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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Wine Red

Classification: Beverage -> alcoholic -> wine -> red

Citations 20

"Determination Of Sulfur Dioxide In Wines By Gas-diffusion Flow Injection Analysis Utilizing Modified Electrodes With Electrostatically Assembled Films Of Tetraruthenated Porphyrin"
Anal. Chim. Acta 1999 Volume 387, Issue 2 Pages 175-180
Carla M. N. Azevedo, Koiti Araki, Henrique E. Toma and Lúcio Angnes

Abstract: Reported is a new method for the determination of both Gee and total SO2 in wine, specially designed for FIA. The method involves separation of the analyte using a flow-through gas diffusion unit, in line with an amperometric detector consisting of a glassy carbon electrode modified with electrostatically assembled films of a tetraruthenated porphyrin. The results demonstrate a good accuracy, comparable with those obtained using the conventional iodometric method. In addition, the method can be readily applied to red, white and rose wines; it is free from interference of the other compounds of wine, consumes small amounts of sample and is faster than the iodometric method.
Sulfur dioxide Electrode Gas diffusion Method comparison

"Determination Of Sulfur Dioxide And Ascorbic Acid In Beverages Using A Dual Channel Flow Injection Electrochemical Detection System"
Anal. Chim. Acta 2000 Volume 416, Issue 1 Pages 105-110
Terence J. Cardwell and Melinda J. Christophersen

Abstract: A new flow injection method is described for the simultaneous determination of ascorbic acid (AA) and sulfur dioxide in red and white wines and various fruit juices. The flow injection manifold consists of a dual channel amperometric detection system, where AA is detected at a glassy carbon electrode set at +0.42 V (versus Ag/AgCl) and sulfur dioxide is detected at a platinum electrode at +0.90 V (versus Ag/AgCl) after separation by a gas diffusion unit. In the application of this method to the analysis of both analytes in wines and fruit juices, the results for white wines, fruit juices and juice concentrates agree well with data obtained by ion-exclusion chromatography. However, in the case of red wines and a sweet white wine, it is necessary to extract the analytes using solid phase extraction on a quaternary amine SAX cartridge before acceptable results are achieved by the new flow injection method. The linear dynamic range for AA is 3-50 mg/l with a detection limit of 1.5 mg/l and for sulfur dioxide the linear range is 0.25-15 mg/l with a detection limit of 0.05 mg/l. The sampling frequency for both analytes is 30/h.
Ascorbic acid Sulfur dioxide Amperometry Electrode Electrode Method comparison Gas diffusion Solid phase extraction

"Sequential Determination Of Total And Volatile Acidity In Wines Based On A Flow Injection-pervaporation Approach"
Anal. Chim. Acta 1999 Volume 381, Issue 1 Pages 23-28
E. Mataix and M. D. Luque de Castro

Abstract: A method for the sequential determination of the total and volatile acidity in wines based on the use of a pervaporator inserted in a continuous manifold is reported. The chemical principle is the color change of bromothymol blue in the presence of the analytes and monitoring of the absorbance at 616 nm. The simultaneous injection of two sample aliquots into two channels allows one of the plugs to be driven to the pervaporator and the other directly to the photometric detector after merging with an indicator stream. After pervaporation, the acceptor stream, also containing the indicator, is led to the photometric detector for monitoring. The detection limits and relative standard deviation are 10 meg L-1, 1.0%, and 0.02 g L-1, 5.0%, for total and volatile acidity, respectively. The method has been applied to white and red wines from different origins and the results obtained an in good agreement with those of the standard method used in Spanish wine industries.
Acidity Spectrophotometry Pervaporation Method comparison Standard method

"Simultaneous Determination Of Ethanol And Glycerol In Wines By A Flow Injection-pervaporation Approach With In Parallel Photometric And Fluorimetric Detection"
Talanta 2000 Volume 51, Issue 3 Pages 489-496
E. Mataix and M. D. Luque de Castro

