A simple strategy for determining ethanol in all types of alcoholic beverages based on its on-line liquid-liquid extraction with chloroform, using a flow injection system and Fourier transform infrared spectrometric detection in the mid-IR

In this work, a simple strategy for the determination of ethanol in all types of alcoholic beverages using Fourier transform infrared spectrometric detection has been developed. The methodological proposal includes the quantitative on-line liquid-liquid extraction of ethanol with chloroform, through a sandwich type cell equipped with a PTFE membrane, using a two-channel manifold; and direct measurement of the analyte in the organic phase, by means of Fourier transform infrared spectrometry. The quantification was carried out measuring the ethanol absorbance at 877 cm⁻¹_, corrected by means of a baseline established between 844 and 929 cm⁻¹. The procedure, which does not require any sample pretreatment (except for the simple degassing of beer and gassy wine samples, and a simple dilution of spirits with water), was applied to determine ethanol in different alcoholic beverages such as beers, wines and spirits. The results obtained highly agree with those obtained by a derivative FTIR spectrometric procedure, and by head space-gas chromatography with FID detection. The proposed method is simple, fast, precise and accurate. Moreover, it can be easily adapted to any infrared spectrometer equipped with a standard transmission IR cell, and provides attractive analytical features, which are comparable to, or better than those offered by other published methods. In consequence, it represents a valid alternative for the determination of ethanol in alcoholic beverages, and could be suitable for the routine control analysis.     

Retention and mass transfer characteristics in reversed-phase liquid chromatography using a tetrahydrofuran-water solution as the mobile phase.

The characteristics of the retention and the mass transfer kinetics in reversed-phase liquid chromatography (RPLC) were measured on a system consisting of a C18-silica gel and a tetrahydrofuran-water (50:50, v/v) solution. These parameters were derived from the first and the second moments of the elution peaks, respectively. Further information on the thermodynamic properties of this system was derived from the temperature dependence of these moments. Some correlations previously established were confirmed for this system, namely, an enthalpy-entropy compensation for both retention and surface diffusion and a linear free-energy relationship. These results are compared with those observed in other similar systems using methanol-water (70:30, v/v) and acetonitnile-water (70:30, v/v) solutions. The contribution of surface diffusion to intraparticle diffusion in C18-silica gel particles was shown to be important. The analysis of the thermodynamic properties of surface diffusion suggests that, in these three RPLC systems, its activation energy is lower than the isosteric heat of adsorption. The nature and the extent of the influence of the mobile phase composition on the parameters describing the retention and the mass transfer kinetics are different but the chromatographic mechanisms involved in RPLC systems appear similar, irrespective of the nature of the organic modifier in the mobile phase.     

Adsorption Characteristics in Reversed-Phase Liquid Chromatography Using Ethanol/Water Mixed Solvent

Adsorption characteristics were studied in a reversed-phase liquid chromatography consisting of an octadecylsilyl (ODS)-silica gel and ethanol/water mixture (70/30, v/v), and were compared with corresponding results obtained by using methanol/water and acetonitrile/water mixtures (70/30, v/v) as mobile phase. Similar tendencies were observed for some adsorption characteristics in the three chromatographic systems. However, the magnitude of the characteristics was not entirely identical in the three systems. Surface diffusion was dominant for intraparticle diffusion in the ODS-silica gel particles irrespective of the type of the organic modifiers in mobile phases. A few correlations were confirmed with regard to surface diffusion, i.e., an enthalpy-entropy compensation and a linear free-energy relation. The analogous correlations on surface diffusion phenomena suggest the similarity in the mechanism of surface diffusion in the three chromatographic systems.     

Analytical Resolution of 4-ARYL-1,2,3,4,5,6,7,8-Octahydroquinazoline-2-Thiones using a Cellulose Chiral Stationary Phase

ABSTRACT

Racemic 4-aryl-1,2,3,4,5,6,7,8-octahydroquinazoline-2-thiones were resolved into their enantiomers by HPLC on cellulose tris(4-methylbenzoate) coated on silica gel using ethanol:n-hexane (70:30) as a mobile phase. A convenient method for preparation of cellulose tris(4-methylbenzoate) chiral stationary phase was described and the enantiomers were characterized by some chromatographic data.     

