Absorbance measurements with

Ap and As are the absorbances measured with p- and s-polarization, respectively, and A0 — (Ap + 2As)/3 is the structural absorbance spectrum that would be measured for an isotropic sample. The order parameter of the main chain can be determined using the Legendre addition theorem (Equation (24)). 

The absorbance measured with a base line at 3300 cm-l or 3 70 cm-l. The calibration curves were linear in the concentration range between 0-5 to 2 mg/ml and the results were in good agreement with those determined colorimetrically. The determination was not interferred with the coexistance of a limited amount of 1 0 possible drug constituents e.g., phenacetin and pyrabital (1 1 ). 

This relationship can be used in kinetic experiments where absorbance (measured with a spectrophotometer) can be monitored rather than concentration directly. 

Other Methods. Protein concentrations were calculated from the 280 nm absorbance measured with a Beckman DB spectrophotometer. The pH of the protein solution was adjusted as necessary with a Radiometer GK2303c pH electrode and an Orion model 401 lonalyzer. was measured with a pulse-height, analyzer-counter modular system consisting of models 40-12B, 49-25, 33-10, 30-19, 29-1, and 10-8 manufactured by Radiation Instrument Development Lab., Des Plaines, 111. 

Pulse-probe transient absorption data on the rise time of prompt species such as the aqueous electron can be used to measure the instrument response of the system and deduce the electron pulse width. Figure 7 shows the rise time of aqueous electron absorbance measured with the LEAF system at 800 nm in a 5 mm pathlength cell. Differentiation of the absorbance rise results in a Gaussian response function of 7.8 ps FWHM. Correcting for pathlength, the electron pulse width is 7.0 ps in this example. 

To save time, start the absorbance measurements with the 0 pg protein standard and proceed in sequence to the 10 pg standard. This way the cuvet does not need rinsing between measinements. 

Whereas the absorbance measured with the concentration sets 1 and 2b are overlapping, the absorbance determined with set Ic are nearly 1 order of... 

The dynamic range, defined as the ratio between maximum and minimum absorbance measured with 1% accuracy, is limited at high absorption values by the stray light and at low absorption levels by the noise. 

Figure 18-9 Precision of replicate absorbance measurements with a diode array spectrometer at 350 nm with a dichromate solution. Filled circles are from replicate measurements in which the sample was not removed from the cuvet holder between measurements. Open circles are from measurements in which the sample was removed and then replaced in the cuvet holder between measurements. Best reproducibility is observed at intermediate absorbance (4 0.3 to 2). Note logarithmic ordinate. Lines are least-squares fit of data to theoretical equations. [Data from J. Galban, S. de Marcos, I. Sanz, C. Ubide, and j. Zuriarrain,/ no/. Chem, 2007, 79,47631.

Fig. 4.12 Absorption (A) and linear dichroism (B) spectra of photosynthetic reaction centers of Blastochloris (formerly called Rhodopseudomonas) viridis at 10 K [12, 13], Aggregates of the pigment-protein complex were embedded in a polyacrylamide gel and oriented by uniaxial squeezing. The spectra are normalized relative to the positive peak near 830 nm. Linear dichroism is expressed as where A and An are the absorbance measured with light polarized...

Figure 4.13 illustrates the use of polarised absorption spectroscopy to measure orientation for a uniaxially oriented polymer. For a single molecule, the absorbance is proportional to the square cosine of the angle between the vibration transition dipole moment and the IR electric field vector E). Thus if 0 = 90°, the absorbance is zero (note that the measurement is sensitive to the alignment of the vibrational dipole moment rather than the chain axis itself). The dichroic ratio R is calculated by ratioing the absorbance measured with E parallel toXs with that measured perpendicular toXs R = A A ). For an assembly... 

Figure 7.5 Experimental setup for the overview absorbance measurements with the ARES spectrograph (1) D2 lamp, (2) tungsten halogen lamp, (3) beam combiner, (4) mechanical shutter, (5,9) toroidal mirrors, (6) sample and blank reservoir, (7) magnetic valve, (8) flame atomizer, (10) entrance slit, (11 -14) pre-dispersing illumination optics, (15,18) spherical mirrors, (16) prism, (17) echelle grating, (19) CCD array detector, (20) Ne lamp, (R1-R5) piezo-electrically controlled rotation units...

Absorbance measurements of the tetrapropylannDnlum uranyl trinitrate complex were made with a Cary Modal 14 recording spectrophotometer and 1-cm. Corex cells. A Teflon 9x9x6 ora. spacer placed In the bottom of the cells permits absorbance measurements with 2 ml. of sanq le. Absorbance measurements of the dlbenzoylmethane coinplex were made with a Beckman DU spectrophotometer and 5>cm. Corex cells. 

---