Investigations of pyrolysed ascorbic acid in an electrothermal graphite furnace by inductively coupled argon plasma mass spectrometry and Raman spectrometry

Abstract

The characteristics of pyrolysed ascorbic acid were investigated by electrothermal vaporization inductively coupled argon plasma mass spectrometry (ETV-ICP-MS) and Raman spectrometry. The signals from the ETV-ICP-MS instrumentation for m/z values of 13, 24, 44 and 52, corresponding to polyatomic species of ¹³C, ¹²C₂, ¹²C¹⁶O₂ and ¹²C⁴⁰ Ar, respectively, indicated three signals in the atomization cycle corresponding to: (i) gaseous compounds, such as hydrocarbons, CO and CO₂ below 580 K; (ii) active carbon species between 600 and 1100 K; and (iii) thermally stable carbon species between 1200 and 2400 K. After the ETV-ICP-MS measurements, more thermally stable carbon residues (i.e., soot) were confirmed in the graphite furnace by eyesight. Raman spectra of pyrolysed ascorbic acid on the pyrolytic graphite (PG) coated graphite furnace inner wall showed that the thermally stable carbon residues were released via decomposition into active carbon species with increasing pyrolysis temperature, and part of the residue remained at 2150 K. However, Raman spectra of the carbon residues on a non-pyrolytic graphite coated graphite furnace wall after repetitive (100 times) pyrolysis of 5%(m/v) ascorbic acid solution at a temperature above 2500 K showed the formation of a PG phase.