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Influence of Sample Mixing Techniques on Engine Oil Contamination Analysis by Infrared Spectroscopy
摘要： For the most reliable and reproducible results for calibration or general testing purposes of two immiscible liquids, such as water in engine oil, good emulsi?cation is vital. This study explores the impact of emulsion quality on the Fourier transform infrared (FT-IR) spectroscopy calibration standards for measuring water contamination in used or in-service engine oil, in an attempt to strengthen the speci?c guidelines of ASTM International standards for sample preparation. By using different emulsi?cation techniques and readily available laboratory equipment, this work is an attempt to establish the ideal sample preparation technique for reliability, repeatability, and reproducibility for FT-IR analysis while still considering the ease and ef?ciency of the technique. This study demonstrates that a stable emulsion within a sample, which depends heavily upon the method, provides a reliably consistent homogenous sample for quanti?cation purposes with FT-IR analysis. Analysis of variance (ANOVA) modeling and limit of detection calculations demonstrate the stability of the emulsion. The results reveal that setting a mixing time for a calibration standard depends on the emulsi?cation process. Inserting a probe directly into a sample (direct sonication) allows for a rapid, stable emulsion with high reproducibility. Indirect sonication produces relatively non-miscible liquids of different densities. The pan-shaker produces a reasonably stable emulsion, but without the long-term stability or quick production time of direct sonication. Reaction time plays a critical role in the rotary mixing method, which leads to a slow development of emulsi?cation.
关键词： mixing methods,lubricating oils,emulsion,water contamination,infrared spectroscopy
更新于2025-09-19 17:15:36
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Using Terahertz Time-Domain Spectroscopy to Discriminate among Water Contamination Levels in Diesel Engine Oil
摘要： Terahertz time-domain spectroscopy (THz-TDS) in the range of 0.5 to 2.0 THz was evaluated for discriminating among water contamination levels (0%, 0.1%, and 0.2%) in diesel engine oil (SAE 15W-40). The absorption coefficient demonstrated potential to discriminate among the three water contamination levels with significant differences among all three levels across the 1.111 to 1.332 THz and 1.669 to 1.934 THz ranges. At each of these frequency ranges, each water contamination level was significantly different from the other two. The 0% water contamination level had the lowest absorption coefficient, while 0.2% water had the highest absorption coefficient. The refractive index demonstrated greater potential to discriminate among water contamination levels with significant differences among all three water levels across the 0.5 to 1.5 THz range. The refractive index of 0% water was the lowest and 0.2% water was the highest across the THz range. Linear regression analysis of the refractive index as a predictor of water contamination level yielded a highly significant equation (p < 0.0001, R2 = 0.99, RMSE = 0.01) when using the refractive indices at 0.5 THz. The refractive indices of these oil samples were promising for discrimination of water contamination. THz spectroscopy should be evaluated for discriminating other engine oil contaminants.
关键词： Terahertz spectroscopy,Diesel,Engine oil,Water contamination
更新于2025-09-09 09:28:46