Speed of analysis

Speed of analysis is not the main reason for using HyperDSC , but there is always a benefit from increased speed of analysis, particularly when the improvement is very marked. In a situation where many samples need to be run for screening or other piuposes the fast analysis times using HyperDSC are a significant benefit. Where 20-30 min are required at slow rates, 2-3 min (or less) maybe all that is required at high rates. The ciuves presented in this chapter may look similar to those taken at slow rates yet many will have taken less than a minute to produce, compared to the tens of minutes for a typical scan, and this gives 

Speed is the most common HPLC optimization criterion. A method is considered optimized if it allows the separation of all relevant components with sufficient resolution in the shortest time possible. Such speed increase only translates into an economical benefit for the laboratory if it actually enables productivity increase of the respective lab. Labs with particularly high sample load are typical beneficiaries of this, but so are all labs that directly profit from knowing analytical results within hours or even minutes after receiving the samples in order to react on it. Productivity increase often requires optimization of the entire lab workflow which will include more than the analytical separation process. It is rather common that samples do not arrive in a ready to inject format and thus require sample preparation 

The HPLC Expert Possibilities and Limitations of Modern High Performance Liquid Chromatography, 

In-process analysis depends very often on fast analysis, no matter on where this occurs - either research or production processes, continuous or batch processes. A reduction in the analysis time always results in a higher information density, which normally translates into an economical benefit downstream. It is an interesting notion the speed potential of modern UHPLC finally enabled the use of liquid chromatography for current in-process analysis, but is yet very rarely found there. 

Open tubular columns. The band broadening obtained in an open tubular column can be expressed by the Golay equation (Golay, 1958). This summarizes the contribution to band broadening from longitudinal diffusion. 

Dq = solute molecular diffusion coefficient in the mobile phase at outlet pressure  

Uq is the mobile phase velocity at column outlet r is the capillary radius k is the capacity factor di is the stationary phase film thickness  

The contribution from the last factor in equation (2.1) is often relatively small and it may be neglected for simplicity (Lee, Yang and Bartle, 1984). If one neglects the band broadening in the stationary phase, the Golay equation can be solved for the minimum height of theoretical plates  

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This experiment uses the molybdenum-blue method to determine the concentration of phosphate in a phosphate/sodium chloride mixture. Elow-injection analysis is used to increase the speed of analysis, allowing students to... 

It is possible to carry out a chromatographic separation, collect all, or selected, fractions and then, after removal of the majority of the volatile solvent, transfer the analyte to the mass spectrometer by using the conventional inlet (probe) for solid analytes. The direct coupling of the two techniques is advantageous in many respects, including the speed of analysis, the convenience, particularly for the analysis of multi-component mixtures, the reduced possibility of sample loss, the ability to carry out accurate quantitation using isotopically labelled internal standards, and the ability to carry out certain tasks, such as the evaluation of peak purity, which would not otherwise be possible. 

This Chapter is concerned with quality and chemical analysis. While it can be shown that the required quality as expressed in terms of sensitivity, speed of analysis etc. is, to some extent, dependent on the particular application for which the analysis is used, in all situations these factors need to be known and features such as accuracy and precision should be as good as can be achieved. Thus, how can the quality of an analysis be measured, how can good quality be achieved, and how can good quality be maintained ... 

Residue chemists will need to continue to improve the speed of analysis. In situ measuring methods that can be applied in the field or processing plant or retail outlet would be particularly useful, so that decisions can be made rapidly which might avert toxicity to humans or wildlife, potential residue problems or unnecessary economic loss. 

Increasing the speed of analysis has always been an important goal for GC separations. All other parameters being equal, the time of GC separations can be decreased in a number of ways (1) shorten the column (2) increase the carrier gas flow rate (3) reduce the column film thickness (4) reduce the carrier gas viscosity (5) increase the column diameter and/or (6) heat the column more quickly. The trade-off for increased speed, however, is reduced sample capacity, higher detection limits, and/or worse separation efficiency. 

An advantage of the microbore gas chromatrography/time-of-flight mass spectrometry (GC/TOFMS) method over the other two approaches is that separation efficiency need not be compromised for speed of analysis. The rapid deconvolution of spectra ( scan rate ) with TOFMS makes it the only MS approach to achieve several data points across a narrow peak in full-scan operation. However, the injection of complex extracts deteriorates performance of microbore columns quickly, and an increased LOD and decreased ruggedness result. Microbore columns may be used in water analysis if the LOD is sufficiently low, but they can rarely be used in real-life applications to complicated extracts. 

Because HPLC and HPCE are based on different physico-chemical principles, HPCE may be expected to address areas in which HPLC has shortcomings [884]. One such area is time of separation. In terms of speed of analysis, selectivity, quantitation, methods to control separation mechanism, orthogonality, CE performs better than conventional electrophoresis and varies from HPLC (Table 4.49). CE has very high efficiency compared to HPLC (up to two orders of magnitude) or GC. For typical capillary dimensions 105—106 theoretical plates are common in CE compared to 20 000 for a conventional HPLC column and... 

Principles and Characteristics Mass-spectral analysis methods may be either indirect or direct. Indirect mass-spectral analysis usually requires some pretreatment (normally extraction and separation) of the material, to separate the organic additives from the polymers and inorganic fillers. The mass spectrometer is then used as a detector. Direct mass-spectrometric methods have to compete with separation techniques such as GC, LC and SFC that are more commonly used for quantitative analysis of polymer additives. The principal advantage of direct mass-spectrometric examination of compounded polymers (or their extracts) is speed of analysis. However, quite often more information can be... 

Speed of analysis Slow Fast Fast Moderate... 

Any analytical method inherently carries with it limitations in terms of speed, allowable uncertainty (as MDL), and specificity. These characteristics of a method (or analytical technique) determine where and how the method can be used. Table 71-1 shows a method to relate purpose of analytical method to the speed of analysis and error types permitted. 

The MALDI-TOF technique was first developed for the analysis of large biomolecules (Karas and others 1987). This technique presents some interesting characteristics. Of these, the high speed of analysis and the sensitivity of the technique have been pointed out as important advantages compared with other methods. In MALDI the samples are cocrystallized with a matrix that is usually composed of organic compounds, such as 3,5-dimethoxy-4-hydroxycinnamic acid (sinapic acid), 2, 4, 6 -trihydroxyacetophenone, a-cyano-4-hydroxycinnamic acid (alpha-cyano or alpha-matrix), and 2,5-dihydroxybenzoic acid (DHB). After the cocrystallization, the laser is fired and the matrix absorbs energy and allows a soft ionization of the samples. Afterward the ions are analyzed by a TOF mass spectrometer. 

The last generation of instruments make it possible to work faster as they offer an increased S/N ratio for the detectors. This results in shorter integration times. Furthermore, the computer-driven reading of microplates with 384 or 1536 wells rather than 96 increases the speed of analysis. Original and new design of the optical path of light and optimized and computer-driven selection of the optical elements and of the mechanical positioning of filters, detectors, or samples... 

The speed of analysis in HPLC is a potential bottleneck for complex sample analysis. Various approaches such as utilizing short columns at high flow rates and the recent focus on 1.5 to 2 /an particles have been reported to increase the speed of analysis. Multidimensional chromatographic approaches have also been demonstrated to increase the throughput of HPLC. The five major parameters that may affect the speed of capillary and nano LC are discussed below. 

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