Separation of the positional isomers of phthalic acids in hydroorganic solvents using capillary electrophoresis

The positional isomers of phthalic acids (ortho-, meta-, and para-) and benzoic acid could be completely separated by capillary electrophoresis (CE). A simple CE method employing direct detection in mixed methanol/water buffers is presented. The effect of the electrolyte buffer system, including pH, buffer concentration, and organic solvent on the electrophoretic mobility of the analytes, is investigated. The electroosmotic flow is reversed using cationic surfactant and cetyltrimethylammonium bromide so that anions are separated under the co-EOF mode. The resolution of the analytes and selectivity could be improved by the adjustment of the methanol content. Ion association with the surfactant in methanol/water buffer is discussed. The validity of the method in terms of sensitivity, reproducibility, and linearity is also reported. The text was submitted by the authors in English.     

The aqueous phase nitration of phenol and benzoic acid studied through flow-gated capillary electrophoresis

The aqueous phase nitration of benzoic acid and phenol was investigated via on-line capillary electrophoresis (CE). The presence of nitrated benzoic acid and phenol was supported through appearance of corresponding molecular ion peaks in ESI-MS measurements, and speciation of the nitrated isomers is achieved via the on-line CE method. The nitrated isomers produced in both reactions were successfully separated in <4?min by addition of 15?mM β-cyclodextrin to the electrophoresis buffer. Sequential separations (on-line analysis) allowed the reaction kinetics to be described. For benzoic acid, reaction yields were low (2–3%) however, results suggest both 3- and 2-nitrobenzoic acid form in a 1–1.4 concentration ratio. In addition, 3-hydroxybenzoic acid also forms in significant quantity under our reaction conditions. For the nitration of phenol, the reaction occurred more rapidly with observed yields between ≈10–30% for individual isomers. The yield of 2-nitrophenol was higher than 4-nitrophenol by a ratio of ≈?1.7–2, but 3-nitrophenol was not detected. For both reactions, nitrated and hydroxylated aromatics were the major products and formation of higher molecular weight oligomers was not observed.     

Separation and migration behavior of positional and structural naphthalenesulfonate isomers by cyclodextrin-mediated capillary electrophoresis

The effects of the type of buffer system, buffer pH, the polarity of electrode, and both the type and the concentration of cyclodextrins (CDs) on the separation and migration behavior of seven positional and structural naphthalenesulfonate isomers in CD-mediated capillary electrophoresis were systematically investigated. The most effective separation conditions were to use 20 mM phosphate buffer with beta-CD at pH 3.0, while the polarity of the electrodes were reversed across the capillary. Under such conditions, these isomers can be separated in 10 min. The results also indicate that the interactions of naphthalenesulfonate derivatives with CDs are strongly affected by the position of the substituent(s) on the aromatic ring. The inclusion complex formation constants of these compounds were evaluated to improve our understanding of the interaction between the naphthalenesulfonate derivatives and CDs. Moreover, the formation constants of naphthalene-2-sulfonate to beta-CD agreed closely with the data in the literature obtained by a spectrophotometric method and by CE methods in various pH buffers.     

Solvent extraction of organic molecules of exobiological interest for in situ analysis of the Martian soil

A solid-liquid extraction method able to perform in situ extraction of organic compounds on Mars is proposed. The extraction efficiency of various organic solvents was tested and compared to that of water. The selected key compounds are molecules of exobiological interest: glycine, alanine, serine, glutamic acid, oxalic acid, benzoic acid, phthalic acid, isophthalic acid, terephthalic acid and 1,3,5-benzenetricarboxylic acid. Among the organic solvents, propanol gives the highest yield of extraction for all the targeted compounds except for benzoic acid. A mixture of propanol and ethyl acetate increases significantly the extraction yield of benzoic acid. The extraction time was considerably reduced (140 h to 15 min) by using sonication. The method is discussed for an easy automation with coupling to an in situ GC-MS space instrument.     

