Low-level determination of non-metals (Cl, Br, I, S, P) in waste oils by inductively coupled plasma optical emission spectrometry using prominent spectral lines in the 130-190 nm range

Abstract

The non-metals Cl, Br, I, S and P were determined in waste oils by inductively coupled plasma optical emission spectrometry (ICP-OES). Prominent spectral lines in the vacuum ultraviolet spectral region between 130 and 190 nm were applied simultaneously with a nitrogen-filled Spectro polychromator. For example, the intense spectral lines for chlorine (Cl 134.72 nm), bromine (Br 163.34 nm), iodine (I 161.76 nm), sulfur (S 180.70 nm) and phosphorus (P 177.50 nm) were used. The detection limits of Cl, Br, I, P and S in undiluted waste oils are 0.9, 1.6, 0.47, 0.04 and 0.07 mg kg ^–1 , respectively. To achieve these detection limits the standard oils and samples were diluted 1+4 (m/m) with kerosene. For the analysis of waste oils, small amounts of oxygen (80 ml min ^–1 ) were added to the outer plasma gas. In order to establish optimized plasma operating conditions for non-metals, a simplex optimization was performed. Compared with metals such as Ba, V, Cd, Al or Ni, a lower nebulizer gas flow and a higher generator power is advantageous to improve the detection limits for the non-metals. Because the detection limit for Cl is more than a factor of 1000 below tolerated limits of waste oil regulations, highly viscous oils could be analyzed after a suitable dilution with kerosene. The determination of the total Cl concentration by ICP-OES can be used as a means of screening for the highest possible concentration of polychlorinated biphenyls (PCBs) in waste oils.