Abstract: A simultaneous method for the determination of ethanol and glycerol in wines based on the coupling of pervaporation-chemical derivatization-photometric detection for ethanol and biochemical derivatization-fluorimetric detection for glycerol is proposed. After separation by pervaporation the ethanol is collected in a K2Cr2O7 acceptor stream and the Cr3+ formed is driven to the spectrophotometer and monitored at 600 nm. The determination of glycerol is based on its oxidation by oxidized β-nicotinamide adenine dinucleotide (β-NAD(+)) catalyzed by glycerol dehydrogenase immobilized on controlled-pore glass, the reduced form of the coenzyme (NADH) being spectrofluorimetrically monitored (lambda(ex) = 340 nm, lambda(em) = 460 nm). The linear determination range is between 1-20% for ethanol and 2-8 g L-1 for glycerol, with RSDs 3 and 2%, respectively. The method applied to red and white Spanish wines, compares well with the official methods for these analytes.
Ethanol Glycerol Spectrophotometry Fluorescence Pervaporation Immobilized enzyme Simultaneous analysis

"Multisyringe Flow System: Determination Of Sulfur Dioxide In Wines"
Analyst 2000 Volume 125, Issue 8 Pages 1501-1505
Marcela A. Segundo, António O. S. S. Rangel, Andreu Cladera and Víctor Cerdà

Abstract: A multisyringe flow system for the spectrophotometric determination of sulfur dioxide in wines is described. The methodology is based on the well-known reaction among SO2, formaldehyde and pararosaniline. The proposed manifold also includes a gas diffusion unit in order to prevent the color interference of red wines in the spectrophotometric measurement. The proposed method was successfully applied to the determination of free SO2 (2-75 mg l-1) and total SO2 (10-250 mg l-1) in wines, just by changing a few operating parameters in the controlling software. A sampling-rate of 25-30 samples per hour was achieved with good repeatability for 10 consecutive injections of wine samples (RSD < 3.2%). The results obtained from 10 wine samples for each determination were statistically comparable to those obtained by the recommended procedure.
Sulfur dioxide Spectrophotometry Gas diffusion Method comparison Multisyringe

"Method Development For Measurement Of Elements In Hungarian Red Wines By Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES)"
Acta Aliment. 2000 Volume 29, Issue 2 Pages 105-122
Csiktusn&aacute;di-Kiss, G. A., Keszler, &Aacute;., Candeaias, M., Bronze, M. R., Boas, L. V., Spaugner, I.

Abstract: ICP-OES (inductively coupled plasma optical emission spectrometry) was used to determine the element content of red wines. Development of the method involves various procedures of sample handling as well as repeatability and reproducibility measurements. Measurements were made for the following 16 elements: Al, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, P, Sr and Zn. The relative standard deviation of repeatability ranged from 0.41% (potassium) to 27% (cadmium) and that of reproducibility varied between 0.73% (boron) to 52% (cobalt). Recovery of the elements was determined by standard addition with results ranging from 90.6% (phosphorus) to 116.2% (boron). After that, 15 red wine samples were measured. Significant differences were found in the Al, B, Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Na, P, Sr and Zn (P<0.001) concentration of wine samples. Correlation studies revealed parallel changes in phosphorus-potassium, phosphorus-magnesium and zinc-manganese concentrations (r=0.857, 0.875, 0.838). According to principal component analysis, measurements of zinc-, sodium-, boron-, copper- and strontium content gave almost the same results as obtained with 16 different elements. According to a two dimensional non-linear map of absolute values of principal component analysis, wines from Szekszard and Eger could be differentiated, whereas the analysis of wines from Villany, the Matra Mountains and Lake Balaton showed overlapping results.
Aluminum Boron Barium Calcium Cadmium Cobalt Chromium Copper Iron Potassium Magnesium Manganese Sodium Phosphorus Strontium Zinc Spectrophotometry Volatile generation Standard method

