“Bad chromatography almost always starts with bad samples.”
TARGET AUDIENCE
- Analytical chemists in food, feed, environmental, pharmaceutical, and biological sectors
- Quality managers, regulatory lab personnel, postgraduate students
HPLC SAMPLES AND SAMPLE PREPARATION TECHNIQUES
LEARNING OUTCOMES
- Classify samples by matrix complexity and analytical risk
- Select preparation strategies aligned to analyte chemistry and detection
- Design ISO 17025-defensible sample preparation workflows
CONTENT OVERVIEW
What Is an HPLC Sample?
- Definition: “sample” vs “test portion” vs “test solution”
- Relationship between:
- Original matrix
- Prepared extract
- Injected solution
- Why HPLC is less forgiving than GC to dirty samples — matrix burden, column sensitivity, detector interference
- Introduction to market-relevant matrices
- Food & feed, environmental, pharmaceutical, biological, botanicals
- Matrix complexity, interference, analyte stability
- Sample collection, storage & integrity
- Simulated chain-of-custody exercises
- Digital lab notebooks for sample tracking
- Matrix complexity ranking (low to extreme)
- Solvent standards
- Pharmaceutical tablets
- Clean water
- Plant extracts
- High-fat foods/biological samples
- 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)
- 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?
- 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)
- Sampling, handling, and storage (ISO 17025 context)
- Sampling Considerations – representativeness, homogeneity, cross-contamination, sample size
- Sample handling and preservation
- Temperature control (refrigeration vs freezing)
- Light-sensitive analytes
- Oxidation-prone compounds
- Use (and misuse) of preservatives
- ISO 17025 requirements
- Sample identification and labeling
- Chain of custody
- Sample acceptance criteria
- Sample rejection and deviation documentation
- (case study: sample rejection decision)
- Physical sample preparation techniques
- Homogenization and size reduction – grinding, milling, blending
- Importance of particle size uniformity
- Risks: heat generation, analyte loss
- Filtration and clarification
- Syringe filters vs vacuum filtration
- Filter materials (PTFE, nylon, PVDF)
- Pore size selection
- Adsorption losses
- Centrifugation
- Phase separation
- Protein precipitation support
- Matrix clarification prior to injection
- (Virtual demo: impact of filtration on chromatograms)
- Solvent-based extraction techniques
- Simple dilution and “dilute-and-shoot” – when it works, when it fails
- Detector limitations (UV vs MS)
- 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
- 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)
- 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)
- 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
- 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
- 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
- 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)
🧪 ONLINE PRACTICAL COMPONENT – VIRTUAL ACTIVITIES
- Matrix:prep method decision trees
- Recovery and matrix-effect calculations
- Evaluation of chromatograms before and after cleanup
- ISO 17025-style sample prep documentation
