Master Practice Quiz- (Spectroscopy Lab, Quinine Fluorescence Lab, FTIR Infrared Lab)

Practice flashcards on key concepts from the Spectroscopy Lab lecture notes.

What type of transitions are observed in UV-Vis spectroscopy?

Electronic transitions.

What is the main light source in the Cary 60 spectrophotometer?

Halogen lamp.

In UV-Vis, what does λmax represent?

Wavelength of maximum absorbance.

What happens to absorbance if concentration increases?

Absorbance increases.

How is Beer's Law expressed?

A = εcl.

Why is it necessary to blank the spectrophotometer?

To account for absorbance by solvent and cuvette.

What material is used for cuvettes in UV-Vis?

Quartz.

What is typically plotted on the y-axis of a Beer's Law plot?

Absorbance.

What is the unit of molar absorptivity?

L/mol·cm.

If absorbance is 0.500 and molar absorptivity is 2000 L/mol·cm with a path length of 1 cm, what is the concentration?

2.5 × 10⁴ M.

Which range is suitable for optimal UV-Vis absorbance measurements?

0.2-1.0.

What is the result if a cuvette is inserted incorrectly?

Distorted or inaccurate absorbance reading.

What formula is used for solution dilutions?

C1V1 = C2V2.

Wavelengths selected for absorbance measurements must correspond to:

Analyte's peaks.

If the sample is too concentrated, what should you do?

Dilute the sample.

Slit width primarily affects:

Resolution and light intensity.

A dirty cuvette may cause:

Scattering and high absorbance.

Higher molar absorptivity indicates:

Stronger light absorption at a given concentration.

What will increasing the path length from 1 cm to 2 cm do?

Double absorbance.

What does LOQ stand for?

Limit of quantitation.

Fluorescence is caused by:

Emission of light after excitation.

What is the excitation wavelength in the quinine lab?

350 nm.

What is the emission wavelength for quinine?

450 nm.

Fluorescence intensity is plotted against:

Concentration.

A blank sample should contain:

Only 0.05 M H₂SO₄.

High PMT gain can cause:

Detector saturation.

Matrix effects are especially significant in samples like:

Urine and complex biological matrices.

Fluorescence emission is always:

Longer wavelength than excitation.

High background in fluorescence may be caused by:

Solvent fluorescence.

If excitation and emission slits are too wide, the result is:

Lower resolution and higher background.

Inner filter effect occurs at:

High sample concentrations.

Photobleaching refers to:

Loss of fluorescence with light exposure.

In a good calibration curve, the slope represents:

Method sensitivity.

Emission scan measures:

Fluorescence emission spectrum.

Excitation scan identifies:

Best excitation wavelength.

Tonic water is used in the lab because it contains:

Quinine.

Higher pH conditions in quinine fluorescence:

Quench fluorescence.

What is the best container for fluorescence samples?

Quartz cuvette.

What is the purpose of blank subtraction in fluorescence?

Remove solvent background.

What increases S/N ratio in FTIR?

More scans averaged.

What does the moving mirror in the Michelson interferometer create?

Interferogram.

What does Fourier Transform convert?

Time domain to frequency domain.

What is ATR primarily used for?

Surface absorption with shallow penetration.

Characteristic absorption near 3400 cm⁻¹ is due to:

O-H stretch.

Where does water vapor interference appear?

3700-3200 cm⁻¹.

What increases the S/N ratio in FTIR?

More scans averaged.

What does poor sample contact in ATR give?

Weak signal.