"Indirect Flow Injection Determination Of Tannins In Wines And Tea By Atomic Absorption Spectrometry"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 357-363
M. C. Yebra, M. Gallego and M. Valc&aacute;rcel*

Abstract: The automated procedure for the indirect determination of tannins in food was based on the precipitation of tannins with copper acetate complex and the determination of the unprecipitated Cu by AAS. The precipitating reagent contained 200 µg/ml of Cu in 0.1 M ammonium acetate of pH 5.2. The flow injection manifold allowed 50 µL of precipitating reagent to be injected into a stream (0.7 ml/min) of sample solution. The flow was propelled through a precipitation coil (2.5 m x 0.5 mm i.d.) and a screen-type stainless-steel filter (pore size 0.5 µm, filter area 3 cm2). The filtrate was diluted with a water stream (2.5 ml/min) and aspirated into the AAS system. Cu was determined at 324.7 nm with an air/acetylene flame. The calibration graph was linear for 1-25 µg/ml of tannic acid with a detection limit of 0.7 µg/ml. The RSD (n = 11) for the determination of 10 µg/ml tannic acid was 2%. The sampling frequency was 80-100 samples/h. The method was applied to white and red wine, and tea. Wine was diluted 50-250-fold before analysis and the pH was adjusted to 5-5.5 with NH3. A 1 g portion of tea was boiled for 10 min with 50 mL water. The mixture was filtered and the filtrate was analyzed after dilution. Recoveries of 250-500 µg of tannic acid from spiked wine and tea were 96.1-104.3%.
Tannins Spectrophotometry Precipitation Filter Complexation Indirect

"Development Of A Potentiometric Procedure For Determination Of Glycerol And 2,3-butanediol In Wine By Sequential Injection Analysis"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 193-199
Gilmara C. Lucaa, Boaventura F. Reisb,*, Elias A. G. Zagattob, Maria Concei&ccedil;&atilde;o B. S. M. Montenegroc, Alberto N. Ara&uacute;joc and Jos&eacute; Luis F. C. Limac

Abstract: A flow sequential injection procedure with potentiometric detection for determination of glycerol and 2,3-butanediol in wine is described. The method was based on reaction of IO-4 ions with glycerol and 2,3-butanediol with the reagent consumption afterwards being continuously monitored by means of a PVC periodate ion selective electrode constructed with tubular configuration and without inner reference solution. The electrode membrane was based on bis(triphenylphosphoranylidene) ammonium periodate dissolved in 2-nitrophenyloctyl ether and immobilized in PVC. In the developed set-up, a 2.0 x 10^-2 mol L-1 sodium periodate solution was used as carrier. To minimize interferences caused by other reducing components in the samples, a mini column packed with the anionic Amberlite IRA 400 (20-50 mesh, OH- form) resin was coupled to a lateral port of the valve. The feasibility of the anal. proposal was ascertained by determining polyols as glycerol in a set of red and white wine. The accuracy of the proposed method was assessed by standard addition samples with glycerol. Recoveries within the 96.0-106.9% range were calculated A sample throughput of 33 per h, a reagent consumption of 9.4 mg of sodium periodate per determination and a relative standard deviation of results lower than 1% were obtained.
Glycerol 2,3-Butanediol Potentiometry Electrode Electrode Electrode Sequential injection Indirect Interferences Apparatus Detector Standard additions calibration Amberlite Resin Column

"Determination Of L-malate In Wine By Flow Injection With Co-immobilized Malate Dehydrogenase-oxaloacetate Decarboxylase"
Talanta 1993 Volume 40, Issue 8 Pages 1163-1165
Nobutoshi Kiba, Mie Oguchi and Motohisa Furusawa

