviolet, UV Fourier transform infrared, FT-IR nuclear magnetic resonance, NMR mass spectrometry, MS) are used to separate, identify, and quantify impurities, as well as establish their structure. Currently the most efficient methods seem to be combined techniques such as GC-MS, LC-MS, liquid chromatography-diode-array detection-mass spectrometry (LC-DAD-MS), LC-NMR, LC-DAD-NMR-MS, etc. [18-20]. 

Metabolism Global metabolic profile via metabolomics (e.g. NMR spectroscopy, liquid chromatography-mass spectrometry (LC-MS), Lactate/pyruvate ratio, glucose and amino acid consumption, succinate dehydrogenase levels... 

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