Separation of T-MAZ ethoxylated sorbitan fatty acid esters by reverse phase chromatography

Summary The method for determination of T-MAZ ethoxylated sorbitan fatty acid esters is described. This work demonstrates that with a less retentive C₈ alkyl bonded phase packing, reverse phase chromatography can be used to analyze nonionic polymer mixtures with a molecular weight range of 900 to 1500. Using a gradient elution, a complete separation of T-MAZ oligomers was achieved, comparable to that obtained by Supercritical Fluid Chromatography (SFC). Isocratic elution is used to quantify T-MAZ and the detection limit is 321 ppm, which is acceptable for polymers with high molecular weights and no UV-absorbing chromophores. This work also shows the comparison of the separations of T-MAZ using gel permeation chromatography and reverse phase chromatography.     

Silicon-containing esters of α-cyanoacrylic acid: synthesis and properties

A number of cyanoacetates have been synthesized: cyanoacetoxymethyitrimethylsilane (1), cyanoacetoxymethylpentamethyldisiloxane (2), cyanoacetoxyetoxymethylpentamethyldisiloxane (3). They were converted by the Knoevenagel reaction to novel esters of a-cyanoacrylic acid (4–13) containing silicon atoms in the ester groups and having the general formula RCH=C(CN)COOCH₂X (where R=H, 4-MeOC₆H₄, MeCH=CH, 2-furyl; X=SiMe₃, SiMe₂OSiMe₃, CH₂OCH₂SiMe₂OSiMe₃). These compounds are capable of copolymerization with esters of cyanoacrylic acid which are the precursors to adhesives for cold curing.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 949–952, May, 1993.     

Condensation of Pyrazol-5-ones Unsubstituted in the Position 1 with β-Keto Esters. Synthesis of Pyrano[2,3-c]pyrazol-6-ones

The thermal condensation of β-keto esters and N-unsubstituted pyrazol-5-ones gives good yields of pyrano[2,3-c]pyrazol-6-ones. Other potential routes for the condensation are not realized. The β-diketones react via another scheme to form noncyclic reaction products.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 444–449, March, 2005.     

High-throughput analysis of phthalate esters in human serum by direct immersion SPME followed by isotope dilution–fast GC/MS

Solid-phase microextraction (SPME) coupled to gas chromatography/mass spectrometry (GC/MS) was applied to the determination of phthalate esters in human serum. The present method decreased the sample preparation time by a factor of 50 by using direct immersion SPME with an 85-m polyacrylate fiber to extract phthalate esters from the matrix. The use of fast GC/MS further improves total analysis time when compared to other techniques. Isotope dilution was successfully applied to improve the precision, reproducibility, and repeatability of the SPME method. The linear dynamic range spans several orders of magnitude from low ppb to ppm levels, and the LOD for the method is 15 pg L^–1 on average with RSDs less than 4% for the six phthalate esters included in this study.     

Some diazinon analogues containing the 4-trifluoromethyl group

Summary Diazinon analogues were prepared containing trifluoromethyl in place of the 4-methyl group and methylthio (2 a), amino (2 b), dimethylamino (2 c), methylphenylamino (2 d), or isopropyl (2 e) in position 2 of the pyrimidine ring. The most active analogue (2 b) was less than half as insecticidal as Diazinon.

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Einige Diazinon-Analoga mit einer 4-Trifluormethylgruppe

Zusammenfassung Es wurden Diazinon-Analoga hergestellt, die anstelle der 4-Methylgruppe die Trifluormethylgruppe und in 2-Position des Pyrimidin-Rings verschiedene Substituenten enthielten.2 a: 2-Methylthio-;2 b: 2-Amino;2 c: 2-Dimethylamino-;2 d: 2-Methylphenylamino-;2 e: 2-Isopropyl-. Das aktivste Analogon war2 b, das allerdings auch weniger als die Hälfte der insektiziden Wirkung des Diazinon aufwies.

     

The Use of Principal Component Analysis for the Study of the Interaction of Anionic Surfactants with Hydroxypropyl-β- Cyclodextrin

The interaction of 11 sulfosuccinic acid ester anionic surfactants with hydroxypropyl--cyclodextrin (HPCD) were determined with reversed-phase thin-layer chromatography and the relative strength of interaction was calculated. The relationship between the strength of interaction and the physicochemical parameters of anionic surfactants was elucidated with principal component analysis (PCA). HPCD interacted with the anionic surfactants decreasing their hydrophobicity. The distribution of the points of the strength of interaction and physicochemical parameters on the two dimensional nonlinear map of PC loadings suggested that the strength of interaction between the anionic surfactants and HPCD is of mixed steric character, with hydrophobic and electronic forces being involved in the interaction.     

Gas chromatographic analysis of free fatty acids and glycerides of milk fat using tetramethylammonium hydroxide as catalyste

Summary Tetramethylammonium hydroxide in methanol has been proposed as a catalyst for preparing methyl esters of both free fatty acids and glycerides of fats. Nevertheless, procedures normally recognized as suitable can be inadequate when the fat under study contains noticeable amounts of low relative molecular mass esters. The method using tetramethylammonium hydroxide has been examined and modified in order to analyze milk fats by capillary GC. The pyrolysis methylation of free fatty acids in capillary injectors has been also studied. The modified method was satisfactory for both neutral and acid milk fats.     

Isopropoxyaluminum 1,1′-biphenyl-2-oxy-2′-perfluorooctanesulfonamide as a catalyst for Tishchenko reaction

Isopropoxyaluminum 1,1′-biphenyl-2-oxy-2′-perfluorooctanesulfonamide (3) has been evaluated as an aluminum-based catalyst for the Tishchenko reaction. Compound 3 was found to exert high catalytic activity in the reaction with aliphatic aldehydes and also enabled smooth dimerization of enolizable aldehydes. This advantage was highlighted by the quantitative formation of ethyl acetate from acetaldehyde by the present system.     

Gas chromatographic analysis of the carboxylic acid composition of valeriana extracts

Summary The gas chromatographic analysis for the qualitatived and quantitative analysis of carboxylic acids present in valeriana extracts in the form of their n-butyl and trifluoroacetylated n-butyl esters is presented. On the basis of the proposed method the amount of four valtrate species, as well as the free carboxylic acid content of valeriana tinctures can be calculated. It is shown that extracts of Valeriana officinalis obtained by using ethanol, acetone, or chloroform as the solvent contain the same carboxylic acids. The determined components, are: formic, acetic, propionic, isobutyric, n-butyric, lactic, isovaleric, n-valeric, 2-hydroxy-isovaleric, isocaproic, n-caproic, caprylic, malic, capric, lauric, myristic, valerenic, palmitic, stearic, arachic, behenic, erucic and lignoceric acids.     

Catalytic hydrolysis of phosphate esters in microemulsions

We have continued our kinetics investigation of the iodosobenzoate (IBA) catalysis of the hydrolysis of p-nitrophenyl diphenyl phosphate (PNDP), in microemulsion media composed of hexadecane in water stabilized by cetyltrimethylammonium bromide and 1-butanol over a range of water mass fractions. We have examined two iodosobenzoic acid derivatives (5-nitro-2-iodosobenzoic acid and 5-octyloxy-2-iodosobenzoic acid) as catalysts. In addition, we have determined by³¹P FT-NMR techniques that the major product of the hydrolysis of PNDP, both in IBA catalyzed and in uncatalyzed media, is diphenylphosphate.