Analytical techniques

Measuring electromagnetic radiation using photons of energy as photons move from its excited state to ground state. Certain wavelengths of energy are absorbed and emitted. The emitted energy can be seen as colors of light

abs= -log(T)

abs = Σbc

• light source - provides the electromagnetic radiation
• monochromator - selects wavelength at a specific region
• sample 
• detector - converts transmitted energy to electrical energy

• filter
• prism
• diffraction grating

1/5 x30 nm = 6nm

300nm - 1200nm

UV

UV and visible spectrum

• light
• monochromator
• heat
• PM tube (detector)

• to block heat and keep light when using an atomic absorbance spectrophotometer
• used with any detector

• light source
• attenuator - controls light intensity
• primary and secondary filter
• sample
• detector

measures the intensity of emitted fluorescent light as photons of energy moves from excited state to ground state.

range of wavelengths transmitted and calculated as width at half the maximum transmittance

• cheapest
• low sensitivity
• no low, no high
• slow
• no external supply

• expensive
• middle sensitivity
• middle linearity
• fast response time
• yes external supply

• most expensive
• highest sensitivity
• best linearity
• fast

• cheap
• high sensitivity
• medium linearity
• fast response time
• responds to 1λ

has a linear array that allows it to responds to a specific wavelength resulting in complete UV/visible spectrum analysis

• wavelength accuracy
• stray light
• linearity

checked by standard absorbing solutions/filters with absorbance of known wavelength

• didymium 
• holmium oxide

• stray light is any outside wavelengths transmitted by the monochromator
• most common causes are reflection of light from scratches or dust particles in light path
• results to absorbance error especially in high absorbance range. Places limits on upper range of linearity

linearity is occurs when a change in concentration results in a straight line calibration curve, via Beer's law

• advantages: greater specificity and sensitivity
• disadvantage: very sensitive to environmental changes

• in emission spectrum, the excitation wavelength is held constant and the emission intensity is measured as a function of the emission wavelength
• in an excitation spectrum the emission is measured at one wavelength while the excitation wavelengths are scanned

• power supply
• electrodes
• buffer
• gel 
• images analysis

• protein with negative charges
• provides electric current

• mobile phase (gas or liquid)
• stationary phase (solid or liquid)

• adsorption
• partition
• steric exclusion
• ion exchange chromatography