Temperature colorimetric

Phosphatase Test. The phosphatase [9001-78-9] test is a chemical method for measuring the efficiency of pasteurization. AH raw milk contains phosphatase and the thermal resistance of this enzyme is greater than that of pathogens over the range of time and temperature of heat treatments recognized for proper pasteurization. Phosphatase tests are based on the principle that alkaline phosphatase is able, under proper conditions of temperature and pH, to Hberate phenol [108-95-2] from a disodium phenyl phosphate substrate. The amount of Hberated phenol, which is proportional to the amount of enzyme present, is determined by the reaction of Hberated phenol with 2,6-dichloroquinone chloroimide and colorimetric measurement of the indophenol blue formed. Under-pasteurization as well as contamination of a properly pasteurized product with raw milk can be detected by this test. 

As an example, take the molecule aminoazobenzene, one of the solutes listed in Table 39. When colorimetric measurements were made at room temperature on very dilute aqueous solutions of HC1, containing a trace of this substance, it was found that neutral molecules and (BH)+ ions were present in equal numbers when the concentration of the HCl was 0.0016 molal.1 At this low concentration the activity coefficient of the HCl is very near unity, and we may use (216) to find how far the vacant proton level provided by the aminoazobenzene molecule in aque-... 

The above system of directly sensing a process stream without more is often not sufficiently accurate for process control so, robot titration is preferred in that case by means of for instance the microcomputerized (64K) Titro-Analyzer ADI 2015 (see Fig. 5.28) or its more flexible type ADI 2020 (handling even four sample streams) recently developed by Applikon Dependable Instruments20. These analyzers take a sample directly from process line(s), size it, run the complete analysis and transmit the calculated result(s) to process operation (or control) they allow for a wide range of analyses (potentiometric, amperometric and colorimetric) by means of titrations to a fixed end-point or to a full curve with either single or multiple equivalent points direct measurements with or without (standard) addition of auxiliary reagents can be presented in any units (pH, mV, temperature, etc.) required. 

In a sensitive and specific colorimetric method 1,1,1-trichloro-2,2-bis(p-methoxyphenyl)-ethane is extracted from plant or animal tissue, using benzene or petroleum ether as the solvent. The solvent is evaporated at room temperature by a current of air and the residue dehydroha log ena ted with 2% alcoholic potassium hydroxide. By petroleum ether extraction the resulting 1,1-dichloro-2,2-bis(p-methoxyphenyl)-ethylene is removed from the reaction mixture. After the solvent is removed by air evaporation the dehydroha log ena ted methoxychlor is isolated from the nonsaponifiable portion of the fats and waxes by dissolving the residue in hot acetone, chilling, and filtering. After the acetone is removed by air evaporation, the residue is treated with 85% sulfuric acid. This produces a red solution with an absorption maximum at 555 m/z, the intensity of which can be read on a colorimeter and is a function of the methoxychlor concentration. Beer s law is obeyed over the range of 1 to 50 micrograms. 

Experimentally, the measurement of reaction rates consists in investigating the rate at which starting materials disappear and/or products appear at a particular (constant) temperature, and seeking to relate this to the concentration of one, or all, of the reactants. The reaction may be monitored by a variety of methods, e.g. directly by the removal of aliquots followed by their titrimetric determination, or indirectly by observation of colorimetric, conductimetric, spectroscopic, etc., changes. Whatever method is used the crucial step normally involves matching the crude kinetic data against variable possible functions of concentration, either graphically or by calculation, until a reasonable fit is obtained. Thus for the reaction,... 

Notes HeLa cells (1 x 106) were formalin-fixed in an equal volume of 1% agarose. After histological processing and paraffin embedding, the cell plugs were rehydrated and resuspended in the indicated buffer. Total protein in the supernatants was assessed colorimetrically after heating at the indicated temperatures and times. The % recovery values are the mean, the standard deviation and relative to a fresh cell lysate from the sample number of cells (for more detail, see Reference 25). 

Figure 15.8 (a) Time course of the activity restoration of formalin-treated RNase A during incubation at 50°C (0-2h) and 65°C (2-4h) in TAE buffer, pH 7.0. (b) Time course of the activity restoration of formalin-treated RNase A during incubation at 65°C in TAE buffers of various pH values. All RNase A preparations were freed of excess formaldehyde by dialysis prior to the assay. The RNase A activity was determined with a colorimetric assay using cytidine 2,3,-cyclophosphate as the substrate as described by Crook et al.54 Note that the slopes of the curves decrease with incubation time at 65°C, which is near the denaturation temperature of native RNase A. This loss of activity is likely due to the competing effect of protein denaturation of the recovered RNaseA at this temperature. See Rait et al.10 for details. 

The amounts oi adsorption of the polymer on latex and silica particles were measured as follows. Three milliliters of the polymer solution containing a known concentration was introduced into an adsorption tube(lO ml volume) which contained 2 ml of latex (C = l+.O wt %) and silica(C = 2.0 wt %) suspensions. After being rotated(l0 rpm) end-over-end for 1 hr in a water bath at a constant temperature, the colloid particles were separated from the solution by centrifugation(25000 G, 30 min.) under a controlled temperature. The polymer concentration that remained in the supernatant was measured colorimetrically, using sulfuric acid and phenol for the cellulose derivatives(12), and potassium iodide, iodine and boric acid for PVA(13). From these measurements, the number of milligrams of adsorbed polymer per square meter of the adsorbent surface was calculated using a calibration curve. 

