Extraction and detection of active principles is a core topic for B. Pharm students focusing on isolating and analyzing bioactive compounds from natural and formulated sources. This introduction covers solvent extraction approaches (maceration, percolation, Soxhlet, ultrasonic and microwave-assisted extraction), solvent selection based on polarity, sample preparation, partitioning and concentration of phytochemicals. It also addresses detection and identification techniques including TLC, HPLC, GC, UV-Vis, IR and mass spectrometry, along with method validation parameters such as specificity, accuracy, precision, LOD and LOQ. Practical aspects of assay development, derivatization and quality control for herbal drugs are emphasized. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which definition best describes an “active principle” in pharmaceutical and herbal analysis?
- A non-therapeutic impurity present in a drug
- A solvent used to extract plant material
- The bioactive compound responsible for a therapeutic effect
- A preservative added to formulations
Correct Answer: The bioactive compound responsible for a therapeutic effect
Q2. Which extraction method is most suitable for continuous hot extraction of a solid sample with a non-volatile solvent?
- Cold maceration
- Soxhlet extraction
- Steam distillation
- Percolation at room temperature
Correct Answer: Soxhlet extraction
Q3. Which factor is most important when selecting a solvent for extracting polar phytochemicals?
- Low boiling point only
- Solvent polarity matching analyte polarity
- Color of the solvent
- Cost irrespective of polarity
Correct Answer: Solvent polarity matching analyte polarity
Q4. Which technique provides a rapid qualitative separation of components in a plant extract using a stationary phase on glass plates?
- HPLC
- TLC
- GC-MS
- Spectrophotometry
Correct Answer: TLC
Q5. Which detection technique directly provides molecular mass information useful for identification of active principles?
- UV-Vis spectrophotometry
- Infrared spectroscopy
- Mass spectrometry (MS)
- TLC visual comparison
Correct Answer: Mass spectrometry (MS)
Q6. What is the main advantage of microwave-assisted extraction (MAE) over conventional maceration?
- Longer extraction time
- Reduced extraction efficiency
- Faster extraction and improved yield
- Requires larger solvent volumes
Correct Answer: Faster extraction and improved yield
Q7. In liquid-liquid extraction, what determines the distribution of an analyte between two immiscible solvents?
- Analyte’s partition coefficient (K)
- Color of solvents
- Amount of glassware used
- Evaporation rate only
Correct Answer: Analyte’s partition coefficient (K)
Q8. Which HPLC detector is most suitable for general quantitation of compounds with chromophores?
- Refractive index detector
- Evaporative light scattering detector
- UV-Vis diode array detector
- Flame ionization detector
Correct Answer: UV-Vis diode array detector
Q9. Which sample preparation step helps remove proteins and large particulates before chromatographic analysis?
- Lyophilization without filtration
- Centrifugation and filtration
- Adding colorant
- Heating to dryness
Correct Answer: Centrifugation and filtration
Q10. Which chromatographic technique requires analytes to be volatile or derivatized to volatile forms?
- HPLC
- GC (Gas Chromatography)
- TLC
- Ion-exchange chromatography
Correct Answer: GC (Gas Chromatography)
Q11. Which parameter assesses the smallest concentration of analyte that can be reliably quantified with acceptable accuracy and precision?
- LOD (Limit of Detection)
- Calibration range
- LOQ (Limit of Quantification)
- System suitability
Correct Answer: LOQ (Limit of Quantification)
Q12. What is the principal role of derivatization in GC analysis of active principles?
- To increase analyte polarity only
- To make non-volatile or thermally labile compounds volatile and stable
- To change detector settings
- To separate solvents
Correct Answer: To make non-volatile or thermally labile compounds volatile and stable
Q13. Which solvent system is generally preferred for extracting non-polar lipophilic constituents such as essential oils and waxes?
- Water
- Methanol
- Hexane or petroleum ether
- Ethanol-water (50:50)
Correct Answer: Hexane or petroleum ether
Q14. Which validation parameter evaluates the closeness of measured values to the true value?
- Precision
- Specificity
- Accuracy
- Robustness
Correct Answer: Accuracy
Q15. Which spectroscopic technique is most informative for identifying functional groups in an isolated active principle?
