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.     

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.     

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.     

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.     

T1 relaxation measurement with solvent suppression

Three solvent-suppression pulse sequences of varying complexity were incorporated into the standard inversion recovery pulse program and experimentally evaluated. The least complex suppression sequence involves a composite 90 degrees pulse. A more complex sequence utilizes an excitation sculpting sequence requiring pulsed field gradients, and the most complex sequence incorporates an excitation sculpting sequence with selective rf pulses and gradient pulses. The quality of the spectral data and the accuracy of T(1) measurements of the investigated suppression schemes were evaluated using three aqueous samples with increasing proton content in the water solvent, i.e. by volume 100% D(2)O, 80/20% D(2)O/H(2)O, and 100% H(2)O. For lines removed from the water resonance the T(1) values were generally very consistent between all pulse sequences tested. For lines less than about 200 Hz from the water signal the T(1) measurements become less reliable but are still possible for most of the tested pulse programs.     

Stretched poly(dimethylsiloxane) gels as NMR alignment media for apolar and weakly polar organic solvents: an ideal tool for measuring RDCs at low molecular concentrations

The measurement of residual dipolar couplings (RDCs), meanwhile a standard method for obtaining structural information in biomolecular NMR, requires partial alignment of the sample. Special demands on alignment media so far limit the applicability of this approach to small molecules in organic solvents. Major limitations are the free scalability of alignment and the suppression of residual signals of the alignment medium to allow effective measurement of low-concentration samples. Here, we present stretched poly(dimethylsiloxane) (PDMS) cross-linked by beta-rays as an alignment medium with no visible impurities in 1H NMR spectra but a single signal at approximately 0.1 ppm that can easily be removed by slightly modified water suppression methods. Besides the free scalability, its applicability to the measurement of RDCs in small molecules at low concentration is demonstrated on a approximately 12 mM sample of spiroindene. The induced alignment tensor in this case can be predicted reasonably well by a simplified model on the basis of steric interactions only.     

Determination of ethanol in alcoholic beverages by high-performance liquid chromatography-flame ionization detection using pure water as mobile phase

A method for the determination of ethanol in alcoholic beverages by high-performance liquid chromatography-flame ionization detection (HPLC-FID) was developed. An FID system could be directly connected to an HPLC system using pure water as a mobile phase. In a durability test using triacontylsilyl (C30)-silica gel stationary phase for 96 h, no significant change in the retention time of four alcohol compounds was observed. So the HPLC separation of alcoholic beverages was carried out on the C30-silica gel stationary phase. On application to the analysis of six kinds of alcoholic beverages, ethanol could be determined accurately by the proposed method.     

Identification and quantification of the main organic components of vinegars by high resolution 1H NMR spectroscopy

A detailed analysis of the proton high-field NMR spectra of vinegars (in particular of Italian balsamic vinegars) is reported. A large number of organic substances belonging to different classes, such as carbohydrates, alcohols, organic acids, volatile compounds and amino acids, were assigned. The possibility of quantification of the substances identified in the whole vinegar sample, without extraction or pre-concentration steps, was also tested. The data validity was demonstrated in terms of precision, accuracy, repeatability and inter-day reproducibility. The effects of the most critical experimental parameters (sample concentration, water suppression and relaxation time) on the analysis response were also discussed. ¹H NMR results were compared with those obtained by traditional techniques (GC-MS, titrations), and good correlations were obtained. The results showed that ¹H NMR with water suppression allows a rapid, simultaneous determination of carbohydrates (glucose and fructose), organic acids (acetic, formic, lactic, malic, citric, succinic and tartaric acids), alcohols and polyols (ethanol, acetoin, 2,3-butanediol, hydroxymethylfurfural), and volatile substances (ethyl acetate) in vinegar samples. On the contrary, the amino acid determination without sample pre-concentration was critical. The ¹H NMR method proposed was applied to different samples of vinegars, allowing, in particular, the discrimination of vinegars and balsamic vinegars.     

