Lecture 5: Quantitative Emission/Absorption
1 From the original definition of kνand S 12 we have 2 When k S 12 as is common for electronic state transitions 1 2 1 21 2 1 12 2 1 12 2 1 12 8 0 0265cm Hz cm Hz g g n A n f n f m c e S e h /kT 1 2 1 2 12 / 12 12 21 1 51 cm g g Af Radiative lifetime of the 2→1 transition
Spectrophotometry Page 1 10 Lab SPECTROPHOTOMETRY
absorbed by anything in the solution other than the compound of interest By definition, the absorbance of the reference blank is set at zero (A = 0) Visible light (see your text) is composed of wavelengths from 400 to 700 nm (nanometers) When visible light passes through a colored solution, some wavelengths are transmitted and others are
Determining the Concentration of a Solution: Beer’s Law
absorbance = -log percent transmittance 100 The relationship between transmittance and absorbance is where T is the transmittance, rather than the T (i e 0 50, not 50 ) The most important lesson to take home from this relationship is the realization that when the absorbance is 1 0, only 10 of the light beam is reaching the detector
Estimating Turbidity (NTU) From Absorption Data
material When measuring absorbance in a UV-VIS spectrometer, the suspended particles block the photons and appear as absorbance and color and reflectivity have little effect However, it should be possible to develop a model of UV-VIS absorption and turbidity NTU A model was developed and reported here MATERIALS AND METHODS
The spectrophotometric determination of boron in tourmalines
The effect of pH on the absorbance of the azomethine H – boron complex was examined The absorbance difference between the test solution and the blank was found to be maximal in the pH range 4 5 – 5 2 The absorbance intensity of the boron–azomethine H complex depends on the concentration of the azomethine H in the solution
Interpreting Nanodrop (Spectrophotometric) Results
Where A=absorbance, ԑ=extinction coefficient, c=concentration and l=path length The Beer‐Lambert law draws a direct correlation between absorbance and concentration While nucleic acids absorb at many wavelengths, they have a peak absorbance of UV light at 260nm
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