Abstract: Oxaloacetate decarboxylase (used as a trapping enzyme) and malate dehydrogenase were co-immobilized on to aminated poly(vinyl alcohol) beads (GS 520; 13 µm) packed into a column (5 cm x 4 mm), using glutaraldehyde (method described). White or red (decolorized using nylon beads) wine was diluted with water, then portions (50 µL) were injected into a carrier stream of glycine buffer of pH 10 containing 0.1 M MgCl2/8 mM NAD+ (0.6 ml/min) and carried to the enzyme reactor (30°C) where the NADH produced was monitored fluorimetrically at 465 nm (excitation at 340 nm). The conversion efficiency of the reactor was 44%, and the relative activities for L- and D-malate were 100 and 9, respectively. Other carboxylic acids did not interfere at concentration. 2 mM. The calibration graph was rectilinear from 0.4-300 µM-L-malate, and the RSD at 20 µM was 1%; the detection limit was 0.2 µM. Recoveries of spiked red wine samples were 97-102%. One reactor could be used to analyze >1400 samples.
l-Malate Fluorescence Interferences Immobilized enzyme Poly vinyl alcohol beads

"Determination Of Reducing Sugars In Wine By Flow Injection Analysis"
Analyst 1987 Volume 112, Issue 11 Pages 1569-1572
Angel Maquieira, M. Dolores Luque de Castro and Miguel Valcarcel

Abstract: Flow injection procedures based on the use of(I) picric acid,(II) Cu(II) - neocuproine and (iii) Nelson - Somogyi reagent were compared, with detection at 520, 460 and 820 nm, respectively. Results for three white and two red wines by all three methods were generally in good agreement with those obtained by a standard procedure. Method(II) had the best and (iii) the poorest precision. However, (iii) was the most rapid procedure as, in contrast to(I) and(II), no pretreatment with activated charcoal was needed. Sampling rates of 40 to 50 h-1 were possible with all three methods.
Glucose Spectrophotometry Method comparison Multidetection

"Determination Of Total And Free Sulfur Dioxide In Wine By Pervaporation-flow Injection"
Analyst 1998 Volume 123, Issue 7 Pages 1547-1549
E. Mataix and M. D. Luque de Castro

Abstract: A simple and interference-free method for the determination of SO2 in wine based on removal of the analyte by pervaporation is proposed. The sulfur dioxide is formed in an acidic stream and removed from the liquid sample at the donor chamber of the pervaporation unit, then collected in an acceptor solution containing p-rosaniline and formaldehyde. The typical colored compound thus formed is monitored photometrically at 578 nm on passage through a flow cell. The linear determination range is between 2.0 and 20 µg/mL with a precision, expressed as relative standard deviation, lower than 3.0%. The method has been successfully applied to the determination of free and total sulfur dioxide in red and white wines and compares well with the standard iodimetric method.
Sulfur dioxide Spectrophotometry Pervaporation Interferences Method comparison Membrane Volatile generation

"Flow Injection Spectrophotometric Determination Of Free And Total Sulfite In Wines Based On The Induced Oxidation Of Manganese(II)"
Anal. Lett. 1998 Volume 31, Issue 13 Pages 2195-2208
Rosa Lina G. N. P. Silva; Cintia S. Silva; Joaquim A. N&oacute;brega; Eduardo A. Neves

Abstract: The sulfur(IV) content in wines was determined with a flow injection spectrophotometric system by treating each sample in the donor channel with sulfuric acid to release free SO2, which diffuses through a PTFE membrane to the acceptor solution containing Mn(II) in acetate buffer at pH 5.5. The induced oxidation of Mn(II) takes place proportionally to the free S(IV) content and the oxidized species formed reacts with iodide to form iodine which can be spectrophotometrically measured at 352 nm. A linear plot of absorbance vs. S(IV) concentration. is observed up to 26 mg SO2/L with a detection limit of 1.0 mg/L. Matrix effects required the standard additions of sulfite to the samples for obtaining accurate results. A previous treatment of the sample with tris(hydroxymethylaminomethane) and EDTA decomposed the hydrogen-sulfite/aldehyde adducts and allowed the determination of the total S(IV) content. As expected, total S(IV) concentration. in wines has been found to be much higher than free sulfite. A recovery-addition experiment with red and white wines led to recoveries varying from 91.5 to 109.7% by applying the free and total sulfite developed procedures. This is a good indication of the accuracy of both proposed procedures.
Sulfite Spectrophotometry Teflon membrane Gas diffusion Indirect Standard additions calibration

