1. Define the Purpose and Scope
Establish the method’s objective before you begin writing.
-
Method Title: Assign a descriptive name (e.g., “HPLC Method for the Quantification of Paracetamol in Tablets”).
-
Objective: State exactly what the method achieves. Identify the analyte, the matrix, and the reason for the measurement.
-
Scope: Define the application range. Specify which samples the method covers and list any known limitations.
2. Outline the Method’s Principle
Explain the scientific foundation of your approach.
-
Summary: Describe the fundamental science (e.g., “This method utilizes HPLC with UV detection to separate and quantify the target analyte based on its unique retention time.”).
-
Chemical Reactions: Detail any reactions that occur during sample preparation.
3. List Materials and Reagents
Detail every item required to ensure different labs can replicate your results.
-
Chemicals: List all reagents, solvents, and standards. Include purity grades, manufacturers, and batch numbers.
-
Water: Specify the required water quality (e.g., deionized or HPLC grade).
-
Gases: Identify necessary gases and their required purity levels (e.g., nitrogen or helium).
-
Sample Matrix: Describe the sample type (e.g., biological fluid or finished product).
4. Specify Instrumentation and Equipment
List the hardware used to develop and execute the method.
-
Main Instrument: State the make, model, and configuration (e.g., Agilent 1260 Infinity II HPLC System).
-
Ancillary Equipment: Include supporting tools like pH meters, balances, and pipettes. Note their required calibration status.
5. Document the Step-by-Step Procedure
Write clear, chronological instructions so a trained analyst can perform the method without assistance.
-
Reagent Preparation: Explain how to mix buffers, mobile phases, and solutions. Include specific calculations and safety warnings.
-
Sample Preparation: Detail the exact steps for weighing, dilution, extraction, and filtration.
-
Standard Preparation: Provide instructions for creating working standards and quality control (QC) samples.
-
Instrument Setup: Define all parameters, including column type, temperature, flow rate, and detector wavelength.
-
System Suitability Tests: Define the pass/fail criteria (e.g., peak tailing or column efficiency) required before starting the analysis.
-
Data Acquisition: Specify the software and settings used to process the results.
6. Define Calculations and Data Reporting
Show exactly how to convert raw data into a final result.
-
Formulas: Provide the mathematical equations for concentration, recovery, and other metrics.
-
Units: State the required units for reporting (e.g., $mg/L$ or $\% w/w$).
-
Reporting: Standardize how to round numbers and format the final report.
7. Summarize Method Validation Results
Provide the evidence that the method is fit for its purpose.
-
Specificity: Prove the method only measures the target analyte.
-
Accuracy: Present recovery study data to show how close results are to the true value.
-
Precision: Include data for repeatability and intermediate precision.
-
Linearity: Show the relationship between concentration and detector response via a calibration plot.
-
LOD & LOQ: State the lowest concentrations the method can detect and accurately quantify.
-
Robustness: Document how small changes in parameters affect the performance.
8. Add Supporting Information (Appendices)
Include supplemental data to assist the user.
-
Example Chromatograms: Attach visuals of a standard, a blank, and a sample.
-
Raw Data References: Link to the location of original data files and validation reports.