Rapid Determination of Preservatives in Cosmetics Using a Core-Shell Column.

Preservatives are frequently added to cosmetics to maintain product quality. Our laboratory quantifies 11 preservatives in cosmetics each year for regulatory purposes. In laboratories, many manufactures also analyze the preservatives in their products for quality control.

[The Configuration of Tadalafil and Tadalafil Analogues Found in Dietary Supplements].

This study determined the configuration of the isomers of tadalafil, nortadalafil, and homotadalafil in dietary supplements. The products purchased over the Internet studied included a honey product and a tablet, which contained tadalafil, and a candy, which contained nortadalafil and homotadalafil. Each of the pharmaceutical ingredients isolated from the products was measured with circular dichroism (CD).

Dispersion stability and rheological properties of silica suspensions in aqueous solutions.

This historical perspective overviews the dispersion stability and rheological properties of fumed and colloidal silica suspensions in aqueous solutions as a function of the volume fraction of silica (ϕ) (where ϕ is ≤0.1). The silica suspensions exist in a gel state at lower ϕ in acidic conditions than at alkaline pH.

Stability and rheological properties of silica suspensions in water- immiscible liquids.

This paper overviews silica suspensions in water-immiscible liquids, with an emphasis on their dispersion stability and rheological properties as a function of the surface characteristics of silica powders at lower silica volume fractions, ϕ, than 0.1. In addition, a critical review is presented the manufacturing process of silica powder by considering their microstructures.

Fumed and Precipitated Hydrophilic Silica Suspension Gels in Mineral Oil: Stability and Rheological Properties.

Hydrophilic fumed silica (FS) and precipitated silica (PS) powders were suspended in mineral oil; increasing the silica volume fraction (φ in the suspension led to the formation of sol, pre-gel, and gel states. Gelation took place at lower φ values in the FS than the PS suspension because of the lower silanol density on the FS surface. The shear stresses and dynamic moduli of the FS and PS suspensions were measured as a function of φ.

Interfacial characteristics of binary polymer blend films spread at the air-water interface.

The interfacial characteristics of binary polymer blend films spread at the air-water interface are reviewed, focusing on their surface pressures, interfacial structures, and dilational moduli as a function of the miscibility. Miscible polymer blend films show thermodynamic, structural, and dynamic properties which are a combination of those from both components in the polymer blend present at the air-water interface. No preferential adsorption is observed and the behavior does not depend on the surface concentration regime.

Silicone oil emulsions stabilized by polymers and solid particles.

Silicone oil emulsions stabilized by various emulsifiers such as polymers, solid particles alone, and solid particles with pre-adsorbed surfactants or polymers are reviewed, focusing on their emulsion stability and rheological properties as a function of the emulsifier concentration. An increase in the concentration of the emulsifier leads to a decrease in the droplet size and an increase in the emulsion stability, irrespective of the emulsifier. Moreover, the overlapping concentration of polymer can be regarded as a criterion for the preparation of emulsions using polymeric emulsifiers.

Surface dilational moduli of polymer and blended polymer monolayers spread at air-water interfaces.

Surface dilational moduli of polymer monolayers, blended polymer monolayers, and polymer particle monolayers spread at air-water interfaces are reviewed, focusing on measurements using surface pressure isotherm, surface pressure relaxation, and oscillating barrier methods. Differences between the surface dilational moduli of condensed polymer monolayers and expanded polymer monolayers are explored. Moreover, the features of the surface dilational moduli in blended polymer monolayers are discussed in terms of their miscibility.

Dispersion method for safety research on manufactured nanomaterials.

Nanomaterials tend to agglomerate in aqueous media, resulting in inaccurate safety assessment of the biological response to these substances. The present study searched for suitable dispersion methods for the preparation of nanomaterial suspensions. Titanium dioxide (TiO2) and zinc oxide (ZnO) nanoparticles were dispersed in a biocompatible dispersion medium by direct probe-type sonicator and indirect cup-type sonicator.

A simple and selective detection method for aristolochic acid in crude drugs using solid-phase extraction.

The official Japanese method for analyzing aristolochic acid I (AA-I) in Asiasarum root using conventional high-performance liquid chromatography (HPLC) is described in the Japanese Pharmacopoeia, Sixteenth Edition. Interfering peaks of AA-I sometimes appear after HPLC analysis of crude drugs. A selective analytical method is needed to determine definitively whether AA-I is present in crude drugs.

