The Measurement of Silicon, Tin, and Titanium in Jet-Engine Oil
A wear metal profile is often prepared for each engine. Typically an early wear-in period of high metals concentration is observed, followed by a plateau of low metals concentration [2]. Impending component failure will be indicated by a rapid increase in wear metal concentration, or the sudden appearance of a metal. The metal type and concentration may also indicate to the analyst and engineers which part of an engine is failing. A change in the concentration of sodium for example, may indicate an antifreeze leakage, the increased presence of lead may indicate the wear of bearings in a diesel engine [3].
Determination of Wear Metals in Aircraft Lubricating Oils by Atomic Absorption Spectrophotometry Using a Graphite Furnace Atomizer
Atomic absorption spectrophotometry equipped with a graphite furnace atomizer has proven to be a very effective technique for determining iron, copper, aluminum, magnesium, and other critical wear metals in lubricating oils. Oil samples are diluted 1:4 with kerosene, and 0.5–20 μL can be analyzed by direct injection into the furnace. Analytical conditions have been established for 10 wear metals. Working curves, times, and temperatures for drying, ashing, and atomizing cycles have been determined. Precision of analysis was determined for standards (dissolved) and samples containing metallic particles (undissolved). The RSDs for 10 runs of 3 ppm Fe, 1 ppm Cu, and 1 ppm Al were 10.0, 4.0, and 3.9 percent, respectively. Metal powders of Fe, Cu, and Al having maximum sizes of 5, 10, and 20–30 μm were analyzed and precisions determined. Comparative analytical results were obtained for Fe particles of 1, 3, 5, 8, 10, 12, and 20–30 μm with the use of various spectrometric techniques. The graphite furnace was shown to be superior to ICP, DCP, flame AA, and rotating disk AES. In the analysis of used oil samples, the graphite furnace gave better precision and analyzability for Fe and Cu than the other instruments considered.
Trace Metals Analysis in Petroleum Products by Atomic Absorption
To provide information for customers who have regional environmental obligations, it was necessary to develop an analytical procedure to analyze for 25 metals in the range from 1 ppb to greater than 5 ppm in petroleum products. Atomic absorption is employed to determine 23 of the elements, namely: Al, Sb, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Fe, K, Pb, Mg, Mn, Mo, Ni, Na, Si, Sn, Ti, V, and Zn. The general procedure is to ash the appropriate amount of sample by absorbing liquid samples on magnesium sulfonate ash aid (Conostan, Conoash M) or potassium sulfonate. Add 5 drops of H2SO4, heat to white fumes, fire, and ash at 650°C. The sulfonated ash is dissolved in dilute acid to provide the aspiration solution. Recovery studies on aluminum, antimony, beryllium, cadmium, and lead in the microgram per gram range are presented.