Flow injection fluorimetric determination of beta-estradiol using a molecularly imprinted polymer

The steroidal compound 17beta-estradiol (E2) is a major estrogen now widely studied because of its potential endocrine disruption effects. The present paper describes a simple, rapid, flow injection (FI) method for the fluorimetric determination of beta-estradiol involving a molecularly imprinted polymer (MIP) packed into a microcolumn. Microwave-assisted extraction, a relatively new technique, was used to help remove the template from the MIP; this improved extraction efficiency. The optimization of the FI parameters and the intrinsic fluorescence of beta-estradiol allowed its direct determination without a derivatization step. When the possible interference of other estrogens was examined, the system displayed excellent specificity for beta-estradiol; no response to the natural estrogens estrone and estriol and the xenoestrogen bisphenol A was recorded. Under optimum experimental conditions, linear calibration graphs were obtained from 4 to 80 microg L(-1) with a detection limit of 1.12 microg L(-1).     

Synthetic and physicochemical studies of divalent metal complexes with cyclic hydrazone and semicarbazone ligands

Summary The syntheses of 3,4,10,11-tetraphenyl-1,2,5,6,8,9,12,13-octaazacyclotetradeca-7, 14-dione-2,4,9,11-tetraene (dbdch) and 6-methoxy-1,6-diphenyl-4-oxo-3,4,5,6-tetrahydro-2,3,5-triazine (bsc) and their complexes with divalent metal ions (copper, nickel, cobalt, zinc, cadmium and mercury) are reported. All compounds were characterized by ¹H n.m.r., ¹³C n.m.r., i.r. and u.v.-vis. spectroscopy and by FAB mass spectrometry; possible structures are presented and discussed.Author to whom all correspondence should be directed.     

Fluorimetric determination of calcium by ion-pair extraction with cryptand 2.2.1 and eosin

A fluorimetric study on the extraction of calcium into 1,2-dichloroethane as an ion-pair, formed between the cryptand 2.2.1-calcium complex and the eosinate anion, is described. Optimum conditions for extraction are established and a new fluorimetric determination of ultratraces of calcium is proposed. A linear working range from 1.5 ng ml^–1 (detection limit) to 100 ng ml^–1 of calcium and a relative standard deviation of ± 2.9% at the 70 ng ml^–1 level are obtained. The equilibrium constants involved in the extraction process have been calculated and refined by the Letagrop-DISTR program. The proposed method has been tested for the direct determination of calcium in sugars.     

Synthesis,biological evaluation and DNA binding properties of novel mono and bisnaphthalimides

A novel series of mono and bisnaphthalimides was synthesized and their antiproliferative activities were evaluated against three tumor cell lines. Bisnaphthalimides 3 and 4, bearing a pyrazine ring fused to the naphthalimide system, showed activities in the order of 10(-8) microM, similar to elinafide. DNA binding properties and the ability to induce DNA damage were studied for some of the most active compounds.     

Influence of the Cyclodextrin Size Cavity in the Complexation of Tetrahydroharmane

The interactions between cyclodextrins and tetrahydroharmane, 1-methyl-1,2,3,4-tetrahydro-9H-pyrido/3,4-b/indole, have been investigated in pH 10.1 aqueous media. Absorption and fluorescence studies, together with lifetime measurements show that tetrahydroharmane forms ground state inclusion complexes with -CD and -CD but not with -CD. Steady state experiments detect only one kind of tetrahydroharmane--CD complex, whereas time resolved measurements reveal the existence of two different types of 1:1 association complexes. The results in -CD are very similar to those in -CD, but the interactions are much weaker.     

