Spectrophotometric determination of copper after adsorption of its 1-phenyl-4,4,6-trimethyl(1H, 4H)-pyrimidine-2-thiol complex onto microcrystalline naphthalene

A selective Spectrophotometric method has been developed for the trace determination of copper after adsorption of its 1-phenyl-4,4,6-trimethyl(1H, 4H)-pyrimidine-2-thiol (PTPT) complex onto microcrystalline naphthalene. The complex is quantitatively adsorbed on naphthalene in the pH range 7.5–11.5, separated by filtration, dissolved in dimethylformamide (DMF) and determined spectrophotometrically at 400 nm. Beer's law is obeyed in the concentration range 2.5–37.5 g of copper in 10 ml of DMF. The molar absorptivity and Sandell's sensitivity are 1.30 × 10⁴1 · mol^–1 · cm^–1 and 0.0048g cm^–2, respectively. Ten replicate analyses of a solution containing 20.0 g of copper gave a mean absorbance of 0.410 with a relative standard deviation of 0.91 %. The interferences of various ions have been studied and the method has been validated by the determination of copper in various standard reference materials, beers, wines, human hair, goat liver and environmental samples.On leave from St. Stephen's College, Delhi 110 007, India     

Ion-exchange selectivity and chromatographic separation of trivalent metals on titanium antimonate

Summary The ion exchange selectivity of trivalent metal ions has been determined on titanium antimonate cation exchanger prepared by coprecipitation of antimony to titanium at different mole ratios. The selectivity sequence Al³⁺<Cr³⁺<Ga³⁺<In³⁺<Fe³⁺ was found for trivalent metal ions at an initial concentration of 10^–4 mol dm^–3 in nitric acid media. A high separation factor ^Ga/Al = Kd^Ga/Kd^Al, 4.8×10³, was observed for the Ga³⁺–Al³⁺ pair on titanium antimonate with an antimony to titanium ratio of 0.34. The effective separation of Ga³⁺ and In³⁺ from Al³⁺ was achieved using a 3 cm×0.5 cm i.d. column containing titanium antimonate with an antimony to titanium ratio of 0.34.     

Chromatographic separation and mass spectrometric identification of positional isomers of polyethylene glycol-modified growth hormone-releasing factor (1-29)

A one-step chromatographic method capable of separating all isomers of polyethylene glycol (PEG)-growth hormone-releasing factor (GRF) (1-29) conjugates was developed. The unmodified GRF (1-29) and seven different isomers of PEG-GRF (1-29) conjugates were separated by using a simple reversed-phase HPLC method depending on the differences of hydrophobicity due to the number and site of PEG attachment. The PEGylation sites of all isomers of PEG-GRF (1-29) conjugates were identified by determining the molecular masses of the Lys-C digested fragments with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. This study is a first report for the separation of all PEG-conjugate isomers and would be useful for further studies to find the promising conjugate by evaluating biological activity and stability of each isomer.     

硫氰酸铵-罗丹明 B-H2O的液-固体系浮选分离铜(Ⅱ)的研究

研究了硫酸铵存在下硫氰酸铵-罗丹明B-H2O的液-固体系浮选分离铜(Ⅱ)的行为及其与常见离子分离的条件.结果表明,当(NH4)2SO4用量为1.0 g,0.1 mol·L-1硫氰酸铵溶液1.5 mL和0.001 mol·L-1罗丹明B溶液2.0 mL时,铜(Ⅱ)以不溶于水的三元离子缔合物(RhB)2[Cu(SCN)4]形式在液-固两相界面定量浮选析出,而Cdd2、Mn2+、Co2+、Ni2+、Al3+等离子在此条件下不被浮选,实现了铜(Ⅱ)与这些离子的定量分离,对合成水样中微量铜(Ⅱ)进行的定量浮选分离测定,浮选富集的平均回收率达101.4%.     

