Batch-cell instruments

Whereas most fixed-cell instruments are power-compensation instruments (because it is possible to place heaters on the base of cells that are not removable), batch-cell instruments are available as either power-compensation or heat-flux designs. One design of a heat-flux, batch-cell instrument is the micro-DSC in (Setaram). The instrument consists of a calorimetric block into which two channels are machined. One channel holds the sample cell, the other holds the reference cell. At the bottom of each channel, between the cell and the block, is a plane-surfaced transducer. The transducers provide a thermal pathway between the cells and the block and are used to maintain the cells at a temperature identical to that of the block. The electrical signal produced by the transducer on the sample side is proportional to the heat evolved or absorbed by the sample. The temperature of the calorimetric block is maintained by a precisely thermostated circulating liquid. The liquid is raised in temperature by a separate heater and is cooled by a supply of circulating water. The precise control of the temperature of the circulating liquid allows scan rates of just 0.001°C min-1 to be attained and ensures that the calorimetric block is insulated from the surrounding environment. 

Malvern Ultrasizer SV After the original research work Alba worked with Malvern Instruments and this led to the development of the Malvern Ultrasizer [237]. The analyzer eovers the size range 0.01 pm to 1,000 pm, at a volume concentration range of 0.5% to 50% for powders and up to 80% for emulsions, employing a frequeney band of 1 MHz to 150 MHz. The Ultrasizer SV features a range of interchangeable measurement cells that can be exchanged in seeonds. Fixed stirred batch cells are available with capacities from 450 ml. Flow cells are available that allow the instrument to be interfaced into particle streams and reactors. 

With fixed-cell instruments, samples must be loaded directly into the calorimetric chamber, and the need for a metal pan or batch cell is eliminated. Such a system... 

Irrespective of whether an instrument employs fixed cells or batch cells, some design considerations are common to all HSDSC instruments. To measure accurately small powers, it is necessary to ensure good baseline stability throughout the course of an experiment. This is usually achieved by maintaining very accurate control of the calorimetric block temperature and ensuring that the properties of the sample and reference cells, such as geometry, cell volume, local environment, thermal conductivity and conduction pathways, and heating rate, are identical. 

HSDSC instruments that employ batch cells are capable of studying heterogeneous systems and, hence, can be used to directly study industrial products, such as creams, powders, or liquids. Perhaps the two most important areas in which HSDSC may be used industrially are stability testing and excipient compatibility. 

A rotational shear cell instrument, such as the FT4 Powder Rheometer, equipped with a 48 mm rotational shear cell and a 30 mL shear measurement vessel. A batch of reference limestone powder (CRM 116), produced and sold by the Commission of European Communities. 

The major causes of spectral variation were (1) instrumental drift, as Goodacre and Kell realized, but also (2) sample history, as discussed above. In particular, variations in the supplier or even the batch of tryptic soy agar (TSA) used for cell culturing led to spectral variations that differed in degree among disparate species. This phenomenon was attributed to the differential metabolic capabilities of the species with respect to the changed nutrients. 

Based on the differences between the solid and liquid density, batch centrifugation techniques are often used in the discovery phase as a convenient tool to separate the cell from the medium. Highspeed ultracentrifugation instruments have... 

Fill a cleaned cuvette with a filtered sample from the actual batch of buffer used to dissolve or dialyze the protein, then place the cuvette in the cell holder of the spectrometer in a reproducible orientation (see Strategic Planning, discussion of Cells). Scan this buffer blank using the same instrument settings as are appropriate for the sample, store the spectrum, and check for any unexpected fluorescence bands. 

Heats of immersion were measured using a batch calorimeter (Pravdic, 1976). It was an isoperibolic instrument with a thermistor detector of an average sensitivity of i 1 m3 (which corresponds to an estimated 13 i3/cm ). A sediment sample sealed in a small glass bulb was brought into the microcalorimeter cell and carefully equilibrated to a... 

Laboratory scale-up in single-mode reactors to produce gram amounts of material can be performed either by the above-mentioned sequential batch processing using various vessel sizes (up to 50 mL) or by employing CF or SF reaction cells (5-50 mL). Conversely, multimode instruments allow for parallel synthesis or applications in large batches up to 1 L total volume and even CF and SF approaches utilizing > 300 mL cells (see below). 

Wilson and coworkers described a custom-made flow-reactor for the Bio-tage Emrys Synthesizer single-mode batch reactor (Fig. 21) that was fitted with a glass-coiled flow cell [67]. The flow cell was inserted into the cavity from the bottom of the instrument and the system was operated either under... 

Perkin Elmer MPF-3 spectrofluorometer. X- and Q-band measurements of EPR spectra were carried out at liquid nitrogen and liquid helium temperatures. Microcalorimetric measurements were performed on a LKB 10700 batch microcalorimeter. Temperature-jump relaxation kinetics were measured using a double beam instrument (18) with a cell adapted for anaerobic work. The relaxation signals were fed into an H.P. 2100 computer and analyzed as described in Ref. 7. The pulse radiolysis exepriments were carried out on the 5-MeV linear accelerator at the Hebrew University. Details of the system have been published previously (19). 

Despite the ever-increasing use of complex instrumentation, the application of feedback control techniques and the use of computers, the science of antibiotic fermentation is still imperfectly developed. Processes are difficult to optimize and no two apparently identical batches will ever be entirely the same. This is because living cell populations change both quantitatively and qualitatively throughout the production cycle and small changes in control parameters, such as a fluctuation in air pressure or a power dip, can potentially impact a batch and the effect may vary dependent upon the age of the batch. Also there tends to be significant batch to batch variation in the complex nutrients commonly used in the fermentations. 

Fig. 1 shows the infrared spectrum of halothane (Ayerst Laboratories Inc. Batch No. 1CKB). The spectrum is that of undiluted halothane in a 0.104 mm. potassium bromide cell vs. a potassium bromide plate. Also, because some of the absorption bands are quite intense, Fig. 1 shows the spectrum of a 4.0 volume percent solution of halothane in carbon disulfide, in a 0.104 mm. potassium bromide cell, vs. a 0.1 mm. cell filled with carbon disulfide. A Beckman Model IR-12 instrument was used. Considering the variety of sample handling techniques used, this spectrum and other published spectra (1-3) are the same. 

---