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At least 649 records · Page 36Linked to original sources
PubMed2001

Effect of ion-exchange site and eluent modifiers on the anion-exchange of carboxylic acids.

The chromatographic behavior of carboxylic acids has been investigated, on three different latex-based anion-exchange columns, in order to define the effect of the ion-exchange site structure on selectivity. The analytical columns produced are characterized by alkyl amines containing zero, one or two hydroxyl groups on the anion-exchange functional site. Divalent carboxylic acids, namely fumaric, maleic, trans-beta-hydromuconic, trans,trans-muconic, oxalic, malonic, succinic, glutaric, adipic, malic, tartaric and mucic acids, have been chosen as test solutes. The performance of the three stationary phases has been studied employing NaOH eluents and has been discussed with respect to the different hydrophilicity of the ion-exchange sites and analytes. Considering on previous results obtained using organic solvents (methanol and acetonitrile) with carbonate eluents on a highly hydrophilic column, the performance of the three exchangers has also been studied using acetonitrile, methanol and n-propanol. The chromatographic behavior was similar for the three columns studied, but the different organic solvents gave variations in selectivity. In order to characterize these differences, particle size measurements of the latices were performed both in pure water and in the presence of each organic solvent studied.

Anion Exchange Resins↗
PubMed1983

Gas-liquid chromatographic determination of N(O,S)-trifluoroacetyl n-propyl esters of protein and non-protein amino acids.

Chromatographic conditions for the determination of protein and non-protein amino acids as their N(O,S)-trifluoroacetyl n-propyl esters are given which allow the separation of about 30 amino acids within 19 min using nitrogen or within 17 min using helium as the carrier gas. Retention times and responses are given for 42 amino acids or related compounds. Only few of them elute together when using a 2 m x 2 mm I.D. glass column filled with 0.65% ethylene glycol adipate on Chromosorb W AW (80-100 mesh). The acylation of the n-propyl esters was investigated with respect to optimal reaction conditions and was found to be best performed at 150 degrees C for 5 min.

Acetic Anhydrides↗
PubMed1985

Affinity chromatography of Drosophila melanogaster ribosomal proteins to 5S rRNA.

The binding of Drosophila melanogaster ribosomal proteins to D. melanogaster 5S rRNA was studied using affinity chromatography of total ribosomal proteins (TP80) on 5S rRNA linked via adipic acid dihydrazide to Sepharose 4B. Ribosomal proteins which bound 5S rRNA at 0.3 M potassium chloride and were eluted at 1 M potassium chloride were identified as proteins 1, L4, 2/3, L14/L16, and S1, S2, S3, S4, S5, by two-dimensional polyacrylamide gel electrophoresis. Using poly A-Sepharose 4B columns as a model of non-specific binding, we found that a subset of TP80 proteins is also bound. This subset, while containing some of the proteins bound by 5S rRNA columns, was distinctly different from the latter subset, indicating that the binding to 5S rRNA was specific for that RNA species.

Animals↗
PubMed1980

Gas chromatography-mass spectrometry of saturated and unsaturated dicarboxylic acids in urine.

Saturated and unsaturated dicarboxylic acids in urine are analyzed within the total profile of organic acids, using the methyl ester derivatives. Twenty-three acids with two carboxyl groups were identified. The method is employed for comparative studies of the excretion of dicarboxylic acids by individuals with normal and with increased fatty acid oxidation. In the group of the unsaturated acids, the cis-trans isomers mesaconic acid and citraconic acid, the two isomers of 3-methylglutaconic acid and muconic acid are characterized by the mass spectra of their methyl esters. The saturated unbranched and even-numbered dicarboxylic acids are elevated during fasting and diabetic ketoacidosis. In the total profile of the organic acids, succinic and adipic acid are indicators for ketoacidotic states.

Diabetic Ketoacidosis↗
PubMed1990

Enzymic oxidation of monoclonal antibodies by soluble and immobilized bifunctional enzyme complexes.

