Analytical Applications - Pharmaceutical Technology

Latest Issue
PharmTech

Latest Issue
PharmTech Europe

Analytical Applications
Several industry experts describe applications in pharmaceutical applications, including on-line total organic carbon analysis, ultra-fast liquid chromatography, rapid microbial testing, and differential scanning calorimetry-Raman Spectroscopy.


Pharmaceutical Technology
Volume 34, pp. s36-s30

DSC–Raman spectroscopy

Kevin P. Menard, PhD, business manager of thermal analysis at PerkinElmer (Shelton, CT)

Differential scanning calorimetry (DSC) and Raman spectroscopy are well-known techniques in pharmaceutical analysis. DSC determines glass transitions, amorphous content, melting temperatures, and enthalpy and estimates the degree of crystallinity. In its fast-scanning mode, DSC also suppresses kinetic changes (i.e., polymorphism and decompositions). This allows measurements to be made before kinetic changes can occur, allowing one to determine the initial polymorphic form as well as measure melting and heat capacity on materials before they decompose. Raman spectroscopy is able to detect changes in chemical composition as well as positional and stereochemical changes in a sample; this allows it to identify specific polymorphic states. Raman spectroscopy, however, has some difficulties in measuring temperature-dependent reactions such as dehydrations and polymorphic rearrangements. These reactions are sensitive to the temperature applied, and care must be taken so that the energy added by the Raman's laser does not affect the data by causing changes in the sample temperature (1). A combination of dual furnace (i.g., power-compensated) DSC and a shuttered laser in an Eschelle Raman spectrometer were found to give minimal increases in bulk sample temperatures (2).

As a hyphenated technique, however, DSC–Raman spectroscopy works well in detecting the changes in polymorphic materials as a function of temperature (3). For example, running a sample of acetaminophen in heating showed a series of peaks corresponding to changes in polymorphic forms, but the changes in the material corresponding to those thermal events are inferred (2). For example, an endothermic peak in the DSC themogram can be a melt, a water loss, or a polymorphic change. Raman spectroscopy allows one to confirm what the transition is; the chemical and structural changes detected from the Raman spectra clarify the DSC data. Because the DSC can performed under a wide range of thermal conditions, including heating and cooling rates from 0.1 to 750 C/min, the combined techinques can be used to characterize the materials' kinetic behavior under a wide variety of conditions. For example, crystallization processes can be studied using DSC–Raman during cooling experiments. Other work has been reported on hydrates and pseudo polymorphs as measuring the reaction of materials by tracking changes in assigned bands in the Raman spectra and the energetic changes (4, 5).

DSC–Raman spectroscopy section references

1. R. Alexander et al., Proceedings of the North American Thermal Analysis Society (NATAS) Annual Conf. (Atlanta, 2008), pp. 131–136.

2. A Dennis, K. Menard, and R. Spragg, Proceedings of the Annual Technical Conf. of the Society of Plastic Engineers (Chicago, 2009), pp 647–653.

3. K. Menard et al., Am. Lab. 42 (1), 21–23 (2010).

4. N. Redman et al., Furey, , Proceedings of NATAS Annual Conf. (Albuquerque, NM, 2003), pp. 120–129;

5. A. Bigalow-Kern et al., J. ASTM, 2 (7), 42–61 (2005).


ADVERTISEMENT

blog comments powered by Disqus
LCGC E-mail Newsletters

Subscribe: Click to learn more about the newsletter
| Weekly
| Monthly
|Monthly
| Weekly

Survey
What role should the US government play in the current Ebola outbreak?
Finance development of drugs to treat/prevent disease.
Oversee medical treatment of patients in the US.
Provide treatment for patients globally.
All of the above.
No government involvement in patient treatment or drug development.
Finance development of drugs to treat/prevent disease.
23%
Oversee medical treatment of patients in the US.
14%
Provide treatment for patients globally.
7%
All of the above.
47%
No government involvement in patient treatment or drug development.
9%
Jim Miller Outsourcing Outlook Jim MillerOutside Looking In
Cynthia Challener, PhD Ingredients Insider Cynthia ChallenerAdvances in Large-Scale Heterocyclic Synthesis
Jill Wechsler Regulatory Watch Jill Wechsler New Era for Generic Drugs
Sean Milmo European Regulatory WatchSean MilmoTackling Drug Shortages
New Congress to Tackle Health Reform, Biomedical Innovation, Tax Policy
Combination Products Challenge Biopharma Manufacturers
Seven Steps to Solving Tabletting and Tooling ProblemsStep 1: Clean
Legislators Urge Added Incentives for Ebola Drug Development
FDA Reorganization to Promote Drug Quality
Source: Pharmaceutical Technology,
Click here