Surface dilational moduli of latex-particle monolayers spread at air-water interface.

Latex particles prepared by radical dispersion polymerization of styrene and diacetone acrylamide (DAAM) in the presence of potassium persulfate as an initiator were spread as particle monolayers at the air-water interface. The surface pressure isotherms of the latex-particle monolayers are almost reversible during the compression-expansion cycles. The surface dilational moduli of the latex-particle monolayers at a fixed surface pressure of 20 mN/m and a fixed frequency of 10 mHz are almost independent of the strain.

Surface dilational moduli of poly (ethylene oxide), poly (methyl methacrylate), and their blend films.

Surface dilational moduli of poly (ethylene oxide) (PEO), poly (methyl methacrylate) (PMMA), and compatible PEO/PMMA blend films spread at the air-water interface were investigated as a function of surface concentration. The surface dilational modulus of an expanded PEO film increased as the surface concentration increased to 0.4 mg/m(2), which corresponds to the limiting surface area of PEO.

Characterization of paraffin oil emulsions stabilized by hydroxypropyl methylcellulose.

To study the relationship between emulsion stability and polymer emulsifier concentration, the preparation of paraffin oil emulsions by hydroxypropyl methylcellulose (HPMC) was carried out with HPMC concentrations below the overlapping concentration (C(*)) of HPMC. The stability of the emulsions incorporating HPMC was investigated by measuring the creaming velocity, volume fraction of emulsified paraffin oil, oil droplet size, and some rheological responses such as the stress-strain sweep curve and strain and frequency dependences of dynamic viscoelastic moduli. The paraffin oil was almost emulsified by HPMC above C(*)/20: the volume fraction of paraffin oil in the emulsion was higher than 0.

Surface dilatational moduli of poly(vinyl acetate) (PVAc) and PVAc-poly(n-hexyl isocyanate) (PHIC) blend films at the air-water interface.

Surface dilatational moduli of poly(vinyl acetate) (PVAc) film and blend films of PVAc and poly(n-hexyl isocyanate) (PHIC) were measured at the air-water interface. PVAc formed a film that was looser and also more stable against strain than the PHIC film. The apparent surface dilatational modulus and surface pressure of the blend films were superimposed on the lower concentration of PVAc, irrespective of the composition of PVAc.

Rapid determination of atropine and scopolamine content in scopolia extract powder by HPLC.

A rapid method that does not require a complicated preparation was developed for determining by HPLC the content of atropine (At) and scopolamine (Sc) in a sample of scopolia extract powder. The sample solution for HPLC was extracted using 0.1 mol/L HCl/methanol (8:2).

Molecular weight dependence of LB morphology of poly(n-hexyl isocyanate) (PHIC).

The morphologies of Langmuir-Blodgett (LB) films of two fractionated poly(n-hexyl isocyanate) (PHIC) and those of their binary mixtures were observed by AFM, together with those of an unfractionated PHIC. The low molecular weight PHIC formed random packing of bundles consisting of rigid rods, while the high molecular weight PHIC formed random packing of bundles consisting of hairy rods. Bundle interpenetration was observed only for the latter in the semidilute regime.

Molecular weight dependence of surface dilatational moduli of poly(n-hexyl isocyanate) films spread at the air-water interface.

The surface dilatational modulus of the monolayer of a well-known semiflexible polymer, poly(n-hexyl isocyanate) (PHIC), at the air-water interface was measured as a function of the molecular weight of PHIC. In the dilute regime, the surface dilatational modulus of PHIC showed a linear response over a measured strain range of 5%-20%. The modulus could be well-separated into the elastic component E' and the viscous component E'', irrespective of molecular weight of PHIC.

Stabilities and rheological properties of coagulated silica sols formed from fumed silica suspensions in the presence of hexadecyltrimethylammonium chloride.

The stability and rheological response of coagulated silica sols formed from fumed silica suspensions were investigated in aqueous KOH solution at pH 11 upon the addition of hexadecyltrimethylammonium chloride (C(16)TAC) as functions of silica and surfactant concentration. The coagulated silica sols with negative charges are stable at given concentration ranges of silica and C(16)TAC, and the C(16)TAC molecules are completely adsorbed on the silica surface in these ranges. The average hydrodynamic diameters of the coagulated silica colloidal sols at C(16)TAC concentrations from 1.

