EFFECTS OF SAMPLE HEATING IN FT-RAMAN SPECTRA OF BIOLOGICAL-MATERIALS

The effects of laser-induced sample heating and fluorescence of biopol ymers in Fourier transform-Raman spectroscopy were investigated. It wa s shown that these two phenomena are essentially independent of each o ther. Methods of quantifying the laser-induced healing were developed and it was shown that measurement of the thermal emission generated by the sample is not sufficient to determine its temperature. The use of a marker compound mixed with the test sample to estimate the sample t emperature was explored. Monitoring the temperature-dependent phase tr ansitions of NH4NO3 provided a crude indication of a minimum sample te mperature. However, using sulphur as a marker and exploiting the relat ionship between the intensities of its anti-Stokes and Stokes bands, i t was possible to estimate the sample temperature with greater confide nce. Using these techniques it was shown that sample temperatures coul d easily reach approximately 400 K under normal laser power inputs. Su ch temperatures are likely to be damaging to biological samples and it is concluded that great care must be exercised when using FT-Raman.