Amounts Of Glycolic Acid Research Articles

Integrated capture and solar-driven utilization of CO2 from flue gas and air

Integrated capture and solar-driven utilization of CO2 from flue gas and air

A kinetic study on the conversion of nylon 12 to methyl 12-hydroxydodecanoate in supercritical MeOH in the presence of carboxylic acid

Polyamides were effectively converted into hydroxyl esters by treatment with supercritical MeOH in the presence of glycolic acid. This transformation progressed smoothly over a period of 240 min, and the presence of glycolic acid accelerated the reaction. Kinetic analyses of the depolymerization of nylon 12 were performed by measuring the product distribution in the reaction mixture. The chemoselectivity of hydroxyl ester formation was linearly dependent on the amount of glycolic acid used. The product distribution of the reaction using pivalic acid was also measured. Simulations based on the actual time-course data enabled the estimation of kinetic parameters. The obtained kinetic parameters revealed that the rate constant for the formation of the hydroxyl ester was significantly enhanced by the presence of glycolic acid. These results clearly indicate that the monomeric unit, an amino ester, underwent a bimolecular substitution reaction with glycolic acid. Based on these results, we proposed a reaction mechanism for the formation of hydroxyl esters. Arrhenius plots of the reaction rates were used to effectively estimate the activation energy for each step.

The effect of poly (lactic-co-glycolic) acid composition on the mechanical properties of electrospun fibrous mats

The aim of this study was to investigate the influence of polymer molecular structure on the electrospinnability and mechanical properties of electrospun fibrous mats (EFMs). Polymers with similar molecular weight but different composition ratios (lactic acid (LA) and glycolic acid (GA)) were dissolved in binary mixtures of N,N-dimethylformamide (DMF) and tetrahydrofuran (THF). The intrinsic viscosity and rheological properties of polymer solutions were investigated prior to electrospinning. The morphology and mechanical properties of the resulting EFMs were characterized by scanning electron microscope (SEM) and dynamic mechanical analysis (DMA). Sufficiently high inter-molecular interactions were found to be a prerequisite to ensure the formation of fibers in the electrospinning process, regardless the polymer composition. The higher the amount of GA in the polymer composition, the more ordered and entangled molecules were formed after electrospinning from the solution in THF-DMF, which resulted in higher Young’s modulus and tensile strength of the EFMs. In conclusion, this study shows that the mechanical properties of EFMs, which depend on the polymer molecule-solvent affinity, can be predicted by the inter-molecular interactions in the starting polymer solutions and over the drying process of electrospinning.

Study of the intrinsic electrochemical properties of spinel LiNi0.5Mn1.5O4

In the past, the electrochemical properties of spinel LiNi0.5Mn1.5O4, i.e. rate capability at room temperature and cycle performance at elevated temperature, were not satisfactory. In this study, the influence of glycolic acid on the electrochemical properties of spinel LiNi0.5Mn1.5O4 was studied. With some amount of glycolic acid as an additional reactant, spinel LiNi0.5Mn1.5O4 was synthesized, and its electrochemical properties were improved. In addition, the mechanism of capacity decay at elevated temperature was also studied, which presents constructive view to further improve the electrochemical properties of spinel LiNi0.5Mn1.5O4.

Elevated lactate in ethylene glycol poisoning: True or false?

Abstract Background There have been an increasing number of reports on false increase of lactate in ethylene glycol poisoning. We recently encountered two cases of ethylene glycol poisoning with very high blood lactate concentrations on ABL blood gas analyzers. Methods Patient plasma lactate concentrations were measured on different chemistry instruments in addition to ABL analyzer. Serum ethylene glycol and glycolic acid were also determined. Lactate values were determined from samples spiked with various amounts of glycolic acid. Results In case 1, all the chemistry instruments produced similar lactate results compared to that by ABL analyzer whereas in case 2, the lactate on the ABL was dramatically elevated compared to that from all the chemistry analyzers. There was no glycolic acid detected in case 1 but high glycolic acid was obtained in case 2. Increased concentrations of glycolic acid resulted in a significant positive interference on lactate measurements on the ABL analyzer but none on other instruments. Conclusions False increase of blood lactate by blood gas analyzers may occur but true increase of lactate can also be observed in ethylene glycol poisoning. Elevated lactate concentrations on blood gas analyzers should be confirmed by a chemistry analyzer in the differential diagnosis of ethylene glycol poisoning.

Elevated lactate in ethylene glycol poisoning: True or false?

Background There have been an increasing number of reports on false increase of lactate in ethylene glycol poisoning. We recently encountered two cases of ethylene glycol poisoning with very high blood lactate concentrations on ABL blood gas analyzers. Methods Patient plasma lactate concentrations were measured on different chemistry instruments in addition to ABL analyzer. Serum ethylene glycol and glycolic acid were also determined. Lactate values were determined from samples spiked with various amounts of glycolic acid. Results In case 1, all the chemistry instruments produced similar lactate results compared to that by ABL analyzer whereas in case 2, the lactate on the ABL was dramatically elevated compared to that from all the chemistry analyzers. There was no glycolic acid detected in case 1 but high glycolic acid was obtained in case 2. Increased concentrations of glycolic acid resulted in a significant positive interference on lactate measurements on the ABL analyzer but none on other instruments. Conclusions False increase of blood lactate by blood gas analyzers may occur but true increase of lactate can also be observed in ethylene glycol poisoning. Elevated lactate concentrations on blood gas analyzers should be confirmed by a chemistry analyzer in the differential diagnosis of ethylene glycol poisoning.

