Laboratory Instrumentation and Analytical Principles Flashcards

In atomic absorption spectrophotometry, what is the light source for measuring a specific element?

Answer: Hollow cathode lamp made of the element being measured

The hollow cathode contains the target element, so it emits that element's exact resonance wavelengths.

In fluorometry, how does the emitted light compare with the excitation light?

Answer: Longer wavelength, lower energy

Some energy is lost before emission (Stokes shift), so emitted light has a longer wavelength.

Fluorescence readings fall below expected at very high analyte concentrations. What is the most likely cause?

Answer: Inner filter effect (concentration quenching)

At high concentrations the sample absorbs excitation and emitted light, reducing measured fluorescence.

How does nephelometry differ from turbidimetry?

Answer: Nephelometry measures light scattered at an angle; turbidimetry measures the decrease in transmitted light

Nephelometers detect light scattered by particles at an angle, while turbidimeters detect the loss of light passing straight through.

In freezing point osmometry, one mole of solute per kilogram of water lowers the freezing point by approximately how much?

Answer: 1.86°C

The molal freezing point depression constant of water is 1.86°C per osmole per kg.

During serum protein electrophoresis at pH 8.6, which protein migrates fastest toward the anode?

Answer: Albumin

Albumin has the strongest net negative charge at pH 8.6, so it moves fastest toward the anode.

In electrophoresis, what is endosmosis (electroendosmosis)?

Answer: Movement of buffer and neutral molecules toward the cathode due to a charged support medium

Negatively charged support media attract positive buffer ions that flow toward the cathode, carrying solvent and weakly charged proteins such as gamma globulins.