Flow injection on-line dialysis coupled to high performance liquid chromatography for the determination of some organic acids in wine

A combined system of flow injection on-line dialysis sample pretreatment and high performance liquid chromatographic separation/detection (FID-HPLC) was developed for simultaneous determination of six organic acids (tartaric, malic, lactic, acetic, citric and succinic acids). A sample or mixed standard solution (400 μL) was injected into a donor stream (water) of FID system and was pushed further through a dialysis cell, while an acceptor solution (water) was held in the opposite side of the dialysis membrane. The dialysate containing organic acids in the acceptor solution was then flowed to an injection loop of the HPLC valve, where it was further injected into the HPLC system and analysed under normal HPLC conditions, using a reversed-phase (C₁₈) analytical column and UV detection (210 nm). The order of elution was tartaric, malic, lactic, acetic, citric and succinic acids with the analysis time of 8 min. The FID system could be operated in parallel with HPLC separation, providing sample throughput of 7.5 h⁻¹. Dialysis efficiencies of six organic acids were in range of 4.6-9.5%. Calibration graphs for all the mentioned organic acids were linear over the range of 250-7500 mg L⁻¹. Precisions for all the organic acids were within 5.4%. The proposed system was successfully applied for analysis of some Thai wines. By spiking wine samples with mixed acid standard solutions, the percentage recoveries in range of 84-104 were found. This system has advantages of fast and high degrees of automation for dialysis sample pretreatment, on-line sample separation and dilution, good clean-up for prolongation of life-time of the HPLC column and low consumption of chemicals and materials.     

Application of co-electroosmotic capillary electrophoresis for the determination of inorganic anions and carboxylic acids in soil and plant extract with direct UV detection

Summary Indirect UV detection in capillary zone electrophoresis (CZE) is frequently used for the determination of inorganic anions and carboxylic acids. However, there are few reports on direct UV detection of these solutes in real samples. This paper describes the use of direct UV detection of inorganic anions and organic acids in environmental samples using co-electroosmotic capillary zone electrophoresis (co-CZE) at 185 nm. The best separation and detection of the solutes was achieved using a fused silica capillary with an electrolyte containing 25 mM phosphate, 0.5 mM tetradecyltrimethylammonium bromide (TTAB) and 15% acetonitrile (v/v) at pH 6.0. Four common inorganic anions (Cl⁻, NO₂ ⁻, NO₃ ⁻ and SO₄ ²⁻) and 11 organic acids (oxalic, formic, fumaric, tartaric, malonic, malic, citric, succinic, maleic, acetic, and lactic acid), were determined simultaneously in 15 min. Linear calibration plots for the test solutes were obtained in the range 0.02–0.5 mM with detection limits ranging from 1–9 μM depending on the analyte. The proposed method was successfully used to determine inorganic anions and carboxylic acids in soil and plant tissue extracts with direct injection of the sample.     

Chromatographic Studies of 34 Organic Acids on Papers Impregnated with Hydroxides of Aluminium and Cadmium

Abstract

Papers impregnated with aluminium hydroxide and cadmium hydroxide have been used for the chromatographic separation of organic acids exist in various biological materials, soil and water. The following important separations: cinnamic acid from hippuric acid; benzoic and m-nitrobenzoic acids from gallic, β-naphthalene acetic, β-naphthoxy acetic, phthalic, quinic and salicylic acids; and salicylic acid from citric, cis-aconitic, malic, quinic, tartaric and trans-aconitic acids can be achieved in common electrolytes (Cd(NO₃)₂, KI, NaCl, NH₄Cl) solution.

Hydroxides¹ show amphoteric behaviour i. e. they may exchange either cations or anions depending upon the pH of the solution, and t h i s may be shown by the following ionic equilibria.     