核磁共振法测定西洛他唑含量

建立核磁共振（1H NMR）法测定西洛他唑含量的方法。采用BrukerAvanceⅢ400MHz核磁共振波谱仪,以1,2,4,5-四氯-3-硝基苯为内标,氘代氯仿为溶剂,zg30脉冲序列。对实验参数如扫描次数、延迟时间等进行优化。西洛他唑质量在5-30mg范围内,样品和内标物的积分面积比值与样品和内标物的质量比值呈现良好的线性关系,线性相关系数r=0．9953,测定结果的相对标准偏差小于0．4％（n=5）。该方法可用于药品的质量控制和监管。     

Determination of ethanol in fuel ethanol and beverages by Fourier transform (FT)-near infrared and FT-Raman spectrometries

Fourier transform-near infrared (FT-NIR) and FT-Raman spectrometries have been used to design partial least squares (PLS) calibration models for the determination of the ethanol content of ethanol fuel and alcoholic beverages. In the FT-NIR measurements the spectra were obtained using air as reference, and the spectral region for PLS modeling were selected based on the spectral distribution of the relative standard deviation in concentration. In the FT-Raman measurements hexachloro-1,3-butadiene (HCBD) has been used as an external standard. In the PLS/FT-NIR modeling for ethanol fuel analysis 50 ethanol fuel standards (84.9-100% (w/w)) were used (25 in the calibration, 25 in the validation). In the PLS/FT-Raman modeling 25 standards were used (13 in the calibration, 12 in the validation). The PLS/FT-NIR and FT-Raman models for beverage analysis made use of 24 standards (0-100% (v/v)). Twelve of them contained sugars (1-5% (w/w)), one-half was used in the calibration and the other half in the validation. Different spectral pre-processing were used in the PLS modeling, depending on the type of sample investigated. In the ethanol fuel analysis the FT-NIR pre-processing was a 17 points smoothed first derivative and for beverages no spectral pre-processing was used. The FT-Raman spectra were pre-processed by vector normalization in the ethanol fuel analysis and by a second derivative (17 points smoothing) in the beverage analysis. The PLS models were used in the analysis of real ethanol fuel and beverage samples. A t-test has shown that the FT-NIR model has an accuracy equivalent to that of the reference method (ASTM D4052) in the analysis of ethanol fuel, while in the analysis of beverages, the FT-Raman model presents an accuracy equivalent to the reference method. The limits of detection for NIR and Raman calibration models were 0.05 and 0.2% (w/w), respectively. It has also been shown that both techniques, present better results than gas chromatography (GC) in evaluating the ethanol content of beverages.     

新型N,N'-二(邻氧乙酸)苄叉丙二胺合铜(II)和镍(Ⅱ)及N-(邻氧乙酸)苄叉丙二胺合铜(Ⅱ)的合成、晶体结构及抑菌活性

在乙醇和水的混合溶液中, 将N,N'-二(邻氧乙酸)苄叉丙二胺(1)与氯化铜反应, 获得配合物Cu(Ⅱ)L1·H2O·0.25CH3CH2OH(2)[L1=N,N'-二(邻氧乙酸)苄叉丙二胺]; 当将反应混合溶液的pH值调至8~9, 获得Cu(Ⅱ)ClL2·3H2O(3)[L2=N-(邻氧乙酸)苄叉丙二胺]; 将N,N'-二(邻氧乙酸)苄叉丙二胺(1)与氯化镍反应, 获得配合物Ni(Ⅱ)L1·2.75H2O(4). 用元素分析、1H NMR和IR谱等方法对所合成的化合物1和配合物2~4进行了表征, 并测定了配合物2~4的晶体结构. 在配合物2中, 铜原子为六配位[CuN2O4], 在配合物3中, 铜原子为六配位[CuN2O3Cl], 在配合物4中, 镍原子为六配位[NiN2O4], 三个配合物均为畸变八面体结构. 抑菌活性大小的顺序: 配合物3>配合物2>化合物1.     

