Analysis of methylisothiazolones by ion pair high-performance liquid chromatography after pre-column derivatisation

Summary Following part I which describes a high-performance liquid Chromatographic determination of methyliso-thiazolones after pre-column derivatization, part II presents a method based on it, for isolation and quantification of these preservatives in cosmetic preparations, especially those with emulsion-like bases. The emulsion is destroyed by extraction in a two-phase-system with simultaneous conversion of the methylisothiazolones. Most of the matrix constituents stay in the organic phase because of their apolar character whereas the highly polar derivatives enter the aqueous phase. Sodium nicotinate is suitable for quantification by the method of internal standard. The recoveries of both methylisothiazolones lie within 90%.

---

Analytik von MethylisothiazoIonen durch Ionenpaar-HPLC nach Vorsäulen-DerivatisierungTeil II. Bestimmung von 2-Methyl-3(2H)-isothiazolon und 5-Chlor-2-methyl-3(2H)-isothiazolon in Cosmetica

---

Part I see: Fresenius Z Anal Chem (1988) 332:813–816

---

Active ingredient Ia+Ib     

Capillar-gas-chromatographische Bestimmung von Alkylphenolen in Harn

Zusammenfassung Es wird ein empfindliches und zuverlässiges Verfahren beschrieben, mit dem die 10 wichtigsten phenolischen Metabolite von Benzol, Toluol, den Xylolen und Ethylbenzol im Harn bestimmt werden. Der mit Schwefelsäure angesäuerte Harn wird einer Wasserdampfdestillation unterworfen. Das Destillat wird mit Dichlormethan extrahiert und im Stickstoffstrom eingeengt (Anreicherungsfaktor 10). Die gas-chromatographische Bestimmung erfolgt auf einer 30 m-Quarzcapillare (SE 54) mit FID-Detektion. Zur Kalibrierung werden wäßrige Standards in gleicher Weise aufbereitet. Als innerer Standard wird 3-Ethylphenol zu Beginn der Aufarbeitung zugesetzt. Für die Alkylphenole (Phenol, o- und p-Kresol; dl-1- und 2-Phenylethanol; 3-Methylbenzylalkohol; 2-Ethylphenol; 2,4-, 2,3- und 3,4-Dimethylphenol) wurde die Präzision in der Serie bei jeweils 2 Konzentrationen untersucht (n=10, ¯x=0,9–41,7 mg/l, s=2,3–16,8%). Die Wiederfindungsraten lagen zwischen 89 und 109%. Die Nachweisgrenze betrug 0,3 mg/ l. Die Linearität des Verfahrens wurde bis zu 50 mg/l überprüft.

---

Determination of alkylphenols in urine by capillary gas chromatography

Summary A sensitive and reliable procedure is described for the determination of ten most important phenolic metabolites of benzene, toluene, xylenes and ethylbenzene. The urine is acidified with sulphuric acid and simultaneously steam-distilled. The distillate is extracted with dichloromethane. The organic phase is reduced in volume for tenfold enrichment. The gas-chromatographic determination is performed on a fused silica capillary (SE 54; 30 m) by FID. For calibration, aqueous standards are subjected to the same treatment as the urinary samples. 3-Ethylphenol is used for internal standardization. For ten alkylphenols (phenol; o- and p-cresol; dl-1- and 2-phenylethanol; 3-methylbenzyl alcohol; 2-ethylphenol; 2,4-, 2,3- and 3,4-dimethylphenol) within-series imprecision has been evaluated for two concentrations (n=10, ¯x=0.9–41.7 mg/l, s=2.3–16.8%). The recovery rates range between 89 and 109%. The detection limit is 0.3 mg/l. Linearity has been tested up to 50 mg/l.

     

Synthesis, characterization, and X-ray crystal structure of a gallium monohydroxide and a hetero-bimetallic gallium zirconium oxide

A monomeric hydroxide of gallium, LGa(Me)OH, containing terminal hydroxide and methyl groups was prepared by the hydrolysis of LGa(Me)Cl in the presence of N-heterocyclic carbene and water [L = HC{(CMe)(2,6-i-Pr2C6H3N)}2] in high yield and in a pure form. LGa(Me)OH was used as a synthon to assemble the first hetero-bimetallic compound with a Ga-O-Zr core, [(LGaMe)(Cp2ZrMe)](mu-O).     

Reversible activation of diblock copolymer monolayers at the interface by pH modulation, 1: Lateral chain density and conformation

This study focuses on the design of chemically regulated surfaces that allow for reversible control of the interactions between biological matter (cells and proteins) and planar substrates. As a tunable interlayer, we use a monolayer of a near-monodisperse poly[2-(dimethylamino)ethyl methacrylate-block-methyl methacrylate] (PDMAEMA-PMMA) diblock copolymer. Owing to the relatively large fraction (50%) of the hydrophobic PMMA block, this copolymer forms a stable Langmuir monolayer at the air/water interface. Both in situ and ex situ film balance experiments suggest that the hydrophilic PDMAEMA block adsorbs to the air/water interface in its uncharged state (pH 8.5), but stretches into the subphase in its charged state (pH 5.5). Optimization of the preparation protocols enables us to fabricate stable, homogeneous diblock copolymer films on hydrophobized substrates via Langmuir-Schaefer transfer at well-defined lateral chain densities. Ellipsometry and X-ray reflectivity studies of the transferred films confirm that the film thickness can be systematically regulated by the lateral chain densities. The transferred copolymer films remain stable in water for about a week, suggesting that they are promising materials for the creation of pH-controlled solid substrates for the support of biological matter such as proteins and cells.