A novel strategy to verification of adulteration in alcoholic beverages based on Schlieren effect measurements and chemometric techniques

A novel strategy to evaluation of adulteration in alcoholic beverages based on the measurement of the Schlieren effect using an automated FIA system with photometric detection is proposed. The assay is based on the Schlieren effect produced when beverage samples are injected in a single-line FIA system that uses water as carrier stream and a light-emitting diode-phototransistor photometer controlled by microcomputer as detector. The flow system presents limited mixing conditions which make possible to create gradients of refractive index (Schlieren effect) in the injected sample zone. These gradients are reproducible, characteristic of each alcoholic beverage and undergo specific modifications when adulterations with water or ethanol are imposed. Schlieren effect data of brandies, cachaças, rums, whiskies and vodkas were treated by SIMCA to elaborate class models applied in the evaluation of alcoholic beverages adulteration. Samples of the original matrix of each sort of beverages were adulterated in laboratory by adding water, methanol and ethanol in levels of 5% and 10% (v/v). These samples were used as test set to validate SIMCA class models. The verification of authenticity using Schlieren effect measurements presented good results making possible to identify 100% of the beverages samples adulterated in laboratory and 93% of the actual adulterated alcoholic beverages with confidence levels of 95%. As principal advantage, the automated system does not use reagents to carry out the analysis.     

流动相组成对外消旋阿苯达唑亚砜对映体拆分的影响

涂敷直链淀粉-三(3,5-二甲基苯基氨基甲酸酯)(ADMPC)于自制的球形氨丙基硅胶上,制备了一种手性固定相。采用高效液相色谱法(HPLC),在正相条件下用该固定相直接拆分了广谱驱虫药物阿苯达唑的代谢产物阿苯达唑亚砜(albendazole sulfoxide, ABZSO)的外消旋对映体。系统地选用了多种二元及三元流动相体系对样品进行拆分,结果表明,流动相中不同种类的醇改性剂及其含量的不同对样品的保留时间和立体选择性有不同程度的影响,甲醇、乙醇等作改性剂用于拆分样品的效果较好;采用三元流动相体系正己烷-     

Advanced solvent signal suppression for the acquisition of 1D and 2D NMR spectra of Scotch Whisky

A simple and robust solvent suppression technique that enables acquisition of high‐quality 1D ¹H nuclear magnetic resonance (NMR) spectra of alcoholic beverages on cryoprobe instruments was developed and applied to acquire NMR spectra of Scotch Whisky. The method uses 3 channels to suppress signals of water and ethanol, including those of ¹³C satellites of ethanol. It is executed in automation allowing high throughput investigations of alcoholic beverages. On the basis of the well‐established 1D nuclear Overhauser spectroscopy (NOESY) solvent suppression technique, this method suppresses the solvent at the beginning of the pulse sequence, producing pure phase signals minimally affected by the relaxation. The developed solvent suppression procedure was integrated into several homocorrelated and heterocorrelated 2D NMR experiments, including 2D correlation spectroscopy (COSY), 2D total correlation spectroscopy (TOCSY), 2D band‐selective TOCSY, 2D J‐resolved spectroscopy, 2D ¹H, ¹³C heteronuclear single‐quantum correlation spectroscopy (HSQC), 2D ¹H, ¹³C HSQC‐TOCSY, and 2D ¹H, ¹³C heteronuclear multiple‐bond correlation spectroscopy (HMBC). A 1D chemical‐shift‐selective TOCSY experiments was also modified. The wealth of information obtained by these experiments will assist in NMR structure elucidation of Scotch Whisky congeners and generally the composition of alcoholic beverages at the molecular level.     

