Importance of Emulsification in Calibrating Infrared Spectroscopes for Analyzing Water Contamination in Used or In-Service Engine Oil

Abstract

Using Fourier transform infrared (FT-IR) spectroscopy we investigated the water content of SAE 15W-40 diesel engine lubricating oil at various levels of contamination to establish instrument calibration standards for measuring water contamination in used or in-service engine oil by the standards of ASTM International. Since some known additives in consumer grade engine oil possess slightly hydrophilic properties, this experiment avoided changing the sample matrix with supplemental additives, such as adding surfactants, to achieve homogeneity of the original sample. The impact of sampling time after contamination on the spectral absorption signature was examined in an attempt to improve the accuracy of water contamination quantification and determine if water-soluble potassium bromide (KBr) windows were suitable for analyzing water in oil emulsions. Analysis of variance (ANOVA) modeling and limit of detection calculations were used to predict the ability to discriminate contamination levels over time. Our results revealed that the amount of water concentration in engine oil could be misinterpreted depending on the timing of the FT-IR measurement of the calibration standard after initial water contamination. Also, KBr windows are not sufficiently etched due to the limited window interaction with water molecules within micelles of emulsions to alter FT-IR spectral signatures.

Partial Least Squares (PLS) Integrated Fourier Transform Infrared (FTIR) Approach for Prediction of Moisture in Transformer Oil and Lubricating Oil

“…Nevertheless, the concentration at which the moisture can be comfortably detected, in another words the limit of quanti cation (LOQ), is suggested at 1000 ppm. is recommendation is in line with the literature ndings where Dong et al [3] propose the LOD at 500 ppm whilst Holland et al [19] postulate at 1000 ppm, agreeing with Fitch [20]. In terms of precision, it is found that the prediction is subjected to high variance, indicative of unstable models.…”

A Microfluidic Sensor Based on Meta-Surface Absorber for Rapid and Nondestructive Identification of Edible Oil Species

“…In most of the recent studies, different traditional technologies, such as gas chromatography method [3], evaporation and distillation [4], near infrared spectrum [5], and voltammetric electronic tongue [6], are used to detect the quality of oil. Although these technologies are very precise, they are complicated to operate and consume a large amount of sample [7].…”

Influence of Sample Mixing Techniques on Engine Oil Contamination Analysis by Infrared Spectroscopy

“…As NMR devices decrease in cost and size, they may become more prevalent for this purpose. However, current industry practices show that FT-IR use is still quite commonplace in this area, and prior research has indicated a need for more specific guidelines, including within the ASTM International standard of practice for using FT-IR [6], in order to maximize emulsions in water contaminated oil samples, particularly when preparing samples for IR calibration [7].…”

“…Instituting calibration standards for FT-IR analysis must begin with a thorough emulsification procedure, to establish an accurate baseline with which to compare an instrument's capabilities of detecting water in oil. A thoroughly emulsified sample is inherently more stable, homogeneous, and representative of the whole, yielding better reproducibility and reliability in results by reducing the variability in IR measurements that arises due to light scattering in samples with larger water droplet sizes [7,10]. Water contamination in used or in-service oil primarily exists in dissolved or emulsified states due to agitation, heat, and pressure caused by oil circulation through an engine.…”