Increasing the Resolution

If two compounds are coeluting with small k, the easiest way of improving the resolution is to increase the retention (increasing k). In GC, this is obtained by reducing the column temperature. In H PLC, this is usually obtained by reducing the solvent strength of the mobile phase. 

The most effective way to increase a is often by changing the stationary phase or the mobile phase (the latter not in GC). 

Note that connecting two columns of equal quality and size will double the plate number, but the resolution will only increase by 

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Separation of families by merely increasing the resolution evidently can not be used when the two chemical families have the same molecular formula. This is particularly true for naphthenes and olefins of the formula, C H2 , which also happen to have very similar fragmentation patterns. Resolution of these two molecular types is one of the problems not yet solved by mass spectrometry, despite the efforts of numerous laboratories motivated by the refiner s major interest in being able to make the distinction. Olefins are in fact abundantly present in the products from conversion processes. 

In the future, it is expected to be possible to make more routine use of additional wave types, specifically shear or S waves (polarised to horizontal and vertical components) which have a transverse mode of propagation, and are sensitive to a different set of rock properties than P waves. The potential then exists for increasing the number of independent attributes measured in reflection surveys and increasing the resolution of the subsurface image. 

The weld depths penetration for gold-nickel alloy and tantalum cylinders have been well controlled by an entirely contactless ultrasound method. Nevertheless, the development of signal and image processing will allow to increase the resolution of the ultrasonic images. Moreover, in order to be able to size quite well the lacks of weld penetration, the simulation of the interaction beam-defect is presently developed in our laboratory. 

The construction of an aberration-corrected TEM proved to be teclmically more demanding the point resolution of a conventional TEM today is of the order of 1-2 A. Therefore, the aim of a corrected TEM must be to increase the resolution beyond the 1 A barrier. This unplies a great number of additional stability problems, which can only be solved by the most modem technologies. The first corrected TEM prototype was presented by Flaider and coworkers [M]- Eigure BE 17.9 shows the unprovement in image quality and interpretability gained from the correction of the spherical aberration in the case of a materials science sample. 

The second interface design that was developed for use with yu-SEC-CZE used the internal rotor of a valve for the collection of effluent from the SEC microcolumn. The volume collected was reduced to 500 nL, which increased the resolution when compared to the valve-loop interface (20). However, a fixed volume again presented the same restrictions on the SEC and CZE operating parameters. An entirely different approach to the interface design was necessary to optimize the conditions in both of the microcolumns. 

At this point, the solution containing the component to be measured (Ax) also contains any other compounds from the original matrix that are soluble in the solvent used in the analysis. For the analysis to be accurate, other components in the matrix cannot interfere by eluting at the same retention time as the components to be measured. For accurate MS analyses, the matrix component must not interfere with production of the ions being measured for either the internal standard or the component to be measured. In some cases, to eliminate interferences, it may be necessary to increase the resolution of the mass spectrometer by narrowing the mass window being monitored. Alternatively, MS/MS can be used to avoid chemical interference (see Chapter 1). 

In this instrnment, the final stage of the triple quadrnpole is replaced by an orthogonal time-of-fiight (ToF) mass analyser, as shown in Fignre 3.10. The con-fignration is typical of the latest generation of ToF instrnments in which a nnmber of reflectrons, in this case two, are used to increase the flight path of the ions and thns increase the resolution that may be achieved. 

The velocity mapping-ion counting technique increases the resolution of imaging data. This is clearly seen when it is compared with the data from the conventional Wiley-McLaren imaging apparatus2 or even the... 

Atoms and molecules in solid state are subject to restricted motions, so that all the interactions which are orientation dependent are not averaged by molecular motion and the spectra are complex it is therefore fundamental to apply approaches able to increase the resolution... 

Resolution or resolving power is the ability of a mass spectrometer, and in particular of its analyzer system, to separate ions with different m/z ratios. An example of mass spectra obtained at different resolutions is reported in Figure 2.1 by increasing the resolution the peak shape becomes more and more narrow thus allowing the separation of ions with their m/z values differing in decimals (10 1—10 3). 

Spectral interferences may arise from the close proximity of other emission lines or bands to the analyte line or by overlap with it. They can often be eliminated or minimized by increasing the resolution of the instrumentation, e.g. changing from a filter photometer to a grating spectrophotometer. Alternatively, another analyte line can be selected for measurements. Correction for background emission is also important and is made by monitoring the emission from a blank solution at the wavelength of the analyte line or by averaging measurements made close to the line and on either side of it. 

Due to the limited peak capacity of the 15 cm analytical column utilized in 2-D nano LC-MS, several elution steps are required to achieve the required separation. The 15 cm analytical column can be replaced with a 100 cm nano LC column to increase the resolution of sample in each step. As shown by Yang,20 a 100 cm column allows the one-step separation of more than 2000 polypeptides from trypsin digest of mouse brain lysate, P2 fraction using XtremeSimple ultrahigh pressure nano LC (Micro-Tech Scientific, Vista, California) and LTQ MS (Thermo Electron, San Jose, California) in 6 hr (Figure 14.16). In addition to the improvement of resolving power with a 100 cm column, it... 

Reflectron An ion lens used in the time-of-flight mass analyser to increase the distance travelled by an ion and thereby increase the resolution of the instrument. 

Column selector valves can be added on as accessories to allow column switching for multi-dimensional chromatography (to increase the resolution of very complex samples such as in proteomics) or for automatic column selection (up to six columns) to facilitate methods development using different columns. 

From the method development and robustness point of view, the temperature is a parameter that controls equilibria such as pK and enantiomer—chiral selector complexation, or induces structural changes in, e.g., proteins.For chiral separations, generally a lower temperature results in better enantioseparation, but even the opposite has been observed. Sometimes a raise in temperature does not so much affect the enantiomeric separation, but increases the resolution between an enantiomer and a matrix component. ... 

Before the immunopreciptation step the chromatin has to be fragmented in order to make interactions accessible and to increase the resolution of the ChIP. Two different methods are commonly used fragmentation via sonication of the chromatin, or an enzymatic digestion with micrococcal nuclease. 

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