"Flow Injection Analysis Of Glycerol Based On Oxygen Consumption Using Glycerol Dehydrogenase And NADH Oxidase"
Anal. Sci. 1994 Volume 10, Issue 3 Pages 445-448

Abstract: Wine was diluted 1:100 with 0.1 M potassium phosphate buffer of pH 8 and mixed with an equal volume of 5 mM NAD+ in the same buffer. Portions (20 µL) were injected into a stream (0.5 ml/min) of 0.1 M glycylglycine/KOH buffer of pH 9.2 containing 60 µM-FAD and 30 mM ammonium sulfate, and carried to a column (6.4 cm x 3 mm i.d.) packed with glycerol dehydrogenase (10 iu) and NADH oxidase (15 or 30 iu) immobilized on CNBr-activated Sepharose 4B (0.2 g); the H2O2 produced was detected amperometrically at -0.7 V using a Clark-type O2 electrode. All determinations were performed at 29°C. The calibration graphs were linear from 0.1-1.5 mM glycerol. At 2.5 mM glycerol an RSD of 0.65% (n = 10) was obtained. The sampling frequency was 25/h. No significant decrease in response was observed over a 25 day period. The results for the determination of glycerol in red and white wines were 6-14% higher than those obtained by the F-kit method (Boehringer Mannheim).
Glycerol Amperometry

"Determination Of Sulfite In White Wine By Amperometric Flow Injection Analysis With An Immobilized Sulfite Oxidase Reactor"
Agric. Biol. Chem. 1989 Volume 53, Issue 9 Pages 2347-2353
Kiyoshi MATSUMOTO, Hiroaki MATSUBARA, Hiroyuki UKEDA and Yutaka OSAJIMA

Abstract: Sample (4 ml) is mixed with 2.5% gelatin solution (1 ml) to remove interfering substances (e.g., polyphenols), filtered, and diluted ~20-fold with 0.1 M phosphate buffer of pH 8.0, and portions (240 µL) are passed in parallel through a column (10 cm x 2 mm) of sulfite oxidase immobilized on CNBr-activated Sepharose 4B and a blank column of Sepharose without the enzyme. The mobile phase is the 0.1 M phosphate buffer, and detection is by amperometry at +0.50 V in a flow-through cell fitted with a Pt-wire working electrode, a vitreous-carbon counter electrode and a reference Ag - AgCl (KCl) electrode. The difference in response for the streams with and without enzyme treatment is used to calculate the SO32- content. Typically, the calibration graph was rectilinear for 1 to 10 ppm of SO32-, the recovery was 94%, and the coefficient of variation at 5 ppm was 2.3% (n = 10). Response was maintained for 20 days and fell to 67% of the original value after 45 days for 5 ppm of SO32-. Results for red wine were erratic, showing that the gelatin treatment does not wholly prevent interference.
Sulfite Amperometry Electrode Immobilized enzyme Buffer Column Interferences

"Determination Of SO2 In Wines Using A Flow Injection Analysis System With Potentiometric Detection"
J. Agric. Food Chem. 1998 Volume 46, Issue 1 Pages 168-172
Alberto N. Ara&uacute;jo, Cristina M. C. M. Couto, Jos&eacute; L. F. C. Lima, and Maria C. B. S. M. Montenegro

