Purity Determination by DSC

Pre-formulation studies are an essential component of drug development process and it provides scientific basis for formulation development. As a part of our pre-formulation development service, Creative Biolabs provides purity determination service by analysis of the DSC melting peak for determining the purity of a material.

It has already been observed that if impurities are present in a material, the melting point will be changed. Less pure compounds will exhibit a broadened melting peak than a pure compound. With the introduction of differential scanning calorimetry (DSC), it has rapidly developed to become a method of quantifying the levels of impurity. DSC is a thermoanalytical technique which measures the amount of energy absorbed or released by a sample when it is heated or cooled, and then providing quantitative and qualitative data on endothermic and exothermic processes.

Figure 1 Introduction of differential scanning calorimetry (DSC)

The principle of using DSC for purity determination is shown in Figure 1. Tested sample is placed in a suitable pan and sits upon a constantan disc with a chromel wafer for measuring the sample temperature. A reference pan sits on a symmetric platform by providing high purity reference sample. Heat flow is measured by comparing the difference in temperature across tested sample and the reference sample.

Creative Biolabs provides precise measurements of heats by DSC and gives sufficient information to support successful purity determinations. The DSC is the simplest analytical method for getting information about the purity and about the crystal form of the sample under investigation. Temperature provided can range from -120°C to 725°C and the temperature is measured with a repeatability of ±0.1°C.

However, not all compounds can be analyzed by DSC. The compounds suitable to be analyzed by DSC for purity scope should meet the conditions below:

• The chemical should be a pure crystalline material.
• Impurity parts should be soluble in the melted compound, but insoluble in the solid state.
• The melting must be a first order transition.
• The analyzed compound must not form conjugates with solvents.
• The analyzed compound should be >95 mol% pure (preferably >97 mol% pure).
• The analyzed compound must all be in the same polymorphic form where polymorphs exist.
• The sample must be prevented from subliming.
• Liquid materials that form glasses on solidification cannot be analyzed in their amorphous state.
• Composition of D-L isomers in materials is not measurable.
• No compounds containing F, Cl, Br, I or other corrosive elements may be submitted for DSC analysis.

Characteristics of Our DSC Platform

• Sensitivity: 6 μW/cm
• Precision: 1%
• Baseline noise: ±5 μW
• Baseline stability: 20 μW (ambient to 200°C); 400 μW (ambient to 600°C)
• Maximum power output: 300 W
• Sample size: From 0.5 mg to 100 mg

For more detailed information, please feel free to contact us or directly sent us an inquiry.

For Research Use Only.