Flame emission viscosity, effects

Other physical interferences are similar to those observed in flame emission and atomic absorption spectroscopy. They include effects due to viscosity and temperature of the sample solution. Any factor that can alter the rate of uptake of the sample solution requires control. The best method to use to control these effects is to prepare a blank with physical properties similar to those of the test sample. 

Organic solvents enhance emitted intensities mainly because of a higher resultant flame temperature (water has a cooling effect), a more rapid rate of feed into the flame because of the generally lower viscosity, and the formation of smaller droplets in the aerosol because of reduced surface tension. The resultant enhancement of spectral line intensity may be 3-to over 100-fold. Conversely, the presence of salts, acids and other dissolved species will depress the intensity of emission from the analyte and underlines the need for careful matching of samples and standards. 

The most commonly used technique of sample introduction is aspiration of the solution into the argon plasma flame. Because of the high temperatures in the flame, many of the problems associated with atomic absorption are eliminated. However, matrix effects such as significant differences in viscosity between sample and standard solutions can still have an effect. When needed, most of the techniques of sample introduction used in atomic absorption spectrophotometry can also be used for sample introduction in emission spectrophotometry [see the review articles " listed in the references]. 

---