Alcohol sensor based on membrane-bound alcohol dehydrogenase

Ethanol is determined by a sensor system using purified, immobilized mernbrane-bound alcohol dehydrogenase frorn Gluconobacter suboxydans, attached to a platinum disk electrode (3 mm diameter), and covered with a dialysis membrane. Hexacyanoferrate (III) is used as the redox acceptor. To correct for the influence of interfering substances, this alcohol sensor is compensated by a control electrode which has no immobilized enzyme. The potential of these platinum electrodes was set at + 350 mV vs. Ag/AgCl. Linearity was observed in the range 0.1–5 mM ethanol, the response time was less than 5 min, the maximum sensitivity was obtained at 45°C and the optimum pH was in the range 4.5–5.5. The sensitivity decreased to 80% of the initial value after 1 month at 30°C. When the alcohol sensor system was applied to the determination of ethanol in alcoholic beverages, a good correlation was obtained between the results and those obtained by gas chromatography.     

Investigation into the structural composition of hydroalcoholic solutions as basis for the development of multiple suppression pulse sequences for NMR measurement of alcoholic beverages

An eight‐fold suppression pulse sequence was recently developed to improve sensitivity in ¹H NMR measurements of alcoholic beverages [Magn. Res. Chem. 2011 (49): 734–739]. To ensure that only one combined hydroxyl peak from water and ethanol appears in the spectrum, adjustment to a certain range of ethanol concentrations was required. To explain this observation, the structure of water–ethanol solutions was studied. Hydroalcoholic solutions showed extreme behavior at 25% vol, 46% vol, and 83% vol ethanol according to ¹H NMR experiments. Near‐infrared spectroscopy confirmed the occurrence of four significant compounds (‘individual’ ethanol and water structures as well as two water–ethanol complexes of defined composition – 1 : 1 and 1 : 3). The successful multiple suppression can be achieved for every kind of alcoholic beverage with different alcoholic strengths, when the final ethanol concentration is adjusted to a range between 25% vol and 46% vol (e.g. using dilution or pure ethanol addition). In this optimum region, an individual ethanol peak was not detected, because the ‘individual’ water structure and the 1 : 1 ethanol–water complex predominate. The nature of molecular association in ethanol–water solutions is essential to elucidate NMR method development for measurement of alcoholic beverages. The presented approach can be used to optimize other NMR suppression protocols for binary water–organic solvent mixtures, where hydrogen bonding plays a dominant role. Copyright © 2014 John Wiley & Sons, Ltd.     

External mass transfer in high performance liquid chromatography systems

External mass transfer in a HPLC system operated in the reversed-phase mode was studied by pulse response experiments, using a column packed with non-porous C(18)-silica gel spherical particles, 18 microm in diameter. The first and second moments of the elution peaks, measured under different flow velocities and temperatures, were analyzed by the moment method to determine the external mass transfer coefficient (k(f)). The dependence of the Sherwood number on the Reynolds and the Schmidt numbers is almost the same as that observed in previous investigations of conventional literature correlations. The exponent of the last two nondimensional parameters was derived as being in the range from 0.28 to 0.41. When the Kataoka equation is used, the mean square deviation was calculated to be 0.21 for the values of k(f) estimated in this study. It is concluded that conventional correlations can be used to estimate k(f) values, even when the particle diameter is of the order of a micrometer.     

An improved method for the measurement of the isotope ratio of ethanol in various samples, including alcoholic and non-alcoholic beverages

The isotope ratios of ethanol, an important constituent or ingredient of some foods and various beverages and fuels, provide information about biological and geographical origin and quality. We have developed an improved method for measuring the isotope ratio of ethanol in various samples by gas chromatography-high temperature conversion or combustion-isotope ratio mass spectrometry (GC-TC/C-IRMS) with headspace solid-phase microextraction (HS-SPME). A HS-SPME method was developed by optimizing several different parameters, including salt addition, incubation temperature and time, and extraction time. The HS-SPME method enabled us to determine the isotope ratio at low ethanol concentrations (0.08 mM) in 50 min with good precision (+/-0.3 per thousand for delta(13)C and +/-5 per thousand for deltaD). An advantage of this technique is that it can be adapted for use with samples which have high viscosity and contain many matrix compounds, such as alcoholic and non-alcoholic beverages.     

