Determination Of Ethanol In Wines Research Articles

Determination of Ethanol in Wine and Distilled Alcoholic Beverages Using a Smartphone as a Detector

This paper describes the application of a smartphone as a detector in the determination of ethanol in distilled beverages. Digital image analysis as an analytical tool is a reality nowadays, and the use of smartphones stands out due to its high accessibility and practicality. The aim is to determine ethanol in distilled beverages using two cheap and simple methods using a smartphone as a detector. Two methods were used, with phenanthroline (method A) and with potassium dichromate (method B) as a reagents and two detectors, spectrophotometer and smartphone. Linear dependence of signal was achieved in the concentration range: from 1.0 to 65.0% (v/v) for method A and from 7.0 to 50.0% (v/v) for method B. The concentration range that is linear with the signal is wide and allows sufficient sensitivity and thus gives the possibility to determine a variety of distilled beverages. Comparison of the obtained results shows that the smartphone and the proposed reagents can be used in routine analysis in quality control of used samples. The results obtained are comparable with the results obtained using a spectrophtometer or with nominal values. The method proved to be simple and inexpensive for the determination of ethanol, does not use expensive reagents neither laborious procedures to carry out the analysis.

Automated in-syringe single-drop head-space micro-extraction applied to the determination of ethanol in wine samples

A novel approach of head-space single-drop micro-extraction applied to the determination of ethanol in wine is presented. For the first time, the syringe of an automated syringe pump was used as an extraction chamber of adaptable size for a volatile analyte. This approach enabled to apply negative pressure during the enrichment step, which favored the evaporation of the analyte. Placing a slowly spinning magnetic stirring bar inside the syringe, effective syringe cleaning as well as mixing of the sample with buffer solution to suppress the interference of acetic acid was achieved.Ethanol determination was based on the reduction of a single drop of 3mmolL−1 potassium dichromate dissolved in 8molL−1 sulfuric acid. The drop was positioned in the syringe inlet in the head-space above the sample with posterior spectrophotometric quantification.The entire procedure was carried out automatically using a simple sequential injection analyzer system. One analysis required less than 5min including the washing step. A limit of detection of 0.025% (v/v) of ethanol and an average repeatability of less than 5.0% RSD were achieved. The consumption of dichromate reagent, buffer, and sample per analysis were only 20μL, 200μL, and 1mL, respectively. The results of real samples analysis did not differ significantly from those obtained with the references gas chromatography method.

Final report on AFRIMETS.QM-K27: Determination of ethanol in aqueous matrix

From within AFRIMETS, the Regional Metrology Organization (RMO) for Africa, the RMO Key Comparison AFRIMETS.QM-K27 was coordinated by the National Metrology Institute of South Africa (NMISA) in 2011. Ten Metrology Institutes participated, comprising three AFRIMETS, two APMP, four EURAMET and one SIM participant. Participants were required to determine the forensic level concentration of two aqueous ethanol solutions that were gravimetrically prepared by the NMISA. Concentrations were expected to lie in the range of 0.1 mg/g to 5.0 mg/g.The accurate determination of ethanol content in aqueous medium is critical for regulatory forensic and trade purposes. The CCQM Organic Analysis Working Group has carried out several key comparisons (CCQM-K27 series) on the determination of ethanol in wine and aqueous matrices. Developing NMIs now had the opportunity to link to the earlier CCQM-K27 studies through the AFRIMETS.QM-K27 study.Gas chromatography coupled to flame ionisation or mass spectrometric detection was applied by eight of the participants, while three participants (including NMISA) applied titrimetry for the ethanol assay.The assigned reference value of the aqueous ethanol solutions was used to link AFRIMETS.QM-K27 to the CCQM-K27 key comparison reference value. The assigned reference values for AFRIMETS.QM-K27 Level 1 and Level 2 were (0.3249 ± 0.0021) mg/g (k = 2) and (4.6649 ± 0.0152) mg/g (k = 2), respectively. The reference values were determined using the purity-corrected gravimetric preparation values, while the standard uncertainty incorporated the gravimetric preparation and titrimetric homogeneity uncertainties.From previous CCQM-K27 studies, the expected spread (%CV) of higher order measurements of ethanol in aqueous medium is about 0.85% relative. In this study the CV for Level 1 is about 12% (10% with two outliers removed) and for Level 2 about 4%.Three of the ten laboratories submitted results within 1.5% of the gravimetric reference value for Level 1; four of the ten participating laboratories submitted mean results within 1.5% of the gravimetric reference value for Level 2. Two of the participating laboratories achieved mean results within 1.5% of the gravimetric reference value for both levels.Participants in the AFRIMETS-K27 study would therefore have benefited from a pilot study in which to test their measurement capability prior to participation in the key comparison. Several NMIs, however, will still be able to make new CMC claims based on their performance in this comparison.Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Sequential injection system for the enzymatic determination of ethanol in alcoholic beverages with in-line dilution

