Evaluating the residence time for cesium removal from simulated Hanford tank wastes using SuperLig® 644 resin

Batch contact and column experiments were performed to evaluate the effect of residence time on cesium removal from two simulated Hanford tank wastes using SuperLig^® 644 resin. The two waste simulants mimic the compositions of tanks 241-AZ-102 and 241-AN-107 at the U.S. Department of Energy (DOE) Hanford site. A single column made of glass tube (2.7-cm i.d.), which contained ~100 ml of H-form SuperLig^® 644 resin was used in the column experiments. The experiments each consisted of loading, elution, and regeneration steps were performed at flow rates ranging from 0.64 to 8.2 BV/h for AZ-102 and from 1.5 to 18 BV/h for AN-107 simulant. The lowest flow rates of 0.64 and 1.5 BV/h were selected to evaluate less than optimal flow conditions in the plant. The range of the flow rates is consistent with the River Protection Project design for the waste treatment plant (WTP) columns, which will operate at a flow rate between 1.5 to 3 BV/h. Batch contact experiments were also performed for two batches of SuperLig^® 644 to determine the equilibrium distribution coefficients (K _d) as a function of Cs concentration. The column experiments revealed that adequate column loading for Cs on SuperLig^® 644 (50% breakthrough at 100 bed volumes) can be achieved for the two simulated Hanford tank wastes at the nominal plant flow rates of 1.5 and 3 BV/h (residence times 40 and 20 minutes). The column performance was marginally improved at flow rates below the nominal rates. At flow rates higher than the nominal, the Cs loading deteriorated significantly. The SuperLig^® 644 was eluted effectively with 0.5M nitric acid. The elution required approximately 15 BVs to reduce Cs concentration to below 1% of initial Cs concentration in the feeds.     

Alkenyl selenols and selenocyanates: synthesis, spectroscopic characterization by photoelectron spectroscopy, and quantum chemical study

Vinyl, allyl, and homoallyl selenols were easily prepared by a chemoselective reduction of the corresponding selenocyanates with aluminum hydrides. Two stable vinyl and five stable allyl conformers of both series were predicted on the potential-energy surface. The interaction of SeH or SeCN groups with the vinyl group has been investigated with UV photoelectron spectroscopy and quantum chemical calculations, using the MP2/cc-pVTZ and B3LYP/cc-pVTZ levels. In the vinyl derivatives, a surprisingly strong direct conjugation of the selenium lone electron pair and the C=C double bond was observed. On the other hand, in allyl position the selenium lone pair is independent on the C=C double bond, and the hyperconjugation between the Se-C bond and the double bond is the ruling effect. Thus is clarified the type and extent of the interaction between the SeH or SeCN group and the unsaturated moiety.     

O-silylated enolate phenylthialkylation: A synthesis of α,β-unsaturated 5- and 6-membered lactones.

ZnBr₂-catalysed phenylthioalkylation of ketene bis(trimethylsilyl)acetals, obtained from carboxylic acids, with appropriate α-chlorosulphides can be used to prepare γ- and δ- lactones.     

Quantitative analysis by high-performance liquid chromatography atmospheric pressure chemical ionization mass spectrometry: The determination of the renin inhibitor CP-80,794 in human serum

A specific method was developed for the quantitative determination of the renin inhibitor CP-BO,794. Serum extracts containing the drug and an internal standard were injected into a standard reverse-phase high-performance liquid chromatography (HPLC) column. The mobile phase, methanol/water (8/2), flowed at 1 ml/min through the column and then via a heated nebulizer interface into a corona discharge atmospheric pressure chemical ionization source. The assay minimum limit of quantification was 50 pg/mL. It exhibits satisfactory accuracy and precision over the range 50 pg/ml, to 10 ng/mL. A minor modification of the HPLC mobile phase was necessary to attain extremely low detection limits. The addition of a structural analogue contributed to enhancing the precision of the assay.     

Barrier to internal rotation in 2,3- and 3,3-difluoropropenal and their methyl derivatives

The conformational stability and structure of 2,3-dimethylpropenal, 2,3-difluoropropenal and their 3,3-dimethyl and 3,3-difluoro derivatives were investigated utilizing ab initio calculations with 3-21G and 6-31G basis sets. For 2,3-dimethylpropenal and 3,3-difluoropropenal the s-trans was predicted to be the low-energy form. In the case of 3,3-dimethylpropenal and 2,3-difluoropropenal the s-cis was predicted by both levels of calculation to be the more stable conformer. Full optimization was performed at the transition states and the barriers to internal rotation were calculated. Methyl and fluorine substitution were found to significantly increase the barrier to interconversion in propenal. The relative change in the barrier depends on the position and the type of the substituent. The trans to cis barrier in 2,3-dimethylpropenal was calculated to be about 3 kcal mol⁻¹ greater than that in 3,3-dimethylpropenal, while the cis to trans barrier in 2,3-difluoropropenal was predicted to be about 7 kcal mol⁻¹ higher than the corresponding one in 3-3-difluoropropenal.     