Single-run ion chromatographic separation of inorganic and low-molecular-mass organic anions under isocratic elution: Application to environmental samples

For the isocratic ion chromatography (IC) separation of low-molecular-mass organic acids and inorganic anions three different anion-exchange columns were studied: IonPac AS14 (9 μm particle size), Allsep A-2 (7 μm particle size), and IC SI-50 4E (5 μm particle size). A complete baseline separation for all analyzed anions (i.e., F⁻, acetate, formate, Cl⁻, NO₂⁻, Br⁻, NO₃⁻, HPO₄²⁻ and SO₄²⁻) in one analytical cycle of shorter than 17 min was achieved on the IC SI-50 4E column, using an eluent mixture of 3.2 mM Na₂CO₃ and 1.0 mM NaHCO₃ with a flow rate of 1.0 mL min⁻¹. On the IonPac AS14 column, it was possible to separate acetate from inorganic anions in one run (i.e., less than 9 min), but not formate, under the following conditions: 3.5 mM Na₂CO₃ plus 1.0 mM NaHCO₃ with a flow rate of 1.2 mL min⁻¹. Therefore, it was necessary to adapt a second run with a 2.0 mM Na₂B₄O₇ solution as an eluent under a flow rate of 0.8 mL min⁻¹ for the separation of organic ions, which considerably enlarged the analysis time. For the Allsep A-2 column, using an eluent mixture of 1.2 mM Na₂CO₃ plus 1.5 mM NaHCO₃ with a flow rate of 1.6 mL min⁻¹, it was possible to separate almost all anions in one run within 25 min, except the fluoride-acetate critical pair. A Certified Multianion Standard Solution PRIMUS for IC was used for the validation of the analytical methods. The lowest RSDs (less than 1%) and the best LODs (0.02, 0.2, 0.16, 0.11, 0.06, 0.05, 0.04, 0.14 and 0.09 mg L⁻¹ for F⁻, Ac⁻, For⁻, Cl⁻, NO₂⁻, Br⁻, NO₃⁻, HPO₄²⁻ and SO₄²⁻, respectively) were achieved using the IC SI-50 4E column. This column was applied for the separation of concerned ions in environmental precipitation samples such as snow, hail and rainwater.     

Analysis of organic acids and phenols of interest in the wine industry using Langmuir–Blodgett films based on functionalized nanoparticles

A chemically modified electrode consisting of Langmuir–Blodgett (LB) films of n-dodecanethiol functionalized gold nanoparticles (S_DODAuNP-LB), was investigated as a voltammetric sensor of organic and phenolic acids of interest in the wine industry. The nanostructured films demonstrated interfacial properties being able to detect the main organic acids present in grapes and wines (tartaric, malic, lactic and citric). Compared to a bare ITO electrode, the modified electrodes exhibited a shift of the reduction potential in the less positive direction and a marked enhancement in the current response. Moreover, the increased electrocatalytic properties made it possible to distinguish between the different dissociable protons of polyprotic acids. The S_DODAuNP-LB sensor was also able to provide enhanced responses toward aqueous solutions of phenolic acids commonly found in wines (caffeic and gallic acids). The presence of nanoparticles increased drastically the sensitivity toward organic acids and phenolic compounds. Limits of detection as low as 10⁻⁶ mol L⁻¹ were achieved. Efficient catalytic activity was also observed in mixtures of phenolic acid/tartaric in the range of pHs typically found in wines. In such mixtures, the electrode was able to provide simultaneous information about the acid and the phenol concentrations with a complete absence of interferences.     

Quantitative analysis of malic and citric acids in fruit juices using proton nuclear magnetic resonance spectroscopy

¹H NMR spectroscopy was applied to the quantitative determination of malic and citric acids in apple, apricot, pear, kiwi, orange, strawberry and pineapple juices. Aspartic acid was studied as a potential interference. The effect of the sample pH on the chemical shifts of signals from malic, citric and aspartic acids was examined and a value of 1.0 was selected to carry out the determination. Integration of NMR signals at 2.89-2.95 and 3.00-3.04 ppm were used for calculating the concentration of malic and citric acids, respectively. At this pH the integrated signals were not overlapped. Sodium 3-(trimethylsilyl)tetradeuteropropionate (TSP) was used as an internal reference. The obtained results applying NMR procedures to analyze the juices from different fruits were compared to those obtained using enzymatic methods and both were in close agreement. The intra- and inter-day repeatability was tested for apple juice (7.86 g l⁻¹ malic acid, 0.32 g l⁻¹ citric acid) and apricot juice (5.06 g l⁻¹ malic acid, 4.79 g l⁻¹ citric acid) obtaining coefficients of variation lower than 3.4% for intra-day measures (n = 10) and lower than 3.8% for inter-day measures (n = 20).     