Application of a novel micro-injector in the determination of indole derivatives in the rat pineal gland by capillary electrophoresis with electrochemical detection

A novel micro-injector has been fabricated for capillary electrophoresis (CE). It was successfully used for the determination of some indole derivatives for example melatonin (MT), serotonin (5-HT), tryptophan (Trp), and 5-hydroxy-tryptophane (5-HTrp) in the rat pineal gland by capillary electrophoresis with electrochemical detection (CE-EC). CE was performed in 0.20 mol L(-1) phosphate buffer (pH 8.0). The compounds investigated can be well separated and detected within 15 min. The working electrode used was a 300-microm diameter carbon electrode positioned opposite the outlet of the capillary. The relationship between peak current and analyte concentration was highly linear in the range from 0.10 to 500 micromol L(-1); detection limits (S/N = 3) were 0.03-0.13 micromol L(-1). The proposed method has been successfully used to analyze real biological samples.     

Reactions of <Emphasis Type="Italic">N</Emphasis>-(Perfluorophenyl)carbonimidoyl Dichloride with Aromatic Acids and Their Derivatives in the Presence of AlCl<Subscript>3</Subscript>. Formation of 2-(Perfluorophenyl)isoindoline-1,3-dione and Its Derivatives

Reactions of N-(perfluorophenyl)carbonimidoyl dichloride with benzoic acid, benzoyl chloride, ethyl benzoate, and also with phthalic acid, phthaloyl dichloride, and phthalic anhydride in the presence of AlCl₃ at 170°C afford2-(perfluorophenyl)isoindoline-1,3-dione. With benzoic acid and benzoyl chloride form also 2-(perfluorophenyl)-3-[(perfluorophenyl)imino]isoindolin-1-one. In reactions with compounds of the benzene series arise also derivatives of arylimidoyl chlorides and amide type compounds containing a CONHC₆F₅ moiety.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 2, 2005, pp. 228–236.Original Russian Text Copyright © 2005 by Petrova, Platonov.     

Analysis of high-mannose-type oligosaccharides by microliquid chromatography-mass spectrometry and capillary electrophoresis

We report on microbore liquid chromatography (microLC) and capillary electrophoresis (CE) separation of glycopeptides and high-mannose-type oligosaccharides, digested from recombinant phospholipase C, expressed in Pichia pastoris. The glycopeptides were subject to microLC/electrospray ionization/mass spectrometry (ESI-MS) and microLC/ESI-tandem MS (MS/MS) analysis that revealed high-mannose structure size variation between Man(7)GlcNAc(2) and Man(14)GlcNAc(2). Then, high-performance CE was applied to identify possible positional isomers of the high-mannose structures. For the CE experiments, the oligosaccharides were released from the glycoproteins by peptide-N-glycosidase F and labeled with 1-aminopyrene-3,6,8-trisulfonic acid (APTS). Excellent separation of the possible positional isomers was attained, suggesting one for Man(9)GlcNAc(2), two for Man(10)GlcNAc(2), three for Man(11)GlcNAc(2), Man(12)GlcNAc(2), and Man(13)GlcNAc(2), and two for Man(14)GlcNAc(2). The CE results provided complementary information to the microLC/ESI-MS and MS/MS data with respect to the possible number of positional isomers.     

