IV. ANALYTICAL TECHNIQUES

8. Special Techniques (NMR, CE, SPME-GC, GC-FTIR)

GC-IRD

  1. What are the calibration and maintenance procedures for the GC-IRD?
  2. What is the sample compartment for the detector on the GC-IRD called?
  3. What are three differences between condensed and vapor phase?

GC/FT-IR DETECTOR

  1. What type of infrared detector must be used in GC-FT-IR instruments?
  2. Why is this type of detector used?
  3. Why must the detector be filled with liquid nitrogen before use?
  4. Describe the function and construction of the IRD’s “light-pipe”.
  5. What is one primary advantage that GC-IRD has over GC-MS?

CE

  1. Why did CE gain popularity in the 1990’s
  2. Why are the number of theoretical plates in CE so much higher than the number of plates obtained in HPLC?
  3. What are some of the advantages/disadvantages of using CE?
  4. What are capillaries usually composed of?
  5. What type of detector is used on most commercial CE’s?
  6. What are the typical limits of detection?
  7. Other than UV, what other detectors can be used in conjunction with CE?
  8. What is meant by electroosmotic flow?
  9. Why is it important to use narrow capillaries?
  10. Why is “migration time” used instead of “retention time”?
  11. What is free zone capillary electrophoresis?
  12. What is micellar electrokinetic capillary chromatography?
  13. Why would a capillary be coated with polyacrylamide?
  14. What is capillary electrochromatography?
  15. What are the advantages of using dynamically coated capillaries over uncoated capillaries?
  16. What is a cyclodextrin?
  17. According to your standard operating procedures, how often should a CE be checked?
  18. How often should the inlet and outlet seals be checked?
  19. How often should a diode array performance test be performed?
  20. Describe the procedures for cleaning the electrodes.
  21. Why is it necessary to make sure that the inside of the electrodes are dry before returning them to the instrument?
  22. What is the proper procedure for cleaning the alignment interface?
  23. What three parts make up the detection system?
  24. What is electrophoresis?
  25. From a practical point of view, what component will affect the most dramatic change in EOF?
  26. What is Joule heating?
  27. What methods are available to limit Joule heating?
  28. What does the term “stacking” mean?
  29. In Capillary Zone Electrophoresis (CZE or Free Solution) CE what do separations rely on?
  30. What is MECC and what is its main strength?
  31. Is the cathode positively or negatively charged?
  32. List and describe the two types of injections that are possible with CE.
  33. What factors contribute to migration time reproducibility?
  34. What might cause a capillary electrophoresis instrument to exhibit a noisy baseline?
  35. Is it possible to determine chirality using CE? If so, how?
  36. Are cyclodextrins used in conjunction with dynamically coated capillaries or uncoated capillaries?
  37. For the following solutes, heroin, amphetamine, methamphetamine and cocaine, in descending order, what is the order of mobility? (Specify the CE mode used).

NMR

  1. Define the following terms: chemical shift, spin-spin coupling constant.
  2. What are some important sample preparation techniques needed to obtain a “clean” NMR spectrum?
  3. Why are deuterated solvents used in NMR?
  4. What does locking the NMR spectrometer mean?
  5. NMR Theory: Sketch the magnetization vector of the nuclei in relation to the magnetic field for each stage of an NMR experiment listed :
  6. The sample is in the probe before the pulse,
  7. Application of a 90 degree pulse,
  8. After the 90 degree pulse (time of precession),
  9. After the 90 degree pulse during T1 relaxation (spin-lattice).
  10. Why is a 45 second relaxation delay used for quantitation experiments?
  11. What does the position of a peak in an NMR spectrum indicate?

QUANTITATION

  1. Define the following terms: Limit of quantitation (LOQ), Limit of Detection (LOD)
  2. Is it advisable to “force the line through the origin” when performing linear regression? (Why or why not?
  3. Describe the preparation of samples and standards used in quantitative analysis?
  4. Describe the term “linearity”.
  5. What is a linear regression analysis, and how is it performed on a set of quantitative data?
  6. Describe the external standard approach to quantitative analysis. How is the sample purity calculated by this approach?
  7. Describe the internal standard approach to quantitative analysis. How is the sample purity calculated by this approach?
  8. What is the main advantage of using an internal standard method for quantitative analysis?
  9. What are the selection criteria for an internal standard?
  10. Perform a least-squares linear regression on the following set of quantitative GC data:
    • Concentration (mg/mL) Area Analyte (pA-sec) Area Istd (pA-sec)
      2.048 497.32 218.23
      1.434 357.5 216.52
      1.024 258.09 225.97
      0.7168 179.96 230.81
      0.512 123.87 222.98
      0.2048 48.28 215.55
  11. What are the slope, intercept and correlation coefficient?
  12. How is a multi-point calibration used in a quantitative analysis?
  13. What are some concerns associated with the use of a single-point calibration for quantitative analysis? How may these concerns be addressed?
  14. A sample of cocaine base is quantitated using a standard of cocaine hydrochloride. What is the correction factor that must be applied to the purity calculation to report as cocaine base? How is this factor determined?
  15. Explain the term “recovery” as it relates to a quantitative analysis.
  16. What is a surrogate standard?
  17. How is a surrogate standard different from an internal standard? How are the two standards similar?

Last Update June 2018

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