- UV-Vis spectrophotometry
- Infrared (IR) spectroscopy
- Fluorescence spectroscopy
- Refractometry
Correct Answer: Infrared (IR) spectroscopy
Q16. During Soxhlet extraction, what happens to the solvent in each cycle?
- It is consumed by reaction
- It evaporates, condenses and percolates through the sample repeatedly
- It polymerizes
- It solidifies on the sample
Correct Answer: It evaporates, condenses and percolates through the sample repeatedly
Q17. Which TLC visualization technique is useful for detecting terpenoids and phenolic compounds after chromatographic development?
- UV light only
- Spraying with anisaldehyde or vanillin reagent and heating
- Direct weighing of the plate
- Using pH paper
Correct Answer: Spraying with anisaldehyde or vanillin reagent and heating
Q18. Which factor does NOT directly affect extraction yield of active principles?
- Particle size of the sample
- Extraction time and temperature
- Solvent-to-sample ratio
- Color of the extraction vessel
Correct Answer: Color of the extraction vessel
Q19. What is the main purpose of method specificity in analytical validation?
- To ensure the method gives the same result regardless of instrument
- To confirm the method measures the analyte of interest in presence of other components
- To speed up the analysis time
- To reduce solvent consumption
Correct Answer: To confirm the method measures the analyte of interest in presence of other components
Q20. Which mobile phase change is commonly used in HPLC to improve separation of a complex plant extract?
- Isocratic elution only
- Gradient elution increasing organic modifier
- Switching to gaseous mobile phase
- Eliminating buffer completely
Correct Answer: Gradient elution increasing organic modifier
Q21. Which pre-treatment is recommended to prevent enzymatic degradation of active principles in fresh plant material prior to extraction?
- Immediate freezing or drying
- Leaving at room temperature for hours
- Mixing with sugary syrups
- Exposure to sunlight
Correct Answer: Immediate freezing or drying
Q22. Which parameter describes repeatability of an analytical method under the same conditions over a short time?
- Accuracy
- Precision (repeatability)
- Specificity
- LOD
Correct Answer: Precision (repeatability)
Q23. Which solvent is commonly used as a universal extractant for a wide range of polar and semi-polar phytochemicals?
- n-Hexane
- Methanol or ethanol
- Carbon tetrachloride
- Diethyl ether exclusively
Correct Answer: Methanol or ethanol
Q24. Which technique couples chromatographic separation with mass spectral detection for structural elucidation?
- HPLC-UV
- TLC with visible detection
- GC-MS or LC-MS
- Simple distillation
Correct Answer: GC-MS or LC-MS
Q25. In preparing a calibration curve for quantitation, what is the most important requirement?
- Random concentration points without replicates
- Known standards covering the expected concentration range with replicates
- Using unknown samples only
- Using a single concentration standard
Correct Answer: Known standards covering the expected concentration range with replicates
Q26. Which extraction approach uses high-frequency sound waves to disrupt plant cell walls and improve release of active compounds?
- Maceration
- Ultrasonic-assisted extraction (sonication)
- Steam distillation
- Cold pressing
Correct Answer: Ultrasonic-assisted extraction (sonication)
Q27. Which parameter is assessed by injecting a standard multiple times prior to analysis to ensure consistent chromatographic performance?
- Limit of detection
- System suitability
- Solvent purity
- Sample homogeneity only
Correct Answer: System suitability
Q28. Which practice helps avoid loss of volatile active principles during concentration of extracts?
- Evaporating at high temperature without control
- Using rotary evaporation under reduced pressure at low temperature
- Leaving solvent to evaporate in open sun
- Boiling strongly on a hot plate
Correct Answer: Using rotary evaporation under reduced pressure at low temperature
Q29. Which test is part of preliminary phytochemical screening to detect the presence of alkaloids?
- Benedict’s test
- Mayer’s or Dragendorff’s reagent test
- Biuret test
- Molisch’s test
Correct Answer: Mayer’s or Dragendorff’s reagent test
Q30. Which statement best describes “standardization” of an herbal extract?
- Adjusting the extract color to match a reference
- Ensuring consistent content of one or more marker active principles and defined quality attributes
- Adding synthetic drugs to enhance potency
- Diluting to an arbitrary concentration
Correct Answer: Ensuring consistent content of one or more marker active principles and defined quality attributes
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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