A sequential injection system for the enzymatic determination of ethanol in wines with spectrophotometric detection was developed. The determination was based on the enzymatic reaction involving ethanol and NAD+ in the presence of alcohol dehydrogenase. A gas-diffusion unit was introduced in the system to perform an in-line dilution. It was possible to operate the system with a reagent consumption of 1.3 mg of NAD+, 0.45 U of ADH, and 32 μL of sample, per assay with a determination rate of 21 h−1.The results obtained from the analysis of wine samples were statistically equivalent to those obtained by the reference method, with good repeatability; the relative standard deviation (n = 10) was <1% with a LOQ of 0.3% (v/v).

Sequential Injection System for the Enzymatic Determination of Ethanol in Wine

A sequential injection system was developed for the enzymatic determination of ethanol in wine. The spectrophotometric determination is based on the enzymatic reaction catalyzed by alcohol dehydrogenase in the presence of NAD+. The system was applied to the determination of ethanol in a range of 0.008-0.024% (v/v) with good repeatability; RSD(n=10) < 2.3%. The results obtained with the developed system showed good agreement with those obtained by using the reference method. The determination rate was 25 h(-1); 1 micromol of NAD+, 1.1 units of enzyme, and 50 microL of sample were consumed per determination; and the waste produced was 2.2 mL per assay.

Automatic Flow Procedure for the Determination of Ethanol in Wine Exploiting Multicommutation and Enzymatic Reaction with Detection by Chemiluminescence

An automatic procedure for the determination of ethanol in wines using a flow system based on multicommutation and enzymatic reaction is described. Alcohol oxidase was immobilized on aminopropyl glass beads and packed in an acrylic column. The peroxide due to enzymatic reaction with ethanol reacted with luminol and generated the chemiluminescence radiation that was monitored by using a laboratory-made detector based on photodiodes. The system manifold comprised a set of 3-way solenoid valves controlled by a microcomputer furnished with electronic interfaces, which ran on software written in Quick BASIC 4.5 to provide facilities to perform on-line sample dilution, reagent addition, and data acquisition. After system parameters optimization, ethanol samples were processed without prior pretreatment. The following suitable features were achieved: linear response ranging from 2.5 to 25% (v/v) ethanol, relative standard deviation of 1.8% (n = 10), detection limit of 0.3% (v/v) ethanol, sampling rate of 23 determinations per hour, and low reagent consumption of 0.23 mg luminol and 7 mg hexacyanoferrate (III) per determination. When the results were compared with those obtained using the AOAC Official Method, no significant difference at the 90% confidence level was observed.

Determination of Ethanol in Wines by Flow Injection Spectrophotometry Using Gas-Diffusion and an Immobilized Enzyme Reactor

A flow injection analysis (FIA) system for the spectrophotometric determination of ethanol in wines using an immobilized alcohol dehydrogenase reactor was developed. A gas diffusion unit was used to achieve a large dilution and to separate ethanol from the matrix. This way, the contact of the sample with the reactor was avoided and possible interferences in the spectrophotometric measurements were significantly reduced. The alcohol dehydrogenase enzyme was immobilized on alkylaminated controlled pore glass, and the consumption of the NAD cofactor was minimized (0.6 µmol per assay) by using the merging zone technique. The detection limit was 0.4% (v/v). Good precision was achieved, with relative standard deviations less than 2.2% (n = 9). For 20 samples of different types of table and Port wines, the results showed good agreement with the OIV usual procedure, the relative deviation being less than 4.4%. Thirty determinations per hour can be carried out within the ethanol concentration range of 5% to 25% (v/v), without any sample pretreatment.

Flow injection, amperometric determination of ethanol in wines after solid‐phase extraction

AbstractEthanol in wines was determined by flow injection analysis with an amperometric detector using an oxidized nickel wire. Solid‐phase extraction with a strong anion exchanger was used to remove interferences such as organic acids from the matrix, and the residue of the extraction was injected directly into the FIA system. The recoveries of ethanol from wines spiked with standards ranged from 101% to 103%. The response of the nickel electrode to ethanol is dependent on the applied potential and the pH of the carrier. The optimal conditions for the detection of ethanol were an applied potential of +0.60 V (vs. Ag/AgCl) in a carrier of 100 mM sodium hydroxide solution. The electrode exhibited a linear response from 10−5 to 10−3 M, with a detection limit of 1 × 10−6 M. The method was demonstrated by the determination of ethanol in wines.