Tertiary amine-mediated synthesis of microporous carbon membranes

Microporous carbon membranes were prepared on an -alumina support by a pyrolysis of cationic tertiary amine/anionic polymer composites. The precursor solutions contain a thermosetting resorcinol/formaldehyde (RF) polymer and a cationic tertiary amine. Three types of cationic tertiary amines with different chain lengths were used, such as tetramethlammonium bromide (TMAB), tetrapropylammonium bromide (TPAB) and cetyltrimethylammonium bromide (CTAB). A porous structure was produced by a decomposition of the amine and the resulting pores assisted the further gasification of the RF polymer at high temperature. The carbon/alumina membranes have thin and continuous carbon top layers with a thickness of 1 μm. Gas permeation tests were performed using single gases of CO₂, O₂, N₂, CF₄, n-C₄H₁₀ and i-C₄H₁₀, as well as binary mixtures of CH₄/n-C₄H₁₀ and N₂/CF₄ at different temperatures between 23 and 150 °C. The carbon membrane prepared using TMAB showed separation factors higher than 650 for the CH₄/n-C₄H₁₀ mixtures and higher than 8100 for the N₂/CF₄ mixture. From the permeation of pure gases with different molecular sizes, the pore sizes of the carbon membrane prepared using TMAB, TPAB and CTAB are estimated to be 4.0, 5.0 and larger than 5.5 Å, respectively, indicating that the micropore size of the carbon membranes is controllable by using different amines.     

Surface modification of soft-glass capillaries for gas chromatography by treatment with water vapour

“Leaching” or “etching” by strong mineral acids seems to be a necessary pretreatment step for the most commonly used deactivation procedures of glass capillaries by reaction with either polyethylene glycol or silylation reagents. The acidic sites which are formed on the surface during this acid treatment cannot be completely removed by the subsequent deactivation process. This drawback can be overcome by performing the leaching with water vapour, resulting in an accumulation of cations at the surface and a decrease in the number of silanol groups. Capillaries of this type show excellent properties for the chromatography of strongly basic compounds. After the wash-out of the alkaline surface layer, the acidity of the support is suited for the chromatography of strongly basic as well as strongly acidic compounds. Due to a lack of reactive acidic sites, special deactivation procedures have to be applied to capillaries produced in this way.     

Phase separation behavior of epoxy resin modified with crosslinked rubber

Low molecular weight liquid rubber (ATBN = amine terminated butadiene acrylonitrile copolymer or CTBN = carboxyl terminated butadiene acrylonitrile copolymer)–DGEBA (diglycidyl ether of bisphenol A) blends indicated upper critical solution temperature (UCST) behavior. The phase separation behavior of the neat and crosslinked rubber (ATBN, CTBN)–epoxy blends was analyzed by a laser light scattering experiment. Lauryl peroxide (LPO) was employed to crosslink the rubber during the initial annealing stage. The onset point of the phase separation in the crosslinked ATBN–epoxy system occurred later than in the case of the neat ATBN–epoxy system. However, the onset point of the phase separation process started earlier in the case of the crosslinked CTBN–epoxy system. The domain correlation length of the crosslinked rubber-added system was smaller than that of the neat rubber-added system.     

Synthesis and Absorption Properties of New Na Specific Adsorbent Li（1＋x）AlxTi（2-x）（PO4）3

A new kind of adsorbent Li（1＋x）AlxTi（2-x）（PO4）3 was synthesized by solid state reaction method. The influence of the content of doping aluminum on the adsorbent Li（1＋x）AlxTi（2-x）（PO4）3 was investigated by XRD, while the morphology of powders was observed by SEM. The investigation of the adsorption properties showed that the adsorbent can selectively adsorb sodium with the adsorption capacity of 11.76 mg/g. The optimum conditions of adsorption are at pH 10.0-11.0 in LiCl solution.     

High performance liquid chromatographic separation of dipeptide and tripeptide enantiomers using a chiral crown ether stationary phase

A chiral stationary phase (CSP) based on (-)-(18-crown-6)-2,3,11,12-tetracarboxylic acid was evaluated for the direct resolution of the enantiomers of dipeptides and tripeptides. The type and concentration of the acid and the methanol content were optimized with regard to retention time and resolution using Ala-Phe as model peptide. A mobile phase consisting of 10 mM sulfuric acid in 70% aqueous methanol was applied to the separation of a set of 16 structurally diverse dipeptides and tripeptides. Generally, the configuration of the amino acid at the N-terminus determined the enantiomer elution order. With a few exceptions the LL- and LD-enantiomers interacted stronger with the CSP compared to the corresponding DD- or DL-enantiomers. The experimental conditions also allowed the simultaneous separation of all four stereoisomers of Ala-Phe. Addition of ammonium sulfate generally reduced retention times and enantiomer resolution. Addition of triethylamine as modifier led to an overall increase of the retention times while the resolution did not show a general trend, increasing in the case of Ala-Ala but decreasing in the case of Ala-Phe.