Multiple Spectrometer Control System

Among pioneering computer-controlled experiments implemented in the nuclear field were the automated fast neutron laboratory at Argonne, the multiple spectrometer control system at Brookhaven, and the NRU reactor-control experiment at the Chalk River Laboratories. At Argonne... 

The MS instrumentation is the most expensive part of the LC-MS system, hence efforts to improve the throughput of the LC-MS analysis often involve the use of parallel multiple columns that feed into a single mass spectrometer. Zeng and Kassel [99] developed an automated parallel analytical/preparative LC-MS workstation to increase the throughput for the characterization and purification of combinatorial libraries. The system incorporates two columns operated in parallel for both LC-MS analytical and preparative LC-MS purifications. A multiple-sprayer ESI interface was designed to support flows from multiple columns. The system is under complete software control and delivers the crude samples to the two HPLC columns from a single autosampler. The authors demonstrated characterization of more than 200 compounds per instrument per day, and purification of more than 200 compounds per instrument per night. De Biasi et al. [100] described a four-channel multiplexed... 

According to Jakisch et al. [79], FTIR spectroscopy is the preferred method for in-line investigation polymer melts and polymer melt reac-tions/kinetics, allowing quantitative determination of all components. FTIR analysis of compound melts enables additive level stability and effectiveness to be observed over multiple extrusion passes. The use of the ATR principle is suitable for in-line analysis of polymer melts in the extruder. The exit of the extruder was equipped with an on-line IR transmission process control system consisting of a 150 /um thick ZnSe melt flow cell. Characteristics of such systems have been described [71,74]. Another process spectrometer with an in situ ZnSe-ATR dipper probe was mounted at different positions in the extruder. For in-line ATR the residence time plays no role. Only the first 5 /xm (corresponding to the penetration depth of the IR radiation) are examined. Minor components are thus detected with difficulty. Jakisch et al. [79] monitored the conversion of styrene-maleic anhydride copolymers (SMA) with fatty amines into styrene-maleimide copolymer (SMI) during reactive extrusion by means of FTIR. In principle, both mid-IR and near-IR spectroscopy with ATR, transmission and diffuse reflectance probes are suitable for quantitative on- and in-line process analysis of multicomponent polymer... 

LC/MS/MS. LC/MS/MS is used for separation and quantitation of the metabolites. Using multiple reaction monitoring (MRM) in the negative ion electrospray ionization (ESI) mode, LC/MS/MS gives superior specificity and sensitivity to conventional liquid chromatography/mass spectrometry (LC/MS) techniques. The improved specificity eliminates interferences typically found in LC/MS or liquid chro-matography/ultraviolet (LC/UV) analyses. Data acquisition is accomplished with a data system that provides complete instmment control of the mass spectrometer. 

Dedicated data systems perform four functions (1) control all operational processes of both the mass spectrometer and integrated peripheral instruments, such as GC or LC systems (2) acquisition and processing of all data (3) local interpretation of acquired data and (4) post-processing of data, including interaction with databases (almost always via the Internet) (Figure 2.44). Connection to the Internet also enables the remote control of multiple systems as well as the off-site diagnosis of failures by instrument manufacturers. 

If the mass spectrometer is equipped with an LC system, then fast fingerprint MS analyses can be performed by injection of a series of different samples by the autosampler unit. This system will allow automated operation of a large series of samples. In addition, it is possible to utilize the flexibility that lies in the use of different mobile phases and the fast variation between them. The LC-MS system is simply operated as an ordinary LC-MS system, but without an analytical column. Typical injection volumes would be between 0.1 and 3 pL, and mobile phase flows between 0.1 and 0.2 mlV min. With this flow, a chromatographic peak will appear between 0.3 and 0.8 min after injection. Total time per analysis will be 1-2 min per injection. With a scan range of m/z 65-1500, a sufficient number of scan spectra (>15 spectra) will be captured for further data processing. Normally, it is preferred to perform multiple injections from the same sample, and the number of injections could be from 3 up to 10, depending on the study. With multiple injections, the precision of the analytical system can be controlled directly from the score plots and, of course, be evaluated relatively to the differences between the samples. 

The light emitted from the excitation source is dispersed and recorded by multiple photodetectors placed behind suitably located exit slits (Fig. 6.65). Fibre-optical techniques can also be used to collect light at a suitable location in the spectrometer focal plane for transmission to a battery of PMT.s. Calibration can be provided using standard solutions or standard electrodes. Using a computer-controlled data collection system the concentrations of the selected elements can be printed out shortly after the introduction of the sample. A complete system frequently incorporates means for automatic sample exchange. 

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