FT: Q2 Flashcards
(32 cards)
A method to measure how much a chemical substance absorbs light by measuring the intensity of light as a beam passes through sample solution
Spectrophotometry
One of the most frequently used tools to determine both the presence and concentration of dissolved chemicals
Spectrophotometer
Measures the amount of photons absorbed after it passes through a sample solution
Spectrophotometer
4 main applications of spectrophotometry
- Qualitative analysis
- Quantitative analysis
- Enzyme assay
- Molecular weight identification
Instrument designed to detect the amount of light energy that is absorbed or transmitted by molecules dissolved in a solution
Spectrophotometer
Classification of a spectrophotometer that uses light over the ultraviolet and visible range
UV-visible spectrophotometer
Classification of a spectrophotometer that uses light over the infrared range
IR spectrophotometer
A solution sample that absorbs light over all visible ranges appears […]
black, in theory
A solution sample that transmits light over all visible ranges appears […]
white
A solution sample that absorbs a specific wavelength appears […]
as its complementary color
The basic structure of spectrophotometers
- Light Source
- Collimator
- Monochromator
- Wavelength Selector
- Cuvette
- Photoelectric Detector
- Digital Display
An instrument that produces a desired range of wavelength of light
Spectrometer
An instrument that detects the amount of photons absorbed and then sends a signal to a digital display
Photometer
A lens that transmits a straight beam of light
Collimator
A prism that splits the beam of light into several component wavelengths
Monochromator
A wavelength selector that transmits only the desired wavelengths
Slit
The amount of photons that goes through the cuvette and into the detector is dependent on […]
the length of the cuvette and the concentration of the sample
The fraction of light that passes through the sample
Transmittance (T)
The amount of light unable to pass through a sample is measured as the […]
absorbance value
Transmittance equation
T = It / Io
where:
- It is the light intensity after the beam of light passes through the cuvette
- Io is the light intensity before the beam of light passes through the cuvette
Absorbance Equation
A = -log(T)
States that there is a linear relationship between the absorbance and the concentration of a sample
Beer-Lambert Law
Beer-Lambert Equation
A = εcl
where:
- A is the absorbance
- ε is the molar absorption coefficient (M^-1cm^-1)
- c is the molar concentration (M)
- l is the optical path length (cm)
An instrument used to measure absorbance and conduct quantitative analysis at the visible light
VIS Spectrophotometer