HPLC determination of 2-furaldehyde and 5-hydroxymethyl-2-furaldehyde in alcoholic beverages

A method for the determination of 2-furaldehyde (F) and 5-hydroxymethyl-2-furaldehyde (HMF) in alcoholic beverages by high performance liquid chromatography (HPLC) is described. A C-18 column and an acetonitrile-water mobile phase with isocratic elution were used. UV detection at 280 nm was carried out. The method was validated according to the EURACHEM guidelines. The procedure offers a high specificity and detection limits of the order of 0.005 μg mL^− 1. Recoveries of 94-103% were obtained from spiked samples at different levels with both analytes. Intermediate precision calculated for a period of 2 months was + 0.8% for HMF and + 0.4% for F. The method was applied to the analysis of alcoholic beverages like bourbon, rum, brandy, liquors and aperitif wines.     

Moment analysis of chromatographic behavior of superficially porous particles

Peak parking experiments were conducted to study the chromatographic behavior in a RPLC system consisting of a column packed with superficially porous C(18)-particles and a mixture of methanol and water (70/30, v/v). The values of the surface diffusion coefficient and the retention equilibrium constant of a column packed with superficially porous C(18)-particles were comparable to those of columns packed with a C(18)-silica monolith and full-porous C(18)-silica gel particles. The flow-rate dependence of HETP was hypothetically calculated by using moment equations to clarify the influence of the structural characteristics on the chromatographic behavior. The column efficiency of a column packed with the superficially porous particles is higher in the high flow-rate range than that with full-porous spherical particles. This is attributed to the smaller contribution of the intraparticulate mass transfer in the superficially porous particles to band broadening. The moment equations are effective for the quantitative analysis of chromatographic behavior of superficially porous particles.     

An effective high-speed countercurrent chromatographic method for preparative isolation and purification of mollugin directly from the ethanol extract of the Chinese medicinal plant Rubia cordifolia

The medicinal plant Rubia cordifolia has been used widely in traditional Chinese medicine (TCM) for its antibacterial, antioxidant and anti-inflammatory activities. In this study, a preparative high-speed countercurrent chromatography (HSCCC) method for isolation and purification of the bioactive component mollugin directly from the ethanol extract of R. cordifolia was successfully established by using light petroleum (bp 60-90 degrees C)/ethanol/diethyl ether/water as the two-phase solvent system. The upper phase of light petroleum/ethanol/diethyl ether/water (5:4:3:1 v/v) was used as the stationary phase of HSCCC. Under the optimum conditions, 46 mg of mollugin at 98.5% purity, as determined by HPLC, could be yielded from 500 mg of the crude extract in a single HSCCC separation. The peak fraction of HSCCC was identified by 1H NMR and 13C NMR.     

Concentration of chlorophenols in water to dialkyated catinonic surfactant-silica gel admicelles

Chlorophenols including monochlorophenol, dichlorophenol, trichlorophenol, tetrachlorophenol, and pentachlorophenol in water were extracted into dialkylated cationic surfactant-silica gel admicelles. The dialkylated cationic surfactants such as didecyldimethylammonium bromide (DC10) and didodedyldimethylammonium bromide (DC12) sorbed on silica gel surfaces to form admicelles at pH 9. Approximately 200mg of DC10 was quantitatively sorbed on 1g of silica gel. The sorption further increased by further addition of DC10. This is in contrast to the fact that the maximum sorption of mono-alkylated cetyltrimethyammonium chloride (CTAC) was only ca. 100mg. Based on the fluorescent spectra of a molecular probe, N-phenyl-1-naphthylamine, DC10- and DC12-silica gel admicelles were more hydrophobic than CTAC-silica gel admicelles. The extents of the extraction of chlorophenols into DC10-silica gel admicelles were greater than those into CTAC-silica gel admicelles. However, the extractions to DC12-silica gel admicelles were insufficient due to leakage of DC12 vesicles. Consequently, DC10-silica gel admicelles were the most adequate for concentrating chlorophenols in water. An admicelle column was prepared by passing aqueous buffer solution of DC10 through a Bond Elut Jr. silica gel solid-phase extraction cartridge. It was successfully applied to the 500-fold concentration of chlorophenols including hydrophilic mono-substituted chlorophenol in water samples prior to their HPLC analysis.     

