Chromatography on-line

An on-line chromatography/atmospheric pressure chemical ionization tandem mass spectrometry (LC-APCI/MS/MS) methods was developed for rapid screen of pharmacokinetics of different drugs, including 5 (98RCM1216). The electron impact mass spectrum of 5 and ethyl 9,10-difluoro-3-methyl-7-oxo-2,3-dihydro-7Ff-pyrido[l,2,3- fe]-l,4-benzoxazine-6-carboxylate was reported (97MI28). Electron impact/Fourier transform... 

Stevenson, S. and Dorn, H. C., 13C dynamic nuclear polarization a detector for continuous-flow, on-line chromatography, Anal. Chem., 66, 2993, 1994. 

Smith and Udseth [154] first described SFE-MS in 1983. Direct fluid injection (DFT) mass spectrometry (DFT-MS, DFI-MS/MS) utilises supercritical fluids for solvation and transfer of materials to a mass-spectrometer chemical ionisation (Cl) source. Extraction with scC02 is compatible with a variety of Cl reagents, which allow a sensitive and selective means for ionising the solute classes of interest. If the interfering effects of the sample matrix cannot be overcome by selective ionisation, techniques based on tandem mass spectrometry can be used [7]. In these cases, a cheaper and more attractive alternative is often to perform some form of chromatography between extraction and detection. In SFE-MS, on-line fractionation using pressure can be used to control SCF solubility to a limited extent. The main features of on-line SFE-MS are summarised in Table 7.20. It appears that the direct introduction into a mass spectrometer of analytes dissolved in supercritical fluids without on-line chromatography has not actively been pursued. 

Alternatives to off- and on-line chromatography are desirable in order to avoid the time-consuming chromatographic step, and are imperative for polymer-bound additive functionalities. 

Foxboro Great Britain Ltd., Technical Bulletin L58X IIP (1993). On-line chromatography. 

In situ Ex-situ, with interfaces for automatic sampling, similar to on-line chromatography Difficult, complex automated set-ups necessary, possible with FIA and/or laboratory robots... 

In principle, most of these methods can be linked to a bioreactor on-line and ex-situ, with interfaces for automatic sampling similar to those used for on-line chromatography (for interfaces, see the chapter by Sonnleitner in this volume). An exception is the analysis of protein patterns by electrophoresis, which is difficult to perform automatically. 

Continuous on-line chromatography - identifying the heavy element daughters... 

The main disadvantages of ESI are (a) the difficulty in handling mixtures of compounds in the case of direct infusion-coelution and (b) the low tolerance of for electrolytes. Thus, the samples must be purified (by on-line chromatography where possible) and desalted before they can be analyzed. The main advantages of ESI are (a) the mass measurement accuracy, (b) the ability to interface directly with HPLC and CE, and (c) the soft ionization, which allows for observation of protein folding and noncovalent interactions. 

The mass spectrometer is a highly sophisticated and computerized instrument, which basically consists of five parts sample introduction, ionization, mass analysis, ion detection, and data handhng. In principle, hquid chromatography is just one of the possible analyte techniques, or the mass spectrometer just another detector for LC. However, on-line chromatography-MS systems offer additional value, especially in terms of selectivity. 

Sandvoss, M. Weltring, A. Preiss, A. Levsen, K. Wuensch, G. Combination of matrix solid-phase dispersion extraction and direct on-line chromatography-nuclear magnetic resonance spectroscopy-tandem mass spectrometry as a new efficient approach for the rapid screening of natural products Application to the total asterosaponin fraction of the starfish Asterias rubens. J. Chromatogr., A 2001, 917, 75-86. 

In the interest of obtaining maximum bioanalytical throughput, some researchers have resorted to direct MS analysis without on-line chromatography. While there are obvious drawbacks to this approach, which include a greater likelihood for ion suppression and a higher occurrence of interfering peaks, the motivation behind FIA is basically twofold (1) a reduction in LC injection duty-cycle time, and (2) the elimination of LC method development. 

The reaction was performed at 703K, using a saturator with cyclohexane at a constant temperature of 284K, and pure hydrogen as carrier gas (20 ml/min). The reaction products were analysed by on-line chromatography (Shimadzu GC-17 ) with a packed Chrompack column (60 m length and 0.32 nm diameter) at 453K. 

Hence, the plantwide control objective is the quality of DCE sent to the cracking section, for which three specifications are required These are the outputs of the plantwide control problem. We assume that they are available by direct concentration measurements, as by IR spectroscopy or on-line chromatography. 

Fulcrand H, Remy S, Souquet JM, Cheynier V, Moutounet M (1999) Study of wine tannins oligomers by on-line chromatography electrospray ionization mass spectrometry. J Agric Food Chem 47 1023-1028... 

Recently, several new methods have been developed for measuring isotope ratios in elemental spedes of some real-world samples, standards, and reference materials using chromatographic separation coupled on-line to MC-ICP-MS. So far, there are about 15 published papers which describe the application of on-line chromatography coupled with MC-ICP-MS to isotopic analysis in elemental species of Hg, Pb, S, Sb, Cl, and Br. In this section, these applications, induding sample preparation, analytical charaderistics of the technique, instrumentation, spedes and isotopes monitored, and some useful results, are discussed. 

Continuous On-Line Chromatography Identifying the Heavy Element Daughters... 

Pfrepper et al. [37, 38] developed this technique further, thereby making it a quantitative technique capable of measuring distribution coefficients values of short-lived isotopes by on-line chromatography. In the conventional off-line chromatography, the distribution coefficient is determined via the retention time (elution position) as... 

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