Determination of naphthenic acids in produced water by using microchip electrophoresis with integrated contactless conductivity detection
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2022
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This study reports for the first time the use of a microchip electrophoresis (ME) device with integrated capacitively coupled contactless conductivity detection (C4D) to analyze naphthenic acids in produced water. A mixture containing 9-anthracenecarboxylic, 1-naphthoic, and benzoic acids was separated and detected using a running buffer composed of 10 mmol L−1 carbonate buffer (pH = 10.2). The separation was achieved within ca. 140 s with baseline resolution greater than 2 and efficiency values ranging from 1.9 × 105 to 2.4 × 105 plates m−1. The developed methodology provided linear correlation with determination coefficients greater than 0.992 for the concentration ranges between 50 and 250 µmol L−1 for benzoic and 9-anthracenecarboxylic acids, and between 50 and 200 µmol L−1 for 1-naphthoic acid. The achieved limit of detection values varied between 4.7 and 7.7 µmol L−1. The proposed methodology revealed satisfactory repeatability with RSD values for a sequence of eight injections between 5.5 and 7.7% for peak areas and lower than 1% for migration times. In addition, inter-day precision was evaluated for sixteen injections (a sequence of four injections performed during four days), and the RSD values were lower than 11.5 and 4.9% for peak areas and migration time, respectively. Five produced water samples were analyzed, and it was possible to detect and quantify 9-anthracenecarboxylic acid. The concentrations ranged from 1.05 to 2.24 mmol L−1 with recovery values between 90.8 and 96.0%. ME-C4D demonstrated satisfactory analytical performance for determining naphthenic acids in produced water for the first time, which is useful for petroleum or oil industry investigation.
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PINHEIRO, Kemilly M. P. et al. Determination of naphthenic acids in produced water by using microchip electrophoresis with integrated contactless conductivity detection. Journal of Chromatography A, Amsterdam, v. 1677, e463307, 2022. DOI: 10.1016/j.chroma.2022.463307. Disponível em: https://www.sciencedirect.com/science/article/abs/pii/S0021967322005003. Acesso em: 28 jun. 2023.