Basic Information
Abstract Number: 1550-4    
Author Name: Richard Spragg Affiliation: PerkinElmer LAS
Session Title: Pharmaceutical Spectroscopy
Event Type: Oral
Event Title: Combining Raman Spectroscopy and Differential Scanning Calorimetry for Pharmaceutical Applications
Presider(s): Ciurczak, Emil Start Time: 02:30 PM ( Slot # 4 )
Date: Tuesday, March 10th, 2009 Location: S504a
Keywords: Other Hyphenated Techniques, Pharmaceutical, Raman, Thermal Analysis

Co-Authors
NameAffiliation
Alexander, RobertPerkinElmer LAS
Borden, FarrelPerkinElmer LAS
Dennis, AndrewPerkinElmer LAS
Ye, PengPerkinElmer LAS

Abstract Content
Understanding the different polymorphs or hydrates of pharmaceutical materials is of critical importance. Among the many techniques used to investigate these are spectroscopic methods such as Raman spectroscopy, and thermal methods such as differential scanning calorimetry (DSC). They are frequently applied to the same materials but have rarely been combined to provide simultaneous measurements. The two techniques are complementary, spectroscopy providing qualitative information while DSC is largely quantitative. Raman spectra can identify particular polymorphs while DSC measurements can reveal relationships between them.
We describe the use of a combined Raman-DSC system. There are two major practical considerations that we address. One is to minimise the effect of the laser excitation energy on the calorimetric performance. The rapid response of a power compensation DSC allows this. The other is to ensure that the Raman spectra are representative of the whole sample observed in the heat flow measurements. We illustrate how this may be verified using Principal Components Analysis of the Raman spectra to generate curves that should show the same transitions as the heat flow data. The examples used include both active ingredients and excipients.

A significant difference between the techniques is that Raman spectroscopy generates multivariate data, while DSC measures a single parameter, heat flow. This makes it possible to distinguish overlapping events with different spectral signatures when they cannot be separated by DSC.