Laboratory-scale operations instruments

When used in laboratory-scale operations CSTRs are frequently referred to as chemostats. Chemostats are often employed in scientific studies intended to elucidate the metabolic processes associated with particular microorganisms because they are better equipped to monitor transient situations involving a transition from one set of operating conditions to another, for example, when there is a shift in the composition of the stream being fed to a unit operating at steady state. By comparison with large-scale CSTBRs, small-scale chemostats are characterized by shorter response times and are more readily instrumented to facilitate acquisition of data that are useful in optimization of the performance of these reactors. 

Whilst all aspects of a laboratory s operation require systematic control, it is the calibration of test equipment which gives rise to most problems and which is also the most expensive. All test equipment and every parameter of each instrument requires formal calibration. For example, it is not good enough to calibrate the force scale of a tensile machine, there are also requirements for speed of traverse, etc. plus associated cutting dies and dial gauges. 

Several companies supply density equipment which was considered suitable for automatic, continuous operation with sufficient precision for calculation of polymerization conversion. These break down into three classes based on mode of operation y-ray absorption, oscillatory frequency of a sample filled tube, and mass measurement at fixed volume. Only one of these, an oscillator-based system distributed by Mettler Instrument Corp. (representing Anton Paar Ag.) has models with dead volumes small enough for laboratory scale experimentation. The other units generally also suffered from narrow density spans when the precision was sufficient for conversion studies. Table... 

Steam sterilizers, or autoclaves as they are also known, are stainless steel vessels designed to withstand the steam pressures employed in sterilization. They can be (i) portable sterilizers, where they generally have internal electric heaters to produce steam and are used for small pilot or laboratory-scale sterilization and for the treatment of instruments and utensils or (ii) large-scale sterilizers for routine hospital or industrial use, operating on dry saturated steam from a separate boiler (Fig. 20.6). Because of their widespread use within pharmacy this latter type will be considered in greatest detail. 

Because pilot-scale furnaces are typically larger and more complex than laboratory-scale combustors, they are often more costly and difficult to operate (but much less costly than full-scale). Although typically better instrumented than full-scale furnaces, the complexity of a pilot-scale system can make obtaining detailed information, such as temperature mapping challenging and time-consuming. In fact, many of the complexities... 

Whilst cake cracking and drop-off are piinc al sources of differences in the yield of actual plant, conq)ared with laboratory-scale tests, other considerations include (1) equality of the pressure differential available for cake formation and (2) equivalence of media condition and resistance. The latter will depend on the age of the medium and the effectiveness of cloth wadung operations. Filtration equipment is generally poorly instrumented. The location of the AP measuring device and the pressure (vacuum) losses present between the measurement and point of filtration will vary ftom station to station. 

Although particle characterization is not an ordinary instrumentation issue, some supporting laboratory scale equipment helps even the commercial operation by defining the realistic nature of the particles in each occasion. Thus it is recommended to have a small, say 5 cm in diameter, cold test unit with a flowmeter and pressure sensors. 

HasweU and Barclay [3] have described a microwave system coupled to an atomic absorption detection system for the analysis of sludges and soils. A major constraint at the present time is that the preferred operation of these types of systems is for sample matrices to be closely matched. A widely varying sample, which exhibits different heating characteristics, wiU either show up as an invaHd result or the time required to cope with this procedure for aU the samples wiU greatly extend the on-Hne analyses time scales. As more of these instrumental systems become Hnked to laboratory information management systems, it wiU become feasible to interact between the control database and the instrumentation so that each sample is treated in an appropriate manner and the optimum time frame is selected for each sample type. When new samples are analysed, the steps could be monitored so that the required time scales are obtained and then stored for future reference. 

TTie introduction of automation on an appreciable scale in a laboratory which has hitherto depended on manual analysis is almost certain to caU for an adjustment of staff expertise, with an increased emphasis on non-chemical support disciphnes. Staffing for the routine operation of the instruments may weU he reduced to provide some cost advantage, hut if the analytical laboratory is part of a multidisciphnary estabhshment, the ancillary needs can be met, at least partly, by internal staffing rearrangement. However, the effect on a small laboratory, staffed mainly by chemists, could he considerable, and this needs to he considered and planned for in advance of installation. 

The experimental batch reactor is usually operated isothermally and at constant volume because it is easy to interpret the results of such runs. This reactor is a relatively simple device adaptable to small-scale laboratory set-ups, and it needs but little auxiliary equipment or instrumentation. Thus, it is used whenever possible for obtaining homogeneous kinetic data. This chapter deals with the batch reactor. 

The introduction of the autoprep and MS-prep systems has proved very successful in providing automated isolation for the vast numbers of synthetic chemistry samples now being produced. Autoprep instruments are now installed in fifteen of the chemistry laboratories within our company (on our site alone) and most see daily use. It is not only synthetic chemistry samples that have been run on these systems, indeed the adoption of these instruments has spread through other departments (e.g. Bio-Metabolism. Pharmacy, etc.) [16,17] as well as other countries. The advantages of the MS-prep system mean that these systems are also in constant demand and see virtual round the clock operation. Aside from standard, unattended purifications they can also be used to provide specific scale-up information (e.g. unequivocal identification of the compound of interest in a scaled-up injection of a crude compound) prior to transferring the method to a standard autoprep system or even a lai er-scale, manual preparative system. The power of both instruments as separative tools increases dramatically in the hands of expert users who have intimate knowledge both of the systems and the capabilities within the software. 

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