Other Evaluation Techniques
PCBs content in used oil is essential for determining how the used oil is going to be recycled or treated. Hence, it’s important to screen PCBs content in bulk used oil. If PCBs content is too high, then the used oil cannot be reprocessed or re-refined. Many screening techniques have been developed for PCBs in used oil, such as total organic halide methods, simplified chromatographic procedures, x-ray fluorescence, or total chlorine determination. The last method is the basis for many commercial colorimetric kits in field test use; unfortunately, these kits only give semiquantitative results. For lower regulatory limits of 50ppm, there is always some uncertainty about the accuracy. A new technique using thermal neutron activation analysis (ITAN) was proposed (Sutcliffe, 1989). Although it produces faster and more accurate PCBs results at a very low cost, it requires access to a reactor and trained personnel, which does not seem very applicable and convenient. The techniques mentioned above are mostly adapted from determination methods of common oil samples. Since it’s not popular or necessary to characterize used oil samples; it’s rare to see a specific method developed mainly for used oil analysis. However, there are still some interesting techniques available. For example, FT-IR technique can be used to monitor lube oil condition coupled with an automated Spectrum™ Used Oil Analyzer (by Perkin-Elmer). When used oil is compared to fresh 99 oil with parameters (shown at different wavelengths) such as soot, hydroxyl, glycol, NOx/carboxylate, sulfate, antiwear loss, ester breakdown, and fuel contaminants in FT-IR spectrums, it provides information on the state of the oil itself and the engine from which the oil comes and ensures that an engine is operating with optimum efficiency. Another technique used to evaluate the remaining useful life (RUL) of lubricant in the engine/equipment is the Remaining Useful Life Evaluation Routine (RULER™). This method utilizes voltammetric technique to indicate how much additive depletion has occurred (Jefferies, 1998). By tracking the readings over operating time, the user is able to identify abnormal operating conditions and predict necessary oil changes.