Temperature controller resolution

Temperature control of the enantioselectivity in the lipase-catalyzed resolutions... 

In the lipase-catalyzed resolution, temperature control of enantioselectivity has been generally accepted for its simplicity and theoretical reliability. Lowering the reaction temperature usually enhances the enantioselectivity. Here, the historical and theoretical backgrounds of the temperature control of enantioselectivity and its applicability to the method are described. Recent literatures for the lipase-catalyzed resolutions to which the low-temperature method seems to be promising to enhance the enantioselectivity are also summarized. 

The effect of temperature on distribution ratios has already been mentioned on page 91. Although the separation proceeds more quickly at elevated temperatures, resolution suffers because of increased rates of diffusion. However, in adsorption TLC only small increases in Rt values are observed even with a 20°C rise. Strict temperature control is not necessary if samples and standards are run at the same time, although large fluctuations should be avoided. The quality of the thin-layer materials, and in particular the presence of impurities in them, determine the extent to which partition, adsorption, ion-exchange and exclusion participate in the sorption process. These factors affect Rr values in an unpredictable manner. Thin layers should be of uniform thickness, between 0.2 and 0.3 mm with thinner layers, local variations in thickness can result in appreciable variations in Rf values. 

The tracking mode performance of the on-chip digital temperature controller of the differential mixed-signal architecture is shown in Fig. 6.11. The measurement was done at room temperature, and the digital code of the reference temperature of microhotplate 1 was increased in steps of 100 digits. Microhotplates 2 and 3 were switched off during the measurement. The resolution of the digital temperature controller was better than 2 °C. 

The on-chip hotplate temperature controller had a resolution of better than 2 °C. A high CO sensitivity was measured with a 0.2 wt % doped Pd nanocrystalline tin oxide, the resolution was 0.2 ppm CO, and the detection limit was 0.1 ppm CO. Such... 

The last and most advanced system presented in this book includes an array of three MOS-transistor-heated microhotplates (Sect. 6.3). The system relies almost exclusively on digital electronics, which entailed a significant reduction of the overall power consumption. The integrated C interface reduces the number of required wire bond connections to only ten, which allows to realize a low-prize and reliable packaging solution. The temperature controllers that were operated in the pulse-density mode showed a temperature resolution of 1 °C. An excellent thermal decoupling of each of the microhotplates from the rest of the array was demonstrated, and individual temperature modulation on the microhotplates was performed. The three microhotplates were coated with three different metal-oxide materials and characterized upon exposure to various concentrations of CO and CH4. 

It is generally required that all methods allow for the monitoring of API and impurities/degradation products in the same chromatographic run, that run times per sample should not be too long, and that for precise and robust quantitative analyses, the separation of the peaks of interest should have target resolutions of >2.0. To allow for easy transfer, the detector response for the nominal concentration of the API (100%, w/w) should be about 75% of the qualified linear dynamic range of the detector. Methods should be temperature controlled (e.g., at 35°C,... 

In our final realization (Fig. 18), the probes use the Helmholtz coil geometry, favoring ease of use and efficient sample temperature control over a wide range of temperature values. The tunable, broad-band probe is inserted into the magnet from below and fixed to the bottom part of the magnet assembly in a simple way reminiscent of most high-resolution NMR systems. Thanks to this design, it is possible to use standard 10 mm NMR sample tubes which are inserted comfortably from above without any need to manipulate the probe. 

An additional advantage of the very low temperature is the smaller dependence of u ) on the temperature. Thus, fluctuations of the temperature during an experiment are less troublesome. It should be taken into account that experiments without temperature control might easily experience 5 °C fluctuations (night/day variation, heating caused by other machines, etc.). This produces a fluctuation of 1-2% of the intensity for a reflection at 1.0 A resolution and up to 10% for a reflection at 0.5 A resolution (assuming it is measurable). 

For the purposes of conversion monitoring of emulsion polymerization, we have found the DMA40D with a precision of +1 x 10 g/cm capable of resolving monomer conversion to +0.2% in the absence of thermostating and sampling errors. On-line, in the presence of such possible errors, a resolution of at least +0.5% can be expected. Care must be taken to ensure a representative sample and good temperature control of the sample stream before introducing it into the instrument. Some example results with this instrument are presented below. 

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