High-purity Acid Research Articles

Facile and Stereoselective Synthesis of (Z)‐15‐Octadecenoic Acid and (Z)‐16‐Nonadecenoic Acid: Monounsaturated Omega‐3 Fatty Acids

Facile syntheses of the monounsaturated omega-3 fatty acids, (Z)-15-octadecenoic acid and (Z)-16-nonadecenoic acid, are presented. Commercially available hydroxy fatty acids were esterified and oxidised, followed by the Wittig reaction to introduce the omega-3 olefinic bond; hydrolysis yielded the omega-3 fatty acids in high purity. An examination of different reaction conditions for the Wittig step found that THF as solvent and coupling temperatures of -78 degrees C gave optimal stereoselectivity, affording the omega-3 olefins in Z:E ratios >or= 97:3. The syntheses have overall yields of approximately 43%, and utilise straightforward, robust chemistry, that may be readily scaled up and reproduced. Also presented is a method for accurately determining the double bond geometry and isomeric purity of the fatty acid products using 1H-13C-HSQC NMR and GC-MS, respectively.

Global amine and acid functional group modification of proteins.

A sequential reaction methodology is employed for the complete derivatization of protein thiols, amines, and acids in high purity under denaturing conditions. Following standard thiol alkylation, protein amines are modified via reductive methylation with formaldehyde and pyridine-borane. Protein acids are subsequently amidated under buffered conditions in DMSO using the coupling reagent (7-azabenzotriazol-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate. The generality of the approach is demonstrated with four proteins and with several amines yielding near-quantitative transformations as characterized by high-resolution Fourier transform mass spectrometry. The developed approach has numerous implications for protein characterization and general protein chemistry. Applications in mass spectrometry (MS) based proteomics of intact proteins (top-down MS) are explored, including the addition of stable isotopes for relative quantitation and protein identification through functional group counting. The methodology can be used for altering the physical and chemical properties of proteins, as demonstrated with amidation to modify protein isoelectric point and through derivatization with quaternary amines. Additionally, the chemistry has applications in the semisynthesis of monodisperse polymers based on protein scaffolds. We prepare proteins modified with azides and alkynes to enable further functionalization via copper(I)-catalyzed 1,3-dipolar Huisgen cycloaddition ("click") chemistry.

Modulation of Immobilized Lipase Enantioselectivity via Chemical Amination

AbstractThe aspartic and glutamic carboxylic groups of the surface of three different immobilized lipases (those from Candida antarctica (form B) (CAL‐B), Thermomyces lanuginose (TLL) and Pseudomonas fluorescens (PFL) have been modified with ethylenediamine (after activation of the carboxylic function with carbodiimide). The exchange of groups with a negative charge for positively charged groups permitted us to greatly alter the activity, specificity and stereoselectivity of the lipase. Thus, in some cases, the activity of the lipases increased after the chemical modification while in other cases the activity was strongly reduced. Moreover, the effect of the experimental conditions on the activity was also strongly altered. Remarkably, the enantioselectivity of the enzymes in the hydrolysis of different mandelic acid derivatives was strongly modulated. For example, amination of the CNBr‐CAL‐B preparation greatly increased the enantioselectivity of the enzyme in the hydrolysis of (±)‐2‐hydroxyphenylacetic acid methyl ester, from an E value of 2 without modification up to E>100, affording (R)‐mandelic acid in high purity (ee>99 % at 50 % conversion) at pH 7 and 4 °C. Thus, the chemical modification of lipases seems to be a very powerful tool to improve their performance as enantioselective biocatalysts.

Production of Aldonic Acids from Monosaccharides by Washed Cells of Burkholderia cepacia and their Calcium Binding Capability

Microbial oxidation of monosaccharides and calcium binding capability of the resulting aldonic acids were investigated. When washed cells of a strain of Burkholderia cepacia were shaken with 15% (w/v) D-galactose, D-mannose, D-xylose and L-arabinose in the presence of CaCO3, corresponding aldonates were produced with yields of 99.4, 93.6, 94.5 and 93.0%, respectively, after 2 d for D-galactose and 8 d for the others. Free aldonic acids of high purity were obtained from the reaction supernatants by the treatment with activated carbon followed by cation exchange resin. The aldonic acids showed lower sequestering capacities compared with EDTA and citrate, suggesting weak binding with a calcium ion. Such weak calcium binding and high aqueous solubility of the aldonates suggested their possible application not to builders of detergents, but to functional saccharides that promote intestinal absorption of minerals.

