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Photon Beams, Dose, and Kerma
Published in Eric Ford, Primer on Radiation Oncology Physics, 2020
Here I is the intensity transmitted through some thickness x, if I0 is the incident intensity. Equation 6.1 is known as Beer’s Law (or the Lambert–Beer Law) and describes exponential attenuation. Note that Equation 6.1 is analogous to Equation 3.2 for exponential decay of the activity of a radioactive source, i.e. A = A0·e−λt. Here instead of λ we have μ and instead of time, t, we have distance, x. The mathematical derivations, however, are identical.
Brain Monitoring Using Optical Imaging and Optical Spectroscopy
Published in Richard A. Jonas, Jane W. Newburger, Joseph J. Volpe, John W. Kirklin, Brain Injury and Pediatric Cardiac Surgery, 2019
As with all forms of conventional optical oximetry, quantitative measurement of pigments such as hemoglobin in vitro using path-resolved NIRS is based upon the principle that changes in the absorbance of light (DA) are related to changes in concentration (DC). In the simplest, nonscattering conditions, this relationship is given by Beer’s Law (A = eCL), where L is the distance light has traveled through the medium (called the optical path length) and e is a constant called the extinction coefficient.10,36In vivo, however, Beer’s Law is inaccurate and inappropriate due to additional light losses caused by light scattering, though it serves as a starting point for such discussions. Of note, the inaccuracies from the use of Beer’s Law can be reduced when changes in concentration, rather than absolute concentration, are measured.
Oxy Radical and Peroxide Formation by Hemoglobin and Myoglobin
Published in Robert A. Greenwald, CRC Handbook of Methods for Oxygen Radical Research, 2018
Winslow S. Caughey, Joseph A. Watkins
The protein concentrations are determined by measurements of visible-Soret spectra by use of Beer’s Law (A = ϵbc) where A is absorbance, b is the pathlength of the cell in cm, ϵ is the extinction coefficient in cm−1mM−1, and c is the concentration in millimoles. Representative extinction coefficients at wavelengths of absorption band maxima for oxy; deoxy, and met species of these proteins are listed in Table 1 for use in the determination of protein concentrations.
Analytical comparability demonstrated for an IgG4 molecule, inclacumab, following transfer of manufacturing responsibility from Roche to Global Blood Therapeutics
Published in Expert Opinion on Biological Therapy, 2022
Radu Mihaila, Dipali Ruhela, Lifang Xu, Sandra Joussef, Xin Geng, Jianxia Shi, Andrea S. Kim, Wendy Yares, Kevin Furstoss, Kent Iverson
Total protein concentration of each inclacumab sample was quantitatively determined via ultraviolet (UV) absorbance using the SoloVPE system. Absorbance at 280 nm was used to calculate the concentration of inclacumab using Beer’s law, A = εlc, where A = absorbance at 280 nm, ε = extinction coefficient of inclacumab (1.54 mL mg–1 cm–1), l = pathlength (variable), and c = concentration of the sample. In this method, the absorbance at 320 nm was subtracted from the absorbance at 280 nm before calculating the concentration. A variable pathlength approach utilized the slope (change of absorbance per change of light pathlength) to calculate the concentration. The absorbance value was directly proportional to the protein concentration. Testing was conducted at Patheon (St. Louis, MO).
Smart UV-spectrophotometric platforms for rapid green analysis of miconazole nitrate and nystatin in their combined suppositories and in vitro dissolution testing
Published in Drug Development and Industrial Pharmacy, 2021
Rania A. Sayed, Ahmed R. Mohamed, Wafaa S. Hassan, Manal S. Elmasry
The utilized sample enrichment technique was developed mainly to provide a solution for the problem of analysis of one or more component(s) present in small concentration in their mixtures so, making their determination easier. Hence, there is a necessity to increase its concentration to abolish the deviation from Beer’s law which appears in the case of small component(s) concentrations. This technique application is very important for mixtures analysis due to the optimum concentration range choice depended mainly on the absorptivity of the compound, its spectral characteristics, and the compound ratio present in the mixture without increasing its concentration in the synthetic binary or ternary mixtures [21]. This technique also can be used to resolve the same problem during analyzing other such drug mixtures of different prepared ratios [22,23]. The enrichment method includes the addition of a fixed amount of standard solution to one or more dilutions of the processed sample solution to bring the cited drug concentration inside its range then, subtracting this fixed concentration before calculation of the claimed drug actual concentration so that improves the analytical signal.
Comparative study of novel green UV-spectrophotometric platforms for simultaneous rapid analysis of flumethasone pivalate and clioquinol in their combined formulation
Published in Drug Development and Industrial Pharmacy, 2021
Rania A. Sayed, Ahmed R. Mohamed, Wafaa S. Hassan, Manal S. Elmasry
In the second set, mixtures were accurately prepared to contain the same concentration ratio of ear drops (0.2 mg FP: 10 mg CL; that is the same ratio as 0.1 µg FP: 5 µg CL). According to this set of mixtures, FP was observed to be in a lower concentration than that of its calibration range. Thus, a novel sample enrichment technique (spectrum addition technique) [10–12] was utilized for the analysis of the studied mixtures that involve FP as a minor constituent. So, this method was utilized to bring FP concentration inside its calibration range. Moreover, it was utilized to make the determination of FP concentration easier and also to eliminate the deviation from Beer’s law that occurs in the case of small concentrations of drugs leading to enhancing the analytical signal. The flasks which included the ratio of the pharmaceutical dosage form were spiked with 7 µg/ml of FP working standard solution. This standard solution of 7 µg/ml of FP was prepared separately into a flask and computed for further calculations. Finally, all prepared solution spectra were scanned from 200 to 400 nm and saved in the computer. Then, the suggested platforms were applied on the produced spectrum.