CONCEPTS IN INSTRUMENTATION

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Total cards: 24•Content version: v4•Public deck•Updated: 8/1/2026

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Front (Question)

Methods of determining the concentration of substance in solution by measuring the amount of light absorbed by that solution after appropriate treatment

Back (Answer)

Spectrophotometry

Front (Question)

Visible light falls between:

Back (Answer)

400 nm - 700 nm

Front (Question)

BEER-LAMBERT LAW (BEER’S LAW) states that:

Back (Answer)

The concentration of a substance is directly proportional to the logarithm of the transmitted light

Front (Question)

In the Beer’s formula A = abc, the “b” represents:

Back (Answer)

b is the length of light path through the solution

Front (Question)

In the Beer’s formula A = abc, the “a” represents:

Back (Answer)

a = Molar absorptivity, the fraction of a specific wavelength of light absorbed by a given type of molecule.

Front (Question)

Components of a spectrophotometer:

Back (Answer)

• Light source • Monochromators • Sample cell/cuvet • Photodetectors

Front (Question)

Most common source of light for work in the visible and near-infrared regions:

Back (Answer)

Incandescent tungsten or Tungsten-iodide lamp

Front (Question)

Most commonly used for ultraviolet (UV) work:

Back (Answer)

Deuterium - discharge lamp & Mercury - arc lamp

Front (Question)

Most commonly used Monochromator (isolate desired wavelength):

Back (Answer)

Diffraction gratings

#10

Front (Question)

Preferred sample cell; advantage over round cuvets in that there is less error from the lens effect, orientation in the spectrophotometer, and refraction

Back (Answer)

Square sample cell

#11

Front (Question)

Sample cell used for applications in the visible rage

Back (Answer)

Glass cuvet

#12

Front (Question)

Sample cell for applications requiring UV radiation:

Back (Answer)

Quartz cuvet

#13

Front (Question)

Used in instruments designed to be extremely sensitive to very low light levels and light flashes of very short duration

Back (Answer)

Photomultiplier (PM) tube

#14

Front (Question)

Measures the quantity of light reflected by a liquid sample that has been dispensed onto a grainy or fibrous solid support

Back (Answer)

Reflectometry

#15

Front (Question)

Application of Reflectometry:

Back (Answer)

• Urine dipstick analysis • Dry slide chemical analysis

#16

Front (Question)

Measurement of concentration is done by detecting the absorption of electromagnetic by atoms rather than molecules.

Back (Answer)

Atomic Absorption Spectrophotometry (AAS)

#17

Front (Question)

Components of AAS:

Back (Answer)

Hollow-cathode lamp - usual light source Flame - breaks chemical bonds and form free, unexcited atoms; serves as sample cells (instead of a cuvet) Monochromator

#18

Front (Question)

Applications of AAS:

Back (Answer)

measurement of unexcited trace metals e.g. calcium and magnesium *Reference method for Ca and Mg

#19

Front (Question)

Measurement if light emitted by excited atoms (flame excites atoms)

Back (Answer)

Flame photometry

#20

Front (Question)

Some metals produce characteristic flame colors: Lithium: Sodium: Magnesium: Rubidium: Potassium:

Back (Answer)

Some metals produce characteristic flame colors: Lithium: RED Sodium: YELLOW Magnesium: BLUE Rubidium: RED Potassium: VIOLET

#21

Front (Question)

Applications of Flame photometry:

Back (Answer)

Widely used before to determine the concentration of Na, K, Li *Now: ISE (Ion-Selective Electrode) for Na, K, Li

#22

Front (Question)

Measurement of the concentration of solutions that contain fluorescing molecules:

Back (Answer)

Fluorometry

#23

Front (Question)

Most common light source of fluorometry:

Back (Answer)

Xenon lamp

#24

Front (Question)

How many monochromators does fluorometry have?

Back (Answer)

2 monochromators set up at 90 degree angle