Analytical Chemistry Exam Review – Spectroscopy, Chromatography & Related Topics

These flashcards cover key concepts from spectroscopy, detectors, lasers, chromatography (GC, HPLC, CE), extraction, atomic and molecular spectrometry, statistics, scanning probe microscopy, and pregnancy test immunoassays to aid exam preparation.

What is the main advantage of a double-beam scanning spectrophotometer?

It simultaneously measures absorbance from both the sample and reference solutions to compensate for source and detector fluctuations.

What device periodically alternates light between sample and reference paths in a double-beam spectrophotometer?

A beam chopper (rotating mirror).

Why are blackbodies useful as light sources in spectroscopy?

They emit a continuous electromagnetic spectrum whose intensity depends only on temperature and is continuous at all wavelengths.

Which lamp is typically used as a UV light source in UV-Vis spectrophotometers?

A deuterium arc lamp.

Which lamp provides visible to near-IR and visible light?

A tungsten lamp.

State Snell’s law for refraction.

n₁ sin θ₁ = n₂ sin θ₂, where n is refractive index and θ the angle.

What condition produces total internal reflection?

If the incidence angle exceeds the critical angle.

Define a laser in one sentence.

Light Amplification by Stimulated Emission of Radiation: a monochromatic, coherent and highly directional light source.

Normal-phase chromatography.

Polar stationary phase. Less polar mobile phase. Increasing the polarity of the mobile phase leads to faster elution times.

Reverse-phase chromatography.

Non-polar stationary phase. More polar mobile phase. Decreased polarity of mobile phase leads to faster elution times.

What does STM stand for and what does it scan?

Scanning Tunneling Microscopy; scans a sharp tip over a conductive surface to map out surface at atomic level.

Which AFM mode is preferred for fragile biological samples?

Tapping mode.

Which AFM mode is fastest but risks surface damage?

Contact mode.

In chemical-force microscopy, why does a COOH-functionalized tip stick more to a COOH-coated surface than CH₃?

Strong hydrogen bonding between COOH groups increases adhesion and friction.

What hormone do pregnancy tests detect?

hCG

Describe the basic ‘sandwich’ immunoassay format of an over-the-counter pregnancy test.

Labelled antibody binds hCG; complex is captured by immobilized second antibody on test line, producing a colored line; excess labelled antibody binds at control line.

False-positive pregnancy test results.

hCG-producing tumors

biochemical pregnancies (early implantation failure)

hormonal hCG supplementation

False-negative pregnancy test results

Testing too early when hCG concentration is below detection limit.

Improperly followed procedures.

Dangerous to fetus and mother because of lack of lifestyle changes.