How to Measure Melting Point in Quality Control?

Measuring the melting point of a substance is a critical quality control (QC) test in pharmaceuticals, as it helps to identify the substance and determine its purity. Here’s how melting point is typically measured in QC:

Methods for Measuring Melting Point

1. Capillary Tube Method: A small sample of the substance is placed in a capillary tube, which is then heated in a melting point apparatus. The temperature at which the substance melts is observed and recorded.
2. Open Capillary Method: Similar to the capillary tube method, but the capillary tube is not sealed.
3. Kofler Hot Stage Method: A small sample of the substance is placed on a hot stage, which is heated slowly. The temperature at which the substance melts is observed and recorded.
4. Differential Scanning Calorimetry (DSC): A thermal analysis technique that measures the heat flow into or out of a sample as it is heated or cooled. The melting point is determined by the peak temperature of the endothermic melting peak.

Equipment Used

1. Melting Point Apparatus: A device specifically designed to measure the melting point of a substance.
2. Thermometer: A device used to measure temperature.
3. Hot Stage: A device used to heat a sample slowly and uniformly.
4. DSC Instrument: A thermal analysis instrument used to measure the heat flow into or out of a sample.

Procedure

1. Prepare the Sample: Obtain a small sample of the substance to be tested.
2. Load the Sample: Load the sample into the melting point apparatus or onto the hot stage.
3. Heat the Sample: Heat the sample slowly and uniformly.
4. Observe the Melting Point: Observe the temperature at which the substance melts and record the result.

Calculations

1. Melting Point: The temperature at which the substance melts is recorded as the melting point.
2. Melting Range: The range of temperatures over which the substance melts is recorded as the melting range.

Reporting Results

1. Melting Point Value: Report the melting point value in degrees Celsius (°C).
2. Melting Range Value: Report the melting range value in degrees Celsius (°C).
3. Uncertainty: Report the uncertainty of the measurement, if applicable.

Regulatory Requirements

1. USP: The United States Pharmacopeia (USP) provides guidelines for measuring the melting point of substances.
2. EP: The European Pharmacopoeia (EP) provides guidelines for measuring the melting point of substances.
3. ICH: The International Council for Harmonization (ICH) provides guidelines for validating analytical methods, including those used to measure melting point.

Read also:

• Melting Point Database
• Identification Tests in Pharmaceutical Analysis
• Pharmaceutical Quality Control Interview Questions and Answers

Resource Person: Dhruv Jayswal