Determination of glycolic acid in cosmetics by online liquid chromatography–Fourier transform infrared spectrometry

An isocratic online liquid chromatography Fourier transform infrared procedure has been developed for the determination of glycolic acid in cosmetics. The method involves the ultrasound-assisted extraction of glycolic acid from the samples with an acetonitrile:phosphate buffer (25 mM, pH 2.7) (3:97 v/v). The extracts were centrifuged and filtered before their injection into the chromatography system, which was equipped with a C18 column and used a flow rate of 150 microL min(-1). FTIR spectra were acquired using a time-resolved rapid scan mode. To calculate the chromatograms, the spectral area was integrated between 1288 and 1215 cm(-1), with baseline correction established between 1319 and 1150 cm(-1), after correcting for the eluent spectral background. Peak area values of the extracted sample chromatograms were interpolated from an external calibration curve. The method provided a limit of detection of 0.034 mg mL(-1) and a relative standard deviation of 6% for five measurements at the 0.174 mg mL(-1) concentration level. Recovery values obtained by spiking 400 mg of three commercially available samples with amounts of glycolic acid from 3.7 to 9.8 mg ranged between 99.6 and 101%. The results obtained for the commercial samples agree well with their declared concentrations. An attempt to directly determine glycolic acid by attenuated total reflectance measurements using partial least squares calibration showed that results were strongly influenced by compounds coextracted from the matrix.

Inhalation and epidermal exposure of volunteers to ethylene glycol: Kinetics of absorption, urinary excretion, and metabolism to glycolate and oxalate

Ethylene glycol (EG) is a widely used liquid. Limited data are published regarding inhaled EG and no data regarding transdermal EG uptake in humans. In order to gain information on the quantitative fate of EG, four male volunteers inhaled between 1340 and 1610 μmol vaporous 13C-labeled EG ( 13C 2-EG) for 4 h. Separately, three of these subjects were epidermally exposed for up to 6 h to liquid 13C 2-EG (skin area 66 cm 2). Plasma concentrations and urinary amounts of 13C 2-EG were determined by gas chromatography with mass selective detection. Additionally, plasma was assayed for 13C-labeled glycolic acid ( 13C 2-GA) and urine for 13C 2-GA and 13C-labeled oxalic acid ( 13C 2-OA). Both EG metabolites were nephrotoxic in animals and humans and embryotoxic in rodents. 13C-labels enabled to differentiate from also determined endogenous EG, glycolic acid (GA), and oxalic acid (OA). Of 13C 2-EG inhaled, 5.5 ± 3.0%, 0.77 ± 0.15%, and 0.10 ± 0.12% were detected in urine as 13C 2-EG, 13C 2-GA, and 13C 2-OA, respectively. The skin permeability constant of liquid EG was 2.7 × 10 −5 ± 0.5 × 10 −5 cm/h. Of the dose taken up transdermally, 8.1 ± 3.2% and up to 0.4% were excreted in urine as 13C 2-EG and 13C 2-GA, respectively. It is calculated that equally long-lasting exposure to 10 ppm vaporous EG or wetting of both hands by liquid EG leads to about the same body burden by EG and metabolites. The amounts of GA and OA excreted daily in urine as a result of exposure (8 h/day) to 10 ppm EG are about 15% and 2%, respectively, of those excreted from naturally occurring endogenous GA and OA.

Successful transplantation of a liver from a donor with fatal ethylene glycol poisoning

Successful transplantation of a liver from a donor with fatal ethylene glycol poisoning

Biodegradable recombinant human erythropoietin loaded microspheres prepared from linear and star-branched block copolymers: Influence of encapsulation technique and polymer composition on particle characteristics