Determination of organic acids in alcoholic and nonalcoholic beverages by reversed-phase high-performance liquid chromatography

A procedure for the quantification of 9 organic acids, acetic, formic, citric, tartaric, lactic, malic, succinic, oxalic, and fumaric, in alcoholic and alcohol-free beverages by reversed-phase HPLC on a Pronto-SIL C18 AQ (300 × 3 mm) column (3 μm) with the mobile phase 5 mM Li₂SO₄ (pH 3.00, H₂SO₄) at the rate 0.5 mL/min and conductometry detection. The analytical ranges made 5–200 mg/L for tartaric, malic, lactic and acetic acids, 2–200 mg/L for the citric and fumaric, 10–400 mg/L for succinic, 15–400 for oxalic, and 20–200 for the formic acids, and so the detection limits: 1 mg/L for tartaric, formic, malic and fumaric, 2 mg/L for lactic, acetic and citric, 5 mg/L for succinic, and 10 mg/L for oxalic acids. The analysis of alcoholic beverages takes 30–40 min, and of non-alcoholic ones, 20–30 min; the standard deviation of the results of analyses does not exceed 5%.     

Determination of water-soluble inorganic and organic species in atmospheric fine particulate matter

The use of ion chromatography (IC) in conjunction with ultrasonic extraction is described for the routine analysis of water-soluble major inorganic ions and organic acids in atmospheric fine particles (PM_2.5). Both the extraction method and the IC analysis were validated using NIST SRM 1648 (urban particulate matter). In addition, the reliability of the IC method was established by intercomparison of results obtained with those from suitable alternative analytical techniques (atomic absorption spectrometry (AAS), proton-induced X-ray emission (PIXE) spectrometry, and UV-Visible spectrophotometry). The validated IC method was successfully applied for field monitoring of PM_2.5 particles collected in Singapore over an extended period of time. The IC analysis revealed that the concentrations of individual ions were in the order, SO₄²⁻ > NH₄⁺ > NO₃⁻ > Na⁺ > K⁺ > Cl⁻, respectively. Among the major ionic components, SO₄²⁻ contributed 50% to the measured water-soluble aerosol mass followed by NH₄⁺ (16.5%) and NO₃⁻ (9.0%). The cations Na⁺, K⁺, Mg²⁺, and Ca²⁺ accounted for 24% of the total water-soluble mass. The IC analysis was performed to quantify the organic acids, which typically account for a small fraction of water-soluble organic compounds in PM_2.5. Oxalate was found to be the dominant species among the organic acids measured in this work.     

LC Determination of Trace Short-Chain Organic Acids in Wheat Root Exudates Under Aluminum Stress

A novel and reliable high-performance liquid chromatographic method for trace short-chain organic acids measurement in wheat root exudates under aluminum stress has been optimized and validated. The chromatographic separation of the short-chain organic acids (citric, oxalic, malonic, succinic, tartaric, malic, and acetic acids) was achieved with Bio-rad Aminex HPX-87H cation exchange resin column. These seven organic acids were identified and quantified in 25 min. Well-shaped peaks were obtained for trace organic acids using dilute sulfuric acid as mobile phase. Under optimum conditions, Bio-rad Aminex HPX-87H column showed distinct advantages of the ability to well separate different short-chain organic acids (especially for tartaric and malic acids, as well as malonic and acetic acids) in wheat root exudates under aluminum stress, and offered accurate and precise results for the analysis of these organic acids. This HPLC method can efficiently eliminate the aluminum’s interference and is quite suitable to the trace detection of trace organic acids in wheat root exudates under aluminum stress.

     

Polyelectrolyte multilayers as stationary phases for open tubular ion chromatography

Polyelectrolyte multilayers deposited on the wall of fused silica capillaries were used as stationary phases in open tubular ion chromatography. The multilayers were formed by flushing the capillaries with solutions of polyanions and polycations such as polydiallyldimethylammonium chloride and dextran sulphate. Columns with several bi-layers were constructed and used in low pressure non-suppressed open tubular ion chromatography of common inorganic anions (F⁻, Cl⁻, NO₃⁻) and cations (Li⁺, Na⁺, NH₄⁺, K⁺, Cs⁺) with contactless conductometric detection. Using sodium benzoate and tartaric acid eluents the separations were typically achieved in less than 35 min with separation efficiencies between 2000 and 9000 theoretical plates. A bi-functional column was prepared that contains both anionic and cationic functional groups and was used for simultaneous separation of anions and cations.     