Organometallic gold(III) compounds as catalysts for the addition of water and methanol to terminal alkynes

Different inorganic and organometallic gold(III) and gold(I) complexes have been tested in the addition of water and methanol to terminal alkynes. Anionic and neutral organometallic gold(III) compounds can efficiently mediate these reactions in neutral media in refluxing methanol. The compounds are added in catalytic amounts (1.6-4.5 mol % with respect to the alkyne). Thus, compounds of the general formula Q[AuRCl(3)], Q[AuR(2)Cl(2)], [AuRCl(2)](2), and [AuR(2)Cl](2) (Q = BzPPh(3)(+), PPN: N(PPh(3))(2)(+) or N(Bu)(4)(+); R = C(6)F(5) or 2,4,6-(CH(3))(3)C(6)H(2)) seem to behave as Lewis acids in nucleophilic additions to triple bonds. Some intermediates could be detected in the stoichiometric reaction between [Au(C(6)F(5))(2)Cl](2) and phenylacetylene that was followed by variable temperature (1)H, (19)F[(1)H], COSY (19)F[(1)H]-(19)F[(1)H], and (2)H[(1)H] NMR experiments. Compound [Au(C(6)F(5))(2)Cl](2) is also able to catalyze the hydration of phenylacetylene at room temperature. A plausible mechanism for the hydration reaction has been proposed.     

On the Reactivity of 1H‐Pyrazino[2,3‐c][1,2,6]thiadiazine 2,2‐Dioxide and Derivatives: Nucleophilic Substitution,Amination, Aldol‐Type Condensation,Oxidation, and Hydrolysis

The reactivity of the 1H‐pyrazino[2,3‐c][1,2,6]thiadiazine 2,2‐dioxide system, structurally related to pteridine, was studied, and a number of novel derivatives were synthesized. The chemical behaviors of these two related fused polyaza systems were compared.     

Quantification of dodecylbenzenesulfonate and tripolyphosphates in solid commercial samples of detergents

Fourier transform infrared spectroscopy has been used for the quantitative determination of dodecylbenzenesulfonate and tripolyphosphate in solid commercial samples of detergents. The only sample treatment consisted of a separation with ethanol. Dodecylbenzenesulfonate was dissolved and tripolyphosphate remained in the insoluble fraction. The method consisted of transmission measurements of KBr pellets. Precision, recovery and determination using both calibration line and standard addition have been optimized. The determination of dodecylbenzenesulfonate has been compared with the UV method.     

Ionization and protonation of MgC3: A theoretical study

A theoretical study of the MgC₃⁺ and MgC₃H⁺ species has been carried out. Predictions for their geometries and vibrational frequencies have been made at both second‐order Møller–Plesset (MP2) and B3LYP levels, whereas electronic energies have been computed at G2 and coupled cluster single and double excitation model augmented with a noniterative triple excitation conection (CCSD(T)) levels. The predicted global minimum for MgC₃⁺ is a rhombic structure (²A₁ electronic state), whereas a T‐shaped structure and an open‐chain isomer lie about 10 and 12 kcal/mol, respectively, higher in energy. In the case of MgC₃H⁺ the predicted global minimum is also a four‐membered ring obtained upon protonation of the most stable neutral isomer. Low ionization potentials and high proton affinities are generally obtained, especially for the most stable MgC₃⁺ isomer. The estimated values at the CCSD(T) level for the predicted global minimum are 7.20 eV [ionization potential (IP)] and 256.5 kcal/mol [proton affinities (PA)]. Therefore, if present in the interstellar medium, MgC₃ should be easily ionized and would react quite easily to give the protonated species. © 2002 John Wiley & Sons, Inc. Int J Quantum Chem, 2001     

Variation in the accumulation levels of N,N-dimethyltryptamine in micropropagated trees and in in vitro cultures of Mimosa tenuiflora

The present article reports the accumulation of N,N-dimethyltryptamine and its metabolic precursors (tryptophan, tryptamine) in different organs of micropropagated Mimosa tenuiflora trees (leaves, flowers and bark) subjected to seasonal variations (January and June), as well as in in vitro cultures (plantlets and calluses) of this plant species. The accumulation of all the tested compounds varied according to the organ, the month of collection, and age of the plant material. In all cases, the neurotoxic compound N,N-dimethyltryptamine (DMT) was detected with the lowest concentration 0.01% dry weight (DW) in flowers, and the highest 0.33% DW in bark. For the in vitro cultures, DMT was present in high yields in plantlets (0.1-0.2% DW), while in calluses this compound was initially detected but its concentration decreased significantly in the subsequent subcultures.