Recombinant human erythropoietin (EPO) and fluorescein isothiocyanate labeled dextran (FITC-dextran) loaded microspheres were prepared by a modified W/O/W double-emulsion technique. Biodegradable linear ABA block copolymers consisting of poly( L-lactide-co-glycolide) A blocks attached to central poly(ethyleneoxide) (PEO) B blocks and star-branched AB block copolymers containing A blocks of poly( L-lactide) or poly( L-lactide-co-glycolide) and star-branched poly(ethyleneoxide) B blocks were investigated for their potential as sustained release drug delivery systems. Microsphere characteristics were strongly influenced by the polymer composition. In the case of the linear block copolymers, a reduced lactic acid content in a linear block copolymer yielded smaller particles, a lower encapsulation efficiency, and a higher initial drug release both in the case of EPO and FITC-dextran. The investigation of the effects of several manufacturing parameters on microsphere formation showed that the process temperature plays an important role. Microsphere formation in a +1°C environment resulted in higher drug loadings without increasing the amount of residual dichloromethane inside the particles. Other parameters such as the homogenization of the primary W/O emulsion and of the W/O/W double-emulsion have less impact on microsphere characteristics. Branched block copolymers containing star-shaped PEO also showed potential for the preparation of drug loaded microspheres. A certain amount of glycolic acid in the copolymer was necessary for the successful preparation of non-aggregating microspheres at room temperature. Again, the processing temperature strongly affected particle characteristics. Microsphere preparation at +1°C allows the formation of microspheres from a polymer not containing glycolic acid, a result which could not be achieved at room temperature. Moreover, compared to microsphere formation at room temperature, the effective FITC-dextran loading was increased. Concerning the EPO loaded microspheres, the amount of EPO aggregated was comparable to that using the linear ABA polymers. A continuous release of the protein from these star-shaped polymers could not be achieved. In conclusion, apart from microsphere preparation in a +1°C environment the choice of the polymer represents the main factor for a successful entrapment of proteins into biodegradable microspheres.

Effect of hydrolytic degradation on the microstructure of poly(glycolic acid): An X-ray scattering and ultraviolet spectrophotometry study of wet samples ultraviolet

The effect of in vitro hydrolytic degradation on the microstructure of unoriented semicrystalline poly(glycolic acid) (PGA) was examined using simultaneous small- and wide-angle synchroton x-ray scattering (SAXS/WAXS) and ultraviolet (UV) spectrophotometry. Samples were degraded in buffer solutions at 37°C and were examined wet to avoid the structural changes that occur on drying. During degradation, the crystal density remained constant, and little change was seen in the lateral extent of the crystal lamellae. The transition layer between the crystalline and amorphous phases roughened slightly. More dramatic changes were seen in the amorphous phase, resulting in sharp increases in the crystallinity, the amount of glycolic acid in the buffer solution, and in the density difference between the crystal lamellae and the layers separating them. These changes indicated a loss of amorphous material that leveled off after 30 days. The lamellar repeat distance fell from around 95 to 80Å in the first 20 days before slowly rising again towards its initial value, changes which are interpreted as reflecting a two-stage loss of amorphous material, in which highly coiled loops and tie chains are degraded faster than taut tie chains. Once the coiled material is removed, the taut chains are able to adopt entropically favorable conformations, pulling the crystals towards each other, lowering the lamellar repeat, and creating internal stresses within the spherulite. As these newly coiled chains degrade, the crystals are released and slowly separate. The changes in long period are also considered in the light of chemical changes during degradation. Such change of chemical environment could affect the affinity for water of the amorphous inter-lamellar regions and affect the swelling. The observed changes in the long period may be a consequence of either or both of these factors. These findings give microstructural information of importance in the prediction and control of mechanical properties during degradation and the diffusivity of other molecules through degrading PGA. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1681–1690, 1997

Recurrence of Nephrocalcinosis After Renal Transplantation in an Adult Patient with Primary Hyperoxaluria Type I

The medical history of a 42-year-old patient with primary hyperoxaluria type I is presented. Primary hyperoxaluria was suspected after renal transplantation, when oxalate deposits were found in a biopsy of the kidney graft. Diagnosis of type I hyperoxaluria was confirmed by the finding that significantly increased amounts of glycolic acid and oxalic acid were excreted. Treatment of the patient with 500 mg pyridoxine daily resulted in a decrease of the excretion of oxalate to normal values.

Studies on Effect of Certain Quinones

The effect of quinone herbicides and fungicides on photosynthetic reactions in isolated spinach (Spinacia oleracea) chloroplasts was investigated. 2,3-Dichloro-1,4-naphthoquinone (dichlone), 2-amino-3-chloro-1,4-naphthoquinone (06K-quinone), and 2,3,5,6-tetrachloro-1,4-benzoquinone (chloranil) inhibited ferricyanide reduction as well as ATP formation. Benzoquinone had little or no effect on these reactions. The two reactions showed a differential sensitivity to these inhibitors. Dichlone was a strong inhibitor of both photosystems I and II; photosystem I was more sensitive to 06K-quinone than was photosystem II, whereas the reverse was true of chloranil. Chloranil and 06K-quinone inhibited ferricyanide reduction and the coupled photophosphorylation to the same extent, whereas dichlone affected photophosphorylation to a greater extent than the ferricyanide reduction.CO(2) fixation was inhibited by all the quinones to varying degrees. In chloroplasts treated with 06K-quinone or benzoquinone, CO(2) fixation was inhibited to a greater extent than the photoreduction of ferricyanide or ATP formation, indicating the possibility that the two quinones may also inhibit certain reactions in the carbon reduction cycle. The effect of dichlone and chloranil, but not of 06K-quinone, was overcome by the addition of reduced glutathione. The quinones caused an increase in the proportion of (14)C incorporated into 3-phosphoglyceric acid and a reduction in the amount of glycolic acid.