QUANTIFICATION OF NAPHTHENIC ACIDS IN OIL-PRODUCED WATER UTILIZING HIGH-RESOLUTION MASS SPECTROMETY AND MULTIVARIATE REGRESSION

Produced water (PW), a major byproduct of offshore oil and gas extraction, contains complex mixtures of chemical contaminants, including naphthenic acids (NAs) - carboxylic acids that pose environmental and operational risks. This study presents a rapid and reliable method for quantifying NAs in PW using a low-volume (1 mL) liquid–liquid extraction (LLE) followed by direct-infusion high-resolution Orbitrap mass spectrometry (ESI(−)-Orbitrap MS). Simulated PW samples were prepared with varying NA concentrations and analyzed through a partial least squares regression (PLS) model enhanced by ordered predictor selection (OPS). The PLS-OPS model demonstrated strong predictive performance with high correlation coefficients for calibration (Rc = 0.996) and prediction (Rp = 0.971), and low root-mean-square errors. These results validate the method's accuracy and potential for early NA detection in low-water-content PW from newly drilled wells, offering significant advantages for environmental monitoring and process optimization in the oil and gas industry.