Quantitative 2D HSQC (Q-HSQC) via suppression of J-dependence of polarization transfer in NMR spectroscopy: application to wood lignin

A quantitative method to record (1)H-(13)C correlation NMR spectra (Q-HSQC) is presented. The suppression of (1)J(CH)-dependence is achieved by modulating the polarization transfer delays of HSQC. In addition, the effect of homonuclear couplings, as well as relaxation during the pulse sequence are discussed. We developed the Q-HSQC approach for the quantitative analysis of wood lignin, a complex polymer where it has been difficult to obtain reliable data on the relative amounts of different structural units. The current method is applicable to a variety of complex mixtures, where normal 1D (1)H- and (13)C-NMR methods fail.     

Synthesis, crystal structure and optical properties of [Ag(UO2)3(OAc)9][Zn(H2O)4(CH3CH2OH)2]: a novel compound containing closed-shell 3d10, 4d10 and 5d10 metal ions

[Ag(UO(2))(3) (OAc)(9)][Zn(H(2)O)(4)(CH(3)CH(2)OH)(2)] (, OAc = CH(3)COO(-)) crystallized from an ethanol solution and its structure was determined by IR spectroscopy, elemental analysis, (1)H NMR, (13)C NMR and X-ray crystallography; it is composed of [Zn(H(2)O)(4)(CH(3)CH(2)OH)(2)](2+) cations and [Ag(UO(2))(3)(OAc)(9)](2-) anions in which triuranyl [(UO(2))(OAc)(3)](3) clusters are linked by the Ag ion.     

多波长叠加近红外吸收光谱法直接测定酒精饮料中的乙醇

利用乙醇在１３８２ｎｍ，１６９１ｎｍ和１７３０ｎｍ处的吸光度值，采用多波长叠加近红外吸收光谱法测定乙醇的含量。结果表明，乙醇在０％～２４％（Ｖ／Ｖ）浓度范围内呈良好的线性关系；回归方程为： Ａ＝ ０． ０１７５４＋ ０． ０４７４７Ｃ；相关系数ｒ＝０． ９９９４。用该法可直接测定葡萄酒、啤酒和黄酒中乙醇的含量，６次平行测定的ＲＳＤ分别为；葡萄酒４．０％，啤酒２．５％，黄酒２．４％。回收率为９７．５％～１０５．０％，本方法具有操作简便，准确和快速等优点。     

Oxidative Addition Reactions of Element–Hydrogen Bonds with Different Polarities to a Gallium(I) Compound

The gallium(I) derivative [Ga({N(dipp)CMe}₂CH)] ( 1 ; dipp=2,6‐diisopropylphenyl) undergoes facile oxidative addition reactions with various element–hydrogen bonds including N? H, P? H, O? H, Sn? H, and H? H bonds. This was demonstrated by its reaction with triphenyltin hydride, ethanol, water, diethylamine, diphenylphosphane, and dihydrogen. All products were characterized by means of single‐crystal X‐ray structure determination, NMR spectroscopy, IR spectroscopy, and mass spectrometry.     

Processing of high resolution magic angle spinning spectra of breast cancer cells by the filter diagonalization method

Proton nuclear magnetic resonance ((1)H NMR) spectroscopy for detection of biochemical changes in biological samples is a successful technique. However, the achieved NMR resolution is not sufficiently high when the analysis is performed with intact cells. To improve spectral resolution, high resolution magic angle spinning (HR-MAS) is used and the broad signals are separated by a T(2) filter based on the CPMG pulse sequence. Additionally, HR-MAS experiments with a T(2) filter are preceded by a water suppression procedure. The goal of this work is to demonstrate that the experimental procedures of water suppression and T(2) or diffusing filters are unnecessary steps when the filter diagonalization method (FDM) is used to process the time domain HR-MAS signals. Manipulation of the FDM results, represented as a tabular list of peak positions, widths, amplitudes and phases, allows the removal of water signals without the disturbing overlapping or nearby signals. Additionally, the FDM can also be used for phase correction and noise suppression, and to discriminate between sharp and broad lines. Results demonstrate the applicability of the FDM post-acquisition processing to obtain high quality HR-MAS spectra of heterogeneous biological materials.     