The determination of ethanol in wine by voltammetry with an internal standard

AbstractA rapid method for the electroanalysis of ethanol is presented that incorporates flow extraction at room temperature, with voltammetric detection and potassium ferrocyanide [K4Fe(CN)6] as internal standard. In 0.1 M NaOH electrolyte, ethanol was oxidised at a platinum comb‐shaped working electrode at −300 mV (vs. a Ag/AgCl reference electrode) and K4Fe(CN)6 was oxidized at +180 mV. The ratio of the anodic peak currents was linear with ethanol concentration in the range of 0.1 to 8.0% (v./v.), and the detection limit (calculated as 3 σ background) was 0.012 % (v./v.) for Osteryoung square wave voltammetry (OSWV) and 0.023 %(v./v.) for cyclic voltammetry (CV). The average extraction efficiency of ethanol from aqueous solutions, at 20 ± 1°C, was 8.5%. The repeatability was in the range of 2.5 to 3.3% RSD (n = 8), and accuracy was in the range of 95.2 to 104.7% for the determination of wine samples. Application to wines compared well with GC and HPLC methods and the nominal ethanol concentration determined by gravimetry. Analytical parameters in CV and OSWV are optimized, and the dependence of the extraction efficiency with temperature and nitrogen gas flow is presented.

A comparative study of some phenoxazine and phenothiazine modified carbon paste electrodes for ethanol determination

AbstractAn amperometric ethanol electrode is described based on carbon paste modified with alcohol dehydrogenase (ADH) and a mediator. The possibility of coupling this enzymatic system with some commercially available phenoxazines [Meldola Blue (MB), Nile Blue (NB) and Brilliant Cresyl Blue (BCB)] and phenothiazines [Toluidine Blue 0 (TBO)], that allows the electrocatalytic oxidation of NADH, was investigated. Different strategies of mediator immobilization in the carbon paste were compared. The most suitable immobilization technique was the coverage of the modified carbon paste surface with a dialysis membrane and the best electrocatalytic structure was the phenothiazine TBO. The TBO(10%)‐ADH(5%)‐modified carbon paste electrode shows steady state signals for ethanol within 30 s. The influence of various experimental conditions was explored for optimum analytical performance. Amperometric detection of ethanol at an applied potential of 50mV (Ag/AgCl) gives linear responses over the concentration range of 10–l0μM, with a detection limit of 5 × 10−6M. The modified electrode was applied to the determination of ethanol in wine.

Determination of ethanol using flow injection enthalpimetry.

A flow injection enthalpimetric method for the determination of ethanol in fuel-grade ethanol, based on the heat of dilution of ethanol, is described. The accuracy and precision were 0.05% of ethanol; interferences by several substances are discussed. A similar procedure was also applied to the determination of ethanol in wines and spirits after distillation, yielding a precision of 0.03–0.1% of ethanol. The sampling rate in both procedures is 110 h–1.

Determination of Ethanol in Wine by Titrimetric and Spectrophotometric Dichromate Methods: Collaborative Study

A dichromate-spectrophotometric method for the determination of ethanol in wine was compared in a collaborative, matched pair study with the AOAC dichromate-titrimetric method, 11.008-11.011. Both methods require distillation of the sample into dichromate. The titrimetric method measures ethanol by titrating the excess dichromate with ferrous ammonium sulfate after conversion of ethanol to acetic acid; the spectrophotometric method directly measures the reduced dichromate formed after oxidation. In addition to comparing the 2 methods, the collaborative study also compared the use of 2 types of assemblies for obtaining the ethanol distillate: the Scott-type, which is used in 11.008-11.011, and the electric Kirk-type. Results of the collaborative study indicated that the repeatability and reproducibility of the official titrimetric method were generally far superior to those of the spectrophotometric method; therefore, adoption of the spectrophotometric method is not recommended. Comparison of titrimetric method results obtained using the 2 types of stills indicated that repeatability and reproducibility were somewhat better when Scott apparatus was used, but measurements using Kirk-type compared well in the range of ethanol concentrations found in table and fortified wines. The Kirk-type distillation apparatus has been adopted official first action as an alternative to Scott apparatus in the dichromate oxidation method for ethanol in wine, 11.008-11.011.

Gas Chromatographic Determination of Ethanol in Wine: Collaborative Study

Abstract After a survey of laboratories using gas chromatographic procedures for wine alcohol analysis, 3 sets of columns and operating parameters were chosen on the basis of comparative reproducibility evaluations run in this laboratory. Fourteen collaborators participated in the study and were given their choice of any one of the 3 columns: (1) 1.8 m × 2 mm id glass, packed with 80-100 mesh Poropak QS; (2) 1.8 m × 2 mm id glass, packed with 0.2% Carbowax 1500 on 80-100 mesh Carbopack C; (3) 1.8 m × 6.35 mm copper, packed with 3% Carbowax 600 on 40-60 mesh Chromosorb T. Standards and samples were diluted 1:100 with 0.1% v/v n-butanol in water before analysis. Eight samples containing from 7.3 to 23.6% ethanol (v/v) were submitted as randomly coded duplicates along with a calibration standard and a practice sample. Two injections each of the diluted duplicates were made. On the basis of the reported results, 2 laboratories were rejected as outliers. The results of the remaining 12 collaborators showed an average reproducibility of 0.142 and a repeatability of 0.036. The method has been adopted official first action.

