Determination of tartaric acid in wines by FIA with tubular tartrate-selective electrodes

A flow injection analysis (FIA) system comprising a tartrate- (TAT) selective electrode has been developed for determination of tartaric acid in wines. Several electrodes constructed for this purpose had a PVC membrane with a complex of quaternary ammonium and TAT as anion exchanger, a phenol derivative as additive, and a more or less polar mediator solvent. Characterization of the electrodes showed behavior was best for membranes with o-nitrophenyl octyl ether as solvent. On injection of 500 μL into a phosphate buffer carrier (pH = 3.1; ionic strength 10^–2 mol/L) flowing at 3 mL/min, the slope was 58.06 ± 0.6 with a lower limit of linear range of 5.0 × 10^–4 mol/L TAT and R² = 0.9989. The interference of several species, e.g. chloride, bromide, iodide, nitrate, gallic acid, tannin, sucrose, glucose, fructose, acetate, and citrate, was evaluated in terms of potentiometric selectivity coefficients. The Hofmeister series was followed for inorganic species and the most interfering organic ion was citrate. When red and white wines were analyzed and the results compared with those from an independent method they were found to be accurate, with relative standard deviations below 5.0%.     

Optimization of a flow injection analysis system for tartaric acid determination in wines

The objective of this work is the development and optimization of a method for tartaric acid analysis in wines that does not require any sample pre-treatment and with adequate accuracy. A flow injection analysis manifold with three channels, using a dialysis unit to eliminate sample matrix interferences and to accomplish on-line dilution, is proposed for the spectrophotometrical determination of tartaric acid in wines making use of its reaction with vanadate. The proposed method is fast, accurate, simple, economic and does not require any sample pre-treatment. Preliminary studies using factorial designs were performed to determine which operational parameters should be included in the optimization stage. The optimization was performed using a modified simplex algorithm with a response function that included sensitivity, deviation from linearity at low concentrations and residence time, used as an inverse measure of sampling rate. The most relevant analytical parameters of the method are presented, including a comparison between the results provided by the proposed method and by an alternative procedure in the analysis of a set of wine samples from Portugal, with tartaric acid values in the range 0.5–4 g l⁻¹.     

Determination of tannic acid by direct chemiluminescence in a FIA assembly

The determination of tannic acid is performed in a FIA assembly on the basis of the analytical output obtained by oxidation of the acid. The analyte solution was daily prepared in a mixture of quinine as sensitiser and perchloric acid and it was injected into a pure water stream acting as a carrier. This solution merges with the mixture potassium permanganate in perchloric medium and the resulting chemiluminescence is monitored. The method was applied over the range 0.5–20 mg l⁻¹ of tannic acid with a LOD 100 μg l⁻¹. The reproducibility was 2.1% and the sample throughput 54 h⁻¹. The influence of foreign substances was studied and the new method is applied to the determination of tannic acid in pharmaceutical and galenic formulations in human urine and surface waters.     

高效液相色谱法分离和测定酒石酸和马来酸

１引言 酒石酸（２,３一二羟基丁二酸）和马来酸（顺丁烯二酸）都是重要的有机化工原料,它们被广泛地应用于有机合成和其它化工生产领域［１］． 酒石酸的制备常用钨酸作为催化剂,由马来酸识水溶液与过氧化氢进行环氧化反应再经水解精制而成,其中常含有微量的没有反应的马来酸,因此,建立有效的分离和测定酒石酸和马来酸的方法,对于酒石酸生产条件的选择与控制,以及产品的质量检测等都有十分重要的意义． 目前尚未发现有关同时分离和测定酒石酸和马来酸的文献报道．我们首次采用反相高效液相色谱法,跟踪监测了酒石酸生产过程中的物…     

Electrochemical behavior of tartaric acid at solid electrodes in aqueous and mixed solutions

Electrochemical behavior of D-tartaric acid at the Pt-, Cu-, Ta-, Cu-Hg-electrodes and the Cd-alloys with Sn, Ni, Hg, and In in aqueous and mixed solutions (water mixtures with acetone, ethanol, dimethylformamide, and pyridine) is studied by voltammetry. It is shown that the tartaric acid voltammograms always show waves related to the hydrogen ion discharge. A method recently suggested by authors allowed calculating the dissociation degrees at different stages, the concentrations of ionized and not ionized forms in dilute solutions of stereoisomers: DL-tartaric, L-tartaric, D-tartaric, and meso-tartaric acids. Simple empiric equations are suggested for the approximate calculating of some dissociation parameters for these acids.     