Site-specific modification of monoclonal antibodies was achieved by oxidation of the carbohydrate moieties of antibodies which are located remote from the antigen binding sites. Sialic acid and galactose are terminal sugars of these carbohydrate chains. Concomitant treatment of the antibodies with neuraminidase and galactose oxidase generated aldehyde groups in the oligosaccharide moieties of immunoglobulins which reacted selectively with amino or hydrazide groups of the matrix. Subsequent immobilization of neuraminidase and galactose oxidase on Eupergit C-adipic dihydrazide proved to be an efficient and selective system for the enzymic oxidation of the monoclonal antibodies without impairing their immunological activity. Oriented immobilization of enzymically oxidized monoclonal antibodies on hydrazide or amino Eupergit C derivatives thus leads to the formation of antibody matrix conjugates which possess high antigen-binding activities.

Antibodies, Monoclonal↗
PubMed2002

Endgroup-based separation and quantitation of polyamide-6,6 by means of critical chromatography.

Polyamide-6,6 is a polycondensation product from the two monomers adipic acid and 1,6-hexamethylenediamine. Depending on the reacted amount of these monomers, different ratios of amine and carboxylic acid endgroups can be formed. Besides linear chains, cyclic polyamides will also be formed. Using critical chromatography, polyamide-6,6 can be separated independently of molar mass. Retention is based solely on endgroup functionality. It is demonstrated that high-molecular-mass polyamide-6,6 (Mw approximately 20,000-30,000) can be separated using this approach. The separation was optimized by using different parameters, such as percentage modifier, temperature and pressure. The concentration of phosphoric acid was used for selective retention of the different endgroup functionalities. Using this property, a new method called critical gradient chromatography was performed where the mobile phase changes from a weak to a strong solvent with respect to the endgroup functionality, while retaining the critical conditions of the backbone unit. Quantification using UV detection is discussed.

Caprolactam↗
PubMed2002

Application of on-line solid-phase extraction-gas chromatography-mass spectrometry to the determination of endocrine disruptors in water samples.

We have applied a method based on solid-phase extraction (SPE), on-line coupled to gas chromatography-mass spectrometry through an on-column interface, to determine a group of endocrine-disrupting compounds in water samples. We have optimised the parameters affecting the SPE process and transfer step and used the method to analyse river, coastal and tap waters. In the full-scan acquisition mode, all the compounds were determined by preconcentrating only 15 ml of water sample. Di-n-butyl phthalate, benzylbutyl phthalate, bis(2-ethylhexyl) phthalate and bis(2-ethylhexyl) adipate at concentrations between 0.02 and 0.5 microg l(-1) were determined in some real samples.

Endocrine Glands↗
PubMed2003

Analysis of low-molecular-mass organic acids using capillary zone electrophoresis-electrospray ionization mass spectrometry.

A capillary zone electrophoresis-electrospray ionization-mass spectrometry (CZE-ESI-MS) method was developed to facilitate identification and determination of eleven low-molecular-mass (LMW) organic acids (i.e. oxalic, lactic, malonic, maleic, citric, tartaric, adipic, glutaric, gluconic, isosaccharinic and succinic acid) in different sample matrices. This CZE method was adapted to suit MS conditions. Sheath liquid, sheath flow and MS parameters were optimized to achieve high mass spectrometric sensitivity. The CZE-ESI-MS procedure showed good sensitivity (limit of detection of < 0.05-0.7 mg/l for all acids), linearity (r2 = 0.9925-0.9998) and reproducibility (2.09-5.34% RSD). The applicability of the CZE-ESI-MS was demonstrated on LMW organic acids in an ale sample. In addition the (here presented) method also provided quantification of fumaric, galacturonic and 2-ketoglutaric acid with high sensitivity.

Acids↗
PubMed2003

Determination of endocrine-disrupting compounds in water samples by on-line solid-phase extraction-programmed-temperature vaporisation-gas chromatography-mass spectrometry.

We developed an automated on-line solid-phase extraction (SPE)-gas chromatography-mass spectrometry method to determine a group of endocrine disruptors in water samples. The interface device used for connecting SPE with GC was a programmed-temperature vaporiser (PTV) whose liner was packed with Tenax. We optimized the parameters that affected both SPE and PTV working in solvent vent mode. The performance of the method was tested with several environmental water samples. The limits of detection of the method were between 0.001 and 0.036 microg l(-1) under full-scan acquisition mode. We determined phthalates and adipate in all real samples at concentrations between 0.11 and 8.10 microg l(-1). Atrazine and p,p'-DDE were also found in an irrigation stream water sample at 0.16 and 0.04 microg l(-1), respectively.

