ANALYTICAL TECH. LEC

Question 1

What is the principle of photometric instrumentation?

Answer 1

Photometry measures light intensity (brightness) as perceived by the human eye; wavelength specificity is not required

Question 2

What is the principle of spectrophotometry?

Answer 2

It determines analyte concentration by measuring light absorbed or transmitted at a specific wavelength through a solution

Question 3

What types of analytes are measured by spectrophotometry?

Answer 3

Analytes that absorb light when exposed to incident radiation

Question 4

What does transmittance (T) represent?

Answer 4

The fraction of incident light that passes through the sample

Question 5

What happens at λmax (wavelength max)?

Answer 5

Maximum absorbance occurs; this gives the best sensitivity for measurement

Question 6

What is the wavelength range of visible light used in chemistry?

Answer 6

Approximately 5 × 10⁻⁷ meters (400–700 nm)

Question 7

Why is knowing wavelength and color important in spectrophotometry?

Answer 7

The observed color is the complementary color of the absorbed wavelength

Question 8

List other types of radiation used in the chemistry department.

Answer 8

Ultraviolet, Infrared, X-ray, Gamma rays

Question 9

What does spectrometry measure?

Answer 9

Concentration by measuring light transmitted or absorbed by molecules in solution

Question 10

What is the key law governing spectrophotometry?

Answer 10

Beer’s Law — concentration is proportional to absorbance

Question 11

What does atomic absorption spectroscopy measure?

Answer 11

Concentration of free atoms by measuring absorbed electromagnetic radiation

Question 12

What analytes are commonly measured by atomic absorption?

Answer 12

Trace metals (e.g., calcium, iron, lead)

Question 13

What is chemiluminescence?

Answer 13

Measurement of light emitted during a chemical reaction (no excitation source)

Question 14

Common clinical or lab uses of chemiluminescence?

Answer 14

Forensics, immunoassays, oxidation reactions

Question 15

What does nephelometry measure?

Answer 15

Scattered light produced by particles in solution

Question 16

What is nephelometry commonly used for clinically?

Answer 16

Immune complexes (e.g., proteins, immunoglobulins)

Question 17

What is a galvanic cell?

Answer 17

A cell where electrons flow spontaneously from low affinity to high affinity electrodes

Question 18

In a galvanic cell, electrons flow from where to where?

Answer 18

Anode → Cathode

Question 19

What is an electrolytic cell?

Answer 19

A cell that requires an external energy source to force electron flow

Question 20

What is the function of ion-selective electrodes?

Answer 20

Detect free ion activity or concentration using electrical potential measurements

Question 21

What is a common example of an ISE?

Answer 21

pH electrode

Question 22

What is thin-layer chromatography (TLC)?

Answer 22

A semiquantitative technique using a sorbent-coated plate where solvent carries samples upward

Question 23

What is liquid chromatography (HPLC)?

Answer 23

A column technique using high pressure, controlled temperature, and detectors to separate analytes

Question 24

How does HPLC identify analytes?

Answer 24

By measuring retention time as eluates pass through the column

Question 25

What is gas chromatography best used for?

Answer 25

Volatile compounds

Question 26

How does volatility affect GC retention time?

Answer 26

Higher volatility → faster elution; higher boiling point → slower

Question 27

Why is mass spectrometry valuable clinically?

Answer 27

It is highly specific and sensitive

Question 28

Common clinical applications of mass spectrometry?

Answer 28

Therapeutic drug monitoring, toxicology, drugs of abuse, newborn screening

Question 29

What technique is mass spectrometry often combined with?

Answer 29

Chromatography

Question 30

What is Beer’s Law equation?

Answer 30

A = εLc = −logT

Question 31

What does ε (epsilon) represent?

Answer 31

Molar absorptivity (constant)

Question 32

How is absorbance related to concentration

Answer 32

Directly proportional

Question 33

What happens to transmittance when absorbance increases?

Answer 33

Transmittance decreases

Question 34

What is potentiometry?

Answer 34

Measurement of analyte concentration by electrical potential difference between electrodes

Question 35

What is coulometry?

Answer 35

Measures analyte amount by total electrical charge required for complete oxidation/reduction

Question 36

How is charge related to analyte concentration in coulometry?

Answer 36

Directly proportional to number of electrons transferred

Question 37

Example of a clinical test using coulometry?

Answer 37

Sweat chloride test