Clicked (AB)2C‐type miktoarm terpolymers: Synthesis,thermal and self‐assembly properties,and preparation of nanoporous materials

A well‐defined (PEO‐PS)₂‐PLA miktoarm terpolymer ( 1 ) was synthesized by stepwise click reactions of individually prepared poly(ethylene oxide) (PEO), polystyrene (PS, polymerized by atom transfer radical polymerization), and polylactide (PLA, polymerized by ring‐opening polymerization) blocks. As characterized by differential scanning calorimetry and small‐angle X‐ray scattering techniques, the terpolymer self‐assembled into a hexagonal columnar structure consisting of PLA/PEO cylindrical cores surrounded by PS chains. In contrast, the ion‐doped sample ( 1‐Li⁺ ) with lithium concentration per ethylene oxide = 0.2 exhibited a three‐phase lamellar structure, which was attributed to the microphase separation between PEO and PLA blocks and to the conformational stabilization of the longest PLA chain. The two‐phase columnar morphology before the ion doping was used to prepare a nanoporous material. PLA chains in the cylindrical core region were hydrolyzed by sodium hydroxide, producing nanopores with a pore diameter of about 14 nm. The resulted nanoporous material sank to the bottom in water, because of water‐compatible PEO chains on the walls. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Book reviews

This work is a thorough investigation on the major operating parameters of the programmable temperature vaporisation (PTV) inlet used for gas chromatographic injection, including injection mode and volume, inlet temperature, vent and purge flow rates. The results clearly demonstrate the advantage of large volume injection in enhancing the detection of polybrominated diphenyl ethers (PBDEs). Partial loss of injected PBDEs occurred during solvent venting and due to incomplete sample transfer. Such loss was minimised by lowering the initial inlet temperature and vent flow and elevating the final inlet temperature. The results show that 50 mL/min vent flow, as low as 0°C initial and higher than 300°C final inlet temperatures produced the relatively high responses. Two mass spectrometric parameters were also evaluated. Indoor dust, lake sediment and human placenta tissue samples were analysed to demonstrate reliability and sensitivity improvement of the PTV large volume injection.     

Solid-Phase Extraction and Capillary Gas Chromatographic Determination of Triazine Herbicides in Water

Abstract

A facile and efficient method is described for the determination of trace quantities of triazine herbicides, terbutryn, prometryn and ametryn in water. The procedure involved preconcentration of water samples by sorption on chromatographic grade silica gel particles with chemically modified surface, being covalently bonded with a nonofunctional C₈H₁₇ group. This was followed by solvent desorption with 2-propanol. The determinative step was achieved by capillary gas chromatography on Supelcowax-10 fused silica column using a nitrogen-phosphorus detector. The limit of detection was 0.1 μg-10 μgL^?1.     

Analysis of PCBs in Biotic Matrices by Two-Dimensional GC-ECD

Abstract

The suitability of three GC-ECD systems for the separation of a model mixture containing various congeners of PCBs together with persistent chlorinated aromatics (pesticides and their metabolites, industrial chemicals) was tested. Analyses were performed on two parallel capillaries, the stationary phase of one of them was always in routine practice very common 5% phenyl-methylpolysiloxane, the second one was either 50% phenylmethylpolysiloxane or 7% phenyl-7% cyanopropyl-methylpolysiloxane. The number of unresolved (coeluted) analytes was significantly reduced in these systems and thus unbiased quantitation of PCBs and other components used for regulation was possible. The utilization of this type of multidimensional chromatography for rapid and reliable analysis of real samples (fish oil, human fat) was documented.     

高效液相色谱法同时测定生物质乳酸发酵液中有机酸及糖类化合物

建立了高效液相色谱(HPLC)同时测定生物质乳酸发酵液中有机酸及糖类的分析方法。使用Bio-Rad Aminex HPX-87H色谱柱,以5 mmol/L的H2SO4为流动相,在柱温55 ℃,流速0.6 mL/min条件下,采用示差折光检测器进行检测。结果表明,该方法可在17 min内实现发酵液中各种有机酸和糖类化合物等的完全分离与定量,6种有机酸和3种糖类化合物在0.15～5.19 g/L范围内的线性关系良好,回归方程的线性相关系数在0.9998以上。将该法用于米根霉发酵液的检测,两个水平的加标回收率为96.91%～103.11%,相对标准偏差(n=6)为0.81%～4.61%。该法适用于微生物发酵液中多种有机酸和糖类的快速、高效分离和定量测定。     

A Photochemistry Technique Using Ultraviolet Irradiation Followed by Gas-Liquid Chromatography to Confirm the Identity of Some Organochlorine Pesticides

Abstract

A procedure involving ultraviolet (UV) irradiation followed by gas-liquid chromatographic (GLC) detection of photodecomposition products to confirm the identity of selected organochlorine pesticides is described. The Irradiation intensity was standardized by determining the position relative to the UV source which resulted in equal GLC peak heights for the parent compound and major photo-decomposition product after 8 minutes of exposure of a solution of heptachlor epoxide in isooctane. Chromatograms showing photo-decomposition patterns for 33 compounds are presented. Observations and comments on the applicability of this technique to organo-chlorine pesticide residue confirmation are reported.     

Use of Micelles in the TLC Separation of Polynuclear Aromatic Compounds and Amino Acids

Abstract

The polynuclear aromatic compounds (PNA): anthracene, napthalene, phenanthrene, pyrene, pyrenecarboxaldehyde, benzo (a) pyrene, benzo (e) pyrene, perylene and fluorene can be chromatographed on polyamide TLC sheets using an aqueous micellar solution cf sodium dodecylsulfate (SDS) as the mobile phase. Reversed micellar solutions (of sodium dioctylsulfosuccinate) were used in a reverse phase chromatographic separation of amino acids. Some amino acids tended to streak slightly rather than move as discrete spots. Conditions could be adjusted, however, so that most of the amino acids and all PNA's would move as spots.     

Liquid Chromatograph Detector for Trace Analysis of Non-Volatile N-Nitroso Compounds

Abstract

A Thermal Energy Analyzer has been interfaced to a high performance liquid chromatograph. The hplc-TEA system can be used for analysis of nanogram amounts of N-nitroso compounds.     

Preparation of Chiral Amino Esters by Asymmetric Phase‐Transfer Catalyzed Alkylations of Schiff Bases in a Ball Mill

The asymmetric alkylation of Schiff bases under basic conditions in a ball mill was performed. The starting Schiff bases of glycine were prepared beforehand by milling protected glycine hydrochloride and benzophenone imine, in the absence of solvent. The Schiff base was then reacted with a halogenated derivative in a ball mill in the presence of KOH. By adding a chiral ammonium salt derived from cinchonidine, the reaction proceeded asymmetrically under phase‐transfer catalysis conditions, giving excellent yields and enantiomeric excesses up to 75 %. Because an equimolar amount of starting material was used, purification was greatly simplified.