University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Email: schalk@unf.edu
Website: @unf

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Fatty acids, free

  • CAS Registry Number: NA

@ ChemSpider@ NIST@ PubChem

Citations 12

"An Automated Flow-reversal Injection - Liquid-liquid Extraction Approach To The Direct Determination Of Total Free Fatty Acids In Olive Oils"
Anal. Chim. Acta 1996 Volume 318, Issue 2 Pages 187-194
Zheng-liang Zhi, Angel Ríos and Miguel Valcárcel*

Abstract: The apparatus consisted of an online sample dilution subassembly which allowed dilution of olive oil with toluene (1:5) and a single-channel flow-reversal manifold equipped with a circulation loop (34 cm x 0.8 mm i.d.) and a flow-through detection cell (18 µL; 10 mm light path) for the liquid-liquid extraction; spectrophotometric detection was at 716 nm. A portion of diluted olive oil was mixed with 0.02 M copper(II) nitrate and adjusted to pH 6.3 with 50% aqueous pyridine then transferred to the loop and circulated at 1.2 ml/min in the flow-reversal mode with a 9 s cycle so that the aqueous phase did not enter the detection cell. The cycle was repeated up to 10 times to generate multipeak absorbance time signals. The calibration graph was linear from 0.01-1.5% oleic acid which corresponded to 0.06-9% FFA in olive oil. The RSD (n = 11) for the determination of 0.119-0.973% FFA was 7.8-4.9%. The frequency was 2 samples/h. The results obtained were confirmed by a manual procedure and by an acid-base titration method.
Oil Spectrophotometry Sample preparation Flow reversal Extraction Automation Method comparison

"Automated Flow Injection Spectrophotometric Non-aqueous Titrimetric Determination Of The Free Fatty-acid Content Of Olive Oil"
Anal. Chim. Acta 1997 Volume 351, Issue 1-3 Pages 291-297
Panayotis G. Nouros, Constantinos A. Georgiou and Moschos G. Polissiou*

Abstract: An automated how injection titrimetric method for the determination of olive oil acidity is proposed. A 175 µl olive oil aliquot is injected in a carrier stream (the titrant) of n-propanol containing 7.5 x 10^-4 M KOH and 4.0 x 10^-5 M phenolphthalein indicator. The sample zone is dispersed in the titrant while flowing at 4.4 mi min-1 through a 1.1 mi Plexiglas mixing chamber and the absorbance of the resulting mixture is continuously monitored at 562 nm, lambda(max), for the basic form of the indicator. The resulting negative absorbance peaks indicate the transition base (red)-acid (colorless)-base (red) of the indicator. Quantitation is based on peak width measurements. Peak widths of 31.7-97 a were measured with a relative standard deviation (RSD) of < 2.1% (n = 10), and the analytical range was 0.15-8.0% (w/w) free fatty acid content calculated as oleic acid. The sampling rate is 30-100 h-1 while n-propanol consumption is only 3-7 mi per run. Recoveries of oleic acid from commercial olive oils ranged from 97.9 to 101.6% (mean 99.5%). The method was applied for the determination of free fatty acid content of thirty two samples of olive oils. Results obtained by the proposed method compare well (0.3-3.6% relative difference, mean 1.5%) with those obtained by the official European Community method that is time consuming and uses gross amounts of organic solvents. Moreover comparison with a Fourier transform infrared F-IR) method reveals that by using the proposed method the useful range can be extended to lower concentrations. 18 References
Oil Spectrophotometry Titrations Organic phase detection Standard method Fourier transform Method comparison Peak width

"Determination Of Free Fatty Acids In Dairy Products By Direct Coupling Of A Continuous Preconcentration Ion-exchange-derivatization Module To A Gas Chromatograph"
Anal. Chem. 1994 Volume 66, Issue 5 Pages 628-634
Evaristo Ballesteros, Soledad Cardenas, Mercedes Gallego, and Miguel Valcarcel

Abstract: A flow injection ion-exchange system coupled to a gas-liquid chromatograph was used for the determination of free fatty acids in dairy products. The pretreatment module permits isolation and pre-concentration of free fatty acids on Amberlite IRA-400 and derivatization of eluted acids with acetyl chloride in methanol. The methyl esters are continuously injected via the injection port to prevent losses of the more volatile esters; they are quantified at the milligram per liter level with a FID detector. The method thus developed was applied to the determination of free fatty acids in milk, cream, and butter samples; fatty acids were also added to some samples to induce rancidity in order to assess the method performance. Copyright 1994, American Chemical Society.
Dairy Products Food Food Cow Ion exchange GC Preconcentration Amberlite

