Assay of the chiral organophosphate, soman, in biological samples

The anticholinesterase, soman, (CH3)3CC(H)CH3O(CH3)P(O)F, consists of four stereoisomers assigned as C(+/-)P(+/-)-soman in which C stands for chirality in the pinacolyl moiety and P for chirality at phosphorus. The four stereoisomers are separated by gas chromatography on an optically active Chirasil-Val column, synthesized and coated in house, or on a Chirasil-Val column identical with the commercially available column when combined with a Carbowax 20M column. This method in combination with an assay based on acetylcholinesterase inhibition shows that the two isomers which do not have anticholinesterase activity, i.e. C(+/-)P(+/-)-soman, are rapidly degraded in rat blood due to hydrolysis by phosphorylphosphatases. Epimeric soman isomers, e.g. C(+/-)P(-)-soman, can be separately assayed on a Carbowax or a CPSil 8 column, using 2H-labeled soman isomers as internal standards. 2H-labeled soman stereoisomers serve as internal standards in GC-assay of all four stereoisomers on Chirasil-Val. For work-up of the four stereoisomers from rat blood the sample is first stabilized by acidification to pH 4.2 at 0 degree C to suppress hydrolysis by phosphorylphosphatases, addition of aluminum ions for complexation of fluoride ions to prevent regeneration of C(+/-)P(-)-soman by free fluoride ions from soman-inhibited carboxylesterase, and addition of (CH3)3CCH2O(CH3)P(O)F to occupy covalent binding sites for C(+/-)P(-)-soman, before extraction with a Sep-Pak C18 cartridge and elution with ethyl acetate. Using a splitless or on-column injection technique and alkali flame ionization detection, the minimum detectable concentration is 30 pg/3-ml blood sample.     

State-of-the-art of NORM nuclide determination in samples from oil and gas production: Validation of potential standardization methods through an interlaboratory test programme

Gas and oil companies frequently encounter build up of Naturally Occurring Radioactive Material (NORM) in their production and processing facilities. In the Netherlands NORM is subject to strict national regulations and, consequently, installations have to be screened on a regular basis. The availability of accurate and reliable NORM sampling and analysis techniques is therefore essential. A number of years ago, the Nederlandse Aardolie Maatschappij B.V. (NAM) actively initiated an investigation on analysis techniques for NORM samples from gas and oil companies. Within this framework, Shell Research Amsterdam organized a four-stage interlaboratory test programme in which representative samples of increasing complexity were analyzed by a number of Dutch institutes. Whereas a large spread in results was observed in the first stage, results in the last stage deviated less than ±10% from the values certified by an independent referee institute, even for comple, sludge samples. It was found that in particular the use of different values for the -yields and branching ratios amongst the institutes was responsible for the initial spread.     

Power-law blinking in the fluorescence of single organic molecules.

The blinking behavior of perylene diïmide molecules is investigated at the single‐molecule level. We observe long‐time scale blinking of individual multi‐chromophoric complexes embedded in a poly(methylmethacrylate) matrix, as well as for the monomeric dye absorbed on a glass substrate at ambient conditions. In both these different systems, the blinking of single molecules is found to obey analogous power‐law statistics for both the on and off periods. The observed range for single‐molecular power‐law blinking extends over the full experimental time window, covering four orders of magnitude in time and six orders of magnitude in probability density. From molecule to molecule, we observe a large spread in off‐time power‐law exponents. The distributions of off‐exponents in both systems are markedly different whereas both on‐exponent distributions appear similar. Our results are consistent with models that ascribe the power‐law behavior to charge separation and (environment‐dependent) recombination by electron tunneling to a dynamic distribution of charge acceptors. As a consequence of power‐law statistics, single molecule properties like the total number of emitted photons display non‐ergodicity.     