Aplicação de cromatografia centrífuga de contra-corrente na purificação de ácido ursólico das folhas de Eugenia brasiliensis Lam.

Os ácidos triterpênicos são metabólitos comuns na família Myrtaceae, especialmente no gênero Eugenia. O ácido ursólico foi descrito como um dos principais constituintes, nas folhas de Eugenia brasiliensis, coletada no Sudoeste do Brasil. Uma partição prévia, por solventes, do extrato etanólico ou do extrato clorofórmico de E. brasiliensis, seguida por uma purificação por cromatografia de contra-corrente de alta velocidade (CCCAV), conduziu ao isolamento do ácido ursólico com alto grau de pureza (> 97%). Esta substância, também foi isolada por cromatografia convencional de coluna aberta (rendimento de 0.22% a partir do extrato etanólico), e caracterizada por 13C-RMN, GC-EM e co-injeção com padrão comercial em CG-DIC, na forma do éster metílico. A técnica de CCCAV, usualmente usada para triterpenos glicosilados, foi aqui aplicada para a aglicona. As fases móvel e estacionária, no experimento de CCCAV, foram geradas pela mistura de n-hexano : acetato de etila : metanol : água, na proporção 10:5:2,5:1. A seleção do sistema de solventes (fases estacionária e móvel) foi determinada pela máxima distribuição eqüitativa do ácido ursólico em ambas as fases, medida por densitometria e monitorada por cromatografia em camada delgada, CCD, usando-se ácido ursólico comercial como referência.

N‐Linked Hydroxylamine Resin: Solid‐Phase Synthesis of Hydroxamic Acids

A novel hydroxylamine resin for solid‐phase synthesis of hydroxamic acids is described. Its facile application is illustrated by the solid‐phase synthesis of various hydroxamic acids. Cleavage is induced under acidic conditions by treatment with trifluoroacetic acid, providing hydroxamic acids in high purity and good yields.

Graphical Abstracts

Synth. Commun. 2005, 35, 2945 N-LINKED HYDROXYLAMINE RESIN: SOLID-PHASE SYNTHESIS OF HYDROXAMIC ACIDS Zheng Yin, KaySiang Low, and PekLing Lye S*BIO Pte Ltd., Singapore A novel hydroxylamine resin for solid-phase synthesis of hydroxamic acids is described. Its facile application is illustrated by the solid-phase synthesis of various hydroxamic acids. Cleavage is induced under acidic conditions by treatment with trifluoroacetic acid, providing hydroxamic acids in high purity and good yields.

Purication of betulinic acid from Eugenia florida (Myrtaceae) by high‐speed counter‐current chromatography

A high yield of betulinic acid (up to 17% from the ethanolic extract) was found in the leaves of Eugenia florida collected in south-eastern Brazil, making this species a potential commercial source of the title compound. Extracts of E. florida were subjected to solvent partition, and rapid high-speed counter-current chromatography (HSCCC) was applied to the semi-crude extracts to afford betulinic acid in high purity. The mobile and stationary phases were derived from the two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (10:5:2.5:1). The developing solvent system (stationary and mobile phases) for optimum HSCCC separation was chosen by dissolving the fraction to be chromatographed in the proposed solvent mixture and determining the amount of betulinic acid in each phase by densitometric TLC. Purified betulinic acid was characterized by 13C-NMR, GC-MS and co-injection of its methyl ester with standards in GC-FID. The HSCCC technique is commonly employed to isolate triterpene glycosides, but is applied in this study to an aglycone.

Trace Element Content of Senna Study Material and Selected Senna-Based Dietary Supplements as Determined by Inductively Coupled Plasma-Optical Emission Spectrometry and Inductively Coupled Plasma-Mass Spectrometry

The efficacy of senna laxative products and the worldwide trend towards self-medication with dietary supplements of a natural origin have fueled several investigations into the potential health effects associated with their use. The goal of this work was to determine the trace element content [aluminum (Al), arsenic (As), barium (Ba), calcium (Ca), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), magnesium (Mg), manganese (Mn), sodium (Na), lead (Pb), strontium (Sr), vanadium (V), and zinc (Zn)] of a bulk senna sample that was procured for use as a study material in one such investigation. In addition, seven commercially available senna-based dietary supplements were purchased and analyzed along with the study material. Samples were digested using high-purity acids and oxidants and were analyzed by inductively coupled plasma-optical emission spectrometry (ICP-OES) and inductively coupled plasma-mass spectrometry (ICP-MS). Differences between the trace element content of the analyzed products were observed. Lead was detected in three of the tested samples (ranging from 0.686 to 1.12 μg g−1), and arsenic was detected in seven samples (ranging from 0.063 to 0.280 μg g−1). Recovery data for fortified control samples and standard reference materials (NIST 1573a Tomato Leaves, NIST 1547 Peach Leaves) indicated accurate and precise method performance.

