HPLC SAMPLES AND SAMPLE PREPARATION TECHNIQUES

“Bad chromatography almost always starts with bad samples.”

HPLC SAMPLES AND SAMPLE PREPARATION TECHNIQUES

CONTENT OVERVIEW

1. Introduction to market-relevant matrices
   • Food & feed, environmental, pharmaceutical, biological, botanicals
   • Matrix complexity, interference, analyte stability
2. Sample collection, storage & integrity
   • Simulated chain-of-custody exercises
   • Digital lab notebooks for sample tracking
3. Matrix complexity ranking (low to extreme)
   • Solvent standards
   • Pharmaceutical tablets
   • Clean water
   • Plant extracts
   • High-fat foods/biological samples
4. Fundamental principles of sample preparation
   • Why sample preparation is necessary
   • Removal of interferents
   • Protection of column and detector
   • Improvement of selectivity and sensitivity
   • Reduction of matrix effects (especially for LC-MS)
5. Sample Preparation Objectives

   Each preparation step should answer at least one of the following:

   • Is the analyte being isolated?
   • Is the matrix being simplified?
   • Is the analyte being concentrated or stabilized?
   • Is the final solvent HPLC-compatible?
6. Key analyte properties guiding sample prep
   • Polarity and logP
   • pKa and ionization behavior
   • Solubility and stability
   • UV/fluorescence activity
   • Susceptibility to degradation (heat, light, oxygen)
7. Sampling, handling, and storage (ISO 17025 context)
   • Sampling Considerations – representativeness, homogeneity, cross-contamination, sample size
8. Sample handling and preservation
   • Temperature control (refrigeration vs freezing)
   • Light-sensitive analytes
   • Oxidation-prone compounds
   • Use (and misuse) of preservatives
9. ISO 17025 requirements
   • Sample identification and labeling
   • Chain of custody
   • Sample acceptance criteria
   • Sample rejection and deviation documentation
   • (case study: sample rejection decision)
10. Physical sample preparation techniques
    • Homogenization and size reduction – grinding, milling, blending
    • Importance of particle size uniformity
    • Risks: heat generation, analyte loss
11. Filtration and clarification
    • Syringe filters vs vacuum filtration
    • Filter materials (PTFE, nylon, PVDF)
    • Pore size selection
    • Adsorption losses
12. Centrifugation
    • Phase separation
    • Protein precipitation support
    • Matrix clarification prior to injection
    • (Virtual demo: impact of filtration on chromatograms)
13. Solvent-based extraction techniques
    • Simple dilution and “dilute-and-shoot” – when it works, when it fails
    • Detector limitations (UV vs MS)
14. Liquid–Liquid Extraction (LLE)
    • Partition coefficient concept
    • Solvent selection strategies
    • pH adjustment to control ionization
    • Advantages and limitations
    • Typical applications: environmental water samples, biological fluids, non-polar analytes
15. QuEChERS and Salting-Out Extraction
    • Principle and workflow
    • Role of buffering salts
    • d-SPE clean-up options
    • Suitability for food, feed, botanical matrices
    • (Online workflow simulation)
16. SOLID-PHASE EXTRACTION (SPE)
    • SPE Fundamentals
      • Retention mechanisms: Reversed phase, Normal phase, Ion exchange, Mixed mode
      • Comparison with LLE
    • SPE Method Development Strategy
      • Sorbent selection
      • Conditioning, loading, washing, elution
      • Solvent strength and selectivity
    • SPE for Different Matrices
      • Food extracts
      • Environmental waters
      • Biological samples
      • Pharmaceutical formulations
    • Online SPE and Column Switching (Conceptual)
      • Advantages of on-line cleanup
      • Automation and reproducibility
    • (Virtual SPE method optimization exercise)
17. SAMPLE PREPARATION FOR BIOLOGICAL MATRICES
    • Biological Matrix Challenges: Proteins, phospholipids, salts; matrix effects and ion suppression
    • Protein Precipitation: Solvent selection (ACN, MeOH); advantages and limitations
    • SPE and LLE in Bioanalysis: Cleanup efficiency, recovery vs reproducibility trade-offs
    • Matrix-Matched Calibration: Why it matters, when it is mandatory
18. DERIVATIZATION IN HPLC
    • Why Derivatize? Improve detectability, enhance selectivity, improve chromatographic behavior
    • Pre-Column vs Post-Column Derivatization: Advantages and risks, stability and reproducibility issues
    • ISO 17025 Considerations: Method validation implications, reagent stability and traceability
19. SAMPLE PREPARATION QUALITY CONTROL
    • Blanks and Controls: Reagent blanks, procedural blanks, matrix blanks
    • Recovery and Trueness: Spiking strategies, acceptable recovery ranges, bias identification
    • Internal and Surrogate Standards: Selection criteria, monitoring extraction efficiency
    • Documentation and Traceability: SOP compliance, deviations and corrective actions
20. COMMON SAMPLE PREPARATION FAILURES & TROUBLESHOOTING
    • Symptoms Seen in Chromatograms: Ghost peaks, broad or split peaks, rapid column degradation, poor reproducibility
    • Root Cause Analysis: Matrix contamination, incompatible solvents, inadequate cleanup, sample instability
    • (Interactive troubleshooting cases)