高效液相色谱法测定铬超富集植物李氏禾根系分泌物中的有机酸

建立了高效液相色谱（HPLC）测定Cr超富集植物李氏禾根系分泌物中低相对分子质量有机酸的分析方法。采用XSelect HSS T3色谱柱（250 mm×4.6 mm,5 μm,Waters）,以40 mmol/L磷酸二氢钾-磷酸缓冲溶液（pH=2.40）作流动相,流速1.0 mL/min,柱温25℃,在波长205 nm处检测。该方法在13 min内简便快速地分离出8种有机酸（草酸、酒石酸、苹果酸、乳酸、甲酸、乙酸、马来酸和柠檬酸）,且峰形良好。有机酸的检出限（LOD）为0.12~12.32 mg/L;草酸的加标回收率为73.15%,其他有机酸的加标回收率为94.54%~109.98%。李氏禾的根系分泌物中各有机酸含量分别为酒石酸（130.90±1.44）μg/g（根干重）、苹果酸（1031.34±4.38）μg/g（根干重）、乳酸（65.54±1.01）μg/g（根干重）、马来酸（0.96000±0.00367）μg/g（根干重）和柠檬酸（201.50±1.13）μg/g（根干重）。该方法简便快速,灵敏可靠,适用于植物根系分泌物样品中有机酸的测定。     

Electrocatalytic behaviour of citric acid at a cobalt phthalocyanine-modified screen-printed carbon electrode and its application in pharmaceutical and food analysis

Cobalt phthalocyanine-modified screen-printed carbon electrodes (CoPC-SPCEs) have been investigated as disposable sensors for the measurement of citric acid. The analyte was found to undergo an electrocatalytic oxidation process involving the Co²⁺/Co³⁺ redox couple. Calibration plots were found to be linear in the range 2 mM to 2.0 M; replicate determinations of a 5.2 mM citric acid (n = 4) solution gave a coefficient of variation of 1.43%. Additions of metal ions, such as Ag⁺, Pb²⁺, Cu²⁺, Fe³⁺ and Ca²⁺, were found not to interfere. The effects of hesperidin, cysteine, ethylenediaminetetraacetic acid (EDTA), ascorbic, formic, malic, malonic, tartaric, oxalic and trichloroacetic acids on the determination of citric acid were examined and, under the conditions employed, only oxalic acid and EDTA were found to give any significant interference. The sensors were evaluated by carrying out citric acid determinations on spiked and unspiked samples of an acid citrate dextrose (ACD) formulation, lime flesh and juice. For lime juice, recoveries were calculated to be 96.8% (% CV = 2.7%) for a sample fortified with 5% citric acid and for ACD 99.4% (%CV = 2.6%) when fortified at 2.30% citric acid. Further studies showed the possibility of determining citric acid concentrations in lime juice and fruit directly, without the need for an added electrolyte. These performance characteristics indicate that reliable data may be obtained for citric acid measurements in such samples. To our knowledge, this is the first report on the electrocatalytic oxidation of citric acid and its application using a CoPC-SPCE.     

Electrogenerated Chemiluminescence Based on Tris(2,2′-bipyridyl) Ruthenium(II) with Hydroxyl Carboxylic Acid

Upon the electrochemical oxidation of tris(2,2′-bipyridyl) ruthenium(II) [Ru(bpy)²⁺₃] and hydroxyl carboxylic acids, for instance, citric acid, tartaric acid, malic acid, and -gluconic acid, bright electrochemiluminescences (ECLs) were observed. Different luminescent reactions were presented depending on the applied potential. The light emission was mainly caused by the reaction between alkoxide radical ion and Ru(bpy)³⁺₃below the potential +1.80 V (vs Ag/AgCl). The luminescence intensity obviously increased because of the more complex reaction process. The luminescence wavelength of 608 nm, which could be found either at higher potential than +1.80 V or in the potential range from +1.30 to +1.80 V, confirmed that ECL was caused by Ru(bpy)²⁺₃*. The factors which affect the determination and HPLC separation of the four acids were also investigated.     

