Free AACC Analytical Techniques Questions and Answers — Questions and Answers
Question 1: What is spectrophotometry used for in clinical chemistry?
- Measuring temperature
- Detecting bacteria
- Determining analyte concentration (Correct answer)
- Counting blood cells
Correct answer: Determining analyte concentration
Spectrophotometry is a fundamental technique in clinical chemistry used to measure the concentration of specific analytes in a sample. It works by measuring the amount of light absorbed or transmitted through a solution at a particular wavelength. The intensity of the absorbed light is directly proportional to the concentration of the substance, allowing for precise quantitative analysis of various chemical components.
Question 2: Which technique separates components based on size or charge?
- Microscopy
- Chromatography (Correct answer)
- Spectroscopy
- Electrolysis
Correct answer: Chromatography
Chromatography is a powerful laboratory technique used to separate mixtures into their individual components based on differences in their physical or chemical properties. Depending on the type of chromatography, separation can occur based on factors such as molecular size, charge, polarity, or affinity. This technique is widely used in clinical chemistry to isolate and identify various substances in complex biological samples.
Question 3: What does a calibration curve help determine?
- Sample color
- Instrument noise
- Concentration of unknowns (Correct answer)
- Reagent volume
Correct answer: Concentration of unknowns
A calibration curve is a fundamental tool in analytical chemistry used to determine the concentration of an unknown sample. It is created by measuring the instrument's response (e.g., absorbance, fluorescence) to a series of solutions with known concentrations of the analyte. By plotting these known concentrations against their corresponding responses, a standard curve is generated, allowing the concentration of an unknown sample to be interpolated from its measured response.
Question 4: Which method measures the emission of light from atoms?
- Titration
- Centrifugation
- Atomic absorption spectroscopy (Correct answer)
- ELISA
Correct answer: Atomic absorption spectroscopy
Atomic absorption spectroscopy (AAS) is an analytical technique used to determine the concentration of specific metallic elements in a sample. While its primary principle involves measuring the *absorption* of light by ground-state atoms, it is a method that fundamentally interacts with atoms using light to quantify elements. The atoms are typically vaporized in a flame or furnace, and the amount of light absorbed at a specific wavelength is proportional to the concentration of the element.
Question 5: What is the principle behind electrophoresis?
- Light diffraction
- Electric charge & size (Correct answer)
- Thermal expansion
- Magnetic pull
Correct answer: Electric charge & size
Electrophoresis is a powerful laboratory technique that separates molecules, such as proteins or nucleic acids, based on their physical properties. The principle relies on applying an electric field across a gel matrix, causing charged molecules to migrate. The rate and direction of migration are determined by the molecule's net electric charge, size, and shape, allowing for effective separation and analysis.
Question 6: What is used as a blank in spectrophotometry?
- Water with analyte
- Standard solution
- Reagent without analyte (Correct answer)
- Air
Correct answer: Reagent without analyte
In spectrophotometry, a blank is used to set the baseline or zero absorbance for the measurement. It typically contains all reagents used in the assay, including the solvent, but *without* the analyte of interest. By measuring the blank, any background absorbance contributed by the reagents or the cuvette itself is subtracted from the sample readings, ensuring that only the absorbance due to the analyte is measured accurately.
Question 7: What can affect the accuracy of photometric readings?
- Low humidity
- Scratched cuvette (Correct answer)
- Green light
- Wavelength settings
Correct answer: Scratched cuvette
A scratched cuvette can significantly affect the accuracy of photometric readings by interfering with the path of light through the sample. Scratches on the cuvette's surface can scatter or absorb light, leading to an erroneous increase or decrease in the measured absorbance. This distortion of light transmission results in inaccurate absorbance values, which in turn leads to incorrect concentration determinations for the analyte.
Question 8: Which analytical method is commonly used to detect drugs?
- Flow cytometry
- PCR
- Gas chromatography (Correct answer)
- Coulometry
Correct answer: Gas chromatography
Gas chromatography (GC) is a powerful analytical method commonly used to separate and detect volatile or semi-volatile compounds in a sample. Its high sensitivity and ability to separate complex mixtures make it ideal for drug screening, identification, and quantification in biological specimens. GC is frequently coupled with mass spectrometry (GC-MS) for definitive identification of drugs and their metabolites.
Question 9: What does Beer's Law relate?
- Mass to speed
- Color to pH
- Absorbance to concentration (Correct answer)
- Volume to temperature
Correct answer: Absorbance to concentration
Beer's Law, also known as the Beer-Lambert Law, is a fundamental principle in spectrophotometry that describes the relationship between the absorbance of light by a solution and the properties of the solution. Specifically, it states that the absorbance of a solution is directly proportional to the concentration of the absorbing analyte and the path length of the light through the solution. This relationship allows for the quantitative determination of analyte concentrations based on their light absorption.
Free AACC Analytical Techniques Questions and Answers
What is spectrophotometry used for in clinical chemistry?