In situ matrix evaporation by isothermal distillation of high-purity reagents for the determination of trace impurities by ion chromatography

In situ matrix evaporation of high-purity acids based on isothermal distillation was achieved in a high-density polyethylene (HDPE) container on a water bath, to avoid contamination from the laboratory environment. The solubility of water and acid vapours in glycerol due to co-association was utilized to achieve complete evaporation. All major sources which contribute to the process blank were taken care of in a simple and effective way. A 50-fold preconcentration with >99.9% matrix removal was achieved for the analysis of low-boiling acids, HCl, HF, HNO3 and H2O2. The non-volatile ions NH4+, Li+, Na+, K+, Mg2+, Ca2+, SO4(2-) and PO4(3-) were determined by ion chromatograph with conductivity detection. The detection limits were 6-130 ng/l with recoveries of 85-110% for all ions studied.

In situ matrix evaporation by isothermal distillation of high-purity reagents for the determination of trace impurities by ion chromatography

In situ matrix evaporation of high-purity acids based on isothermal distillation was achieved in a high-density polyethylene (HDPE) container on a water bath, to avoid contamination from the laboratory environment. The solubility of water and acid vapours in glycerol due to co-association was utilized to achieve complete evaporation. All major sources which contribute to the process blank were taken care of in a simple and effective way. A 50-fold preconcentration with >99.9% matrix removal was achieved for the analysis of low-boiling acids, HCl, HF, HNO 3 and H 2O 2. The non-volatile ions NH 4 +, Li +, Na +, K +, Mg 2+, Ca 2+, SO 4 2− and PO 4 3− were determined by ion chromatograph with conductivity detection. The detection limits were 6–130 ng/l with recoveries of 85–110% for all ions studied.

Determination of low-abundance elements at ultra-trace levels in urine and serum by inductively coupled plasma-sector field mass spectrometry.

A procedure is described for the determination of Y, Zr, Nb, Ru, Rh, Pd, Ag, Sb, Te, Hf, Ta, W, Re, Os, Ir, Pt, Au, Tl, Bi, and U in human urine and serum at concentrations relevant to the occupationally unexposed population. Sample preparation was limited to tenfold dilution with 2% HCl. A combination of a sample-introduction system designed to provide enhanced sensitivity and the use of water and acids of high-purity has resulted in limits of quantification (LOQ) in the sub-nanogram per liter range for 13 analytes. Instrumental background caused by release of analytes (Y, Zr, Ag, Sb, Au, Tl, Bi, U) from different parts of the sample-introduction system was found to be the major limitation in obtaining even better LOQ. Nevertheless, detection capabilities of the proposed procedure were adequate for all elements except Ru, Pd, and Rh. Despite of the use of high-resolution mode for these analytes some unresolved spectral interferences might still be present. For 13 elements an external accuracy assessment was accomplished by participation in proficiency testing and inter-comparison programs. Results obtained for pooled urine and serum were compared with concentrations reported for occupationally unexposed populations in recent publications.

Evaluating specific adhesion of Plasmodiumfalciparum-infected erythrocytes to immobilised hyaluronic acid with comparison to binding of mammalian cells

A feature of infection with Plasmodium falciparum is the ability of parasite-infected erythrocytes to adhere to vascular endothelial cells and accumulate in vital organs, associated with severe clinical disease. Hyaluronic acid was recently identified as a receptor for adhesion and has been implicated in mediating the accumulation of parasites in the placenta. Here, we report in vitro assays to measure specific adhesion of infected erythrocytes to hyaluronic acid that is distinct from binding to chondroitin sulphate A, another glycosaminoglycan implicated as a receptor in placental malaria. In this study, specific adhesion of mature stage infected erythrocytes to hyaluronic acid of high purity immobilised on plastic surfaces was abolished by pre-treating hyaluronic acid with a specific hyaluronate lyase from Streptomyces, whereas the same treatment of chondroitin sulphate A had little effect. Adhesion to hyaluronic acid could not be explained by the presence of chondroitin sulphate A or other glycosaminoglycans in the hyaluronic acid preparations. Chinese hamster ovary cells bound in a similar manner in the assays and confirmed that hyaluronic acid was appropriately immobilised for cell adhesion. In contrast to parasites, these cells did not adhere to chondroitin sulphate A. The adsorption of hyaluronic acid onto plastic surfaces was also confirmed by the use of a specific hyaluronic acid-binding protein. Fixing cells with glutaraldehyde at the completion of adhesion assays reduced the number of parasites remaining adherent to hyaluronic acid, but not to chondroitin sulphate A or CD36. These findings have important implications for understanding and evaluating interactions between P. falciparum and hyaluronic acid that may be involved in disease pathogenesis.

