Maintenance and Robustness

The spectrometer accumulates more pollution after each analysis, especially if the system is used to analyze matrix extracts. With a quadrupole, the pollution starts at the level of the ion volume before affecting the lenses and the result is an increase in background noise in the mass spectra and therefore in the chromatograms. Sensitivity is therefore reduced but a slightly polluted quadrupole remains operational, especially if operated with an internal standard. 

With an internal ionization ion trap, the neutrals adsorb on the electrodes. When the electrodes are polluted, the quadrupolar field is perturbed and the calibration of the analyzer is no longer operational. The mass spectra recorded under these conditions are therefore unusable. In summary, an internal ionization ion trap is not very robust. It does not operate properly even if slightly polluted. For this reason, most applications developed for ion traps concern weakly pollutant matrices, in particular the analysis of water. 

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Three types of trays dominate the market sieve, valves and bubble-cap. Numerous commercial shapes exist. Sieve trays are low-cost in purchasing and maintenance, and robust in operation, can be designed for high throughput, but are penalised by a relatively low turndown, of about 2 1. The resistance to fouling is good, the entrainment moderate. The pressure drop can be lowered below down to 3 to 4 mbar. The market share of sieve trays is about 25%. 

TOF mass spectrometers are very robust and usable with a wide variety of ion sources and inlet systems. Having only simple electrostatic and no magnetic fields, their construction, maintenance, and calibration are usually straightforward. There is no upper theoretical mass limitation all ions can be made to proceed from source to detector. In practice, there is a mass limitation in that it becomes increasingly difficult to discriminate between times of arrival at the detector as the m/z value becomes large. This effect, coupled with the spread in arrival times for any one m/z value, means that discrimination between unit masses becomes difficult at about m/z 3000. At m/z 50,000, overlap of 50 mass units is more typical i.e., mass accuracy is no better than about 50-100 mass... 

Most process Raman instruments have few, if any, moving parts and thus are quite stable and robust. This reduces the number of parts likely to need replacement. The laser and detector shutter are the most common service items. Special utilities and consumables are not required. Proper enclosure selection allows instruments to survive harsh environments, such as installation outdoors or around vibrations. An instrument built to accurate specifications and well installed is unlikely to require much care or daily attention. However, it is important to remember that there is no such thing as a maintenance-free instrument. Limited additional maintenance will ensure robust performance for years. 

A rapid, sensitive, reversed-phase HPLC method for the separation of BHA isomers was described by Berridge et al. (117). Using a column packed with Hypersil ODS of 3-/nn particle size and with a mobile phase consisting of an acetonitrile-water mixture, it was possible to detect less than 0.5 ng of the isomers injected. The procedure is reliable and robust and compared to another HPLC method, claimed to have a more stable, longer-lasting column requiring only occasional maintenance (117). 

FIGURE 11—59- Use of conventional antipsychotics to lead in or top up" atypical antipsychotics. One of the most important and justified uses of antipsychotic polypharmacy is to lead in to treatment with a conventional antipsychotic when an unmedicated patient is acutely psychotic, combative, or out of control. Such patients may also require periodic top-up for bouts of aggressiveness, which allows more rapid and robust relief of symptoms than an additional dose of the maintenance atypical antipsychotic can provide. 

Is effort focused on critical aspects of the computer system development and maintenance Is the change control process defined, procedurafized, and robust ... 

Physically robust and stable. In general, the system must require little maintenance and withstand the process operating conditions (e.g., temperature and pressure). The sensor signal must be unaffected by typical environment in a processing plant (e.g., mechanical vibration, electrical interference) and amenable to control operations. 

This approach was pioneered by Hayward et al. [2] for the automated analysis of potential agricultural chemicals by means of eoluttm-bypass thermospray (TSP) MS-MS. The method was found to provide the required information in approximately 70% of the MS stmetural confirmations performed at the Agricultural Research Division of American Cyanamid. Subsequently, an automated routine MS eharaeterization of potential drug eompounds was reported by Tiller and Lane [3] at Glaxo. Both particle-beam (PBl) in positive-ion chemical ionization (Cl) mode and TSP interfaeing were investigated. The TSP system was found to be more robust, to require less maintenance, and to be easier to use. 

A common, simple and robust method is the maintenance of a constant p02 in the culture broth by variation of stirrer speed and aeration rate. To avoid shear... 

Other considerations in assessing efficacy are process reliability and robustness. The EDT must be able to destroy the materiel with minimal downtime for maintenance. Further, the ability of a technology to operate without failure under a wide range of conditions and within the schedule constraints for BGCAPP and PCAPP was also considered. 

Laser resonators should have appropriate laser transition, good control of out-coupUng, high quality factor to ensure the desired temporal regime of emission, control of the mode stiucture and beam size, control of the thermal field (dissipation of heat, external cooling). Technical requirements include mechanical robustness, volumetric compact, lowest maintenance, and simple replacement of parts/ comjMjnents. 

The economic viability of a vehicle is, aside the total running cost, depending on the value stability. A long utilization and lower maintenance cost are key factors. All the components up to the overall system need to be designed to achieve a certain lifetime rehabUity and robustness. 

The low-tech system, i.e., a donkey system, is the opposite. It requires less manpower, although it still needs more than natural reactors. Because of needing little maintenance and having potential for a continuous operation for a decade without fuel replacement, it can be sited in an isolated island or in a remote area. Of course, it would be necessary to design the reactor to be robust to disturbance and less dependent on control system operations. It maybe easier to understand it as a typical passive safety system. For example, reactor control against disturbance does not require a rapid response as in the case of control rods but expects reactivity feedbacks, such as the Doppler effect to work. Additionally, natural circulation, which is driven by buoyancy force generated by difference in coolant temperature, should be employed in such reactors rather than pumps. 

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