Blocking of capillaries as fouling mechanism for dead-end ultrafiltration

In this paper plugging of capillaries in the potting is investigated. A lot of research has been done on fouling of the membrane surface (pore blocking, cake filtration) but research on other types of membrane fouling like plugging of capillaries is not so common. Experiments were performed with a lab-scale test installation under constant flux conditions with synthetic feed water containing ferric hydroxide flocks as a fouling component. The experiments showed that during operation capillaries became blocked by fouling plugs. The presence of blockages, especially in the potting at the concentrate side of the capillaries, could not be detected by measuring the clean water resistance. However such blockages did result in an increased forward flush pressure. A combination of the clean water resistance and the forward flush pressure is suitable for determining the fouling of a membrane and the effectiveness of a cleaning procedure. The part of the capillaries in the potting is not backwashed and therefore the hydraulic as well as the chemical cleaning is not efficient at this place.     

A new method for the quantitative continuous elution and collection of TLC Spots without damaging the layer

Summary A method is described which combines the attractive properties of ascending TLC with the advantage of a continuous removal and collection of the products successively reaching the top. This is achieved by using as support for the thin layer a glass capillary which continuously removes the solvent reaching the top by means of pressure applied from outside, without damaging the layer. The fractions thus obtained are led either directly to some detecting device or to a microfraction collector in order to be analyzed later on. An auxiliary device has been constructed which allows the application of the component mixture at the bottom of the layer without touching the layer. The same layer can now be used repeatedly; its performance does not decrease after at least ten runs. Micro-weighing is used as detection method.

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Zusammenfassung Es wird ein Verfahren beschrieben, das die vorteilhaften Eigenschaften der aufsteigenden Dünnschicht-Chromatographie mit der kontinuierlichen Abnahme und Sammlung des Eluates verbindet. Dies wird dadurch erreicht, daß die Dünnschicht auf einer Capillare aufgetragen ist, die die am oberen Rand ankommende Flüssigkeit unter Einwirkung eines äußeren Drucks laufend ableitet, ohne daß die Schicht geschädigt wird. Die einzelnen Fraktionen werden in einem Kollektor gesammelt oder unmittelbar einem geeigneten Detektor zugeleitet. Hier wird die Mikrowägung zu diesem Zweck benutzt. Zum Auftragen der Probelösung wurde eine Hilfsvorrichtung entwickelt, durch die es ermöglicht wird, die Schicht nicht zu berühren und mehrfach zu benutzen.

     

The influence of crystallinity on the secondary glass transition in polycarbonate

Summary Dynamic mechanical properties of polydian carbonate were measured with a vibrating reed method for various degrees of crystallinity (up to ca. 20 %). The explored temperature region was from — 180 °C to 120 °C; the frequency was about 100 Hz. Crystallinity was measured by density and thermal measurements.In the region of the -relaxation in polydian carbonate crystallinity appears to have no influence on tg . The storage modulus increases somewhat with increasing crystallinity and consequently the loss compliance decreases in the region of the -relaxation.

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Zusammenfassung Dynamisch-mechanische Eigenschaften des Polykarbonats von BisphenolA, wurden mit Hilfe der vibrating-reed-Methode für verschiedene Kristallisationsgrade gemessen. Der Temperaturbereich war von — 180 °C bis 120°C; die Frequenz war etwa 100 Hz. Die Kristallinität wurde aus Messungen der Dichte und der Schmelzenthalpie bestimmt. Es zeigte sich im Gebiet der -Relaxation kein Einfluß der Kristallinität auf tg .Der Modul nimmt mit der Kristallinität etwas zu und dementsprechend nimmt die Verlustkomplianz im Gebiet der -Relaxation ab.

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With 6 figures and 2 tables     

Reactions of halogenoquinolizinium bromides with aniline,isopropylamine and liquid ammonia

The reactions of quinolizinium bromide ( QB ) and its four monobromo derivatives with aniline, isopropylamine and liquid ammonia have been investigated. With aniline 2- and 4-bromo QB undergo substitution, whereas 1- and 3-bromo QB do not react at all. With liquid ammonia all bromo derivatives and the parent compound react with ring opening. This diversity in the reaction course is explained in terms of the HSAB principle. 2-BromoQB reacts with isopropylamine under formation of 2-isopropylamino QB . Two molecules of isopropylamine are involved in this substitution, as we isolated an intermediate: 1-isopropylamino-4(2-pyridyl)-3-isopropyliminio-1-butene bromide ( 13 ). The structure of the latter compound was confirmed by X-ray analysis.