CPC Chemical Analysis & Techniques 2 — Questions and Answers
Question 1: In atomic absorption spectroscopy (AAS), what is the primary function of the hollow cathode lamp?
- To ionize the sample atoms
- To emit radiation at the specific wavelength of the analyte element (Correct answer)
- To atomize the sample solution
- To detect the transmitted radiation
Correct answer: To emit radiation at the specific wavelength of the analyte element
The hollow cathode lamp emits characteristic radiation at the same wavelength absorbed by the analyte element, enabling selective detection.
Question 2: Which chromatographic parameter describes the ability of a column to separate two adjacent peaks?
- Retention factor (k)
- Resolution (Rs) (Correct answer)
- Plate height (H)
- Capacity factor
Correct answer: Resolution (Rs)
Resolution (Rs) quantifies the degree of separation between two adjacent peaks based on their retention times and peak widths.
Question 3: In potentiometry, what does the Nernst equation relate?
- Current to analyte concentration
- Electrode potential to ion activity (Correct answer)
- Conductance to ionic strength
- Absorbance to concentration
Correct answer: Electrode potential to ion activity
The Nernst equation relates electrode potential to the logarithm of ion activity, forming the basis for ion-selective electrode measurements.
Question 4: What is the purpose of an internal standard in quantitative GC analysis?
- To calibrate the detector wavelength
- To compensate for sample preparation and injection variability (Correct answer)
- To increase column resolution
- To identify unknown compounds by retention time
Correct answer: To compensate for sample preparation and injection variability
An internal standard corrects for variability in sample preparation, injection volume, and instrument response by normalizing peak areas.
Question 5: Which technique measures the mass-to-charge ratio of ions to identify chemical compounds?
- Infrared spectroscopy
- Mass spectrometry (Correct answer)
- Nuclear magnetic resonance
- Raman spectroscopy
Correct answer: Mass spectrometry
Mass spectrometry separates and detects ions based on their mass-to-charge ratio (m/z), providing molecular weight and structural fragmentation data.
Question 6: In Karl Fischer titration, what species is being quantitatively determined?
- Dissolved oxygen
- Water content (Correct answer)
- Sulfur compounds
- Chloride ions
Correct answer: Water content
Karl Fischer titration is a highly specific and sensitive method for determining trace water content in chemical samples.
Question 7: What does LOD (Limit of Detection) represent in analytical chemistry?
- The highest concentration measurable without dilution
- The lowest concentration distinguishable from the blank signal (Correct answer)
- The concentration at which calibration becomes nonlinear
- The precision of replicate measurements
Correct answer: The lowest concentration distinguishable from the blank signal
LOD is the lowest analyte concentration that can be reliably distinguished from background noise, typically defined as blank signal plus three standard deviations.
CPC Chemical Analysis & Techniques 2
In atomic absorption spectroscopy (AAS), what is the primary function of the hollow cathode lamp?