Chromatography Practice Test

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• Which statement about gradient elution is false?
• Why might isotopically labeled internal standards be preferred over structural analogs for LC-MS quantitation?
• Which strategy primarily increases chromatographic efficiency?
• What is gradient time and re-equilibration, and why are they important for reproducibility in gradient elution?
• What is the effect of using an end-capped column on tailing?
• Chromatography aims to
• If t_R = 4.0 minutes and t_M = 1.0 minute in an HPLC run, what is the retention factor k' and what is the typical desirable range for k' in HPLC?
• In reversed-phase HPLC, how does pH influence the retention of ionizable analytes?
• Can an Rf value be exactly 0?
• Which metric is used to quantify peak separation in a chromatogram?
• Which detector provides structural information and high sensitivity?
• Which statement best describes how temperature affects chromatographic separation?
• What happens if the solvent is too polar?
• Baseline separation means peaks are completely separated at baseline; broader peaks or tailing affect resolution.
• What does a smaller Rf value indicate?
• Why is column equilibration with mobile phase important before sample injection?
• Which practice helps reduce tailing due to silanol interactions?
• Which statement best describes gradient elution in liquid chromatography?
• In normal-phase TLC, the retention factor (Rf) is best described as:
• Which statement about TLC Rf values is true?
• Why is silica gel considered polar?
• What is orthogonal analysis in chromatography method development and why is it beneficial?
• How is the limit of detection (LOD) defined via signal-to-noise?
• Which statement best describes polar vs nonpolar behavior on silica gel?
• What is the trade-off when increasing column length in LC?
• Which of the following is a common stationary phase for TLC?
• What is headspace sampling, and when is it advantageous?
• What property primarily determines the speed of migration in normal-phase TLC?
• Which statement correctly describes normal-phase chromatography (NPC) and reversed-phase chromatography (RPC) in terms of stationary/mobile phases and the retention of nonpolar analytes?
• What is the purpose of a guard column and when should it be used?
• What role does a mass spectrometer play in LC-MS, and what information does it provide?
• Which statement about the height of a theoretical plate H is true?
• The pigments separated by Tsvet are primarily involved in which biological process?
• Define robustness in method validation and provide an example.
• How does end-capping of silica columns influence peak tailing and peak symmetry?
• On a polar silica gel stationary phase, which type of compound is expected to elute fastest under typical conditions described?
• How do you compute chromatographic resolution Rs for two adjacent peaks, and what Rs value indicates baseline separation?
• What factors influence selectivity in liquid chromatography, and how can pH and ionic strength be used to adjust it?
• What does N represent in chromatography and how is the height of a theoretical plate defined?
• What are common sample preparation approaches before chromatographic analysis for trace-level analysis?
• Baseline drift in chromatography is caused by which factors, and how can it be mitigated?
• What is the main purpose of column chromatography?
• If a TLC plate shows multiple spots, what does this indicate about the mixture?
• What is a primary reason for using internal standards in LC-MS quantitation?
• Which pigments did Tsvet separate?
• How does size-exclusion chromatography differentiate molecules, and what is meant by the void volume?
• In chromatography, how is the limit of detection (LOD) defined and typically estimated?
• Isotopically labeled internal standards are used in LC-MS to mitigate matrix effects because:
• Which of the following is a common strategy to achieve chiral separation if a chiral column is not available?
• How do you determine the dead time experimentally in LC?
• What is the baseline in TLC?
• In normal-phase TLC, which compounds move slowest?
• Describe a strategy to resolve co-eluting compounds when orthogonal separation is not feasible?
• Why are residuals important when evaluating a calibration curve?
• In system suitability testing, what does a spike injection verify?
• How is TLC used with column chromatography?
• What is a common consequence of using too high a flow rate in chromatography?
• What is peak symmetry and why is it important for integration accuracy?
• What is a chromatographic baseline, and how can drift arise?
• What is the purpose of buffering mobile phases in HPLC, and how does pH control influence retention?
• Which statement best describes the principle behind chromatography as used by Tsvet?
• What adsorbent did Tsvet use in his original experiment?
• If a compound interacts strongly with the stationary phase, it will elute:
• What happens if the mobile phase pH is near the silica pKa during a run?
• A chromatographic peak has t_R = 6.0 min and baseline width W_0.5 = 0.5 min. Using N = 5.54 (t_R/W_0.5)^2, what is the theoretical plate number N?
• Why can a chiral stationary phase separate enantiomers, and what are typical strategies to achieve this?
• How do FID and ECD detectors differ in principle and selectivity in GC?
• In GC, why is the choice of carrier gas important, and what are typical options?
• What does TLC stand for?
• In GC, which statement about carrier gas properties best reflects typical practice?
• Which statement best describes when gradient elution should be used relative to isocratic?
• Why is split injection used in gas chromatography, and what is its typical impact on sensitivity and quantitation?
• What is the purpose of mobile phase pH control in reverse-phase HPLC of acidic or basic analytes?