Salt splitting in a three-compartment membrane electrolysis cell

A three-compartment membrane cell was used to investigate the electrohydrolysis of sodium sulphate for the regeneration of acid and base. The membranes used were Pall R1010 cation exchange and Pall R1030 anion exchange. The effect of flow rate, current density and initial salt concentration on the performance of the cell (current efficiencies, transport properties and product concentrations) are reported. The performance of this configuration is compared to a two-compartment cell in terms of current efficiencies, power consumption and product concentrations. The three-compartment configuration has the advantage of producing high purity acid and base, but at a greater operating cost.

Metabolism of 18:4n-3 (stearidonic acid) and 20:4n-3 in salmonid cells in culture and inhibition of the production of prostaglandin F2α(PGF2α) from 20:4n-6 (arachidonic acid)

Arachidonic acid (AA; 20:4n-6) is the precursor of a range of highly biologically active derivatives, collectively termed eicosanoids, including prostaglandins, thromboxanes, leukotrienes and lipoxins, that act as autocrine hormones regulating many physiological processes including haemostasis, reproduction, immune and inflammatory responses. Eicosapentaenoic (EPA; 20:5n-3) and dihomo-γ-linolenic (20:3n-6) acids modulate eicosanoid metabolism by both inhibiting the conversion of AA to eicosanoids whilst simultaneously being converted to eicosanoids with different, often attenuated, properties compared to their AA homologues. Eicosatetraenoic acid (20:4n-3) is a naturally occurring C20 polyunsaturated fatty acid (PUFA), present in fish oil at levels of around 1–2%, that has been suggested to be the active metabolite responsible for the anti-inflammatory effects of plant oils containing stearidonic acid (18:4n-3). However, the biochemical properties of 20:4n-3 in terms of cellular biology have rarely been investigated, partly due to difficulties in obtaining the fatty acid in high purity. In this paper, we describe methods for the medium scale laboratory preparation of high purity 20:4n-3, and investigate its metabolism in fish cell culture systems which normally contain significant amounts of n-3 PUFA. Thus the incorporation and metabolism of 18:4n-3 and 20:4n-3, and their distribution in phospholipid classes was studied in an established cell line from Atlantic salmon (Salmo salar) (AS), and the effects of 20:4n-3 on eicosanoid production studied in freshly isolated macrophages from rainbow trout (Oncorhynchus mykiss). Both 18:4n-3 and 20:4n-3 were preferentially esterified into phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine in contrast with the accumulation of AA in phosphatidylinositol. Incorporated 18:4n-3 was readily converted to 20:4n-3, and both fatty acids were further desaturated and elongated to EPA and 22:5n-3 but not 22:6n-3. Supplementation with 20:4n-3 decreased the conversion of AA into prostaglandins, as demonstrated by the decreased levels of PGF2α produced in trout macrophages supplemented with 20:4n-3 and AA compared to cells supplemented with AA alone. In addition, 20:4n-3 was converted into eicosanoids in fish cells as indicated by the presence of Δ17,18 12-HETE, Δ17,18 PGE1 and Δ17,18 PGF1α in extracts from rainbow trout macrophages incubated with 20:4n-3.

Determination of polonium-210 in phosphoric acid

Polonium-210 in phosphoric acid has been recognized as a significant source of alpha contamination of processed Si-wafers for memory devices of computer. In the present work, a convenient method was developed for the determination of trace210Po in phosphoric acid of high purity. For the determination,209Po was used as a yield tracer. The present method consists of (1) addition of the tracer to 5 ml aliquot of phosphoric acid sample, (2) pH adjustment (to 2) of the sample solution to make up electrolytic solution, (3) electrodeposition for the simultaneous achievement of Po separation and preparation of counting source on stainless-steel disc, and (4) alpha-ray spectrometry. By the developed method, more than 95% of Po was separated from phosphoric acid sample onto counting disc. The minimum detectable radioactivity of210Po in 5 ml of phosphoric acid was about 0.03 mBq by counting the electrodeposited alpha-activity for 10 days under a counting efficiency of ≈30%.