Temperature of measurement varies between 22.5-35°C. 6 O. P. = osmotic-pressure measurements t = light-scattering measurements C. = colorimetric measurements S. D. = sedimentation and diffusion measurements. 

The typical differential scanning colorimetric (DSC) traces shown in Figure 9.2 compare the thermal transitions of similar low-DEG-content PEN and PET resins. The fact that the glass transition temperature (Tg) of PEN is 45-50 °C higher than that of PET has a major influence on the processing and performance of PEN applications. In addition, the fact that PEN S Tg is 20-25 °C above the boiling point of water has a significant effect on the thermal stability potential of many hot, aqueous exposure applications. 

However, near-stoichiometric Fe " ion binding to NifU-1 or NifU was observable only in experiments conducted at 2°C in anaerobic samples that had been pretreated with dithiothreitol to ensure reduction of any intrasubunit or intersubunit disulfides. At room temperature, <10% of the NifU-1 or NifU was in a Fe bound form, and colorimetric analysis indicates that the remainder of the Fe is in solution was in the form of free Fe " ion. Hence this mononuclear Fe -bound species is more likely to be an intermediate in the reduction of Fe ion by NifU or NifU-1 rather than an initial step in cluster assembly on the NifU-1 domain of NifU. In this connection, it is important to note that Fe is rapidly reduced to Fe by cysteine in aqueous solution (Schubert, 1932). The physiological significance (if any) of the apparent ferric reductase activity associated with the NifU-1 domain of NifU remains to be established. 

In the measurement of nitrqgen dioxide with this technique, it is thermochemically converted to nitric oxide by reaction with molybdenum at about 200 C. The extent of possible interferences at various monitoring sites from nitrogen compounds other than amhionia, which does not interfere unless the temperature is considerably higher than 2(X) C, remains to be assessed. The instrumentation of this procedure is inherently more reliable than the original colorimetric analyzers. Unfortunately, the mutual equivalence in monitoring situations of data obtained by these two techniques has not yet been evaluated. This is particularly important for the data from California, where the colorimetric method has been used for more than 20 yr. 

The total free chlorine in wastewaters as measured by colorimetric techniques constitutes both the dissolved molecular chlorine, hypochlorite ion, OCl, and hypochlorous acid. An equilibrium exists between these species, the concentrations of which depend on the temperature and pH of the waste-water. Concentration of the hypochlorous acid may be estimated from the K value or from the ratio (33% of the measured concentration of free chlorine). The free chlorine may be measured by amperometric titration after the addition of a phosphate buffer solution to produce a pH between 6.5 and 7.5. The sample is titrated against a standard solution of phenylarsine oxide. Alternatively, the syringaldazine (3,5-dimethoxy-4-hydroxybenzaldazine) colorimetric test may be performed. This color-forming reagent in 2-propanol yields a colored product with free chlorine, the absorbance of which may be... 

We (K1) attempted to develop a noncompetitive assay based on the anti-idiotype antibodies for a conjugated bile acid metabolite, ursodeoxycholic acid 7-A-acetyl-glucosaminide (UDCA 7-NAG), which is expected to serve as a diagnostic index for an autoimmune disease, primary biliary cirrhosis. In our assay, the hapten UDCA 7-NAG, a /3-type antibody, and a biotin-labeled a-type antibody were simultaneously added to a microtiter plate coated with an F(ab )2 fragment of a specific anti-UDCA 7-NAG antibody, then incubated at room temperature for 8 h. Bound biotin was then detected with HRP-labeled streptavidin, whose enzyme activity was measured using o-phenylenediamine/H202 as a substrate. This noncompetitive assay system provided a subfemtomole-order sensitivity (detection limit 118 amol) that was 7 times lower than the competitive immunoassay using the same anti-hapten antibody (K2), even with a common colorimetric detection (Fig. 13). Somewhat improved specificity was also obtained namely, better... 

The dye-clay composites were prepared by dispersing the clays in each solvent containing the dye at a quantity of 10-200% of the CEC. This experimental procedure led to almost complete intercalation at room temperature for 2-7 days. The composite was recovered by filtration and washing several times with each solvent for eliminating an excess of dye, and then dried in air. Assuming that the loss of dye adsorbed on the surface was fairly small upon washing, the net weight of dye intercalated was estimated from the residual dye concentration in a solvent measured by a colorimetric analysis. 

Figure 12.6 Colorimetric response (CR) values obtained upon exposure of the liposome array to lipopolysaccharides from different Gram negative bacteria for ( ) Trp and ( ) Tyr. AU values are the average of at least four experiments. RT, room temperature [liposome] w 0.6 mM, [LPS] 2.2mg/mL, [SDS] = 2 mM, [EDTA] = 1 mM. See supporting information for details.

Add 100 pL of AETS and incubate for 6 min at room temperature for visualization by colorimetric reaction. 

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