Simple and rapid analysis of sennoside A and sennoside B contained in crude drugs and crude drug products by solid-phase extraction and high-performance liquid chromatography.

The sennoside A (SA) and sennoside B (SB) contents of various samples of crude drugs were determined using solid-phase extraction (SPE) and HPLC. The samples examined were crude drugs (senna leaf, senna pods, and rhubarb), conventional crude drug products, and Kampo formulations. The sample solution was purified using an Oasis MAX cartridge, which has strong anion-exchange and reversed-phase properties.

Effects of perfluorosulfonic acid adsorption on the stability of carbon black suspensions.

Carbon black particles were stabilized by the adsorption of perfluorosulfonic acid (PFSA) onto their surfaces in a mixture of water and isopropyl alcohol. The resulting carbon black suspensions were characterized by measurements of the adsorbed amounts of PFSA, the hydrodynamic diameter of carbon black particles with adsorbed PFSA, and by steady state shear viscosity measurements as functions of the PFSA and carbon black particle concentrations. An equilibrium adsorption of PFSA on carbon black particles was established within 1 day, and the resulting adsorption isotherm was dependent on the carbon black particle concentration; the amounts of adsorbed PFSA decreased with increased carbon black particle concentration.

Simple and rapid analysis of aristolochic acid contained in crude drugs and Kampo formulations with solid-phase extraction and HPLC photodiode-array detection.

Simple and rapid analysis of aristolochic acid (AA) in crude drugs and Kampo extracts using a solid-phase extraction method and HPLC-PDA analysis was investigated. Extraction of AA from samples was accomplished by adding methanol containing 1% ammonia. The addition of ammonia ionized the AA of acidic substances so that they adhered to an acrylamide copolymer of a strong anion exchange resin (Sep-Pak QMA) coupled to diol silica easily.

Rheological properties of colloidal gels formed from fumed silica suspensions in the presence of cationic surfactants.

Rheological responses of colloidal gels formed from fumed silica suspensions in aqueous KOH solution at pH 11 by the addition of cationic surfactants, such as dodecyltrimethylammonium chloride (C12 TAC) and hexadodecyltrimethylammonium chloride (C16 TAC) have been investigated as functions of silica and surfactant concentrations. Stable and aggregated fumed silica suspensions with negative charges cause gelling by adding the cationic surfactants through electrical neutralization of their micelles. The resulting critical strain and storage modulus of the gelled silica suspension increase with an increase in the surfactant concentration, irrespective of the cationic surfactant.

Structural control of peptide-coated gold nanoparticle assemblies by the conformational transition of surface peptides.

Gold nanoparticles having peptide chains on the surfaces have been prepared yb ring-opening polymerization of gamma-methyl L-glutamate N-carboxyanhydride with fixed amino groups on the nanoparticle surface as an initiator. The number of peptide chains on the surface was adjusted to ca. 2 molecules per gold nanoparticle by controlling the number of fixed amino groups on the surface.

pH-induced reversible conformational and morphological regulation of polyleucine grafted polyallylamine assembly in solution.

One of the essential parts in the molecular mechanism of biological properties is the structural changes of proteins induced by stimuli. An amphiphilic copolymer, poly(L-leucine) grafted polyallylamine as a simple model of proteins, has been prepared by NCA polymerization with free amino groups of polyallylamine as an initiator. Here, we report the pH-induced reversible conformational and morphological regulation of the amphiphilic copolymer, whose hydrophobic peptide graft chains have no pH-sensitive groups, in an aqueous solution containing 50 vol % trifluoroethanol.

AFM studies on LB films of poly(n-hexyl isocyanate), poly(vinyl acetate), and their binary mixtures.

LB films of rigid-rod-like poly(n-hexyl isocyanate) (PHIC), flexible poly(vinyl acetate) (PVAc), and binary mixtures of PHIC as well as of PHIC and PVAc transferred on a mica surface from the air-water interface were observed by AFM. The grain structure of three individual PHIC samples in the AFM images changed shape from a rigid rod to a coiled rod with an increase in the molecular weight due to changes in the chain rigidity of PHIC. On the other hand, the AFM image of PVAc was similar to that of a mica surface, indicating that PVAc forms a uniform and homogeneous film.