"Determination Of Short-chain Fatty Acids In Raw Milk Using A Microbial Sensor And The Relationship With Milk Quality"
Anal. Sci. 1994 Volume 10, Issue 4 Pages 683-685
H. UKEDA, Y. FUJITA, M. SAWAMURA and H. KUSUNOSE

Abstract: The sensor comprised an immobilized microbial membrane (preparation details given) attached to a PTFE membrane and an O2 electrode. The microbial membrane was fixed to the OI2 electrode by a dialysis membrane of a cellulose tubing. In the FIA system milk (20 µL) was injected into the carrier solution of 0.2 M potassium phosphate buffer of pH 7 (1 ml/min) which passed through a mixing coil (60 cm x 0.8 mm i.d.) to a flow-through cell equipped with the microbial electrode. The concentration of the short-chain fatty acids in the milk was expressed as the concentration equivalent to butyric acid. The sampling frequency of the microbial sensor was 15 samples/h. The calibration graph was linear for 0.11-2.8 mM butyric acid. The microbial sensor was applied to the evaluation of milk quality.
Milk Sensor Dialysis

"Determination Of The Free Fatty-acid Content In Fats And Oils By Flow Injection Analysis With Electrochemical Detection"
Anal. Sci. 1995 Volume 11, Issue 6 Pages 979-982
K. TAKAMURA, T. FUSE and F. KUSU

Abstract: A flow injection analytical method using a walljet-type electrochemical detector was developed for determining the content of free fatty acids. A simple flow injection system was constructed. An ethanol solution containing 3 mM 2-methyl-1,4-naphthoquinone and 38 mM LiClO4 served as the carrier solution. The flow-signal response for higher fatty acids was linear between 25 and 1500 pmol test-1. The free fatty acid content in various fat and oil samples was determined by both the present and conventional titration methods. The present method was found to be not only highly sensitive with high reproducibility, but also quite simple and rapid. (10 references)
Oil Electrode Method comparison

"Feeding Of Silage Effluent To Dairy Cows"
Acta Agri. Scand. A 1997 Volume 47, Issue 1 Pages 20-30
Ashild T. Randby

Abstract: Three feeding experiments, each with 24 cows, were performed to evaluate the use of effluent from grass silage as feed. The quality of silages produced in open-drainage silos and closed-drainage silos was also compared. Silage and effluent were fed ad libitum with concentrate supplements. Animals readily consumed effluent at 30 kg day-1 on average, equivalent to 2.2 kg dry matter (DM) day-1. Silage intakes decreased by 1 kg DM day-1 when silage plus effluent was fed as compared with silage alone, while total roughage intake (silage plus effluent) increased by 1.2 kg DM day-1. Milk yields and fat, protein, and lactose contents (analyzed by FIA) tended to increase for cows receiving effluent. Increases in milk yield were small, however, relative to the increases in DM intake, indicating reduced feed conversion efficiency when effluent was fed. Intakes of silage stored in the presence of effluent tended to be lower than those of silage from which effluent had been drained, but milk yield and milk composition were unaffected.
Cows Milk

"The Lipoxygenase Sensor, A New Approach In Essential Fatty Acid Determination In Foods"
Biosens. Bioelectron. 1997 Volume 12, Issue 11 Pages 1089-1099
Michael Schoemaker, Rainer Feldbr&uuml;gge, Bernd Gr&uuml;ndig and Friedrich Spener

Abstract: Both an enzyme electrode and enzyme column with immobilized lipoxygenase, respectively, were used for the determination of essential fatty acids. The former was applied in a batch system, the latter was part of a fully automated flow injection analysis (FIA)- system. The oxygen consumption due to the lipoxygenase catalyzed oxygenation of essential fatty acids was monitored amperometrically. Both systems were compared with regard to linear ranges of the calibration plots, sensitivities, detection limits, apparent Michaelis- Menten constants and lifetimes. The enzyme electrode showed different sensitivities for linoleic and α-linolenic acids, the most common essential fatty acids. The reason for this was not a second oxygenation step by lipoxygenase in case of α-linolenic acid, but a different dialytic behavior of the two substrates. Hence, only the FIA-system was used for the determination of these fatty acids in real matrices such as vegetable oils and margarines. In the presence of detergent the triglycerides of the hydrophobic food samples were converted into water soluble glycerol and free fatty acids by a 15 min incubation with a ready to use lipase/esterase-mix, thus avoiding the use of organic solvents for analysis. Results obtained by the enzymatic FIA-system were in excellent agreement with those obtained by standard gas chromatography.
Food Oil Amperometry Sensor Immobilized enzyme Method comparison

"Flow Injection Analysis: An Alternative To Automation For Determination Of Analytical Parameters In Oils"
Grasas Aceites 1990 Volume 41, Issue 3 Pages 270-276
Luque De Castro, M.D.;Garcia Mesa, J.A.

