Beiträge der Radiotracertechnik zur Rationalisierung einer großtechnischen Anlage zur Caprolactamproduktion

This paper reviews ways in which radioactive tracer techniques can he used to improve the efficiency of a caprolactam production plant, Residence time spectra and material distributions in different parts of the plant were measured by application of sodium 24, bromine 82 and technetium 99m. The investigations led to improved cumeneoxidators and gave useful informations on the catalytic decomposition of the phenolic tar and the hydrogenation process of phenol. It could he shown that the construction of the lactam extractor must he varied and the results of the tracerexperiments made in the distillation unit contributed to a higher quality of the final product.     

Chemoselective Esterification of Phenolic Acids in the Presence of Sodium Bicarbonate in Ionic Liquids

Chemoselective esterification of phenolic acids with dialkyl sulphates or alkyl halides in the presence of sodium bicarbonate in 1,3‐dialkylimidazolium ionic liquids is reported in excellent yields and less reaction time as compared to organic solvents.     

Two-stage latexes of polystyrene acrylates

ABSTRACT

The modification of decomposition rate of the potassium persulfate initiator during the synthesis of “two-stage latexes” polystyrene-ethyl acrylate (EtA) of butyl acrylale (BuA) and of 2-ethylhexyl acrylate (EHA) is studied. This rate is minimum for BuA and maximum for EHA, in good agreement with the value of solubility parameters. The appearance of poryacrvlaf.es determines the existence of water bonded to the polar polymer. The amount of water bonded increases in the sequence PEtA?PBuA?PEHA, function of the modification of the diameters of the particles resulted from the latexes obtained.     

Quantitative determination of sodium stearyl fumarate in a tablet formulation from continuous manufacturing using a high-pH reversed-phase HPLC method

This study demonstrates the first use of a reversed-phase (RP) high-performance liquid chromatography method with a high-pH buffer for the analysis of sodium stearyl fumarate (SSF) from a tablet formulation. After examining the retention time and peak shape using various buffer concentrations, buffer pH, and RP stationary phases, an optimized method was established using the XBridge® BEH C18 at high pH. This column was further evaluated for method specificity, accuracy, precision, linearity, stability, and sensitivity. Finally, the method was successfully used as a convenient and robust analytical procedure to accurately quantitate SSF in stratified tablets from a continuous manufacturing process to confirm the excipient uniformity throughout the process.     

Analysis of toldimfos in porcine muscle and bovine milk using liquid chromatography–triple quadrupole mass spectrometry

An analytical method was developed for the detection of toldimfos sodium residues in porcine muscle and bovine milk using liquid chromatography–triple quadrupole tandem mass spectrometry (LC–MS/MS) analysis. The drug was extracted from muscle and milk using 10 mm ammonium formate in acetonitrile and then purified using n ‐hexane. The drug was well separated on a Luna C₁₈ column using a mixture of 10 mm ammonium formate in ultrapure water (A) and acetonitrile (B) as the mobile phase. Good linearity was achieved over the tested concentration range (0.005–0.03 mg/kg) in matrix‐matched standard calibration. The determination coefficients (R ² ) were 0.9942 and 0.9898 for muscle and milk, respectively. Fortified porcine muscle and bovine milk contained concentrations equivalent to and twice the limit of quantification (0.005 mg/kg) yielded recoveries in the range of 75.58–89.74% and relative standard deviations of ≤8.87%. Samples collected from large markets located in Seoul, Republic of Korea, tested negative for toldimfos sodium residue. In conclusion, ammonium formate in acetonitrile can effectively extract toldimfos sodium from porcine muscle and bovine milk without solid‐phase extraction, which is usually required for cleanup before analysis. This method can be applied for the routine analysis of toldimfos in foods of animal origins.     

Synthesis and rheological investigation of self‐healable deferoxamine grafted alginate hydrogel

Deferoxamine grafted alginate (SA‐DFA) was successfully synthesized via amidation of sodium alginate with deferoxamine mesylate as determined by H‐NMR and elemental analysis. SA‐DFA with different graft yield was obtained by adjusting the ratio of sodium alginate and deferoxamine mesylate. It was found that aqueous solution of SA‐DFA could form hydrogel spontaneously due to hydrogen bonding interactions, which also endowed the SA‐DFA hydrogel with self‐healing capability. The healing efficiency of SA‐DFA hydrogels ranged from 53.64 to 90.16%. In addition, surface morphologies of SA‐DFA hydrogels before/after self‐healing process were demonstrated by SEM images. We anticipated that such self‐healable alginate hydrogel would be applied in the field of wound healing. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 856–865     

Direct Observation of an Oxepin from a Bacterial Cytochrome P450‐Catalyzed Oxidation

The cytochromes P450 are hemoproteins that catalyze a range of oxidative C?H functionalization reactions, including aliphatic and aromatic hydroxylation. These transformations are important in a range of biological contexts, including biosynthesis and xenobiotic biodegradation. Much work has been carried out on the mechanism of aliphatic hydroxylation, implicating hydrogen atom abstraction, but aromatic hydroxylation is postulated to proceed differently. One mechanism invokes as the key intermediate an arene oxide (and/or its oxepin tautomer). Conclusive isolation of this intermediate has remained elusive and, currently, direct formation of phenols from a Meisenheimer intermediate is believed to be favored. We report here the identification of a P450 [P450_cam (CYP101A1) and P450_cin (CYP176A1)]‐generated arene oxide as a product of in vitro oxidation of tert‐butylbenzene. Computations (CBS‐QB3) predict that the arene oxide and oxepin have similar stabilities to other arene oxides/oxepins implicated (but not detected) in P450‐mediated transformations, suggesting that arene oxides can be unstable terminal products of P450‐catalyzed aromatic oxidation that can explain the origin of some observed metabolites.     

Complexation Based Voltammetric Determination of Pantoprazole Sodium in Pharmaceutical Formulations and Rabbit Plasma

Square wave adsorptive stripping voltammetric (SQWASV) method has been utilized to confirm and elucidate the possible complexation reaction between pantoprazole sodium and cobalt as a transition metal in Britton‐Robinson buffer (pH=7.0). The current signal due to the oxidation process was a function of the amount of pantoprazole sodium, pH of the medium, cobalt concentration and accumulation time at the electrode surface. The oxidation peak current has varied linearly with the concentration over the range of 0.1–9.0 nM. The limit of detection was found to be 0.04 nM. The validity of the method was successfully applied for the determination of pantoprazole sodium in pharmaceutical formulations with a pharmacokinetic study in rabbit plasma. The simplicity, rapidity, sensitivity and selectivity of this method make it a very attractive alternative to the other existing methods in the quality control laboratories.