Abstract: This paper describes the development and application of a flow injection analysis system manifold comprising a gas diffusion unit and a potentiometric detector to the determination of free and total SO2 in white and red wines. A homogeneous crystalline iodide double-membrane tubular electrode was used as detector. SO2 determination based on the Ripper method was carried out by dosing the iodide formed in the oxidation of SO2 with iodine, followed by the separation of the formed compound through a diffusion Teflon membrane. The results obtained from the analyzes of free and total SO2 in 30 wine samples showed good agreement between the proposed method and the rapid assay method recommended by the UE and OIV. The relative error deviations of the results obtained by both methods were <6%. This procedure is suitable for samples with ~3.2-180 mg L-1 SO2, performing determinations of 75-100 samples h-1.
Sulfur dioxide Potentiometry Electrode Electrode Stopped-flow Method comparison Gas diffusion

"Determination Of Total Sulfite In Shrimp, Potatoes, Dried Pineapple, And White Wine By Flow Injection Analysis: Collaborative Study"
J. AOAC Int. 1990 Volume 73, Issue 1 Pages 35-42
Sullivan JJ, Hollingworth TA, Wekell MM, Meo VA, Saba HH, Etemad-Moghadam A, Eklund C, Phillips JG, Gump BH

Abstract: A method for the determination of total sulfite in shrimp, potatoes, dried pineapple, and white wine by flow injection analysis (FIA) was collaboratively studied by 8 laboratories. In the method, the sample solution is reacted with sodium hydroxide to liberate aldehyde-bound sulfite. The sample stream is acidified to produce SO2 gas, which diffuses across a Teflon membrane in the gas diffusion cell into a flowing stream of malachite green. The degree of discoloration of the malachite green is proportional to the amount of sulfite in the sample solution. Red wine was included in the study but interlaboratory precision for these samples was not satisfactory and correlation with Monier-Williams results was poor. The present method is not recommended for use with these samples. For shrimp, potatoes, dried pineapple, and white wine, average reproducibility (RSDR) of results was 25% for samples at 10 ppm SO2 and 10% for samples at greater than 50 ppm. Overall average reproducibility was 14%. Recoveries of sulfite added to samples averaged 80%. Comparison of FIA with the Monier-Williams method indicated comparable results by the 2 methods. The FIA method has been adopted official first action for determination of greater than or equal to 5 ppm total sulfite in shrimp, potatoes, dried pineapple, and white wine.
Sulfite Spectrophotometry Diffusion Teflon membrane Method comparison Gas diffusion

"Determination Of Free (pH 2.2) Sulfite In Wines By Flow Injection Analysis: Collaborative Study"
J. AOAC Int. 1990 Volume 73, Issue 2 Pages 223-226
Sullivan, J.J.;Hollingworth, T.A.;Wekell, M.M.;Meo, V.A.;Etemad Moghadam, A.;Phillips, J.G.;Gump, B.H.

Abstract: A method for the determination of free sulfite in wine by flow injection analysis (FIA) is described. The method involves liberation of sulfur dioxide from the wine at pH 2.2, with detection by decolorization of a malachite green solution. The method was collaboratively studied, and the results indicated an average reproducibility of 12% for white wine samples (average level 12.1 ppm SO2) and 26% for red wine samples (average level 3.1 ppm). When the FIA method was compared to an aeration/oxidation method, the results indicated a high degree of correlation between the 2 methods. The FIA method has been adopted by AOAC official first action. Red or white wine was injected into a flow injection analysis (FIA) system and mixed with 0.5 M citric acid reagent (pH ~2). The SO2 produced diffused across a PTFE membrane in a gas diffusion cell into a flowing stream of malachite green solution. The degree of decolorization, which was proportional to the amount of SO2, was measured spectrophotometrically. Data from 7 laboratories indicated an average reproducibility of 12% for white wine (mean 12.2 ppm SO2) and 26% for red wine (mean 3.1 ppm). The results agreed with those from an aeration/oxidation method. It is recommended that the FIA method be adopted official first action, with the note that the method measures both free SO3-2 and any combined SO3-2 that is labile under the conditions used.
Sulfite Spectrophotometry pH Membrane Mixing Gas diffusion Teflon membrane Indirect Method comparison

