Thermogravimetric and Raman Investigations on the Mechanism of Decomposition of Lead Compounds on Tungsten Surfaces

The thermal decomposition of lead phosphate on a tungsten surface was studied to determine how lead decomposes on a tungsten atomizer as well as what lead compounds are present after drying and pyrolysis in Electrothermal Atomic Absorption Spectroscopy. A 1 to 3 molar ratio of lead to phosphate was studied using thermogravimetric analysis and Raman Spectroscopy. Studies showed the formation of the stable lead pyrophosphate around 200°C for every lead phosphate sample tested, with a maximum temperature for lead loss at 700°C in a hydrogen atmosphere. These studies also showed that prior to 450°C, hydrogen plays no role in the chemistry of lead compound formation. The behavior of lead in the presence of interferences such as sodium chloride was also studied. Research shows no interference of sodium chloride with lead phosphate in the condensed phase on the tungsten surface. Lead phosphate in the presence of horse serum was also studied and it was determined that the maximum pyrolysis temperature in a biological sample is 700°C in a hydrogen atmosphere. Raman spectra of in situ heating of samples confirmed formation of the lead pyrophosphate. X-ray diffraction was used to confirm final TGA heating residues on some samples.