Tartradiamide formation by thermolysis of tartaric acid with alkylamines

The formation of N,N′-dialkyltartramides by microwave-assisted reactions and by conventional thermolysis was investigated. Thus, the thermolysis of l-tartaric acid with n-hexylamine at 200 °C showed that all the possible stereoisomers of N,N′-dihexyltartramide were formed albeit with partial racemization only. The same was observed for the microwave-assisted reaction.     

酒石酸掩蔽铝-丁二酮肟重量法测定镍钴铝三元氢氧化物中镍

镍钴铝三元氢氧化物中Ni质量分数为45%~60%、Al为0.5%~1.5%,丁二酮肟沉淀镍的pH条件下,Al3+会水解沉淀而干扰测定。试验对丁二酮肟重量法进行改进,采用酒石酸作为Al的掩蔽剂,从而建立了酒石酸掩蔽铝-丁二酮肟重量法测定镍钴铝三元氢氧化物中Ni含量的方法。试验评价了Al对丁二酮肟重量法测Ni的干扰,并确定了酒石酸的最佳掩蔽用量,测定实际样品801505型镍钴锰三元氢氧化物（Ni0.8Co0.15Al0.05(OH)2）和851005型镍钴锰三元氢氧化物（Ni0.85Co0.1Al0.05(OH)2）的RSD（n=11）分别为0.24%、0.31%,加标回收率分别为100.20%、99.68%,且测定值与ICP-AES基本一致。     

Kinetic study of the tartaric acid-periodate reaction: Determination of tartaric acid using an improved periodate-selective electrode

The preparation of an improved liquid-membrane periodate-selective electrode is described. The electrode exhibits rapid and near-Nernstian response in the range 2 × 10⁻⁶-10⁻² M. The electrode was used to monitor the course of the tartaric acid-periodate reaction. A potentiometric reaction rate method for the rapid and accurate determination of tartaric acid has been developed. A total of 0.4–120 μmol of tartaric acid has been determined with relative error of about 2.0%. The method has been applied to the determination of tartaric acid in pharmaceutical preparations and to the determination of small amounts of tartaric acid in impure citric acid.     

Spectrophotometric determination of tartaric acid with beta-naphthol

Tartaric acid (50-800 mug) is reacted with beta-naphthol (5 mg) in 90 % sulphuric acid (2 ml) for 30 min on a steam-bath. The solution is cooled and diluted to 25 ml with 90% sulphuric acid and the absorbance is measured at 603 nm. Several absorption maxima are observed and the ratio and intensity of these depend on the concentration of acid during and after the reaction, and on the beta-naphthol concentration. All tartaric acid isomers give essentially the same colour and absorbance. Interference studies are reported.     

血红蛋白催化化学发光反应联用流动注射测定甘油三酯

基于甘油三酯在脂肪酶的催化作用下水解生成甘油, 甘油在甘油激酶催化作用下生成甘油-3-H3PO4, 甘油-3-H3PO4在磷酸甘油氧化酶的作用下释放出过氧化氢, 利用血红蛋白(Hb)模拟酶催化过氧化氢-鲁米诺的化学发光体系, 结合流动注射技术, 建立了血红蛋白催化化学发光法联用流动注射技术测定人体血清中的甘油三酯的新方法, 并将该法用于血清中甘油三酯含量的测定. 该法线性范围为2.26×10-4～2.26×10-6 mol/L (r=0.9955), 检出限为7.5×10-7 mol/L.     

Determination of lithium in wines by ion chromatography

Lithium ion can be added as a denaturing agent to wines unsuitable for consumption. Accuracy of flame atomic emission spectroscopy with direct nebulization, which is commonly adopted for discovering illegal use of denatured wines, was found to be compromised by Na+, K+, NH4+, Mg2+, Ca2+ and ethanol contained in wine. Ion chromatography (IC) was tested in order to propose an alternative method for legal controls. Experimental design was used to investigate the influence on the accuracy of the determination of Li+ at ppb levels, of Na+ and ethanol content of wine and of fluctuations of eluent flow-rate and composition. It turned out that IC quantification of Li+ can be affected by eluent parameters rather than by wine composition. Since the former can be maintained under the operators control, while the latter cannot, IC was judged preferable to AES for legal controls of Li+ in wines.     

