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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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A green single-tube sample preparation method for wear metal determination in lubricating oil by microwave induced plasma with optical emission spectrometry
摘要： A straightforward and rapid single-tube sample pretreatment for wear metals determination in used lubricating oils was developed in this work as an alternative to the reference pretreatment method (ASTM). A D-optimal mixture design on a three-component solution was performed. The optimal composition for the proposed sample preparation emulsion was 2 % v/v of xylene, 9.5 % v/v of Triton?X-114 and 88.5 % v/v of H2O. The determination of 18 wear metals was carried out by microwave induced plasma with optical emission spectrometer (MIP OES), and the results of the two sample preparations - conventional and proposed- were statistically compared. Also, a certified standard “wear metals in used lubricating oils” for pretreatment validation was used. The developed method was as effective as the reference method indicated by ATSM, similar in speed and simplicity, but superior from the environmental and economic point of view. The proposed pretreatment allowed Ag, Al, Ba, Ca, Cd, Cr, Cu, K, Mg, Mn, Mo, Ni, Pb, Si, Sn, Ti, V and Zn determination, with LOQ between 1.40 mg kg-1 for Ca and 6.34 mg kg-1 for Pb. The precisions established as the relative standard deviation (RSD) were better than 6.2%. The proposed method avoid sample handling, reducing contamination risks and analyte losses, affording significantly improvement on wear metal quantification.
关键词： Microwave induced plasma atomic emission spectrometry,Mixture experimental design,Wear metals,Green single-tube sample preparation,Used lubricating oils
更新于2025-09-11 14:15:04