Detector interface

A Finnigan Ion Trap Detector (ITD), a small mass spectrometer for capillary chromatography, is the third detector interfaced with the gas chromatograph. The control of the ITD, the data collection, and the identification of species, by a library... 

Standards with a poor UV chromophore (4-methyl-2-pentanone, 1-chlorododecane, and stearic acid) were analyzed on a Perkin-Elmer 3920 gas chromatograph with a flame ionization detector and a 30-m SE-54 wall-coated open tubular (WCOT) fused-silica capillary column (J W Scientific). The injector temperature was 200 °C the detector interface temperature was 280 °C. The carrier gas was He at 16.5 lb/in.2, and the makeup gas was nitrogen at a flow of 40 cm3/min. Splitless l-/zL injections of the 25,000 1 concentrates were made by starting with an oven temperature of 45 °C and the oven door open after 2.75 min, the oven door was closed and the temperature was programmed at 4 °C/min to 280 °C, which was held for 8 min. The syringe was kept in the injection port for 15 s after injection. 

In HPLC the sample is dissolved in a solvent that is miscible with the mobile phase and injected onto the column via a sample valve. Separation takes place on a chromatographic column which can be temperature controlled if required. The separated sample components are recorded by a detector interfaced to a computer (Fig. 7.2). HPLC exhibits a significantly higher separation performance than classical column chromatography (LC) introduced above. This is accomplished in HPLC by use of stationary phases having a small particle diameter (dp = 3 to 10 pm for analytical separations). Since these particles strongly re-... 

Sample molecules that are too large to enter the pores of the support material, which is commercially available in various pore dimensions, are not retained and leave the column first. The required elution volume Ve is correspondingly small. Small molecules are retained most strongly because they can enter all the pores of the support material. Sample molecules of medium size can partly penetrate into the stationary phase and elute according to their depth of penetration into the pores (Fig. 7.3). No specific interactions should take place between the molecules of the dendrimer sample and the stationary phase in GPC since this can impair the efficiency of separation by the exclusion principal. After separation the eluate flows through a concentration-dependent detector (e.g. a UV/VIS detector) interfaced with a computer. One obtains a chromatogram which, to a first approximation, reflects the relative contents of molecules of molar mass M. If macromolecules of suitable molar mass and narrow molar mass distribution are available for calibration of the column, the relative GPC molar mass of the investigated dendrimer can be determined via the calibration function log(M) =f( Vc). 

Gas Chromatography instrument with detector interface only... 

Residual solvents are amenable to GC/MS analysis because they possess sufficient volatility to enter the gas phase without thermolytic decomposition, and they do not typically interact with the sample introduction system (i.e., GC separation column, detector interface, or detector) in such a manner as to cause irreversible surface adsorption or surface catalyzed decomposition. The application of GC/MS for identification of residual solvents is best illustrated with an example. Fig. 1 shows a total ion chromatogram (TIC) from the headspace GC/MS analysis of a drug substance dissolved in a relatively high boiling solvent... 

When designing biosensors, it is essential to study and tmderstand each component that constitutes this complex system as well as aU the factors that influence its unique performance and limitations [5,6]. Despite an important number of publications in the biosensor field, several aspects require further optimization and improvements many of these could be related to inadequate materials and insufiftcient understanding of the underlining mechanism. Since the properties and the type of the material used are largely connected with the transducer and the transducer/detector interface, a considerable attention must be paid to the nature of electrode material. The rapid... 

Figure 15 EDS detector interface to dedicated STEM Figure 4). Note orientation of detector with respect to sample and incident-beam direction...

GC-MS Analysis and Identification. A portion of the acidic fractions were quantitatively converted to methyl esters using a BF3-methanol reagent. The procedure used was that of Metcalfe and Schmitz (8). The esterified acidic fractions were analyzed using a coupled gas chromatograph-mass spectrometer (GC-MS) system consisting of a Varian Moduline 2700 gas chromatograph equipped with a flame ionization detector interfaced by a jet separator to a Du Pont Instruments Model 21-490 mass spectrometer. A 10 ft x 1/8 in o d stainless steel column packed with 10% stabilized DEGS on 80/ 100 mesh Chromosorb W AW DWCS was used. The He flow rate was 30 ml/min. The column temperature was held 5 minutes at 30°C, then... 

UV at 220 nm was chosen as the method for purity determination. U V detectors interface seamlessly as in-line detectors with LC-MS systems, are extremely robust, reproducibile and sensitive at the required sample concentrations. No HPLC detector has uniform response across all compounds [38 1]. Evaporative light-scattering detection (ELSD) is reported to offer a more universal response factor [38], but the response factors compared to UV at 220 nm were... 

The advantages of SFC for improved separation and detector interfacing accrue from the nature of the supercritical fluid (10). 

Figure 4.8 The gas-flow proportional counter (a) A simplified representation of the detector structure, (b) The preamplifier-detector interface. (Reprinted by courtesy of EG G ORTEC.)...

An important specialized use of TLC involves the separation, identification, and measurement of radioisotopes. The principal methods used are autoradiography, liquid scintillation counting, and direct scanning using a radiation detector interfaced with a computer for data collection. Radiolabeled compounds are used in radiotracer methods to follow the course of chemical and biochemical reactions, e.g., the study of pesticide metabolism in plants and animals (205), and drugs in humans. 

Quantitation of N-acetylnorheroin in heroin hydrochloride samples was by gas chromatography on a Perkin Elmer 900 Gas Chromatograph (column 6 ft. x 1/4 in.) temperature initial 180°C, final 270°C, program rate 4°C/min. Flame Ionization Detector, interfaced with Spectra-Physics Autolab System I Computing Integrator, measured peak areas in y volts Carrier gas nitrogen 60 ml/min. Authentic heroin hydrochloride samples were prepared by dissolving ca. 60 mg/ml in methanol. Standard N-acetylnorheroin (prepared by procedure described below) was 5.0 mg/ml. Sample... 

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