A novel linkage for the solid-phase synthesis of hydroxamic acids

A novel linkage for the solid-phase synthesis of hydroxamic acids is described and its facile application for the solid phase synthesis of peptidyl, succinyl and urea-type hydroxamic acids is illustrated. Cleavage is induced under mild acidic conditions by treatment with formic acid in THF, providing hydroxamic acids in high purity and fair to good yields.

Fundamental Properties of Aqueous Solutions of Nonionic Surfactants Prepared from Oleic Acid of High Purity

Fundamental properties such as micellar weight, critical micelle concentration and cloud point were determined for aqueous solutions of polyoxyethylene (20) sorbitan monooleate (POESO) and polyoxyethylene (n) oleyl ether [POEOE and POE (10) 0E for n=20 and 10, respectively] recently prepared from oleic acid of high (>99%) and low purity. HPLC analysis and measurement of hydroxy value were conducted to clarify the distribution of the oxyethylene chain. For POESO and POEOE, no significant correlation between the above properties and oleic acid purity could be found. For POE (10) OE, however, the cloud point was higher for greater purity. This was confirmed by the temperature dependence of light scattering intensity.

A TFA-cleavable linkage for solid-phase synthesis of hydroxamic acids

A novel linkage for the solid-phase synthesis of hydroxamic acids is described. The linkage is stable to all reagents commonly used in Fmoc peptide synthsis. Cleavage is induced by treatment with trifluoroacetic acid, providing hydroxamic acids in high purity and good yields.

Microwave-assisted Acid Dissolution of Sintered Advanced Ceramics for Inductively Coupled Plasma Atomic Emission Spectrometry

The microwave-assisted acid dissolution of sintered bodies of 28 structural and electronic advanced ceramic materials was systematically evaluated. These materials included zirconia-based ceramics, such as m-ZrO2 (a non-stabilized monoclinic zirconia), Ca-PSZ and Mg-PSZ (two partially stabilized zirconias), Y-FSZ (a fully stabilized zirconia) and Ce-TZP, Yb-TZP and Y-TZP/Ce (three tetragonal polycrystalline zirconias); alumina-based ceramics, such as Al2O3, mullite and spinel; ceria-based ceramics, such as CeO2–Gd2O3 (cubic ceria gadolinia); titania-based ceramics, such as TiO2; titanate-based ceramics, such as Al2TiO5, BaTiO3 and BIT (bismuth titanate); lead titanate-based ceramics, such as Ca-PT, La-PT, Nd-PT, Sm-PT and Gd-PT; lead zirconate titanate-based ceramics, such as PZT and PLZT; niobate-based ceramics, such as PMN (lead magnesium niobate); non-oxide-based ceramics, such as AlN, BN, Si3N4 and SiC; and oxide and non-oxide-based ceramics, such as β′-sialon (silicon aluminium oxynitride). Fifteen acids or mixtures of acids were tried, including HCl, HNO3, H2SO4, aqua regia, H2SO4–(NH4)2SO4 and mixtures of these acids with HF and with H2O2. A commercially available laboratory medium pressure microwave oven was used. Eleven optimized microwave methods were developed. These methods are simple (three stages maximum), fast (15–35 min digestion time) and mild (20–60% of the microwave oven power). By applying these microwave methods, it was possible to dissolve completely all the sintered advanced ceramics, except SiC and β′-sialon. These two non-oxide ceramics were the only samples that could not be dissolved by any of the acids or mixtures of acids tested. The microwave-assisted acid dissolution was compared for ICP-AES with conventional dissolution procedures, i.e., alkali fusion in a platinum crucible and in a graphite crucible and acid decomposition by conductive heating at elevated pressure (in a PTFE bomb). It was demonstrated that microwave-assisted dissolution presents many advantages over the other procedures. When compared with acid decomposition by conductive heating in a PTFE bomb, one of the most important advantages is the drastic shortening of the digestion time from hours to minutes. When compared with alkali fusions, one of the most important advantages is the use of smaller amounts of high-purity acids, which contain less impurities than the fluxes; because of this, matrix effects and contamination from the attack reagents are lower, and consequently there is an improvement in the analytical figures of merit of ICP-AES.