Single Analyzers

The advantages and disadvantages of single analyzers need to be examined within the context for which they will be used rather than for their overall attributes. For example, a simple quadrupole, 

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Instruments are available that can perform MS/MS type experiments using a single analyzer. These instruments trap and manipulate ions in a trapping cell, which also serves as the mass analyzer. The ion trap and fourier transform ion cyclotron resonance (FT-ICR) mass spectrometers are examples. 

The use of hber optics and hber-optic multiplexing can increase the number of analysis points, and hence can reduce the overall costs related to a single analyzer. This approach has been used successfully with NIR instrumentation, where typically up to eight points can be handled. As noted earlier, the use of hber optics with IR Fourier transform instruments has in the past been limited. New hber materials with improved optical throughput are available, and also with the considered use of IR lasers, the role of hbers for IR applications is expected to increase. Although in the past commercial multiplexers have been available for mid-lR hber systems, their use has not been widespread. 

An extension of linear regression, multiple linear regression (MLR) involves the use of more than one independent variable. Such a technique can be very effective if it is suspected that the information contained in a single dependent variable (x) is insufficient to explain the variation in the independent variable (y). In PAT, such a situation often occurs because of the inability to find a single analyzer response variable that is affected solely by the property of interest, without interference from other properties or effects. In such cases, it is necessary to use more than one response variable from the analyzer to build an effective calibration model, so that the effects of such interferences can be compensated. 

The use of and Q prediction outlier metrics as described above is an example of a model-specific health monitor , in that the metrics refer to the specific analyzer response space that was used to develop a PLS, PCR or PCA prediction model. However, many PAT applications involve the deployment of multiple prediction models on a single analyzer. In such cases, one can also develop an analyzer-specific health monitor, where the and Q outlier metrics refer to a wider response space that covers all normal analyzer operation. This would typically be done by building a separate PCA model using a set of data that covers all normal analyzer responses. Of course, one could extend this concept further, and deploy multiple PCA health monitor models that are designed to detect different specific abnormal conditions. 

In yet other versions Ihe processor is part of the analyzer and may be dedicated to, and integral to, a single analyzer at Ihe analyzer location with all analyzer and processor functions described performed locally. 

Another means of economy is the analysis of multiple samples with parallel columns in a single analyzer to given an additional sample throughput of at least eight times greater than at present (P2). 

As mass spectrometers are relatively expensive, the exhaust gas of three or more bioreactors is typically directed to a single analyzer. This is possible because the offgas analysis is done outside the bioreactors themselves. However, the multiplexing of the streams results in added complexity with regard to sample handling and routing, particularly if concerns of cross contamination need be addressed. The contamination issue is usually handled by placing ultrafilters in the exhaust lines. Care, however, must be taken to... 

Once fhe gas sample has been properly condifioned, if can be analyzed in one or more analyzers, depending on whaf gases are being measured. Figure 7.25 shows a single analyzer used to measure the oxygen concentration... 

In the earliest phase of this effort, the analytical conc trations of a single analyzed specimen were encoded onto two IBM cards with eighty column format, of which six were given to identification numbers, one a letter denoting the substance (A = ceramics, W = obsidian, etc.) and one the number 1 or 2 for the first and second card. The remaining 72 columns per card were formatted as 18 groups, each of 4... 

Process MS is a reliable technique that can provide rapid and precise multicomponent analysis on process streams. The ability to monitor multiple sample points with a single analyzer makes MS very economical for many applications, even with the high cost of the analyzer itself Maintenance requirements on modern MS analyzers are on a par with or lower than most other analyzer technologies. In addition to permanent installations for routine process control, these attributes also make process mass spectrometry extremely useful for process development and troubleshooting. 

Analyzers may be combined, almost in a mix-and-match manner, into sophisticated tandem instruments, e.g., QqQ, QTOF, and LIT-FT-ICR, which are capable of providing signihcantly more information than single analyzer systems. Tandem analyzers are also referred to as mass spectrometer/mass spectrometer (MS/MS) instruments. These terms apply to the combination of two (or more) analyzers to attain improved detection limits or to provide hitherto unavailable structural information. Tandem often implies that the instruments utilize like analyzers, such as in... 

A certain amonnt of structural information, snch as sequencing of peptides, can be obtained from single-analyzer MALDl-TOF systems used in the reflectron mode becanse some ions leaving the ion source are metastable (Section 3.3.1.2) and fragment as they move down the flight tube the process is called post-source decay (PSD). The technique is limited because it is not possible to preselect ions for fragmentation and becanse stepwise changes in the parameters of the reflectron are needed to obtain prodnct ion spectra. 

Mass spectrometric systems come in a variety of configurations multiple sample introduction and ionization methods may be combined with single analyzers or coupled into MS/MS formats, using the same or different types of mass analyzer. Although most instrument formats are capable of multiple functions, one configuration is often better suited to a specific analysis. For instance, the collection of spectra in TOF instruments is much faster and more sensitive than with quadrupoles therefore, TOF systems... 

Despite the current emphasis on MS/MS instrumentation for a rapidly increasing number of applications, single-analyzer (MS) systems remain important because they provide valuable information for identification of compounds or the monitoring of selected ions for quantification. Single analyzer instruments are usually easier to operate and maintain, and less expensive, than MS/MS systems. 

Ion Activation and Fragment Formation in Single-Analyzer Instruments... 

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