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 confi gurations for residual carbon content (RCC) determination. The effects of c arbon compound source (urea, L-cysteine, and glucose), sample medium, and i nternal standards on RCC determination were systematically evaluated. All m easurements were carried out with two ICP spectrometers using the carbon at omic emission lines: 247.857 and 193.025 rim. The results obtained using ax ial and radial configurations showed that both the carbon source and the sa mple medium did not affect significantly the emission intensities. The samp le medium only caused drastic influence when H2SO4 was employed probably du e to transport interference that can be corrected employing Y as internal s tandard. The sensitivity attained using axial view ICP-OES was 20-fold bett er than that reached using radial view ICP-OES based on the slopes of the a nalytical curves at the most sensitive wavelength (193.025 mn). Using radia l and axial ICP-OESs, high concentrations of Fe (> 100 mg l(-1)) interfered at 247.857 nm wavelength. An addition-recovery experiment was made by addi ng 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 sa mples were acid-digested using a closed-vessel microwave-assisted procedure and RCC was determined using both ICP-OES configurations. (C) 2001 Elsevie r Science B.V. All rights reserved.