立体选择性萃取分离反式DV菊酸对映体

研究了反式DV菊酸对映体在含有手性选择体酒石酸酯的水-有机相双相体系中的萃取分配行为,考察了有机稀释剂种类、酒石酸酯的浓度、温度、水相的pH值、酒石酸酯烷基链长度对分配系数(D)和分配因子(α)的影响.研究表明:三氯甲烷作稀释剂时萃取分离效果较好;温度升高使分配系数增大,分离因子减小;分配系数随pH的升高而降低,随着酒石酸酯浓度的增大而增大,分离因子随pH的升高和酒石酸酯浓度的增大先增加后降低,pH和酒石酸酯浓度分别为4.50和0.40mol/L时取得较好的分离效果;取代烷基链长对分配系数(D)和分离因子(α)亦有较大影响.     

酒石酸酯立体选择性萃取分离功夫菊酸对映体

研究了功夫菊酸对映体在含有手性选择剂酒石酸酯的水-有机相双相体系中的萃取分配行为,考察了水相的pH、酒石酸酯的浓度、磷酸盐浓度、温度和酒石酸酯烷基链长度对分配系数(K)和分离因子(α)的影响.研究结果表明:分配系数(K)随pH的升高而降低,随着酒石酸酯浓度的增大而增大,分离因子(α)随pH的升高和酒石酸酯浓度的增大先增加后降低,pH和酒石酸酯浓度分别为5.50和0.30 mol/L时取得较好的分离效果;分配系数(K)和分离因子(α)都随磷酸盐浓度增大而减小;温度、取代烷基链长对分配系数(K)和分离因子(α)亦有较大影响.     

Determination of proteins by amperometric titration with 12-phosphotungstic acid at rotating gold electrodes

Amperometric titration of various protein fractions and human serum with 12-phosphotungstic acid at the rotating gold electrode is described. The titrant is electroreducible and its concentration may be monitored by poising an amperometric indicator electrode at a potential of -0.25 V vs. SCE. In 1.0 M hydrochloric acid, well defined titration curves of proteins may be obtained in the presence of airsaturated solutions. The relative standard deviation of replicate samples is 0.2–0.3% in the range 2–4 g of protein per 1 in the sample solution. The technique is principally applicable to homogeneous mixtures of proteins.     

Chiral recognition conducted by tartaric acid derivatives in nonaqueous media

Chiral recognition of hydroxycaboxylic acid, amino acid and 1,2-diol derivatives using diastereomeric complexation based on hydrogen bond with L(+)-N,N′-diisopropyl-tartramide (DIPTA) is described.     

Resolution of N-methylamphetamine enantiomers with tartaric acid derivatives by supercritical fluid extraction

The resolution of N-methylamphetamine (MA) was carried out with the resolution agents O,O′-dibenzoyl-(2R,3R)-tartaric acid monohydrate (DBTA) and O,O′-di-p-toluoyl-(2R,3R)-tartaric acid (DPTTA). After partial diastereomeric salt formation, the unreacted enantiomers were extracted by supercritical fluid extraction (SFE). The effects of resolution agent molar ratio to the racemic mixture (mr), extraction pressure (P) and temperature (T) on the resolution efficiency were studied. The best chiral separation was obtained at a quarter of an equivalent resolution agent molar ratio for both resolution agents. Extraction conditions [pressure (100–200 bar), temperature (33–63 °C)] did not influence the resolution efficiency, which makes the enantiomer separation robust. In one extraction step, both enantiomers can be produced with high enantiomeric excess (ee) and remarkable yield (Y). Using DBTA as a resolution agent ee_E=83%, Y_E=45% for the extract and ee_R=82%, Y_R=42% for the raffinate were obtained.     

Determination of polyphenols in wines by liquid chromatography with UV spectrophotometric detection

This paper describes a new chromatographic method for the determination of polyphenolic compounds in wines. The method is based on the separation of analytes by reversed-phase mode in a C18 column (2.6 μm particle size) and UV absorption spectroscopy. The elution gradient is generated from 0.1% formic acid aqueous solution and acetonitrile as an organic modifier. Experimental conditions including pH, percentage of organic modifier and elution gradient profile have been thoroughly optimized using experimental design. A multi-objective function has been defined as a criterion for obtaining a satisfactory compromise among number of compounds separated, resolution and analysis time. Multi-detection at 280, 310 and 370 nm has been utilized in order to work under the most appropriate wavelengths for each compound. Figures of merit including linearity ranges, precisions, detection limits and recoveries have been established under selected experimental conditions using synthetic standards and commercial red wines. The method has been applied to analyze red wines from various Spanish regions.