Determination of residual carbon by inductively-coupled plasma optical emission spectrometry with axial and radial view configurations

In this work it was evaluated the performance of inductively-coupled plasma optical emission spectrometers (ICP-OESs) with axial and radial view configurations for residual carbon content (RCC) determination. The effects of carbon compound source (urea, -cysteine, and glucose), sample medium, and internal standards on RCC determination were systematically evaluated. All measurements were carried out with two ICP spectrometers using the carbon atomic emission lines: 247.857 and 193.025 nm. The results obtained using axial and radial configurations showed that both the carbon source and the sample medium did not affect significantly the emission intensities. The sample medium only caused drastic influence when H2SO4 was employed probably due to transport interference that can be corrected employing Y as internal standard. The sensitivity attained using axial view ICP-OES was 20-fold better than that reached using radial view ICP-OES based on the slopes of the analytical curves at the most sensitive wavelength (193.025 nm). Using radial and axial ICPOESs, high concentrations of Fe (>100 mg l-1) interfered at 247.857 nm wavelength. An addition-recovery experiment was made by adding urea to an acid-digested sample and all recoveries were in the 100±5% range for axial and radial measurements. At this wavelength, R.S.D. <2.0% (n=10) and detection limits of 33 and 34 mug ml-1 C, were measured for ICP-OESs with radial and axial configurations, respectively. Biological samples were acid-digested using a closed-vessel microwave-assisted procedure and RCC was determined using both ICP-OES configurations.