Determination of trace elements in Egyptian molasses by instrumental neutron activation analysis

Multielement neutron activation analysis has been applied to the determination of macro, micro and trace amounts of Al, Br, Ca, Cl, Co, Cr, Cs, Fe, K, La, Mg, Mn, Na, Rb, Sc and V in molasses of Kom Ombo, Edfu, Armant, Naga Hammady and Abu Korkass cane sugar factories. The threshold element concentrations are acceptable and below the safety. Differences in element concentrations may be related to different botanic textures and structures, different compositions of sugar cane plants, corrosion of containers or changes in soil as a result of geochemical differentiation. The method is sensitive down to 0.038 ppm of V. The relative errors due to counting statistics are in the range of 0.2–11%.     

Microdetermination of the fluoride ion using an amplification reaction

Summary A new simple, rapid and accurate amplification micro method for fluoride determination is described. It is based on the reaction between the sparingly soluble calcium iodate and the fluoride ion. After adding isopropyl alcohol to the solution, so that its final concentration is 65%, and filtering, an equivalent amount of the iodate is obtained. The latter is titrated iodometrically resulting in a six-fold amplification of the titre. The method is reproducible over a range from 0.4–8 mg fluoride ion. The mean recovery is 99.69%, after applying a correction factor due to potassium iodate solubility.

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Zusammenfassung Ein Multiplikationsverfahren zur Mikrobestimmung von Fluorid wurde beschrieben. Es beruht auf der Umsetzung zwischen dem schlecht löslichen Calciumjodat und Fluorid. Nach Zusatz von i-Propylalkohol, bis die Lösung 65% davon enthält, wird filtriert. Die äquivalente Jodatmenge wird jodometrisch titriert. Zwischen 0,4 und 8 mg Fluorid sind die Ergebnisse reproduzierbar. Bei Anwendung eines Korrekturfaktors wegen der Löslichkeit von Kaliumjodat wurden 99,69% Fluorid wieder gefunden.

     

Synthesis of an asymmetrical tripodal tetraamine ligand and its five-coordinate copper(II) complex

A simple synthesis has been devised for the tripodal 3,3,4-tetraamine ligand N{(CH2)3NH2}2{(CH2)4NH2} (L). This ligand forms a copper(II) complex, [Cu (LH)Cl2]ClO4 (7), the structure of which has been determined by X-ray diffraction. The cation contains a five-coordinate copper atom, bonded to two chloride ions, the two propylamine groups and the tertiary nitrogen atom of the ligand; the arrangement is a distorted trigonal bipyramid, in which the two primary amine groups occupy the axial positions. The butylamine group of the ligand does not coordinate to copper but is protonated. It is involved in hydrogen bonding to the perchlorate ion. The e.p.r. spectrum of [Cu(dpt)Cl2] is very similar to that of (7), suggesting that it also has a trigonal bipyramidal structure. This revised version was published online in June 2006 with corrections to the Cover Date.     

Selection of a Representative Matrix for Calibration in Multianalyte Determination of Pesticides in Vegetables by Liquid Chromatography-Electrospray Tandem Mass Spectrometry

An analytical method for determining residues of twenty pesticides by liquid chromatography (LC) coupled to electrospray ionisation (ESI) tandem mass spectrometry (MS-MS) in eight commodities, cucumber, tomato, pepper, green bean, eggplant, zucchini, melon and watermelon, has been developed and validated. On one hand, calibration curves prepared in solvent were compared with calibration curves prepared in a blank matrix extract of each target matrix. On the other hand, calibration curves and recoveries for each commodity were compared. Cucumber was selected as potential reference matrix for the target vegetables.     

A tetra-coordinate nickel(II) complex as neutral carrier for nitrate-selective PVC membrane electrode

The potentiometric response properties and applications of a tetra-coordinate nickel(II) complex with relatively high selectivity toward nitrate ion are described. The nickel(II) complex of 5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradeca-4,6,11,13-tetraene was used as a neutral carrier into plasticized poly(vinyl chloride) (PVC) membrane. The influence of several variables was investigated in order to optimize the potentiometric response and selectivity of the electrode. The resulting membrane electrode incorporating 31.0% PVC, 61.0% dioctyl phthalate (DOP) as plasticizer, 3% methyltrioctylammonium chloride (MTOAC) as a cationic additive and 5% carrier (all w/w) demonstrates a Nernstian response slope of −59.6 mV per decade over the concentration range of 5×10⁻⁶-1×10⁻¹ M NO₃⁻. The electrode exhibits a fast response time (≤10 s), a detection limit of 2.5×10⁻⁶ M, and can be used over a wide pH range of 4-12. The electrode shows improved selectivity in comparison to most of the previously reported nitrate-selective electrodes. It was successfully applied to the determination of nitrate ion in natural water samples.