Bis[2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulpho propylamino)phenolato]cobaltate(III) as a counter ion for the extraction and spectrophotometric determination of long-chain quaternary ammonium salts and tertiary alkylamines in the presence of each other

The singly charged complex anion bis[2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulphopropylamino)phenolato]cobaltate(III) is intensely purple-violet and is stable over the pH range 1–13. Its absorption spectrum remains the same over this pH range. At pH2, it forms extractable ion pairs with long-chain quaternary ammonium ions and protonated alkylamines. Only the quaternary ammonium ions are extracted into chloroform at pH 11, hence separate extractions allow both types to be determined. The absorbance of the organic phase is measured at 594 nm. The apparent molar absorptivity is 7.0 × 10⁴ l mol^?1 cm^?1. Calibration graphs for zephiramine, benzethonium and hexadecylpyridinium ions are linear over the range 0.1–2 × 10^?6 M. The only interference found was from anionic surfactants. The method is applied to hair and fabric conditioners.     

Formamide as an efficient nitrogen nucleophile for the Michael addition to nitroalkenes

Secondary acyclic formamide serves as an efficient nucleophile to nitroalkenes to give corresponding Michael adducts in good yields. The nitro group in the adducts was useful for further heterocyclic synthesis.     

Asymmetric conjugate addition of α-keto esters to nitroolefins catalyzed by chiral CuII hydroxo complexes

As a part of our research project on hard anion-late transition metal complexes as mild acid–base catalysts, we describe herein that Cu^II hydroxo complexes having chiral N-substituted-diaminocyclohexanes are mild and selective catalysts, which are applicable to the catalytic asymmetric conjugate addition of α-keto esters to nitroolefins. The reaction proceeded diastereoselectively without the detectable formation of self-aldol products, affording the corresponding coupling products with anti-stereochemistry in an enantioselective manner.     

Highly sensitive simultaneous quantification of indoxyl sulfate and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid in human plasma using ultra-high-performance liquid chromatography coupled with tandem mass spectrometry

Indoxyl sulfate and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid are uremic toxins that accumulate in renal failure and have been reported to decrease the activities of the drug-metabolizing enzyme cytochrome P450 3A and the drug transporter organic anion transporting polypeptides 1B, respectively. In this study, we established and validated an assay for simultaneous quantification of indoxyl sulfate and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid in human plasma. The samples were pretreated by solid-phase extraction, and measured by ultra-high-performance liquid chromatography–tandem mass spectrometry. The validation results for this assay were within the acceptable limits recommended by the US Food and Drug Administration, with a lower limit of quantitation of 0.05 μg/mL for both indoxyl sulfate and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid. Recovery rates of indoxyl sulfate and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid corrected by internal standard were 100.7–101.9 and 100.2–101.3%, respectively. Matrix effects of indoxyl sulfate and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid corrected by internal standard were 101.1–105.5 and 97.0–103.8%, respectively. The validated assay was used to analyze indoxyl sulfate and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid concentrations in the plasma samples of healthy volunteers and patients with chronic kidney disease. All the measured plasma indoxyl sulfate and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid concentrations were within the calibration ranges. This novel method may contribute to predicting the activities of drug-metabolizing enzymes and drug transporters in individual patients.     

Adsorption characteristics of monomeric/gemini surfactant mixtures at the silica/aqueous solution interface

The adsorption of the monomeric/gemini surfactant mixtures at the silica/aqueous solution interface has been characterized on the basis of quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy (AFM) data. The gemini surfactant employed in this study was cationic 1,2-bis(dodecyldimethylammonio)ethane dibromide (12-2-12). This surfactant was mixed with monomeric surfactants (dodecyltrimethylammonium bromide (DTAB), hexadecyltrimethylammonium bromide (HTAB), and octaoxyethylenedodecyl ether (C(12)EO(8))) in the presence of an added electrolyte (NaBr). The key finding in our current study is that the addition of the gemini surfactant (12-2-12) makes significant impact on the adsorption properties even when the mole fraction of 12-2-12 is quite low in the surfactant mixtures. This is suggested by the experimental results that (i) the QCM-D adsorption isotherms measured for the monomeric/gemini surfactant mixtures shift to the region of lower surfactant concentrations compared with the monomeric single systems; (ii) the adsorbed layer morphology largely depends on the mole fraction of 12-2-12 in the surfactant mixtures, and the increased 12-2-12 mole fraction results in the less curved surface aggregates; and (iii) the addition of 12-2-12 yields a relatively rigid adsorbed layer when compared with the layer formed by the monomeric single systems. These adsorption properties result from the fact that the more favorable interaction of 12-2-12 with the silica surface sites drives the overall surfactant adsorption in these mixtures, which is particularly obvious in the region of low surfactant concentrations and at the 12-2-12 low mole fractions. We believe that this knowledge should be important when considering the formulation of gemini surfactants into various chemical products.     

Method and mechanism of vapor phase treatment–total reflection X-ray fluorescence for trace element analysis on silicon wafer surface

Vapor phase treatment (VPT) is a pretreatment with hydrofluoric acid vapor to raise the sensitivity of total reflection X-ray fluorescence spectroscopy (TXRF) for trace metal analysis on silicon wafers. The International Organization for Standardization/Technical Committee 201/Working Group 2 (ISO/TC201/WG2) has been investigating the method to analyze 10⁹ atoms/cm² level of metallic contamination on the silicon wafer surface. Though VPT can enhance the TXRF signal intensity from the metallic contamination, it has turned out that the magnitude of the enhancement varies with the type of methods and the process conditions. In this study, approaches to increase TXRF intensity by VPT are investigated using a fuming chamber in an automated VPD instrument. Higher signal intensity can be obtained when condensation is formed on the sample surface in a humidifying atmosphere and with a decreasing stage temperature. Surface observations with SEM and AFM show that particles with ~ 4 μm in diameter are formed and unexpectedly they are dented from the top surface level.