高效液相色谱-紫外检测法同时测定食品接触材料中7种苯多酸及其衍生物的特定总迁移量

建立了高效液相色谱-紫外检测(HPLC-UV)同时测定5种食品模拟物(10%(v/v)乙醇、20%(v/v)乙醇、50%(v/v)乙醇、3%(w/v)乙酸和橄榄油)中偏苯三甲酸、偏苯三甲酸酐、间苯二甲酰氯、间苯二甲酸、对苯二甲酰氯、邻苯二甲酸、对苯二甲酸的特定总迁移量(SML(T))的方法。用食品模拟物浸泡待测样品,冷却至室温并混匀,水基食品模拟物经亲水性聚四氟乙酸针头过滤器过滤后进样;橄榄油用0.1%(w/v)乙酸铵水溶液提取后,下层清液用亲水性聚四氟乙烯针头过滤器过滤后进样。用Synergi Polar-RP色谱柱(250 mm×4.6 mm, 4 μm)分离,梯度洗脱,检测波长为232 nm。5种食品模拟物中的定量限为0.1~0.2 mg/kg;水基食品模拟物在0.5~12 mg/L、橄榄油食品模拟物在0.5~12 mg/kg范围内线性关系良好(r² > 0.99991); 1.25、2.5、6.25 mg/kg水平的加标回收率为94.3%~105%,相对标准偏差为0.1%~2.3%。结果表明,该方法的色谱分离和线性关系较好,回收率和准确度高,完全满足欧盟(EU)No 10/2011法规附表2中7种苯多酸及其衍生物的SML(T)的限量要求,并已应用于实际样品的检测。     

Study of low-molecular weight organic acids in maize roots under the stress of cadmium using capillary zone electrophoresis

An indirect CE method was developed for the study of low-molecular weight organic acids (LMWOAs) in maize under the stress of cadmium. The influences of indirect reagents (phthalate, salicylic acid, and benzoic acid), coion concentration, and pH were studied. A buffer composed of 15 mmol/L benzoate and 0.2 mmol/L CTAB (pH 5.7) was used in the organic acid determination. The detection limit ranged between 0.5 and 6 micromol/L. The RSD (n = 14) of the method was found to be in the range of 0.11-0.49% for migration time and 1.25-4.72% for peak area. In the maize roots, obvious increases of LMWOAs were observed when the plants were under the stress of cadmium and/or organic acids. The recovery of standard organic acids added in real samples ranged from 85 to 116%.     

新型杯[4]芳烃高效液相色谱固定相的制备及表征

合成了一种新型的杯[4]芳烃高效液相色谱键合固定相,考察了它的反相色谱行为．通过对多环芳烃、二取代苯的位置异构体、苯甲酸酯和邻苯二甲酸酯的分离,发现该键合相具有显著的反相特征,对位置异构体具有很高的识别能力,其分离明显优于C18柱,并讨论了可能的分离机理．     

DFT and ab initio study of structure of dyes derived from 2-hydroxy and 2,4-dihydroxy benzoic acids

We present a detailed analysis of the structural, infrared spectra and visible spectra of a series of azo dyes preparation of salicylic acid and 2,4-dihydroxy benzoic acid derivatives as the coupling component. The preparation of these azo dyes with salicylic acid and 2,4-dihydroxy benzoic acid derivatives (salicylic acid, methyl salicylate, ethyl salicylate, butyl salicylate, methyl 2,4-dihydroxy benzoate, ethyl 2,4-dihydroxy benzoate, salicylaldehyde, salicylamide, 2,4-dihydroxy benzamide, salicylaldoxime) have been investigated theoretically by performing HF and DFT levels of theory using the standard 6-31G* basis set. The optimized geometries and calculated vibrational frequencies are evaluated via comparison with experimental values. The vibrational spectral data obtained from solid phase FT-IR spectra are assigned modes based on the results of the theoretical calculations. The observed spectra are found to be in good agreement with the calculations.     

A novel LIF-CE method for the separation of hyaluronan- and chondroitin sulfate-derived disaccharides: Application to structural and quantitative analyses of human plasma low- and high-charged chondroitin sulfate isomers