Graphene Paste Electrode: Analytical Applications for the Quantification of Dopamine,Phenolic Compounds and Ethanol

This work reports the analytical applications of a graphene paste electrode (GrPE) for the quantification of dopamine, ethanol and phenolic compounds. Dopamine was detected by differential pulse voltammetry‐adsorptive stripping with medium exchange at submicromolar levels even in the presence of high excess of ascorbic acid and serotonin. The electrocatalytic activity of graphene towards the oxidation of NADH and the reduction of quinones allowed the sensitive amperometric determination of ethanol and phenols using GrPE modified with alcohol dehydrogenase/NAD⁺ or polyphenol oxidase, respectively, with successful applications in real samples like alcoholic beverages and tea.     

Application of WET sequence for the detection of the ligand signals resonating close to water

An efficient pulse sequence for observing the ligand signals resonating close to the water signal has been developed by incorporating the WET technique into the saturation transfer difference pulse sequence. Although several pulse sequences have been developed for observing a ligand binding with a protein receptor, the ligand signals resonating close to the water were undetectable owing to the interference of the huge water signal in the samples containing 95% ¹H₂O. On the point of sample preparation, it is preferable to avoid the solvent exchange in the protein samples. In the proposed pulse sequence, a WET sequence is incorporated for the selective suppression of the water resonance. The efficient water suppression and the clear observation of the bound ligand signals close to the water have been demonstrated using the lysozyme‐glucose complex. Copyright © 2009 John Wiley & Sons, Ltd.     

Application of MATLAB package for the automation of the chemometric processing of spectrometric signals in the analysis of complex mixtures

We describe three types of automatic software for the chemometric processing of spectrometric data. The software was developed in the MATLAB working environment and includes data import, mathematical preprocessing, chemometric analysis, and generation of a report file. The software is designed to solve problems regarding identification of some components of multicomponent mixtures, determination of compounds with overlapping signals, and differentiation of samples by their spectral responses. To test the software, we present examples of spectrometric analyses of coffee, fruit juices, and alcoholic beverages using chemometric methods of independent component analysis (ICA) and partial least squares–discriminant analysis (PLS–DA). In particular, we simulated electronic absorption spectra for the identification of three artificial colors (E110, E102, and E122) in alcoholic beverages, NMR spectra for the simultaneous determination of five components (acetic acid, γ-aminobutyric acid, arginine, acetaldehyde, and proline) in orange juice without using reference standards, and NMR spectra of coffee samples to determine its varietal authenticity (Arabica or Robusta). The duration of automatic chemometric processing did not exceed 1 min per sample. The developed software can be optimized for other matrices and/or brands of spectrometers.     

1H detection in MAS solid-state NMR spectroscopy of biomacromolecules employing pulsed field gradients for residual solvent suppression

In this communication, we demonstrate the feasibility of 1H detection in MAS solid-state NMR for a microcrystalline, uniformly 2H,15N-labeled sample of a SH3 domain of chicken alpha-spectrin, using pulsed field gradients for suppression of water magnetization. Today, B0 gradients are employed routinely in solution-state NMR for coherence order selection and solvent suppression. We suggest to use gradients to purge water magnetization which cannot be suppressed using conventional water suppression schemes. The achievable gain in sensitivity for 1H detection is in the order of 5 compared to the 15N detected version of the experiment (at a MAS rotation frequency of 13.5 kHz). We expect that this labeling concept which achieves high sensitivity due to 1H detection, in combination with the possibility to measure long range 1H-1H distances as we have shown previously, to be a useful tool for the determination of protein structures in the solid state.