Isotachophoretic separation of alkylsulfonates and determination of methanesulfonic acid as main component and as trace component in pharmaceutical drug substances

Alkylsulfonates from methanesulfonic acid to decanesulfonic acid were separated by isotachophoresis with conductivity detection in a common electrolyte system at pH 4.8. The electrolyte system consisted of 10 mM HCl buffered with epsilon-aminocaproic acid (pH 4.8) and 0.1% methylhydroxyethylcellulose (MHEC) acting as the leading electrolyte. The terminating electrolyte was 20 mM caproic acid also containing 0.05% MHEC. Current settings of 250 microA for the first and 50 microA for the second capillary were applied. On one hand, the method was applied to the determination of the content of methanesulfonate as the salt forming agent (mesilate) in a recently registered drug substance. The results obtained by ITP were compared with an orthogonal titration method. On the other hand, due to the column-coupling configuration of the electrophoretic instrument, the method could be extended to the trace determination in the ppm range in order to monitor methanesulfonic acid as an impurity in a drug substance. The validation confirmed the linearity of the method between 1 and 10 mg/l, limits of detection and quantification below 1 mg/l, recovery rates from 92.4 to 95.4%, and repeatability with a R.S.D. of 3.8% (six runs with a 4 mg/l spiked sample). Finally, three batches of a newly produced drug substance could be checked for methanesulfonic acid giving results of below 0.0014% (concentration related to the drug substance).     

Direct enantiomeric TLC resolution of dl-penicillamine using (R)-mandelic acid and l-tartaric acid as chiral impregnating reagents and as chiral mobile phase additive

DL-Penicillamine has been resolved into its enantiomers by normal-phase TLC using L-tartaric acid as chiral impregnating reagent as well as chiral mobile phase additive, while (R)-mandelic acid has been found to be successful as a chiral impregnating reagent. The solvent system acetonitrile-methanol-water (5:1:1, v/v) was found to be successful when L-tartaric acid was used as impregnating agent while the solvent combination acetonitrile-methanol-(0.5% l-tartaric acid in water, pH 5)-glacial acetic acid (7:1:1.1:0.7, v/v) was successful as mobile phase as it contained L-tartaric acid as the chiral additive. (R)-mandelic acid was successful as chiral impregnating reagent with ethyl acetate-methanol-water (3:1:1, v/v), as the mobile phase. The effects of concentration of chiral selectors, temperature and pH were examined on enantiomeric resolution. The spots were detected with iodine vapors and the detection limits were found to be 0.12 microg for each enantiomer of penicillamine with L-tartaric acid, under both the conditions, and 0.11 microg with (R)-mandelic acid.     

A dual role of phenylboronic acid as a receptor for carbohydrates as well as a quencher for neighboring pyrene fluorophore

A simple amino acid based compound (1) containing a phenyl boronic group and pyrene fluorophore showed an enhanced fluorescence in aqueous solutions at physiological pH through suppression of the photoinduced electron transfer from pyrene to boronic acid on carbohydrate binding. The compound exhibited an interesting fluorescence change depending on pH with decreased emission intensity at acidic pH but enhanced emission intensity at basic pH unlike the fluorescent carbohydrate chemosensors using a PET process with amine and aryl-boronic acid. We have characterized a dual role of phenylboronic acid as a receptor for carbohydrates as well as a quencher for the fluorescence of pyrene fluorophore.     

Hydrothermal CO2 Reduction by Glucose as Reducing Agent and Metals and Metal Oxides as Catalysts

High-temperature water reactions to reduce carbon dioxide were carried out by using an organic reductant and a series of metals and metal oxides as catalysts, as well as activated carbon (C). As CO₂ source, sodium bicarbonate and ammonium carbamate were used. Glucose was the reductant. Cu, Ni, Pd/C 5%, Ru/C 5%, C, Fe₂O₃ and Fe₃O₄ were the catalysts tested. The products of CO₂ reduction were formic acid and other subproducts from sugar hydrolysis such as acetic acid and lactic acid. Reactions with sodium bicarbonate reached higher yields of formic acid in comparison to ammonium carbamate reactions. Higher yields of formic acid (53% and 52%) were obtained by using C and Fe₃O₄ as catalysts and sodium bicarbonate as carbon source. Reactions with ammonium carbamate achieved a yield of formic acid up to 25% by using Fe₃O₄ as catalyst. The origin of the carbon that forms formic acid was investigated by using NaH¹³CO₃ as carbon source. Depending on the catalyst, the fraction of formic acid coming from the reduction of the isotope of sodium bicarbonate varied from 32 to 81%. This fraction decreased in the following order: Pd/C 5% > Ru/C 5% > Ni > Cu > C ≈ Fe₂O₃ > Fe₃O₄.     

