In-line interface

Another interface commonly used for connecting HPLC to a mass spectrometer is not a true in-line interface. It is a robotically controlled spotter plate system for collecting samples from the HPLC to be injected into the MALDI time-of-flight laser ionization mass spectrometer for analyzing proteins and large peptides. The effluent sample dropped in the plate well is mixed with an ionization matrix already present, solvent and volatile reagents are evaporated, and the plate is then placed into the injector target and blasted with a pulsed laser to volatilize and ionize sample into the atmosphere of the interface where it can be drawn into the mass spectrometer. 

W.F. Noh and P.R. Woodward, SLIC (Simple Line Interface Calculation), Lecture Notes in Physics, No. 59, Springer-Verlag, New York, 1977. 

Figure 2. Total energies of ordered (LIq structure, squares), random (circles) and segregated (triangles) fee RhsoPdso alloys as a function of the number of neighboring shells included in the local interaction zone. Values obtained by the LSGF-CPA method are shown by filled symbols and full lines. The energies obtained by the reference calculations are shown by a dashed line (LMTO, ordered sample), a dotted line (LMTO-CPA, random sample), and a dot-dashed line (interface Green s function technique, segregated sample).

Turnkey operation A complete fabrication line or system, such as an extruder with a thermoformer line with upstream and downstream equipment. Controls interface all the equipment in-line from material delivery to the end of the line handling the product for in-plant storage or shipment out of the plant. 

Fig. 3. Reduced time plots, tr = (t/t0.9), for the contracting area and contracting volume equations [eqn. (7), n = 2 and 3], diffusion-controlled reactions proceedings in one [eqn. (10)], two [eqn. (13)] and three [eqn. (14)] dimensions, the Ginstling— Brounshtein equation [eqn. (11)] and first-, second- and third-order reactions [eqns. (15)—(17)]. Diffusion control is shown as a full line, interface advance as a broken line and reaction orders are dotted. Rate processes become more strongly deceleratory as the number of dimensions in which interface advance occurs is increased. The numbers on the curves indicate the equation numbers.

Figure 2.2 Schematics of (a) in-line and (b) Z-spray electrospray interfaces. From applications literature published by Micromass UK Ltd, Manchester, UK, and reproduced with permission.

One of the major problems with this type of interface, not unsurprisingly, is clogging of the pinhole. For this reason, the HPLC system has to be kept scrupulously clean with solvents being passed through narrow filters to remove any solid particles and in-line filters being incorporated to ensure that column material does not find its way into the probe. 

In the loop interface the fluid from the extraction cell passes continuously through an injection loop and into a collection vessel. Injection of a predetermined fraction of the extract onto a packed column is made by switching the loop so that it is in-line with the flow of fluid to the analytical... 

On-line SFE-packed capillary SFC is an interesting development in comparison with SFE-cSFC, because of the higher loadability and shorter analysis times. In comparison with SFE-pSFC, the advantages are a lower pressure drop, higher efficiency (theoretical number of plates) and lower flow-rates, resulting in easier interfacing with FID or MS instruments. 

In chromatography-FTIR applications, in most instances, IR spectroscopy alone cannot provide unequivocal mixture-component identification. For this reason, chromatography-FTIR results are often combined with retention indices or mass-spectral analysis to improve structure assignments. In GC-FTIR instrumentation the capillary column terminates directly at the light-pipe entrance, and the flow is returned to the GC oven to allow in-line detection by FID or MS. Recently, a multihyphenated system consisting of a GC, combined with a cryostatic interfaced FT1R spectrometer and FID detector, and a mass spectrometer, has been described [197]. Obviously, GC-FTIR-MS is a versatile complex mixture analysis technique that can provide unequivocal and unambiguous compound identification [198,199]. Actually, on-line GC-IR, with... 

The obvious alternative for the in-line flow-through cell in HPLC-FTIR is mobile-phase elimination ( transport interfacing), first reported in 1977 [495], and now the usual way of carrying out LC-FTIR, in particular for the identification of (minor) constituents of complex mixtures. Various spray-type LC-FTIR interfaces have been developed, namely, thermospray (TSP) [496], particle-beam (PB) [497,498], electrospray (ESP) [499] and pneumatic nebulisers [486], as compared by Som-sen et al. [500]. The main advantage of the TSP-based... 

The potential plateau (pitting potential) is said to be insensitive to pH changes in the medium-pH region.67 This is in line with the model suggesting the accumulation of hydrogen ions at the O/S interface to very high concentrations, when the very small initial concentration (at pH above 2) becomes irrelevant. 

A novel fiber optic sensor concept using antibody-antigen reactions at a glass-liquid interface was reported by Daehne146. The reaction of antibodies immobilized onto the surface of fused silica fiber optic or planar waveguides with antigens in solution was detected by interaction with the evanescent wave. By detecting in-line fluorescence, the measurement of human IgG is described. 

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