"Sequential Injection Analysis Of Free And Total Potassium In Wines Using Potentiometric Detection And Microwave Digestion"
Am. J. Enol. Vitic. 2003 Volume 54, Issue 1 Pages 46-49
N&eacute;stor Z&aacute;rate, Alberto N. Ara&uacute;jo, Maria Concei&ccedil;&atilde;o B.S.M. Montenegro, and Ricardo P&eacute;rez-Olmos

Abstract: An automatic procedure for the determination of free and total potassium in wines is described that combines sequential injection analysis with potentiometric detection. A sequential injection mounting is coupled to a microwave system to conduct the on-line digestion of the sample, thereby making the injection of samples possible without prior treatment. Free potassium was determined by injecting 110 µL of sample and forwarding it to the detection system. In the evaluation of total potassium, the sample was previously digested with 390 µL of hydrogen peroxide for 60 seconds at 700 W in a microwave oven. Using an optimized mounting, 10 samples of different wine types were analyzed (white, red, and port), and results were then compared with those provided by flame emission photometry. Relative standard deviations obtained were always below 3% and sampling rate attained was about 14 samples per hour.
Potassium Sample preparation Sample preparation Spectrophotometry Potentiometry Apparatus Automation

"Correlation Of Wine Phenolic Composition Versus Cyclic Voltammetry Response"
Am. J. Enol. Vitic. 2002 Volume 53, Issue 4 Pages 294-302
Paul A. Kilmartin, Honglei Zou, and Andrew L. Waterhouse

Abstract: Cyclic voltammetry has been used to quantify antioxidants at a carbon electrode in white wines diluted to 10% and red wines diluted to 0.25% in a model wine solution (12% ethanol, 0.033 M tartaric acid adjusted to pH 3.6). The first peak near 400 mV (versus Ag/AgCl) was due to phenolic compounds with an ortho-diphenol group or to gallic acid, while a small feature at 300 mV was seen in red wines containing higher levels of myricetins (triphenol on the flavonoid B-ring), and a peak or shoulder at 470 mV was ascribed to quercetin glycosides. The integral of the current to 500 mV was then used as a measure of the lower oxidation potential phenolics, reported as gallic acid equivalents, and compared to traditional measures of total phenols in wines. A peak at 640 mV in red wines was associated with malvidin anthocyanins and was smaller in an older red wine sample, while further oxidation current beyond 700 mV prominent in white wines was due to meta-diphenol or isolated phenol groups and other oxidizable compounds. Simulated voltammograms constructed from high-pressure liquid chromatography results for six monomeric phenolics were in good agreement with the experimental voltammograms for the white wines, while a higher proportion of the current for the red wine samples was due to oligomeric phenolics.
Antioxidants Phenol Voltammetry Quality Sample pretreatment

"Tyrosinase Biosensor For The Measurement Of Wine Polyphenolics"
Am. J. Enol. Vitic. 2001 Volume 52, Issue 3 Pages 219-222
William T. Jewell and Susan E. Ebeler

Abstract: Polyphenolics are a broad class of compounds present in many fruits, vegetables, and their products, including grapes and wines. Phenolics are important in winemaking as they contribute many sensorial properties to wines and determine the aging potential of red wine. Current measurements involve monitoring colorimetric chemical reductions and can be time-consuming and generate chemical waste. Biosensors are relatively new analytical devices that offer many advantages over current analytical procedures. In this study, a simple tyrosinase-based biosensor was constructed for the measurement of wine polyphenolics. Excellent correlation was shown between the biosensor and the Folin-Ciocalteu assay for simple phenolics and for model and finished wines. Our results show the tyrosinase-based biosensor to be a rapid, simple, and accurate method for measurement of concentration and reduction potential of polyphenolics in wines.
Phenols, poly Sensor Method comparison