Augmenting ICP-OES Sensitivity for Trace Element Analysis in Crude Oil via High-Efficiency Micro-Ultrasonic Nebulization

Abstract

Sensitive trace elements analysis in crude oil via inductively coupled plasma optical emission spectrometry (ICP-OES) is highly desirable for the petroleum industry. However, the conventional pneumatic nebulization (PN) sample introduction system suffers from extremely low nebulization efficiency (<5%), leading to inadequate sensitivity. Herein, a novel high-efficiency (∼85%) micro-ultrasonic nebulization (MUN) designed for ICP-OES was successfully developed. Under optimized conditions, MUN-ICP-OES achieved up to 17-fold sensitivity enhancements across 12 tested elements compared to conventional PN-ICP-OES, despite a 10-fold reduction in sample consumption. Notably, the MUN system permits independent adjustment of the carrier gas, lowering its flow rate extends aerosol residence time in the plasma, further boosting sensitivity without compromising nebulization efficiency. Furthermore, the MUN-ICP-OES demonstrated robust resistance to organic matrix interference and excellent long-term stability, achieving a relative standard deviation of 0.2% over 30 consecutive measurements using Ga as an internal standard. Compared to PN-ICP-OES, the limits of detection for the 12 elements in crude oils improved by 1–2 orders of magnitude. The accuracy of the proposed method was validated using a certified reference material, and results for actual crude oils showed excellent agreement with ICP–MS. Overall, this study validates that employing MUN as a high-efficiency sample introduction system significantly elevates the analytical capabilities of ICP-OES, thereby facilitating the precise quantification of trace elements in complex energy and environmental matrices.