The report describes a rapid and simple CE method using LIF detection for the analysis of unsaturated disaccharides obtained from enzymatic depolymerization of plasma chondroitin sulfate (CS) isomers. The disaccharide reducing groups were labeled with 2-aminoacridone (AMAC). The fluorotagged products can be separated by reversed-polarity CE using a sodium acetate buffer, pH 3.8, in the presence of 0.05% methylcellulose. The choice of the appropriate electrophoretic conditions was performed after a deep analysis of the most important parameters affecting analyte separation. In particular, the effect of both run buffer concentration and pH on resolution, efficiency, migration times, and peak area was evaluated. The selected electrophoretic conditions allowed us to separate the CS isomers-derived Delta-disaccharides in less than 12 min, also resolving the nonsulfated disaccharides released from CS isomers from those released from hyaluronan (HA). Moreover, these conditions gave a good reproducibility of both the migration times (CV%, 0.25) and the peak areas (CV%, 1.4). Intra- and interassay CV were 5.37 and 7.23%, respectively, and analytical recovery was about 86%. The applicability of the above method to the quantitative and structural disaccharide analyses of plasma CS isomers was investigated. Data obtained from 44 healthy human subjects were compared with those obtained by a fluorophore-assisted carbohydrate electrophoresis (FACE) reference assay, by using the Passing and Bablok regression and Bland-Altman tests. The developed method could represent a good tool for an ultrasensitive analysis of CS isomers in biological samples from different sources, particularly when samples are available in very low amounts.     

The solubilities of benzene polycarboxylic acids in water

The solubilities in water of all benzene polycarboxylic acids are discussed, using data determined in this work (benzoic, terephthalic, trimellitic, trimesic, and pyromellitic acids) and available from the literature (benzoic, phthalic, isophthalic, terephthalic, hemimellitic, trimelitic, trimesic, mellophanic, prehnitic, pyromellitic, benzene-pentacarboxylic and mellitic acids). The apparent molar enthalpies of solution at the saturation point for these benzene polycarboxylic acids were determined from the temperature dependence of the solubilities.     

Simultaneous Determination of Inorganic Anions and Organic Acids in Environmental Samples by Capillary Zone Electrophoresis with Indirect UV Detection

Capillary zone electrophoresis (CZE) with indirect UV detection was developed for the simultaneous determination of inorganic anions and organic acids in environmental samples. Various aromatic acids (benzoic, phthalic, trimellitic, and pyromellitic acids) were evaluated as background electrolytes (BGEs) to give high resolution and detection sensitivity. Co-electroosmotic conditions such as the concentration of BGE, electrolyte pH, and EOF modifier were systematically investigated. Three inorganic anions and ten organic acids were determined simultaneously in 10 min using an electrolyte containing 10 mM phthalic acid, 0.5 mM myristyltrimethylammonium bromide (MTAB), and 5% methanol (MeOH) (v/v) at pH 5.60. Linear plots for the test solutes were obtained in the concentration range 0.01–1.0 mM with detection limits in the range 5–30 μM. The proposed method was successfully demonstrated for the determination of inorganic anions and organic acids in natural water, soil, and plant extracts after direct sample injection.     

Cotton-Mouton constants for benzoic and phthalic acids

The Cotton-Mouton effect was used to investigate benzoic, phthalic, isophthalic, and terephthalic acids. The additive tensor characteristics of the magnetic susceptibility ellipsoid were obtained for the C_ar-COOH fragment. Magnetic and electric double refraction, dipole moment, and quantum chemistry methods were used to study the spatial structure of phthalic acid in solution.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1568–1571, September, 1993.     

Electrochemical derivatization‐capillary electrophoresis‐contactless conductivity detection: A versatile strategy for simultaneous determination of cationic,anionic, and neutral analytes

The simultaneous determination of cationic, anionic, and neutral analytes in a real sample was demonstrated by coupling electrochemical (EC) derivatization with counter‐EOF CE‐C⁴D. An EC flow cell was used to oxidize alcohols from an antiseptic mouthwash sample into carboxylic acids at a platinum electrode in acid medium. The carboxylates formed in the derivatization process and other sample ingredients, such as benzoate, saccharinate, and sodium ions, were separated in counter‐flow mode and detected in one run in Tris‐HCl buffer, pH 8.6. Fewer than 5 min were needed to complete each analysis with the automated flow system comprising solenoid pumps for the management of solutions. Insights into the electrochemistry of benzoic acid, present in the sample matrix, were also gained by EC‐CE‐C⁴D; more specifically, by applying potentials higher than 1.47 V to the platinum electrode, some formiate and minute amounts of salicylate were detected.     

