Determination Of Long-chain Fatty Acids Research Articles

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.

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 in-syringe-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 (R2 ≥ 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 0.01-0.05mgL-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%.

Determination of long-chain fatty acids in bryophyte plants extracts by HPLC with fluorescence detection and identification with MS

A sensitive method for the determination of long-chain fatty acids (LCFAs) (>C20) using 1-[2-( p-toluenesulfonate)-ethyl]-2-phenylimidazole-[4,5-f]-9,10-phenanthrene (TSPP) as tagging reagent with fluorescence detection and identification with post-column APCI/MS has been developed. The LCFAs in bryophyte plant samples were obtained based on distillation extraction with 1:1 (v/v) chloroform/methanol as extracting solvent. TSPP could easily and quickly label LCFAs at 90 °C in the presence of K 2CO 3 catalyst in DMF. Eleven free LCFAs from the extracts of bryophyte plants were sensitively determined. Maximal labeling yields close to 100% were observed with a five-fold excess of molar reagent. Separation of the derivatized fatty acids exhibited a good baseline resolution in combination with a gradient elution on a reversed-phase Eclipse XDB-C 8 column. Calculated detection limits from 1.0 pmol injection, at a signal-to-noise ratio of 3, were 26.19–76.67 fmol. Excellent linear responses were observed with coefficients of >0.9996. Good compositional data were obtained from the analysis of the extracted LCFAs containing as little as 0.2 g of bryophyte plant samples. Therefore, the facile TSPP derivatization coupled with HPLC/APCI/MS analysis allowed the development of a highly sensitive method for the quantitation of trace levels of LCFAs from biological and natural environmental samples.

Ion-pair dynamic liquid-phase microextraction combined with injection-port derivatization for the determination of long-chain fatty acids in water samples

Ion-pair dynamic liquid-phase microextraction coupled to injection-port derivatization has been developed for the determination of long-chain fatty acids in water samples by gas chromatography–mass spectrometry (GC–MS). In this procedure, long-chain fatty acids (C 14, C 16 and C 18) were converted into their ion-pair complexes with tetrabutylammonium hydrogen sulfate and then extracted by organic solvent (1-octanol) impregnated in the hollow fiber. The dynamic nature of the extraction was represented by the repeated movement of the acceptor phase (organic solvent) in the hollow fiber that was controlled by a syringe pump. Ion pairs of fatty acids quantitatively formed butyl esters in the injection-port of the gas chromatography. Several parameters such as injection temperature, purge-off time, organic solvent, ion-pair reagent, pH, agitation speed, extraction time and the syringe pump parameters (plunger speed and dwell time) have been optimized. The limits of detection were in the range 0.0093–0.015 ng mL −1 (at a signal-to-noise ratio of 3) under GC-MS-selected ion monitoring mode and the relative standard deviations were between 7.7% and 11.5%. The method was successfully applied to measure long-chain fatty acids in real water samples.

Determination of long-chain fatty acids in heart and skeletal muscle by capillary gas chromatography

A reliable and sensitive technique is presented to monitor the total content of non-esterified fatty acids (FAs) and the relative fatty acyl composition in biological material, with special reference to cardiac and skeletal muscle. The separation and quantification of FA were accomplished by capillary gas chromatography. Since in muscle tissue, the amount of FA represents approximately 0.2% of the total esterified and non-esterified fatty acid pool, precautions should be taken to avoid hydrolysis and/or transmethylation of esterified fatty acyl moieties during the assay procedure. In particular, attention should be paid to storage of tissue samples, disruption of tissue prior to lipid extraction and contaminants increasing the blank of the assay. The content of FA in human vastus lateralis muscle at rest amounted to 77±14 nmol g −1 wet weight. The content of FA in the cardiac ventricles of normal rats was 338±76 nmol g −1 dry weight. Diabetes induced by streptozotocin caused a significant 4.8-fold increase in the FA content of rat cardiac ventricular tissue.

Study of fatty acid profiles in cancer cells grown in culture using gas chromatography-mass spectrometry

The determination of long-chain fatty acids in the phospholipid, triglyceride and free fatty acid fractions of HT29/219 colon cancer cells grown in a medium containing either foetal calf serum or horse serum, was carried out using gas chromatography - mass spectrometry. Several bonded-phase capillary columns were tested for the separation of the fatty acid methyl esters, and a 30-m poly(ethylene glycol) column was found to give optimum separation. The mass spectrometer was set to the multiple ion detection mode to increase the sensitivity of the recording of the characteristic ions, consisting of the molecular ion and the base peak. The phospholipid and triglyceride compositions of the cells were different when the cells were grown in media containing different sera. Differences were also found in the turnover of the acids in the different lipid fractions, the phospholipids being the most important, when the cells were grown in different media. The cellular metabolism and turnover of certain fatty acids differed from others in the same cell. These differences emphasise the importance of a precise knowledge of the lipid composition of the culture medium in in vitro studies of cancer cells.

Piperidyl and morpholinyl esters as derivatives for the structural determination of long-chain fatty acids by mass spectrometry

Piperidyl and morpholinyl esters have been prepared by the reaction of (saturated, unsaturated and branced) fatty acid chlorides with N-piperidine ethanol, N-(2-hydroxyethyl)-morpholine and 4-hydroxy-N-methylpiperidine, respectively. The structural requirements and fragmentation mechanisms involved in these remotely interacting esters are systematically examined using electron impact mass spectrometry. The most promising derivative for fatty acid analysis seems to be N-methyl-4-piperidyl esters with stable molecular ions and other diagnostically useful peaks. Brancing points and double bond position can easily be recognized but cis and trans isomers yield quite similar mass spectra.

Adrenoleukodystrophy: diagnosis and carrier detection by determination of long-chain fatty acids in cultured fibroblasts.

In cultured fibroblasts of adrenoleukodystrophy (ALD) patients and most heterozygotes, concentrations of long-chain fatty acids (greater than C22) were significantly higher than in controls when cells were assayed 4-5 days after reaching confluence. Intermediate values were found in three independent cultures of a girl with manifest ALD, suggesting that a significant proportion of her fibroblasts does not express the defect. Though long-chain fatty acid concentrations in heterozygotes were somewhat higher than expected, suggesting a slight preponderance of defective cells, it may be too early to conclude that somatic selection is a consistent finding in cultured fibroblasts of ALD carriers.

Phthalate interference in gas-chromatographic determination of long-chain fatty acids in plasma.

Phthalates leached from plastic tubing or other plastic devices may interfere with gas-chromatographic determination of long-chain fatty acids in plasma. In the case of hospitalized patients who have received infusions or had blood drawn through plastic tubing, gas chromatography/mass spectrometry may be required for accurate determination of such fatty acids.

A combined micro-and semi-micro colorimetric determination of long-chain fatty acids from plant cutin

Re-examination of the colorimetric fatty acid determination with copper nitrate, followed by complex formation with DIECA has shown that the method is not reliable if applied as described by Duncombe (1962, 1963): The Cu concentration is too high, the DIECA concentration much too low and the wavelength chosen (440 mμ) is suitable only for very low fatty acid concentrations.

The spectrophotometric determination of long-chain fatty acids containing ketonic groups. With particular reference to licanic acid

The spectrophotometric determination of long-chain fatty acids containing ketonic groups. With particular reference to licanic acid