Endocrine Glands↗
PubMed1999

Oriented immobilization of chymotrypsin by use of suitable antibodies coupled to a nonporous solid support.

In order to eliminate the kinetic limitation of chymotryptic hydrolysis of proteins due to diffusion, nonporous hydroxyalkyl methacrylate solid support was developed and used for oriented immobilization of chymotrypsin by means of suitable polyclonal antibodies. Nonporous microspheres were prepared by dispersion copolymerization of 2-hydroxyethyl methacrylate and ethylene dimethacrylate in an alcohol-toluene mixture stabilized with cellulose acetate butyrate. The resulting particles were 1.2 microm in diameter and possessed narrow size distribution. After modification with adipic acid dihydrazide they contained 2 micromol of reactive groups available for coupling of anti-chymotrypsin antibodies. Prepared immunosorbent adsorbed 166.7 microg of chymotrypsin per 1 g of dry carrier. Immobilized chymotrypsin retained practically 100% of its native proteolytic activity. Kinetic parameters of catalysis by chymotrypsin immobilized via this way were improved due to the good steric accessibility of the enzyme active site for high-molecular-mass substrates, when digestion of proteins in batch experiments was used.

Antibodies↗
PubMed2000

Effect of stationary phase hydrophobicity and mobile phase composition on the separation of carboxylic acids in ion chromatography.

In a previous work, we studied the retention behavior of monovalent and divalent carboxylic acids on a highly cross-linked polystryene-divinylbenzene anion-exchange column (IonPac AS4A-SC) using a carbonate-based buffer, and a retention model was applied to the chromatographic data obtained. In this work we characterized the retention of carboxylates (formic, acetic, propionic, lactic, pyruvic, oxalic, malonic, succinic, fumaric, maleic, tartaric, glutaric, adipic, malic, mucic, trans-beta-hydromuconic, trans,trans-muconic acids) on a column with higher hydrophilicity (IonPac AS11) according to analyte and stationary phase properties, using previously investigated eluent compositions and comparing the retention data obtained. Moreover, the effect of organic modifiers (CH3OH and CH3CN) in the eluent on the retention factors was also evaluated. The chromatographic data obtained on the IonPac AS11 column were fitted by the retention model and allowed one to obtain and to compare ion-specific selectivity constants (parameters of the model) with the ones obtained with the previous column.

Carboxylic Acids↗
PubMed2000

Determination of phthalate esters in water samples by solid-phase microextraction and gas chromatography with mass spectrometric detection.

Solid-phase microextraction (SPME) with an 85 microm polyacrylate fiber, coupled to gas chromatography-mass spectrometry was used to determine six phthalate esters and bis(2-ethylhexyl) adipate in water samples. The variables affecting the SPME absorption process were optimized and the method developed was applied to analyze both tap and commercial mineral water samples as well as water from the Ebro river and fishing and industrial ports. For real samples, the linear range in full scan acquisition mode was between 0.02 and 10 microg l(-1) for most compounds, and the limits of detection of the method were between 0.006 and 0.17 microg l(-1). Commercial water samples contained in recipients which were made from different materials were analyzed, and the influence of the material of the recipients on the concentration of phthalates was evaluated.

Esters↗
PubMed1979

Treatment of glutaryl-CoA dehydrogenase deficiency (glutaric aciduria). Experience with diet, riboflavin, and GABA analogue.

The autosomal recessive inherited disorder glutaryl-CoA dehydrogenase deficiency (glutaric aciduria) runs a progressive course with severe choreoathetosis and dystonia, eventually leading to total helplessness and early death. Theree patients were observed during therapeutic trials with a protein-low diet, riboflavin and GABA analogue. Diet and riboflavin had a slight-to-moderate effect on the clinical symptoms; the excretion of glutaric acid and 2-amino-adipic acid decreased considerably during treatment. Regression of neurologic symptoms was observed during treatment with GABA analogue. It is concluded that the patients should be treated as early as possible with protein-low diet, riboflavin, and GABA analogue.

2-Aminoadipic Acid↗
PubMed1985

Urinary dicarboxylic acids in Reye syndrome.