Solubilization of Terfenadine,Riboflavin, and Sudan III by Aqueous Multi-basic Organic Acids

ABSTRACT

The aqueous solubility of terfenadine, riboflavin, and Sudan III (water-insoluble compounds) was enhanced by the addition of multi-basic organic acids, including citric, glutaric, malic, malonic, and tartaric acids. The variations of physical properties (density, viscosity, electrical conductivity, pH, and surface tension) against acid concentration (0–3.6 M at 25°C) were measured in order to explore possible mechanisms of solubility enhancement. Apart from the partial molar volumes, the measured physical properties varied nonlinearly with acid concentration. Glutaric acid contributes to solubility enhancement of terfenadine and Sudan III more than citric acid, with the latter slightly more effective towards riboflavin. Tartaric acid is the least effective, while malic and malonic acids occupy an intermediate position. Among the organic acids examined, only glutaric acid solutions exhibit significant surface activity, which lends itself to solubility enhancement of the three hydrophobic drugs (interfacial packing of 55 ± 3 Å² at the air–water interface, critical aggregate concentrations (CAC) at 1.8 ± 0.4 M). In contrast, all five organic acid solutions of terfenadine demonstrate more effective lowering of the surface tension of water, with the terfenadinium acid salts exhibiting interfacial packing of 108 ± 9 Å² at the air–water interface. On the other hand, organic acid solutions of riboflavin and Sudan III exhibited essentially no surface activity, aside from the intrinsic contribution of the organic acids themselves. Thus, self-association of glutaric acid contributes to the solubility enhancement of the three hydrophobic drugs. This combined with the surface activity of terfenadinium acid salts explains the higher tendency of glutaric acid to solubilize terfenadine. Mixed micellization of terfenadinium glutarate and glutaric acid occurs with an interfacial packing of 166 ± 18 Å² at the air–water interface. The corresponding CAC were estimated at 3.1 ± 0.2 mM for terfenadinium glutarate and 8.0 ± 0.4 mM for glutaric acid. Intermolecular hydrogen bonding with the extensive hydroxyl group network of riboflavin reflects the higher affinity of citric acid than glutaric acid towards riboflavin. The variability in solubility enhancement exhibited by tartaric, malic, and malonic acids appears to be a result of the interplay between several factors including intra- vs. inter-molecular hydrogen bonding, slight organic acid surface activity, and acid hydration.     

Rapid simultaneous determination of amines and organic acids in citrus using high-performance liquid chromatography

Rapid analytical method for the simultaneous separation and determination of amines and organic acids is a vital interest for quality control of citrus and their products. In the present study, a simultaneous high performance liquid chromatography (HPLC) method for the rapid separation of three amines and two organic acids was developed. Chromatographic separation of compounds was achieved using Xbridge C₁₈ column at ambient temperature, with an isocratic mobile phase of 3 mM phosphoric acid at a flow rate of 1.0 mL min⁻¹. A photodiode array (PDA) detector was used to monitor the eluent at 223 nm and 254 nm with a total analysis time of 10 min. Extraction of amines and organic acids from citrus juice was optimized. The method was validated by tests of linearity, recovery, precision and ruggedness. The limit of detection (LOD) and limit of quantification (LOQ) for amines and ascorbic acid were determined to be 5 ng and 9.8 ng, respectively. All calibration curves showed good linearity (R² ≥ 0.9999) within the test ranges. The recoveries of the amines and organic acids ranged between 84% and 117%. The identity of each peak was confirmed by mass spectral (MS) analysis. The developed method was successfully applied to analyze the content of amines and organic acids in six different species and two varieties of citrus. Results indicate that mandarin and Marrs sweet orange contain high level of amines, while pummelo and Rio Red grapefruit had high content of ascorbic acid (137-251 μg mL⁻¹) and citric acid (5-22 mg mL⁻¹). Synephrine was the major amine present in Clementine (114 μg mL⁻¹) and Marrs sweet orange (85 μg mL⁻¹). To the best of our knowledge, this is the first report on simultaneous separation and quantification of amines and organic acids in Marrs sweet orange, Meyer lemon, Nova tangerine, Clementine, Ugli tangelo and Wekiwa tangelo.     