Development of a capillary electrophoretic method for the separation of diastereoisomers of a new human immunodeficiency virus protease inhibitor

A capillary electrophoretic (CE) method was developed for the separation of diastereoisomers of a new human immunodeficiency virus (HIV) protease inhibitor TMC114. In total 16 isomers of this drug have been synthesized (eight pairs of enantiomers). We succeeded in the separation of the eight diastereoisomers, but no enantiomers could be separated. Because of the high similarity and water-insolubility of these isomers, the separation is a real challenge. Different CE modes were tried out: capillary zone electrophoresis (CZE), nonaqueous capillary electrophoresis (NACE), micellar electrokinetic capillary chromatography (MEKC), and microemulsion electrokinetic capillary chromatography (MEEKC). Only MEEKC offered resolution of these compounds.     

Fast analysis by gas-liquid chromatography. Perspective on the resolution of complex fatty acid compositions

Separation of fatty acids as methyl ester (FAME) derivatives has been carried out using short and highly polar capillary column developed for fast gas-liquid chromatography (GLC) applications. The GLC parameters have been optimized in order to achieve separation of FAME ranging from 4:0 (butyric acid) to 24:1 in less than 5 min. Milk fat that has by far the most complex fatty acid composition among edible fats and oils has been used to optimize the method. The volume of the oven has been reduced in order to allow for a heating rate of 120 degrees C/min and to rapidly cool-down to the initial temperature (50 degrees C) of the GLC program. The GLC conditions developed are not suitable to achieve separation of positional and geometrical isomers of octadecenoic acid but are useful to perform separation of major fatty acids in milk fat. The conditions developed could be used to analyze edible fats and oils or biological samples such as plasma or red blood cell lipids. The results confirmed that short and highly polar fast columns operating under optimal conditions could be used to separate the fatty acids in various matrices.     

Application of a novel micro-injector in the determination of indole derivatives in the rat pineal gland by capillary electrophoresis with electrochemical detection

A novel micro-injector has been fabricated for capillary electrophoresis (CE). It was successfully used for the determination of some indole derivatives for example melatonin (MT), serotonin (5-HT), tryptophan (Trp), and 5-hydroxy-tryptophane (5-HTrp) in the rat pineal gland by capillary electrophoresis with electrochemical detection (CE–EC). CE was performed in 0.20 mol L^–1 phosphate buffer (pH 8.0). The compounds investigated can be well separated and detected within 15 min. The working electrode used was a 300-μm diameter carbon electrode positioned opposite the outlet of the capillary. The relationship between peak current and analyte concentration was highly linear in the range from 0.10 to 500 μmol L^–1; detection limits (S/N = 3) were 0.03–0.13 μmol L^–1. The proposed method has been successfully used to analyze real biological samples.     

Supramolecular liquid crystals formed by hydrogen bonding between a benzocrown-bearing stilbazole and carboxylic acids

The mesomorphism of hydrogen bonded complexes formed between 4'-carboxybenzo-15-crown-5 stilbazolyl ester (CBCSE) as proton acceptor and carboxylic acids as proton donors is discussed. CBCSE is a monotropic mesogen, forming a nematic phase upon quench cooling. A total of 32 hydrogen bonded complexes has been studied. Hydrogen bonding with carboxylic acids stabilizes the nematic phase, and/or induces a smectic A (SmA) phase. CBCSE forms 1:1 complexes (molar ratio) with alkanoic acids (fatty acids) and 2:1 complexes with alkanedioic acids. None of these proton donors is a mesogen itself, but the hydrogen bonded complexes are. The influence of the chain or spacer length on the transition temperatures is discussed. Besides the homologous series of the alkanoic and alkanedioic acids, the following carboxylic acids were used in this study: diglycolic acid, pyridine-2,6-dicarboxylic acid, 4-dodecyloxybenzoic acid, 3,4-bis(dodecyloxy)benzoic acid, 2,3,4-tris(dodecyloxy)benzoic acid and 3,4,5-tris(dodecyloxy)benzoic acid, phthalic acid, isophthalic acid and terephthalic acid.