Temperature sensitivity samples

Temperature Sensitivity. Samples of Au-acetone colloid were subjected to boiling and freezing. Upon returning to room temperature the colloids remained stable and no flocculation had occurred. These results indicate that steric stabilization33,43) (solvation) is a very important mechanism. Charge-stabilized colloids generally flocculate when subjected to such extremes of temperature.(56)... 

Once a bulk sample is selected, a laboratory sample must be prepared for analysis (Figure 28-2). A coarse solid sample should be ground and mixed so that the laboratory sample has the same composition as the bulk sample. Solids are typically dried at 110°C at atmospheric pressure to remove adsorbed water prior to analysis. Temperature-sensitive samples may simply be stored in an environment that brings them to a constant, reproducible moisture level. 

Temperature Sensitivity Samples. Materials for sensitivity tests were mixed by the methods described above. Marshall specimens were... 

The sample temperature may be controlled by measuring the Stokes I anti-Stokes intensity ratio of Raman scattered radiation (Schrader et al., 1990), Eq. 2.4-10. This is of importance when temperature-sensitive samples or phase transitions are investigated. 

An alternative method to steam sterilization for temperature-sensitive samples could be y-irradiation. Comparative studies on SLN sterilization by steam and y-rays were conducted by Schwarz and others [38,41,42]. Lecithin-stabilized SLN proved to be superior to poloxamer-stabilized SLN for the process of steam sterilization. However, this difference was not observed for y-sterilized samples, which indicates the importance of heat-induced changes. Compared to steam sterilization at 121 °C,... 

Many samples are stable at only low temperatures, say 0-4 °C, and temperature sensitive samples are normally kept cold by a gas stream, sometimes with an enclosure (Hovmoller 1981 Bartunik and Schubert... 

SFE with carbon dioxide offers several advantages compared to classical solvent extraction methods (1) it is very selective (2) it is fast, because of lower viscosity and approximately 10 times higher diffusion coefficients and (3) CO is neither flammable nor explosive and is nontoxic. SFE is suitable for oxidizable and temperature-sensitive samples. In addition, no reactions occur between extraction medium and. sample compounds and on-line coupling is possible with both. supercritical fluid chromatography (SFC) and gas chromatography. 

Independent on/off pulser Enables safe treatment of temperature-sensitive samples at high intensity. Both on and off cycles are independently controllable from 0.1 to 10 s. 

Standardizing the Method Equations 10.32 and 10.33 show that the intensity of fluorescent or phosphorescent emission is proportional to the concentration of the photoluminescent species, provided that the absorbance of radiation from the excitation source (A = ebC) is less than approximately 0.01. Quantitative methods are usually standardized using a set of external standards. Calibration curves are linear over as much as four to six orders of magnitude for fluorescence and two to four orders of magnitude for phosphorescence. Calibration curves become nonlinear for high concentrations of the photoluminescent species at which the intensity of emission is given by equation 10.31. Nonlinearity also may be observed at low concentrations due to the presence of fluorescent or phosphorescent contaminants. As discussed earlier, the quantum efficiency for emission is sensitive to temperature and sample matrix, both of which must be controlled if external standards are to be used. In addition, emission intensity depends on the molar absorptivity of the photoluminescent species, which is sensitive to the sample matrix. 

In similar work, Sturgeon et al. [125] compared direct furnace methods with extraction methods for cadmium in coastal seawater samples. They could measure cadmium down to 0.1 pg/1. They used 10 pg/1 ascorbic acid as a matrix modifier. Various organic matrix modifiers were studied by Guevremont [116] for this analysis. He found citric acid to be somewhat preferable to EDTA, aspartic acid, lactic acid, and histidine. The method of standard additions was required. The standard deviation was better than 0.01 pg/1 in a seawater sample containing 0.07 pg/1. Generally, he charred at 300 °C and atomised at 1500 °C. This method required compromise between char and atomisation temperatures, sensitivity, heating rates, and so on, but the analytical results seemed precise and accurate. Nitrate added as sodium nitrate delayed the cadmium peak and suppressed the cadmium signal. 

There are several types of RI detector, all of which monitor the difference between a reference stream of mobile phase and the column effluent. Any solute whose presence alters the refractive index of the pure solvent will be detected, but sensitivity is directly proportional to the difference between the refractive index of the solute and that of the solvent. At best they are two orders of magnitude less sensitive than UV/visible detectors. All RI detectors are highly temperature-sensitive, and some designs incorporate heat exchangers between column and detector to optimize performance. They cannot be used for gradient elution because of the difficulty in matching the refractive indices of reference and sample streams. 

Hamilton Umicon Lumicon chemi- and biolumium assay luminometer This equipment is used in test-tube scale luminescent immunoassays. With its sample compartment (thermostatted by means of Peltier elements, which allow the temperature to be set from 15°C to 40°C with a precision of 0.1°K) this instrument is suitable for the measurement of temperature-sensitive bioluminescence resulting from enzymic reactions and also in phagocyte-mediated luminescence measurements. 

The goal of the project is to determine the concentration of caustic in an aqueous stetam containing 6-11% caustic and 12-17% salt. The requirement for the catssic determination is to predict the concentration to 0.1 wt.% (Icr). Because NIR spectroscopy of aqueous systems is known to be sensitive to temperatEsre fluctuations, another factor that must be considered is the temperature ofiae sample, which can vai from 50 to 70 C. 

One must also keep in mind that these experiments are measuring the temperature sensitivity of a particular composition, in which the entire sample is heated to the experimental temperature. Ignition sensitivity can also be discussed in terms of the relative ease of ignition due to other types of potential stimuli, including static spark, impact, friction, and flame. 

The yield of strand breaks appears to be relatively independent of sample irradiation temperature, as discussed above. This implies that competing processes do not have much impact on reactions 1,2, 5, and 8. That is, the competitions between holes tunneling from the solvent to DNA and deprotonation of HsO " and between hole tunneling form the sugar phosphate to the bases and deprotonation of the sugar are fairly temperature-insensitive (from 4 to 300 K). In contrast, the mobility of the holes and excess electrons centered on the bases is very temperature-sensitive, zero at 4 K, onset at —40 K, and highly mobile at 180 K. By our model, the mobility is controlled by the proton transfer... 

Lowering the temperature produces the opposite effect. The polymerization reaction depends on abstraction first the balance of the reaction favors polymerization, and a high-density foam is produced. This is a complicated effect when incorporating a temperature-sensitive component in the foam. We will discuss the addition of living cells into a foam sample later. Controlling the temperature is an important consideration. Unfortunately, foam quality is sacrificed because the reaction must be conducted at reduced temperatures. 

Quantitative spectrographic analyses for trace elements in high-temperature ash samples of coal have been reported by Abemethy et ah (1), Zubovic et ah (2,3,4,5), Rao (6), and Hunter and Headlee (7). We felt that it was desirable to develop additional analysis methods, especially for the direct-reading spectrometric technique, in which small changes of some matrix constituents might cause relatively large variations in results because of the increased sensitivity of the detection system. A... 

To identify the rate limiting steps, we carried out a series of parallel experiments one in which we determined the rate of thermal equilibration of cylindrical temperature-sensitive gels in response to different temperature driving forces and the other in which we determined the rate of swelling or shrinking of identical gel samples under identical conditions. 

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