Urethane-hydrolyzing enzyme from Citrobacter sp

Urethane, a cancer-causing chemical, was reported to contaminate alcoholic beverages such as whisky, liquor, wine and sake. Enzymatic removal of urethane would be a possible approach to remove this potentially hazardous chemical from alcoholic beverages. We found that Citrobacter sp. isolated from mouse feces stoichiometrically decomposed urethane to ethanol and ammonia. We named this enzyme "urethanase." Partially purified urethanase could hydrolyze several carbamates and some amides. However, urea, N-alkyl ureas and ethyl esters of organic acids were not hydrolyzed at all. These results suggest that urethanase belongs to the category of amidase. The enzyme was inactive in high concentrations of alcohol and at acidic pH and was practically ineffective for the elimination of urethane from alcoholic beverages.     

Determination of ethyl carbamate in alcoholic beverages: an interlaboratory study to compare HPLC-FLD with GC-MS methods

An international interlaboratory study on the determination of ethyl carbamate in alcoholic beverages by a new HPLC-FLD and by the official GC-MS methods is presented. The aim of this study was to improve the knowledge about precision and accuracy parameters of the new method and to compare the performance of both HPLC and GC methods. Five different samples representing table wines, fortified wines (red and white), distilled spirits, and wine spirits were available for analysis by each participant. Despite the low number of participants (6), the results obtained by the laboratories using the HPLC-FLD method are comparable to those obtained by GC-MS methods. The present study emphasizes the possibility to use, as routine, a much simpler analytical method than the current reference method by GC-MS for ethyl carbamate determination in alcoholic beverages.     

Determination of purine contents of alcoholic beverages using high performance liquid chromatography

The purine contents of alcoholic beverages were determined in order to utilize them in the dietary care of gout and hyperuricemia. In the management of these diseases, restriction of both alcohol and purine intake are important. The method employed in this study is a quantitative determination of purine contents by HPLC. Alcoholic beverages were hydrolyzed to corresponding purine bases, which were then separated by HPLC, and base peaks were identified using an enzymatic peak‐shift technique. This method is sufficiently accurate and reproducible to examine the purine contents of various alcoholic beverages that patients consume. Purine contents were as follows: spirits, 0.7–26.4 µmol/L; regular beer, 225.0–580.2 µmol/L; low‐malt beer, 193.4–267.9 µmol/L; low‐malt and low‐purine beer, 13.3 µmol/L; other liquors, 13.1–818.3 µmol/L. Some local and low‐alcohol beers were found to contain about 2.5 times more purines than regular beer. As some alcoholic beverages contain considerable amounts of purines, we recommend that excess consumption of these beverages be avoided. These data should be useful in the management of hyperuricemia and gout, not only for patients but also for physicians. Copyright © 2009 John Wiley & Sons, Ltd.     

Determination of alcohols in alcoholic beverages by micro high-performance liquid chromatography with indirect photometric detection

Aliphatic alcohols in alcoholic beverages were determined by micro high-performance liquid chromatography with indirect photometric detection. Theophylline was added to the mobile phase as the visualization agent. Ethanol, propanols and butanols could be determined by this method.     

Flow injection colorimetric method using acidic ceric nitrate as reagent for determination of ethanol

Ceric ammonium nitrate has been used for qualitative analysis of ethanol. It forms an intensely colored unstable complex with alcohol. In this work, a simple flow injection (FI) colorimetric method was developed for the determination of ethanol, based on the reaction of ethanol with ceric ion in acidic medium to produce a red colored product having maximum absorption at 415 nm. Absorbance of this complex could be precisely measured in the FI system. A standard or sample solution was injected into a deionized water donor stream and flowed to a gas diffusion unit, where the ethanol diffused through a gas permeable membrane made of plumbing PTFE tape into an acceptor stream to react with ceric ammonium nitrate in nitric acid. Color intensity of the reddish product was monitored by a laboratory made LED based colorimeter and the signal was recorded on a computer as a peak. Peak height obtained was linearly proportional to the concentration of ethanol originally presented in the injected solution in the range of 0.1-10.0% (v/v) (r² = 0.9993), with detection limit of 0.03% (v/v). With the use of gas diffusion membrane, most of the interferences could be eliminated. The proposed method was successfully applied for determination of ethanol in some alcoholic beverages, validating by gas chromatographic method.