Semiquantitative determination of residues of amphetamine in sewage sludge samples

A procedure based on HPLC and mass spectrometric detection has been developed for screening of residues of the illicit drug amphetamine in sewage sludge. Sample pretreatment consisted in extraction by 50 mM formic acid and methanol (80:20 v/v), followed by adjustment of the pH to 10 and preconcentration by SPE at poly(di-vinylbenzene)-N-vinylpyrrolidone. HPLC separation of the extract was done on a C18 RP with a mixture of 50 mM formic acid and methanol (80:20 v/v) as mobile phase. The mass spectrometer was operated in the MS2 and MS3 mode using the transition from m/z 136 to 119 and from m/z 119 to 91. Due to the complex matrix, ionization suppression effects as well as shifts in the sensitivity of the detector within a series of runs could not be fully excluded. Therefore, quantitation was done by standard addition together with external standards, so that semiquantitative results could be obtained down to concentrations of 2 microg/kg sewage sludge. Samples taken from various municipal sewage treatment plants indicate that amphetamine residues are ubiquitous in urban areas.     

Densitometric HPTLC Method for Analysis of Triterpenoids in the Leaves of Jovibarba sobolifera (Sims.) Opiz (Hen and Chickens Houseleek)

JPC – Journal of Planar Chromatography – Modern TLC - High performance thin-layer chromatography (HPTLC) combined with densitometry has been used for analysis of the triterpenoid...     

Studies on mesoporous niobosilicates synthesized using F127 triblock copolymer

A detailed characterization of cage-like mesoporous SBA-16 niobosilicate with tailored features of the structure is reported. The materials were synthesized in a EO₁₀₆PO₇₀EO₁₀₆(F127)-water system under acidic conditions and the pore diameters were tuned by varying the hydrothermal treatment temperature and time. The effects of the synthesis parameters on the structural/textural properties of the cubic Im3m niobosilicates have been investigated systematically. We show that the total pore volume, pore diameter, and micro-/mesopores ratio can be controlled very efficiently by changing the synthesis parameters.     

Some extremal bounds for subclasses of univalent functions

In this paper we obtain the sharp lower bound for , for functions f that are k-uniformly convex in the unit disk U. Next we consider the problem of finding the minimum of for functions f that are k-uniformly convex in the disk of radius r. Corresponding results for the class of starlike functions related to the class of k-uniformly convex functions are presented.     

A study of the intermolecular interactions of tolmetin/N-acetyl-l-tyrosine ethyl ester complex

The formation of tolmetin/N-acetyl-l-tyrosine ethyl ester (ATEE) complex has been reported by means of both theoretical and experimental studies, including quantum mechanical calculations as well as UV–vis absorption, fluorescence and time-resolved spectroscopy measurements. It has been found that the fluorescence of ATEE is quenched due to the formation of a non-fluorescent complex between ATEE and tolmetin in the ground state. The geometrical parameters of ATEE/tolmetin complex have been determined with the use of the DFT method applying the B3LYP correlation-exchange functional and 6-31G(d) basis set. The results of experiments indicated the static ATEE quenching by tolmetin. Additionally, the experimental and theoretically predicted Gibbs free energy of complexation has been calculated.     

Spectroscopic Studies of Quinobenzothiazine Derivative in Terms of the In Vitro Interaction with Selected Human Plasma Proteins. Part 1

Plasma proteins play a fundamental role in living organisms. They participate in the transport of endogenous and exogenous substances, especially drugs. 5-alkyl-12(H)-quino[3,4-b][1,4]benzothiazinium salts, have been synthesized as potential anticancer substances used for cancer treatment. Most anticancer substances generate a toxic effect on the human body. In order to check the toxicity and therapeutic dosage of these chemicals, the study of ligand binding to plasma proteins is very relevant. The present work presents the first comparative analysis of the binding of one of the 5-alkyl-12(H)-quino[3,4-b][1,4]benzothiazinium derivatives (Salt1) with human serum albumin (HSA), α-1-acid glycoprotein (AGP) and human gamma globulin (HGG), assessed using fluorescence, UV-Vis and CD spectroscopy. In order to mimic in vivo ligand–protein binding, control normal serum (CNS) was used. Based on the obtained data, the Salt1 binding sites in the tertiary structure of all plasma proteins and control normal serum were identified. Both the association constants (K_a) and the number of binding site classes (n) were calculated using the Klotz method. The strongest complex formed was Salt1–AGP_complex (K_a = 7.35·10⁴ and 7.86·10⁴ mol·L⁻¹ at excitation wavelengths λ_ex of 275 and 295 nm, respectively). Lower values were obtained for Salt1–HSA_complex (K_a = 2.45·10⁴ and 2.71·10⁴ mol·L⁻¹) and Salt1–HGG_complex (K_a = 1.41·10⁴ and 1.33·10⁴ mol·L⁻¹) at excitation wavelengths λ_ex of 275 and 295 nm, respectively, which is a positive phenomenon and contributes to the prolonged action of the drug. Salt1 probably binds to the HSA molecule in Sudlow sites I and II; for the remaining plasma proteins studied, only one binding site was observed. Moreover, using circular dichroism (CD), fluorescence and UV-Vis spectroscopy, no effect on the secondary and tertiary structures of proteins in the absence or presence of Salt1 has been demonstrated. Despite the fact that the conducted studies are basic, from the scientific point of view they are novel and encourage further in vitro and in vivo investigations. As a next part of the study (Part 2), the second new synthetized quinobenzothiazine derivative (Salt2) will be analyzed and published.     

Serjanic Acid Glycosides from Chenopodium hybridum L. with Good Cytotoxicity and Selectivity Profile against Several Panels of Human Cancer Cell Lines

Two triterpene saponins, including a novel serjanic acid derivative, were isolated from Chenopodium hybridum L. (Amaranthaceae) aerial parts. Their structures were elucidated by a combination of spectroscopic methods (MS, 1D and 2D NMR). Both compounds were evaluated for cytotoxicity and selectivity on skin, prostate, gastrointestinal, thyroid and lung cancer cells. Their effect was dose and time-dependent with varied potency, the highest against prostate PC3 and melanoma WM793, where IC₅₀ was lower than the reference drug doxorubicin. Structure–activity relationship is briefly discussed.     

Theoretical analysis of solvent effects on nitrogen NMR chemical shifts in oxazoles and oxadiazoles

Using quantum chemistry methods we have evaluated the solvent effects on the ¹⁴N NMR chemical shifts in five oxa- and oxadiazoles dissolved in twelve solvents. These solvents differ in their polarity with the dielectric constants varying from 2 to 80. Moreover, three of them have a hydrogen-bond donor character. All possible hydrogen-bonding in the water solution with the oxygen and nitrogen (hydrogen-acceptor) centers in oxazoles (2) and oxadiazoles (3) have been considered in our studies. It has been shown that both the pure solvent and hydrogen-bonding effects are significant and result in ¹⁴N magnetic shielding increase. In water solutions the pure solvent effect is larger than the hydrogen-bonding effect. In addition, the solvent effect has been analyzed in terms of its direct and indirect contributions. It should be emphasized that our theoretical results for ¹⁴N chemical shifts in oxa- and oxadiazoles remain in a very good agreement with the accurate experimental data.     

Error bounds for non-selfadjoint PDE eigenvalue problems

We introduce a posteriori bounds for the eigenfunctions (eigenvalues) of non-selfadjoint diagonalizable PDE-eigenvalue problems which incorporates an inexact solution of the corresponding generalized matrix eigenvalue problem. The estimates combine the standard perturbation results with the saturation assumption for the eigenfunctions. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)