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
Website: @unf

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Classification: Oil -> olive

Citations 8

"Direct Automatic Determination Of Polyphenols In Olive Oils In The Aqueous Phase Of A Flow Injection Liquid-liquid Extraction System Without Phase Separation"
Anal. Chim. Acta 1990 Volume 235, Issue 2 Pages 441-444
José A. G. Mesa, Pilar Linares, M. D. Luque de Castro and M. Valcárcel

Abstract: Olive oil was merged with a hexane stream (diagram of manifold given) and then mixed with the carrier stream of 0.1 M NaHCO3 - 1% Folin - Ciocalteu reagent (1:1). The flow direction was changed by synchronization with the sample injection such that the organic phase never reached the flow cell. The absorbance of the aqueous phase was measured at 750 nm. The system was flushed with ethyl ether after each series of runs. The method was applied in the analysis of 6 olive oils and results agreed well with those obtained by conventional methods. The calibration graphs were rectilinear bewteen 100 and 900 µg mL-1. Sampling frequency was 28 h-1.
Phenols Spectrophotometry Sample preparation Phase separator Flowcell Extraction Organic solvent

"Direct Automatic Determination Of Bitterness In Virgin Olive Oil By Use Of A Flow Injection - Sorbent Extraction System"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 367-374
J. A. Garía-Mesa, M. D. Luque de Castro* and M. Valcárcel*

Abstract: In the manifold shown, 20 µL of the oil was injected into a hexane carrier stream and passed through a column of C18-bonded silica to remove the sample matrix. With use of methanol as intermediate solvent, the bitter substances were carried by aqueous 50% methanol to a flow cell for spectrophotometry at 225 nm. The column was washed in the reverse direction with methanol, hexane and methanol and then reconditioned with aqueous methanol between samples. Results, expressed as absorbance at 255 nm divided by the oil concentration. (g dl-1), agreed with those obtained by a manual batch method; analysis times by the respective methods were 5 and 50 min. An automated version of an existing batch method for the determination of bitterness in virgin olive oil was developed. The automatic method is based on flow injection analysis (FIA) principles and is implemented by coupling an FIA manifold to a solid-liq. retention unit in which the sample matrix is retained on a C18-bonded silica-packed minicolumn, the analytes being monitored by UV spectrophotometry and the retained matrix being eluted in the opposite direction to detection, so it never reaches the detector. The automatic method clearly surpasses its manual counterpart in terms of solvent savings, anal. time (5 vs. 50 min) and labor requirements (none of the tedious preliminary steps of the manual method need be implemented). The relative standard deviation was 1.26% for K225 (absorbance at 225 nm/oil concentration. in g/100 mL) = 0.55.
Bittering compounds Spectrophotometry Sample preparation Solid phase extraction Method comparison C18

"Membrane Extraction-preconcentration Cell Coupled Online To Flow Injection And Liquid Chromatographic Systems. Determination Of Triazines In Oil"
Anal. Chim. Acta 1995 Volume 304, Issue 3 Pages 323-332
R. Carabias Martínez*, E. Rodríguez Gonzalo, E. Hernández Fernández and J. Hernández Méndez

Abstract: The membrane extraction-pre-concentration (MEP) cell consisted of two channels separated by a Celgard 2500 membrane (0.025 mm thick, 45% porosity, 0.04 µm effective pore size). Oil samples diluted with hexane (1:4) were propelled through one channel and the acceptor solution was propelled through the other channel. The acceptor solution was held stationary during the extraction-pre-concentration period while the diluted oil sample was circulated continuously. The MEP cell was coupled online to FIA or HPLC systems for the determination of triazines in vegetable oils. The FIA system used 0.1 M HClO4 as the acceptor solution. At the end of the 5-15 min MEP period, the acceptor solution was propelled to the diode-array spectrophotometer where the total triazines were determined at 220 nm. The calibration graphs were linear (range not given) with detection limits of 0.91 ppm. RSD (n = 10) were 6%. The HPLC system used 5 mM HClO4 in methanol/H2O (9:1) as the acceptor solution. After MEP, the acceptor solution was analyzed on a 5 µm Spheri-5-RP 18 column (25 cm x 4.6 mm i.d.) with 50% aqueous acetonitrile as mobile phase (1.25 ml/min) and detection at 220 nm. Calibration graphs for the determination of atrazine, ametryne, prometryne and terbutryne in corn, sunflower and olive oil were linear for 0.05-20 ppm and the detection limits were ~e;0.1 ppm. RSD (n = 10) were 10%.
Herbicides Atrazine Ametryne Prometryne Terbutryne Spectrophotometry HPLC Sample preparation Celgard Membrane Preconcentration Extraction

