Lecture 01, 2

• What are the four methods for quantitative analysis of a substance?

  External calibration, internal calibration, standard addition, normalisation
• What is the primary goal of chemical analysis?

  To identify a compound and quantify it
• How is quantitative analysis defined in analytical chemistry?

  Determination of abundance of substances in a sample
• How can concentration be expressed in quantitative analysis?

  Molar, ppm, mol/dm³, mol/L
• What hormone does a pregnancy test detect?

  Human chorionic gonadotrophin (HCG)
• When is HCG secreted in the body?

  After the fertilised egg implants in the uterus
• What is the analyte in blood glucose monitoring?

  Glucose
• What type of reaction occurs in blood glucose monitoring?

  A redox reaction
• What is used to quantify analytes in a sample?

  Response signal from the instrument
• What is the most common method for quantifying analytes?

  Calibration
• What is an external standard in quantitative analysis?

  A reference substance of the compound
• How are standard solutions prepared in the external standard method?


  Separately from the sample solutions
• What happens to peak area as concentration of standard increases?

  Peak area increases
• What does R² indicate in a calibration curve?

  How close points are to the line of best fit
• What is the role of the BP in pharmacopoeia testing?

  Provides quality standards for pharmaceutical substances
• What is a one-point calibration used for?

  Testing for purity of an API
• What is a key advantage of the external calibration method?

  Easy to prepare and interpret
• What is a disadvantage of the external calibration method?

  Matrix interferences can affect results
• What does the internal standard method compensate for?

  Analytical errors due to sample losses
• What is added to solutions in the internal standard method?

  A compound at a known concentration
• How is the internal standard method different from the external standard method?

  Uses peak area or height ratio for calibration
• What should an internal standard ideally do?

  Be recovered similarly to the analyte
• What can cause injection issues in quantitative analysis?

  Variability in the amount injected
• What is the advantage of using internal standards?

  Improves precision from sample preparation errors
• What is a disadvantage of the internal standard method?

  Need to choose an appropriate internal standard
• What are the key differences between external and internal standard methods?

  • External standard:
  • Reference substance prepared separately
  • Uses absolute values for calibration
  • Internal standard:
  • Reference substance added to all solutions
  • Uses peak area or height ratio for calibration
• What are the steps involved in quantifying titrations?

  1. Monitor colour change
  2. Add base to acid for reaction
  3. Measure endpoint to determine concentration
• What are the steps involved in quantifying chromatography?

  1. Identify peaks representing molecules
  2. Ensure narrow peaks for accuracy
  3. Use reference standard for comparison
• What are the challenges in internal standard calibration with complex samples?

  • Salts can precipitate and block columns
  • Need for solid-phase extraction to isolate analyte
  • Losses during sample preparation affect results
• What is the relationship between peak area and concentration in chromatography?

  • Peak area is directly related to analyte concentration
  • Equation: A = kVC
  • V is constant for HPLC, variable for GC