LC Determination of Trace Short-Chain Organic Acids in Wheat Root Exudates Under Aluminum Stress

A novel and reliable high-performance liquid chromatographic method for trace short-chain organic acids measurement in wheat root exudates under aluminum stress has been optimized and validated. The chromatographic separation of the short-chain organic acids (citric, oxalic, malonic, succinic, tartaric, malic, and acetic acids) was achieved with Bio-rad Aminex HPX-87H cation exchange resin column. These seven organic acids were identified and quantified in 25 min. Well-shaped peaks were obtained for trace organic acids using dilute sulfuric acid as mobile phase. Under optimum conditions, Bio-rad Aminex HPX-87H column showed distinct advantages of the ability to well separate different short-chain organic acids (especially for tartaric and malic acids, as well as malonic and acetic acids) in wheat root exudates under aluminum stress, and offered accurate and precise results for the analysis of these organic acids. This HPLC method can efficiently eliminate the aluminum’s interference and is quite suitable to the trace detection of trace organic acids in wheat root exudates under aluminum stress.     

A rapid automated method for wine analysis based upon sequential injection (SI)-FTIR spectrometry

A new process control methodology for the simultaneous determination of sugars, alcohols and organic acids in wine based on multivariate evaluation of mid-IR transmission spectra of wine samples is presented. In addition to ethanol several lower level wine components (glucose, fructose, glycerol, citric-, tartaric-, malic-, lactic- and acetic acid) were determined. To establish a multivariate calibration model a set of 72 calibration solutions was prepared and measured, using a novel, fully automated sequential injection (SI) system with Fourier transform infrared (FTIR) detection. The resulting spectra were evaluated using a partial least square (PLS) model. The developed PLS model was then applied to the analysis of real wine samples containing 79–91 g L^–1 ethanol, 5.9–8.1 g L^–1 glycerol, 0.4–6.9 g L^–1 glucose, 1.5–7.5 g L^–1 fructose, 0.3–1.6 g L^–1 citric acid, 1.0–1.7 g L^–1 tartaric acid, 0.02–3.2 g L^–1 malic acid, 0.4–2.8 g L^–1 lactic acid and 0.15–0.60 g L^–1 acetic acid, yielding results which were in good agreement with those obtained by an external reference method (HPLC-IR). The short analysis time (less than 3 min) together with high reproducibility makes the newly developed method applicable to process control and screening purposes (average of the standard deviations calculated from four repetitive measurements of six different real samples: ethanol: 0.55 g L^–1, glycerol: 0.037 g L^–1, glucose: 0.056 g L^–1, fructose: 0.036 g L^–1, citric acid: 0.020 g L^–1, tartaric acid: 0.010 g L^–1, malic acid: 0.052 g L^–1, lactic acid: 0.012 g L^–1 and acetic acid: 0.026 g L^–1). Received: 21 January 1998 / Revised: 5 March 1998 / Accepted: 6 March 1998     

离子排斥色谱法同时测定果汁中11种有机酸

 用离子排斥色谱法实现了对果汁中 11种有机酸 (草酸、柠檬酸、酒石酸、苹果酸、抗坏血酸、乳酸、琥珀酸、甲酸、乙酸、戊二酸、富马酸 )的分离测定。以 17mmol/L硫酸为淋洗液 ,样品在ICE ION 30 0离子排斥柱上分离后 ,用紫外检测器在 2 10nm处测定其中的有机酸。各组分质量浓度测定的相对标准偏差在 1.5 %～ 9.8% (n =10 )。     

逐级提取-高效液相色谱法快速测定植物组织中8种有机酸

针对植物组织中草酸存在的不同形态,建立了水和稀盐酸作为提取介质的逐级提取方法,获得了水溶态和酸溶态草酸及乙醇酸、乙醛酸、酒石酸、苹果酸、乙酸、柠檬酸、琥珀酸等有机酸。采用Hypersil ODS (200 mm×4.6 mm, 5 μm)色谱柱,以5 mmol/L磷酸二氢钾水溶液(pH 2.8)作为流动相,在进样量5 μL、检测波长210 nm、柱温30 ℃的条件下,通过分时段控制流速实现了8种有机酸的快速分离,同时去除了盐酸对酸溶态草酸测定的干扰。本方法精确灵敏、回收率高、重复性好,可应用于实际样品的测定分析。