• Which compounds generally have the highest Rf values on silica gel TLC?
• What is a typical application area for 2D-LC?
• In environmental analysis, chromatography is used to?
• What is the role of the column oven in modern HPLC?
• Why was Tsvet's work initially overlooked?
• Which statement about detector response factor usage in multi-analyte quantitation is true?
• In what scenario is planar chromatography particularly useful?
• Which compound is commonly used as an unretained marker to determine the dead time tM in LC on a C18 column?
• Which statement describes the stationary phase in TLC as accurate?
• What is size-exclusion chromatography and what determines separation in SEC?
• In normal-phase TLC, which statement best describes the stationary phase?
• What is the stationary phase in column chromatography?
• What are the two phases in chromatography?
• What feature of silica gel drives its polarity?
• What is chromatographic selectivity and how can you experimentally improve it?
• Which statement correctly distinguishes partition chromatography from adsorption chromatography, with appropriate examples?
• What is the fundamental difference between theoretical plates and real plate number in chromatography?
• Which component is responsible for introducing the sample into the flow stream in an HPLC system?
• In Rf calculation, which distance is the numerator?
• Define ruggedness in method validation and explain how it is assessed.
• Distinguish between LOD and LOQ and typical criteria for their determination.
• In forensic science, chromatography is used to?
• What is TLC mainly used for?
• What does a retention time tell you in chromatography?
• What outcome on TLC suggests a pure compound?
• Explain the meaning of the term 'theoretical plates' and its significance in chromatography column performance.
• Split injection in GC: what must be done to determine true concentration when a split ratio is used?
• Which detector is universal but typically less sensitive than mass spectrometry?
• Which scenario favors using isocratic elution?
• What is dead time t_M and how is it measured?
• Which statement about the baseline in TLC is true?
• What is a detector response factor and how is it used in quantitation with multiple analytes?
• What is the effect of increasing column temperature on viscosity and retention time?
• What are the three main purposes of chromatography?
• Which statement about k' (capacity factor) is true?
• In chromatography, why might isocratic elution be inadequate for analyzing analytes with wide polarity ranges?
• Why should a good internal standard not co-elute with analytes?
• For typical adjacent peaks, a common target Rs value for baseline separation is greater than?
• What happens to compounds that interact strongly with the stationary phase?
• In GC, what is the relationship between selectivity and efficiency, and how does column chemistry influence each?
• Which statement best describes the primary purpose of column chromatography?
• In the van Deemter equation, what does the A term (eddy diffusion) represent?
• What is the mobile phase in column chromatography?
• How does column temperature affect retention and peak shapes in LC?
• Explain tailing factor and how it affects quantitation and resolution. What causes tailing?
• In chromatography, what is retention time t_R?
• What factors influence mass spectrometric detection in LC-MS, particularly ionization methods like ESI vs APCI?
• Why use isotopically labeled internal standards in LC-MS quantitation?
• In thin-layer chromatography, what does the Rf value represent, and how is it used?
• How is the capacity factor k' calculated?
• Two compounds with similar polarity on a normal-phase plate will have migration that is:
• A compound that moves far up the plate is typically:
• Define injection solvent effect.
• Which year did Mihail Tsvet invent chromatography?
• How far above the bottom edge of a TLC plate is the baseline drawn?
• In LC chromatography, what is a ghost peak and what are common causes?
• In LC-MS analysis, what are matrix effects and how can they be mitigated?
• In normal-phase TLC, how does polarity relate to Rf?
• Describe retention mechanism in ion-exchange chromatography and how pH and counterions influence it.
• What tool is used to spot samples on a TLC plate?
• In HPLC, what is the effect of increasing the mobile-phase flow rate on column efficiency and analysis time?
• How should a chromatogram with a blank, a standard, and a sample spike be interpreted for system suitability?
• How can TLC spots be visualized?
• Which of the following is a primary use of thin-layer chromatography?
• How can sample preparation affect chromatographic outcomes, including recovery and interference?
• Which strategy would generally help separate a pair of polar solutes on a normal-phase TLC plate?
• Which application area is correctly paired with chromatography?
• What is gradient elution in HPLC, and when is it preferred over isocratic elution?
• What type of chromatography did Tsvet develop?
• Which elution mode is typically more suitable for analytes with wide polarity range and why?
• To improve separation of polar compounds on normal-phase TLC, which mobile phase choice is typically used?
• Headspace sampling is typically used for analyzing which type of analytes?
• In the van Deemter equation, what does H denote?
• How does a polar compound behave in column chromatography?
• What is the linear dynamic range of a detector, and why is it important for quantitation?
• TLC can be used to monitor what in relation to reactions?
• What is the stationary phase?
• Compare the retention mechanisms of reversed-phase and ion-exchange chromatography.
• Explain detector saturation and when it becomes a concern in quantitative LC-UV methods.
• Define LOD and LOQ and explain how they differ from calibration range.
• Define the selectivity factor α and its role in peak separation.