碳纳米管的化学修饰以及作为润滑油添加剂的摩擦学性能研究

采用硫酸和硝酸混合酸对催化裂解法(CVD法)制备的多壁碳纳米管(MWNNTs)进行纯化,然后运用硬脂酸对碳纳米管进行表面修饰,并研究了硬脂酸修饰后的碳纳米管的表面状况以及作为润滑油添加剂的摩擦学行为．实验结果表明,在硫酸催化剂作用下,通过酯化反应碳纳米管能够被硬脂酸包覆,并且硬脂酸修饰的碳纳米管作为润滑油添加剂能够显著提高基础油的减摩抗磨性能,当添加量为0．15％左右时,润滑油的减摩抗磨性能最佳,与基础油相比可以使摩擦系数下降10％左右,磨损量下降30％～60％．     

锆-铝复合氧化物的制备及酸腐蚀对其表面性质的影响

利用溶胶－凝胶技术制备了ZrO2-Al2O3复合氧化物,考察了不同的投料比时复合氧化物的物理化学性质,比较了不同浓度酸腐蚀前后氧化物微球的比表面积、孔径、表面酸碱性及复合氧化物中氧化锆、氧化铝摩尔比等物理化学参数的变化。     

The Development of Boronic Acids as Sensors and Separation Tools

Synthetic receptors for diols that incorporate boronic acid motifs have been developed as new sensors and separation tools. Utilizing the reversible interactions of diols with boronic acids to form boronic esters under new binding regimes has provided new hydrogel constructs that have found use as dye‐displacement sensors and electrophoretic separation tools; similarly, molecular boronic‐acid‐containing chemosensors were constructed that offer applications in the sensing of diols. This review provides a somewhat‐personal perspective of developments in boronic‐acid‐mediated sensing and separation, placed in the context of the seminal works of others in the area, as well as offering a concise summary of the contributions of the co‐authors in the area. DOI 10.1002/tcr.201200006     

Determination of tin as stannite-kesterite and cassiterite in ores

Tin is stannite-kesterite and as cassiterite in a tin-bearing ore can be determined by the selective decomposition of the stannite-kesterite phase with a mixture of sodium nitrate and acetic acid.     

Phenylboronic acid and dopamine as probe set for electrochemical detection of saccharides

A novel electrochemical approach for detection of saccharides via indicator displacement assay was presented. In this system, 2-fluorophenylboronic acid and dopamine (DA) were performed as probe set. The electrochemical properties of DA and the binding to 2-fluorophenylboronic acid in phosphate buffer at different pH values were investigated by cyclic voltammetry. After addition of fructose to the solution, a competition for the binding 2-fluorophenylboronic acid occurred that led to the release of the DA. The regenerate oxidation current of DA increased with increasing fructose concentration. Under optimized experimental conditions, the peak current was linearly related to fructose concentration in the range of 0.3-5.0 mmol/L with a detection limit of 0.1 mmol/L. In addition, the interaction between 2-fluorophenylboronic acid and other cis-diol compounds such as glucose, galactose and mannose was investigated.     

Organocatalyst-mediated enantioselective intramolecular aldol reaction featuring the rare combination of aldehyde as nucleophile and ketone as electrophile

The trifluoroacetic acid salt of 2-(pyrrolidinylmethyl)pyrrolidine was found to be an effective organocatalyst of an asymmetric intramolecular aldol reaction, affording bicyclo[4.3.0]nonane derivatives with a high enantioselectivity, in which the rare combination of aldehyde as a nucleophile and ketone as an electrophile was realized.     

