Absorbance optimal range

The ratio of absorbance at 260 and 280 nm are used to assess protein contamination. A DNA sample is pure if measurement provides a ratio of about 1.8. The ratio of absorbance at 260 and 230 nm are calculated to assess possible reagents contamination, with an optimal range from 2.0 to 2.2. If the ratio is appreciably lower in either case, it may indicate the presence of protein, phenol, or other contaminants [8, 9, 13]. 

Figure 16.27 illustrates the dependence of the relative error on the transmittance, calculated for a constant error of 0.01 T in reading the scale. It is evident from the figure that, while the minimum occurs at 36.8% T, a nearly constant minimum error occurs over the range of 20 to 65% T (0.7 to 0.2 A). The percent transmittance should fall within 10 to 80% T (A = 1 to 0.1) in order to prevent large errors in spectrophotometric readings. Hence, samples should be diluted (or concentrated), and standard solutions prepared, so that the absorbance falls within the optimal range. 

The maximum relative errors caused by this approximation are given in Table 3.10 for the extremely non-optimal range of natural absorbances between =5 and . =0. 

Methadone is a p receptor agonist with special properties that make it particularly useful as a maintenance agent. Rehably absorbed orally, it does not reach peak concentration until about 4 hours after administration and maintains a large extravascular reservoir (Kreek 1979). These properties minimize acute euphoric effects. The reservoir results in a plasma half-life of 1—2 days, so there are usually no rapid blood level drops that could lead to withdrawal syndromes between daily doses. Effective blood levels are in the range of 200-500 ng/mL. Trough levels of 400 ng/mL are considered optimal (Payte and Khouri 1993). There is wide variability among individuals in blood levels with identical doses (Kreek 1979), and some have inadequate levels even with doses as high as 200 mg/day (Tennant 1987 Tenore 2003). 

In a cryogenic experiment, one or several detectors are used for a definite goal for which they have been optimized. For example, in CUORE experiment described in Section 16.5, the sensors are the Ge thermistors, i.e. thermometers used in a small temperature range (around 10 mK). One detector is a bolometer made up of an absorber and a Ge sensor. The experiment is the array of 1000 bolometers arranged in anticoincidence circuits for the detection of the neutrinoless double-beta decay. Note that the sensors, if calibrated, could be used, as well, as very low-temperature thermometers. Also the array of bolometers can be considered a single large detector and used for different purposes as the detection of solar axions or dark matter. 

Scenario A student determined that the optimal wavelength for the absorbance of FeSCN2+ experiment was 445 nm. Then the student prepared samples of known concentrations of FeSCN2+ ranging from 4.0 x 10 5 M to 1.4 x 10 4 M. The samples were then examined by means of a spectrophotometer and their transmittances recorded. From the transmittance, the absorbance was calculated and graphed. Next, he mixed 5.0 mL of 2.0 x 10 3 M Fe(N03)3 with 5.0 mL of 2.0 x 10 3 M KSCN. This solution was then analyzed in the spectrophotometer and through extrapolation, he was able to determine that the concentration of FeSCN2+ at equilibrium was 1.3 x 10" M. 

Based on minimizing the photometric error, what range of absorbances is optimal for absorbance spectroscopy What is the relative dynamic range of absorbance measurements ... 

As soon as the protein is activated with the heterobifunctional crosslinker, the extinction coefficient determined for pure Amb a 1 no longer applies because the heterobifunctional crosslinker absorbs at 280 nm. At this step in the production of AIC, the manufacturing overhead cost requires the use of a fast protein assay, whereas the exact stoichiometry of the subsequent reaction dictates the use of an accurate and precise method. Hence we developed a new extinction coefficient for the activated protein based on experimental data and demonstrated that within the normal activation range of 9 to 12 crosslinkers per Amb a 1, the new extinction coefficient remained constant. The concentration of the purified activated Amb a 1 determined by this direct absorbance A280 method is more precise and accurate than could be assigned by a colorimetric assay. Consequently, the activated Amb a 1 concentration allows for the accurate addition of 1018 ISS required to consistently produce AIC with optimal activity. 

Compared to absorbance detection, direct detection of proteins rich in aromatic amino acids by the intrinsic fluorescence of tryptophan and tyrosine residues provides enhanced sensitivity without the complexity of pre- or postcolumn derivatization. The optimal excitation wavelengths for these amino acids are in the 270- to 280-nm range. 

The Aspt, Ace-K, Caf and Na-Benz contents were determined by using spectra fort he mixtures studied above were registered in the spectral range 190-300 nm using 0.1 N HjPO solution as a reference and the absorbance values were recorded every 5 nm from these spectra. By apphcation of the PLS-2 algorithm a model was optimized using three factors for Aspt, Ace-K, Caf and Na-Benz calculated by analysis of the optimized PLS-2 model. 

In some cases, a less optimal wavelength is used. The absorption observed will be sufficient to stay in the dynamic range of the detector. This is documented by the example of the nitrate ion that still absorbs at 230 nm, but almost not at all at 254 nm. When the analysis is run at 254nm instead of 233 nm, it results in an overall higher signal (Eigure 5). 

Sakai et al. determined procaine by a colorimetric method that was proposed for the assay of procaine on the basis of solvent extraction [39]. Tetrabromophenolphthalein ethyl ester anion was added to an aqueous solution containing procaine, and the extract took on a red color (absorbance maximum of the extract at 580 nm). The optimal pH range for extraction of the drug from the aqueous solution was found to be 8-9. Procaine was found to form a 1 1 associated ion pair compound with the reagent in 1,2-dichloroethane. 

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