Quantitative Determination of Ethanol in Wine by Gas chromatography

A method is described for specific quantitative analysis of ethanol in wine by gas chromatography. This method, which uses an internal standard and flame ionization detector, is more accurate and more precise than methods commonly used. Statistical analysis of data from typical winery samples shows that the standard error of estimate for the method is 0.07% (v/v) over the range 7 to 24% (v/v). The estimate of the standard deviation of the chromatography for duplicate injections is 0.02% (v/v). The gas-liquid chromatography method determines ethanol separately from the other wine components that interfere in other methods, and without distillation or chemical reaction. When large numbers of samples are analyzed, advantages include short analysis time per sample and potential for extensive automation.

Determination of Ethanol in Wine by Chemical Oxidation: 1969 Studies

Abstract The micro dichromate procedure for ethanol in wine was subjected to a successful collaborative study in 1968 and adopted as official first action. In 1969 all analyses using this method were run in duplicate at the Gallo laboratories and results for a number of different wine types were selected at random and tabulated. From 23 to 34 sets of duplicate determinations were evaluated for 14 different wine types. Average alcohols ranged from 11.55 to 23.47% and standard deviations varied from 0.039 to 0.070%. Nine different analysts participated in the study and no one analyst performed both determinations on a given sample. In view of the fact that these results correspond very closely to those obtained in the 1968 collaborative study and that many members of the wine industry are now successfully using this method, it is recommended that the method be adopted as official final action.

Collaborative Study of the Determination of Ethanol in Wine by Chemical Oxidation

Abstract A collaborative study was conducted on a chemical or dichromate oxidation procedure for etlianol in wine. The method is based on the steam distillation of ethanol from a 1 ml wine sample into an acidified solution of potassium dichromate, followed by heating 20 min at 60°C to complete the oxidation of the ethanol to acetic acid. The unreacted dichromate is determined by titration with a standard ferrous ammonium sulfate solution, using o-phenanthroline as an indicator. Eleven collaborators participated in the study, of whom seven were familiar with the method and four were not. Eight samples with alcohol content ranging from 11.8 to 23.5% by volume were analyzed. The standard deviations of the reported answers on the identical samples varied from 0.024 to 0.063% in the range of 11.8–20% ethanol and rose to 0,161% in the sample which contained 23.3% ethanol by volume. This reproducibility is better than has been reported with other commonly used methods, and it is recommended that the method be adopted as official first action.

Spectrophotometric Determination of Ethanol in Wine

A variation of the micro-dichromate method for the determination of ethanol in wine was devised. Reproducible pipetting of a 1-ml sample was achieved through the use of an automatic diluter. Distillation of the sample into an acidic potassium dichromate solution in a 50-ml volumetric flask permitted simple dilution to volume after heating 20 minutes at 60° C. Percent alcohol by volume was then determined from a direct digital concentration spectrophotometer af 600 mµ after standardization with a known ethanol-water mixture, similarly distilled and reacted. The method eliminates the need for a standard ferrous ammonium sulfate solution as a titrant and the normal indicator solution as well as the difficulties encountered with a 1-ml volumetric pipette.

Semi-Automatic Determination of Ethanol in Wine by the Micro-Dichromate Method

An apparatus is described that automatically performs the distillation necessary for determination of ethanol by the micro-dichromate method. if the sample is pipetted into an empty still, especially if it is warm, if too much Experiments show that results are low water is used in the still, or if the end point of the titration, which is difficult for an inexperienced analyst to see, is passed. Results are high it the K₂Cr₂O₇ is impure, so primary-standard K₂Cr₂O₇ is recommended. The importance of goodquality distilled water is discussed, and the calibration of volumetric glassware is emphasized. It is suggested that a standard ethanol-water solution be analyzed each day as a check on both analyst and the apparatus. Statistical analysis on 752 results recently obtained shows a standard deviation of ±0.075 for single determinations, a most probable error of ±0.036 for a single average result when duplicate determinations are made, and a standard deviation of ±0.10 at the 95% confidence limit.

Determination of Ethanol in Wine by Gas-Liquid Partition Chromatography

The results of determining the ethanol content in samples A and B by the four methods discussed are summarized in table I. From the data shown it can be concluded that the dichromate method and the moderate speed gas chromatographic method compare favorably in accuracy. They also compare in time for analysis. The pycometer method is the least accurate and is the most time consuming. The high speed gas chromatographic method is slightly less accurate than the dichromate and moderate speed gas chromatographic methods but is more accurate than the pycnometer method and is very rapid and specific.