Benzohydroxamic acid as a reductometric titrant determination of manganese in ores and alloys

Benzohydroxamic acid has been employed as a reductometric titrant for the determination of manganese in various ores and alloys. The determination is based on the fact that benzohydroxamic acid reduces Mn(VII) quantitatively to Mn(II) in 1.5N sulphuric acid.     

反相高效液相色谱法测定饲料添加剂阿散酸中的阿散酸及掺假物质对氨基苯磺酸

建立了用于饲料添加剂阿散酸质量控制的反相高效液相色谱法。采用的色谱条件: Waters Bondapak C18柱(150 mm×4 mm, 5 μm)分离,以甲醇-水(用稀磷酸调节pH至2.9) (1:4, v/v)作流动相,流速1.0 mL/min,紫外检测波长为244 nm。在优化的色谱条件下,阿散酸和掺假物质对氨基苯磺酸在3 min内实现了基线分离。阿散酸和对氨基苯磺酸的线性范围均为5～200 mg/L,检出限(S/N=3)分别为0.20 mg/L和0.15 mg/L。该方法简便快速,适合饲料添加剂阿散酸的分析以及监测对氨基苯磺酸掺假。     

Efficient Synthesis of meso-Tetraarylporphyrins Using I2 as Catalyst and IBX as Oxidant

meso-Tetraarylporphyrins are synthesized from pyrrole and substituted benzaldehydes by a catalytic amount of I₂ as catalyst and o-iodoxybenzoic acid (IBX) as oxidant in two steps and one flask. The advantages of this method include the use of inexpensive and easily available catalyst, avoidance of heavy consumption of CH₂Cl₂, innocuous oxidant, and good yields.     

Determination of amine-containing phosphonic acids and amino acids as dansyl derivatives

Conditions are selected for the analytical separation of (N-phosphonomethyl glycine), products of its microbiological conversion, glutamic acid, and alanine as dansyl derivatives using reversed-phase HPLC: column (250 × 4.6 mm) ReproSil-PAH EPA; mobile phase, methanol + 20 mM CH₃COONa (pH 5.1) (20: 80); rate of mobile phase, 1 mL/min; working detector wavelength, 330 nm. The duration of separation is 35 min. The lower limits of the analytical range (in ng) for dansyl derivatives are as follows: glyphosate, 8.2; aminomethyl phosphonic acid, 24.2; glutamic acid, 9.4; alanine, 12.6: glycine, 17.7; and sarcosine, 19.3. The TLC study of dansyl derivatives of amino acids was performed on sorbfil plates PTSH-P-V using two-dimensional chromatography in the systems ethyl acetate-isopropanol-24% aqueous ammonia (45: 35: 20) in the first direction and chloroform-methanol-acetic acid (25: 5: 1) in the second one. For determining phosphonic acids (glyphosate and aminomethyl phosphonic acid), a version of one-dimensional chromatography with the sequential use of two systems, chloroform-methanol-acetic acid (25: 5: 0.2) and ethanol-24% aqueous ammonia (7: 3), was proposed.     

光替代谷氨酸氧化酶及荧光法测定谷氨酸

在弱碱性介质中,紫外光的照射引起谷氨酸的光化学反应,产生Ｈ２Ｏ２和ＮＨ３,与谷氨酸氧化酶存在下的酶促反应等效。利用氯化血红素（ｈｅｍｉｎ）作为过氧化酶的替代物,催化Ｈ２Ｏ２与对羟基苯乙酸（ＨＰＡ）的偶合荧光反应,建立了间接荧光法测定谷氨酸的方法。     

An evaluation of some simple sulfonic acids as nonaqueous titrants

The simple aliphatic and aromatic sulfonic acids show evidence of possibilities as new titrants in a glacial acetic acid medium. Excellent precision is obtained in potentiometric titrations with both ethane- and methane sulfonic acids with a standard deviation of 0.2%. Benzenemonosulfonic and naphthalenesulfonic acids both give an average precision of 0.4%. In visual titrations with with crystal violet indicator, the color changes at the end-point are very sharp. The chief advantage of these acids as titrants lies in the fact that they dissolve readily in glacial acetic acid and can be titrated to give reproducible results with the glass-calomel electrode system. None of the sulfonic acids tested was as strong a titrant as perchloric acid, but, unlike perchloric acid, they did not form precipitates or gels in the titration with potassium acid phthalate.     