• Which factors determine the choice of carrier gas in gas chromatography, and what are the typical characteristics of common carrier gases?
• What are planar chromatography techniques and give two common examples?
• What role do pH and salt play in ion-exchange chromatography elution?
• Outline a basic gradient optimization approach using two solutes to maximize resolution.
• What factors contribute to peak tailing in LC and how can tailing be mitigated?
• What constitutes acceptable linearity in a calibration curve for chromatography?
• Why do silanol groups on silica columns cause tailing for basic compounds, and how can this be mitigated?
• What is affinity chromatography and when is it advantageous?
• If the stationary phase is polar and the mobile phase is nonpolar, what description fits the expected migration of nonpolar solutes compared to polar solutes under the same conditions?
• Between hexane and acetone under the same conditions, which tends to have a higher Rf on a normal-phase plate?
• The mobile phase is described as:
• Which statement correctly defines the selectivity factor alpha and its effect on resolution Rs?
• In normal-phase TLC, which compounds move fastest up the plate?
• In reversed-phase HPLC, nonionized forms of ionizable solutes are typically more hydrophobic and show what behavior?
• If a compound is highly polar, what is the expected effect on its Rf on silica gel TLC?
• In ion-exchange chromatography, what factors govern the binding and elution of analytes?
• How does gradient elution affect run time and re-equilibration requirements compared to isocratic?
• If two adjacent peaks exhibit Rs of 2.0, what does this indicate?
• What is split ratio and how does it affect sensitivity and sample consumption?
• Why do compounds separate during chromatography?
• Why are internal standards used in chromatographic quantitation, and what properties should a good internal standard have?
• Where should the solvent level be relative to the baseline in TLC development?
• How does increasing column length impact resolution and backpressure in LC?
• What is the stationary phase in TLC?
• Which parameter is inversely related to peak broadening and related to the plate count?
• Which parameter is typically varied to test robustness?
• In HPLC method development, what is the typical approach to mobile phase pH for ionizable compounds, and what are the implications for retention and peak shape?
• Explain method transfer between laboratories and key considerations.
• In chromatography, which statement about the mobile phase is correct?
• In what year was the term chromatography first used?
• In food testing, chromatography is used to?
• Which statement about the mobile phase is correct?
• What is the fundamental difference between partition chromatography and adsorption chromatography?
• What happens to compounds that interact weakly with the stationary phase?
• Which statement best describes the effect of increasing the number of theoretical plates on chromatographic peaks?
• Is column chromatography generally fast or slow?
• Which statement best differentiates LOQ from LOD in quantitative chromatography?
• Can an Rf value be greater than 1?
• In pharmaceuticals, chromatography is used to?
• If the mobile phase becomes more polar, polar compounds typically move ?
• State the van Deemter equation and briefly describe each term.
• Which of the following correctly represents the Van Deemter equation and what each term represents?
• In affinity chromatography, provide a typical ligand-target pair used in practice.
• What is chromatography?
• What mainly governs separation in normal-phase TLC?
• What is the formula for resolution Rs between two peaks and what does a higher Rs indicate?
• How can TLC determine purity?
• What is affinity chromatography and provide an example of a ligand-target pair exploited in this technique.
• Which observation indicates detector saturation during a chromatographic run?
• What is an internal standard (IS) and external standard method in quantitative chromatography? Give advantages of IS approach.
• Explain accuracy, precision, and bias in method validation.
• Which statement accurately describes the mobile phase in column chromatography?
• Which compounds generally have the lowest Rf values on silica gel TLC?
• How does a nonpolar compound behave in column chromatography?
• What does a larger Rf value indicate?
• In gradient LC, peak capacity is estimated from gradient time and which parameter?
• Which major chromatographic mode is correctly paired with its primary separation principle?
• What does Rf stand for?
• Explain the difference between normal-phase and reversed-phase chromatography.
• Describe GC vs GC-MS detectors and typical analyte classes for each.
• The limited early recognition of Tsvet's chromatography work was due to which factors?
• How is the number of theoretical plates N calculated from a chromatographic peak?
• When should TLC development be stopped?
• What is the formula for Rf?
• What is the mobile phase in TLC?
• Which GC detector is a universal detector for organic compounds?
• In reversed-phase HPLC, what best describes the distribution of solutes?
• What is a typical guideline for injection volume optimization in HPLC?
• What is back pressure in LC, and which factors influence it?
• How can TLC identify the number of compounds in a mixture?
• How can you recognize injection overload or detector saturation in a chromatogram?
• Which statement about chromatography is true?
• Why should TLC samples not be too concentrated?
• The stationary phase is described as:
• If polar compounds remain near baseline while nonpolar travel far, what does this indicate about the stationary phase?
• Which description correctly identifies the TLC stationary phase used in the standard setup described?
• What is robustness in method validation, and how is it tested?
• What is two-dimensional LC (2D-LC) and in what scenarios is it typically employed?
• What best describes carryover in chromatography and how is it minimized?
• Which statement best describes how diffusion affects peak broadening in chromatography?