Abstract: Flow injection methods for oil analysis are reviewed, including determination of iodine value, free fatty acids and phenolic compounds. (25 references).
Oil Automation Review

"Automated Free Fatty Acid Determination Using Flow Injection Analysis Solvent Extractions"
J. Am. Oil Chem. Soc. 1987 Volume 64, Issue 7 Pages 1004-1007
John S. Canham and Gilbert E. Pacey

Abstract: The sample (100 µL) was injected into the carrier (toluene) stream which then segmented with the reagent (Cu(II) - pyridine) stream and passed (1.4 mL min-1) through a coil of PTFE tubing (0.5 m x 0.5 mm). The stream then entered the membrane separator (3.5 cm x 0.2 cm) and the absorbance of the toluene phase, containing the Cu(II) - fatty acid complex, was measured at 699 nm. The calibration graph was rectilinear in the range 60 µM to 6 mM oleic acid. Precision was ~1%. Solvent-extraction flow injection analysis (flow diagram presented) improved the rate of sampling, sensitivity and precision, and reduced the amount of reagent used and the hazards from toxic fumes.
Feed Spectrophotometry Sample preparation Optimization Phase separator Solvent extraction Teflon membrane

"Automated Method For Determination Of Free Fatty Acids"
J. Am. Oil Chem. Soc. 1981 Volume 58, Issue 10 Pages 935-938
Lars-G&ouml;sta Ekstr&ouml;m

Abstract: An automated colorimetric method is described for determining free fatty acids (FFA) in vegetable oils using the flow injection analysis (FIA) technique. In this procedure, an almost linear relationship exists between the peak height and the FFA concentration. Liquid samples can be poured directly into the sample cups on the sampler for an automatic analysis of the FFA content. The dynamic range of this method is from 0.01 to almost 5%. Samples with higher FFA content must be diluted before analysis. The sample capacity is 12-20 injections/hr. No evidence of the existence of the earlier proposed cage-like complex (Cu(II)(FFA)2)2 in the organic phase was observed in this study.
Oil Spectrophotometry Sample preparation Automation Extraction

"Colorimetric Assay For Free Fatty Acids In Butter Using Flow Injection And Immobilized Enzymes"
J. Food Sci. 1991 Volume 56, Issue 5 Pages 1229-1232
Schooner, F.;Simard, R.E.;Pandian, S.

Abstract: Butyrate kinase was extracted from frozen Escherichia coli DH5 pJc7 and purified by sonic oscillation in a buffer solution containing dithiothreitol, followed by centrifugation, hydrophobic interaction chromatography with an octyl-sepharose (4 cm x 2.5 cm) and a phenyl-sepharose (10 cm x 2.5 cm) column in series, dialysis, ultrafiltration, affinity chromatography on Matrex Red A (4 cm x 2.5 cm), chromatography on a phenyl-sepharose column (4.5 cm x 1.5 cm) and ultrafiltration. The enzyme was immobilized on porous glass beads and packed in a glass tube as a biosensor coupled with a flow injection analysis (FIA) system. Butter samples were analyzed by the batch method as described by Rose et al. (Methods in Enzymology, 1955, 1, 591) and by FIA coupled with the biosensor. Optical density was read at 510 nm. Detection limits were 25 ppm for the FIA system and 5 ppm for the batch method.
Food LC Spectrophotometry Sensor Sample preparation Buffer Extraction Filtration Immobilized enzyme Porous glass beads Dialysis

"Determination Of Free Fatty Acids In Foods By Flow Injection"
J. Sci. Food Agric. 1994 Volume 66, Issue 4 Pages 473-478
Rosa Puchades*, Alicia Suescun, Angel Maquieira

Abstract: Milk fat from cow and ewe milk was extracted by the method of Garcia Olmedo et al. (Anal. Bromatol., XXXI, 227) using a rotary evaporator instead of a Soxhlet extractor. Cocoa butter was extracted using the industrial process of NATRA SA (Valencia, Spain). The extracts or olive oils were homogenized with toluene in an ultrasonic bath and the homogenate injected into a carrier stream of toluene (0.95 ml/min). The carrier stream merged with a reagent stream of aqueous copper acetate/pyridine reagent of pH 6.1 (0.84 ml/min) and the solutions were mixed in a reaction coil (30 cm x 3 mm diameter). The mixed solution passed into a phase separator containing a lipophilic membrane and the copper-pyridine colored complex in the organic phase was measured spectrophotometrically at 716 nm. The calibration graph for oleic acid was linear for 0.1-5 M with reproducibility RSD (n = 12) of 1.9% at 0.3 mM and 0.8% at 2 mM. The precision RSD (n = 3) was 1.09% and recoveries were 98-101%. The effects of interferences on the method is discussed.
Food Spectrophotometry Method comparison