Studies of substituted dihydroxy-p-benzoquinones as precipitate-exchange reagents

Studies of the barium salts of bromanilic acid, nitranilic acid and polyporic acid show that they are not superior to barium chloranilate as reagents for determining sulfate. Improved syntheses of polyporic acid and atromentin are presented; two new syntheses of barium bromanilate, and one new synthesis of barium nitranilate and of barium polyporate are also presented. Ultraviolet absorption spectra show that polyporic acid forms a dimer in dimethylsulfoxide solution.     

Trivalent molybdenum as volumetric reducing agent

Summary The purpose of the present investigation is to introduce trivalent molybdenum as a new analytical reducing agent, in hydrochloric as well as sulphuric acid media.The solution is prepared in 9N acid by electrolytic or mercuryreduction of the hexavalent form. It is preferentially stocked and used in high acid concentrations, whereby its stability in air is optimal, falling to half its titer after nearly two months. It has been tested with success as reductant for ceric, dichromate, ferric and vanadate. It has the advantage of being used in ordinary opened burettes. Titrations were followed potentiometrically in general, and alternately visually in decinormal media, whereby molybdenum blue appears at the end-point. The percentage error in fifteen discussed experiments never surpassed ±1%. Some oxidation titrations were also undertaken using iodate and bromate, with the same degree of accuracy, provided they were conducted in 6N acid. In weaker acid concentrations, equilibria were more slowly attained, with a more or less pronounced deviation, due to some oxidisability that necessitates controlled inert atmosphere.     

Photodecomposition of several compounds commonly used as sunscreen agents

The photolysis reactions of three compounds commonly used as a sunscreen agents, Parsol 1789 (1-[4-(1,1-dimethylethyl)phenyl]-3-(4-methoxyphenyl)-1,3- propanedione), Oxybenzone ((2-hydroxy-4-methoxyphenyl)phenyl-methanone) and Padimate O (2-ethylhexyl-4-(dimethylamino)benzoate), were investigated to provide a chemical background to aid in the understanding of the photosensitization of the sunscreen agents. Photolysis was carried out in cyclohexane for 70–140 h using a mercury vapor lamp (450W) without excluding oxygen.

Irradation of Parsol 1789 in cyclohexane yielded tert-butylbenzene, p-tert-butylbenzoic acid and p-methoxybenzoic acid; products obtained from the combination of the sunscreen with the solvent included the cyclohexyl esters of p-methoxybenzoic acid, p-tert-butylbenzoic acid and methanoic acid; products obtained from the solvent included cyclohexanol, cyclohexanone and dicyclohexyl ether.

Irradiation of Oxybenzone in the cyclohexane for 100 h produced no detectable products by either gas or liquid chromatographic analysis. Oxybenzone was recovered unchanged and no products were observed from the photoinitiated reaction of oxygen with the solvent.

Irradiation of Padimate O in cyclohexane yielded the ethylhexyl esters of p-aminobenzoic acid, p-monomethylaminobenzoic acid and p-dimethylamino (o/m)-methylbenzoic acid, as well as products from the photoinitiated reaction of oxygen with the solvent.     

Conversion of Waste Tyres into Carbon Black and their Utilization as Adsorbent

Pyrolysis has the potential of transforming used tyres into useful recyclable products. Pyrolytic carbon black is one of the most important products of tyre pyrolysis. Waste tyres were pyrolysed at 450 °C in a batch reactor under atmospheric pressure. The recovered pyrolytic carbon black residues were studied to investigate their characteristics for use as a possible adsorbent. EDX elemental analysis and surface area determinations were used to investigate the distinctive features of pyrolytic carbon black. Due to various inorganic additives of the original tyre that contaminated the carbon black obtained, it was treated with acid for demineralization. The demineralized carbon black was activated at 900 °C in a furnace. It was observed that acid treatment and activation increased the surface areas and decreased the concentration of contaminants. Furthermore, adsorption characteristics of methylene blue on acid‐treated and activated carbon black (prepared via acid treatment) were compared with those of commercial activated carbon in liquid phase adsorption. It was found that adsorption capacity of methylene blue on acid‐treated activated carbon black was greater.