Determination of long-chain fatty acids in anaerobic digester supernatant and olive mill wastewater exploiting an in-syringe dispersive liquid-liquid microextraction and derivatization-free GC-MS method

Abstract

Long-chain fatty acids (LCFA) are commonly found in lipid-rich wastewaters and are a key factor to monitor the anaerobic digesters. A new simple, fast, precise, and suitable method for routine analysis of LCFA is proposed. The system involves insyringe-magnetic stirring-assisted dispersive liquid-liquid microextraction (DLLME) prior to gas chromatography-mass spectrometry (GC-MS) without a derivatization process. Calibration curves were prepared in an ethanol solution (R 2 ≥ 0.996), which was also useful as disperser solvent. Hexane was chosen as the extraction solvent. Several parameters (pH, ionic strength, extraction solvent volume, stirring time) were optimized in multivariate and univariate studies. Limits of detection (LODs) were found in the range 0.01-0.05 mg L −1 and good precision inter-day (RSDs≤7.9%) and intra-day (RSDs≤4.4%) were obtained. The method was applied to quantify LCFA in supernatants of anaerobic digesters and olive mill wastewaters (OMW). Palmitic, stearic, and oleic acids were the most abundant fatty acid in the analyzed samples and the relative recoveries for all of them were between 81 and 113%.

Simultaneous determination of 22 fatty acids in total parenteral nutrition (TPN) components by gas chromatography-mass spectrometry (GC-MS)

“…29,30 Due to the complex chemistry of FAs, there is a multitude of analytical techniques developed for FA quantication, including several GC-MS methods. These developed methods, however, are either (1) targeting only essential fatty acids; [31][32][33] (2) imposing limitations to some fatty acids of interest; 11,13,23,[34][35][36] (3) mostly focused on fatty acid extraction from human samples; 13,15,18,23,34,[36][37][38] (4) have complicated sample preparation technique, 4,32,39,40 (5) merely evaluating dysregulated fatty acids; 23,41,42 and (6) needing analytical method validation. 10,12,14,20,43 Thus, there is a need for straightforward GC-MS methods that allow the analysis of FAs as classied by their chain length and degree of unsaturation and are suitable for industrial routine applications, particularly in evaluating the quality of the TPN products.…”