Urine from 12 patients with Reye syndrome was examined by gas-liquid chromatography for identification of organic acids. Large amounts of lactic acid, dicarboxylic acids (adipic, suberic, and sebacic), and 3-OH butyric acid were noted. The mean (+/- SD) total dicarboxylic acid concentration was 0.98 +/- 0.24 mg/mg creatinine, compared with 0.006 +/- 0.010 mg/mg creatinine in controls, n = 140; the mean in patients with Reye syndrome was higher (1.40 +/- 0.26 mg/mg creatinine, n = 8) when the samples were obtained prior to initiation of therapy, but declined rapidly after administration of hypertonic glucose, exchange transfusion, and osmotic diuretics. The total urine excretion of dicarboxylic acids plus urine ketones at the time of presentation correlated well with the plasma lactate (r2 = 0.9676) and peak blood ammonia (r2 = 0.9216) levels. Our results document the occurrence of significant dicarboxylic aciduria in Reye syndrome and indicate that fatty acid metabolism is more impaired in this disorder than previously appreciated.

Ammonia↗
PubMed1996

Distinction of dicarboxylic aciduria due to medium-chain triglyceride feeding from that due to abnormal fatty acid oxidation and fasting in children.

Increased amounts of dicarboxylic acids are excreted in human urine under conditions of medium-chain triglyceride (MCT) feeding, abnormal fatty acid oxidation (FAO) and fasting. Criteria to distinguish dicarboxylic aciduria originating from MCT feeding and other conditions are needed in urinary organic acid profiling for detecting inborn errors of metabolism. Patterns of dicarboxylic aciduria in children under various conditions were compared. The relative amounts of medium-chain saturated dicarboxylic acids in urine are not reliable for identifying MCT-induced dicarboxylic aciduria. On the other hand, low ratios of unsaturated to saturated dicarboxylic acids (<0.1) and 3- hydroxydecenedioic to 3-hydroxydecanedioic acids were found to be useful in identifying dicarboxylic aciduria due to MCT ingestion. Additional unique features of dicarboxylic aciduria from MCT are low ratios of 3-hydroxydodecanedioic to 3-hydroxydecanedioic acid (<0.14) and 3-hydroxyadipic to adipic acid (<0.02).

Caproates↗
PubMed2003

Dietary low-dose sucrose modulation of IQ-induced genotoxicity in the colon and liver of Big Blue rats.

Earlier studies have indicated that sucrose increases 2-amino-3-methylimidazo[4,5-f]quinoline (IQ)-induced aberrant crypt foci in the colon. In this study, we investigated the role of sucrose in IQ-induced genotoxicity of the colon mucosa and liver. Big Blue rats were fed with IQ (20 ppm in feed) and/or sucrose (3.45 or 6.85 wt.% in feed) for 3 weeks. IQ increased DNA strand breaks in the colon, whereas the mutation frequency was increased in the liver. The level of IQ-induced DNA adducts was elevated in both colon mucosa cells and liver. In the liver, high sucrose intake increased the level of DNA adducts above that of IQ and low sucrose intake. Oxidative DNA damage detected in terms of 7-hydro-8-oxo-2'-deoxyguanosine by HPLC-EC, or endonuclease III or formamidopyrimidine DNA glycosylase sensitive sites were unaltered in the colon and liver. Expression of ERCC1 and OGG1 mRNA levels were unaffected by IQ or sucrose feeding. Biomarkers of oxidative stress, including Vitamin C, malondialdehyde and protein oxidations (gamma-glutamyl semialdehyde and 2-amino adipic semialdehyde) were unaltered in plasma and in liver. In conclusion, sucrose feeding increases IQ-induced genotoxicity in liver but not in colon, suggesting different mechanisms for sucrose and IQ in colon mutagenesis.

Animals↗
PubMed2001

Chemical industry reduces emissions--from production to the consumer.

Responsible care has always been an important issue at a chemical industry like Bayer. In recent years, the company has made extensive efforts to further improve its products and processes with regard to environmental protection and safety. In this contribution, a number of examples will highlight recent achievements of Bayer in the field of low or no emission processes and products. Examples are given in the fields of production-integrated environmental protection measures (new and improved processes e.g., for the production of adipic acid), the application of integrated environmental protection measures (2K-PUR water-borne coatings for cars) and product-integrated environmental protection measures (targeted application of insecticides/Attract and Kill) as a new low emission method to control insect pests.

Air Pollution↗