"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.
Fatty acids, free 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
Fatty acids, free Spectrophotometry Titrations Organic phase detection Standard method Fourier transform Method comparison Peak width

"Spectrophotometric Determination Of Periodate With Salicylaldehyde Amidinohydrazone Using Flow Injection. Determination Of Glycerol In Vegetable Oils"
Analyst 1989 Volume 114, Issue 8 Pages 989-990
Juan Jos&eacute; Berzas Nevado and Pablo Valiente Gonz&aacute;lez

Abstract: A 0.2 mL sample containing 50 ppm of IO4- was injected into a carrier stream of water (1 mL min-1) and then mixed with 0.06% salicylaldehyde amidinohydrazone solution followed by 0.25 M NH4Cl - NH3 buffer (pH 9.2) (both 1 mL min-1). The absorbance was measured at 490 nm; the calibration graph was rectilinear. Glycerol was determined by treatment with excess of IO4- and set aside for ~30 min before analysis as above. Oil was dissolved in CHCl3 before analysis. Recoveries from olive and sunflower oil were quantitative. The sampling rate was 20 h-1. Periodate has been determined using flow injection with spectrophotometric detection on the basis of the red color obtained when salicylaldehyde guanylhydrazone (SAG) and periodate were mixed in a basic medium. The carrier stream was de-mineralised water. The reagent stream was an aqueous SAG solution and another stream contained an ammonia buffer (pH 9.2) solution. The calibration graph was linear between 5 and 50 p.p.m. of periodate when the injection volume was 200 µL. The relative standard deviation (n= 10) was 1.0% and the detection limit, corresponding to a signal to noise ratio of 3, was 0.35 p.p.m. The proposed method was applied to the determination of glycerol in vegetable oils using the Malaprade reaction.
Periodate Glycerol Spectrophotometry Buffer

"Organic-phase Enzyme Electrode For The Determination Of Phenols In Olive Oils"
Anal. Lett. 1992 Volume 25, Issue 8 Pages 1399-1409
Wang, J.;Reviejo, A.J.;Mannino, S.

Abstract: A polished graphite disc (3 mm diameter) was covered with a solution of tyrosinase in 0.05 M phosphate buffer (pH 7.4) and was dried with a heat gun. Olive oil was dissolved in CHCl3 containing 0.1 M tetrabutylammonium bromide and saturated with the phosphate buffer. Amperometric wall-jet detection of phenols was performed at -0.2 V in a flow injection system (0.4 mL min-1) with a 20 µL sample loop. Quantitation was effected by the standard-additions method. The detection limit was 0.4 µM (0.8 ng) of phenol with an analysis rate of 60 samples h-1. The calibration graph was rectilinear up to 0.6 mM.
Phenols Electrode Amperometry Electrode Electrode Standard additions calibration

"Automation Of Techniques For Oils Analysis. Determination Of UV Absorbance By Flow Injection Analysis"
Grasas Aceites 1990 Volume 41, Issue 6 Pages 418-422
Garcia Mesa, J.A.;Uceda Ojeda, M.;Luque De Castro, M.D.;Valcarcel, M.

Abstract: A method is described, using a flow injection system (illustrated), for the individual and simultaneous measurement of the absorbance of oils at 270 and 232 nm. Sampling rates are 60 and 20 h-1 for individual and simultaneous measurement, respectively; coefficient of variation are 1 to 2.5%. The method was applied in the determination of the absorbance of olive oil.
Spectrophotometry Automation