Highly sensitive spectrophotometric methods for the determination, validation and thermogravimetric analysis of antiulcer drugs, nizatidine and ranitidine in pure and pharmaceutical preparations

Two sensitive, simple and rapid UV and second order derivative spectrophotometric methods were developed for the determination of nizatidine and ranitidine hydrochloride in pure form and pharmaceutical preparations. For the first method, UV spectrophotometic method, nizatidine was determined at 325 nm and ranitidine at 325.5 nm with detection limits of 0.07 and 0.04 μg/mL, respectively. For the second method, the distances between two extremum values (peak-to-peak amplitudes), 328/356.5 nm for nizatidine and 326/357 nm for ranitidine were measured in the second order derivative-spectra. The detection limits were found to be 0.02 μg/mL for nizatidine and 0.016 μg/mL for ranitidine, respectively. The thermal analysis of the two drugs was studied by Thermogravimetric Analysis-Differential Scanning Calorimetry (TGA-DSC) techniques. Enthalpy changes were obtained 121.9 and 124.15 J/g for nizatidine and ranitidine, respectively. The proposed method was successfully applied to the analysis of pharmaceutical preparations. The results were in good agreement with those obtained using the reference method; no significant difference were found in the accuracy and precision as revealed by the accepted values of t- and F-tests.     

Correction: Dermatan sulfate in tunicate phylogeny: Order-specific sulfation pattern and the effect of [→4IdoA(2-Sulfate)β-1→3GalNAc(4-Sulfate)β-1→] motifs in dermatan sulfate on heparin cofactor II activity

After the publication of the work entitled "Dermatan sulfate in tunicate phylogeny: Order-specific sulfation pattern and the effect of [→4IdoA(2-Sulfate)β-1→3GalNAc(4-Sulfate)β-1→] motifs in dermatan sulfate on heparin cofactor II activity", by Kozlowski et al., BMC Biochemistry 2011, 12:29, we found that the legends to Figures 2 to 5 contain serious mistakes that compromise the comprehension of the work. This correction article contains the correct text of the legends to Figures 2 to 5.     

Quantitative Analysis of Acetazolamide in Solid Dosage Forms with 1H-Nmr Spectroscopy

A rapid and specific proton magnetic resonance spectroscopic method was developed for determining acetazolamide in tablets. Maleic acid was used as the internal standard and DMSO-d₆ served as the NMR solvent. the concentration of drug per unit dose was calculated from the integration values for the resonance signals of acetazolamide at 2.14 ppm and maleic acid at 6.20 ppm. the method using commercial products gave comparable results of those obtained by the method of USP XXIII.     

Conditional pressure and coding

We use pressure to obtain invariants for bounded-to-one block homomorphisms between Markov shifts. These invariants enable us to show that if there is a bounded-to-one block homomorphism between Bernoulli shifts given by probability vectorsp andq thenq may be obtained fromp by a permutation. The invariants may be viewed as conditional pressures; a convergence theorem for eigenmeasures of Ruelle operators motivates the definition of conditional pressure and helps establish our invariants for regular isomorphism of Markov shifts. It follows that Bernoulli shifts given by probability vectorsp andq are regularly isomorphic iffq is a permutation ofp. We employ our invariants also in the context of a finite equivalence. Finally we indicate that ratio variational principles yield further invariants.     

A New Stationary Phase for Hydrophilic Interaction Chromatography: Polyacrylate-Based Hydrophilic,Monosized-Porous Beads with Zwitterionic Molecular Brushes

Hydrophilic, polyacrylate-based, monosized-porous beads with zwitterionic molecular brushes were synthesized as a new stationary medium for hydrophilic interaction chromatography. Monosized-porous poly(glycerol-1,3-diglycerolate diacrylate-co-glycerol dimethacrylate), poly(GDGDA-co-GDMA), beads 5 μm in size were obtained by a staged-shape template polymerization. As an initiator for surface-initiated atom transfer radical polymerization (SI-ATRP), bromine functionality was obtained on the beads by reacting their hydroxyl groups with 3-(aminopropyl)triethoxysilane and α-bromoisobutyryl bromide, respectively. Zwitterionic molecular brushes on the hydrophilic poly(GDGDA-co-GDMA) beads were generated by SI-ATRP of a sulfobetaine monomer, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide (MESH). Poly(MESH)-grafted poly(GDGDA-co-GDMA), poly(MESH)g-poly(GDGDAco-GDMA), beads were slurry packed into the microbore columns with 2 mm i.d. and evaluated as stationary medium for the separation of organic acids, nucleosides and peptides using microbore columns in hydrophilic interaction chromatography with the plate numbers up to 30,000 plates m⁻¹.

     

Comparing Singlet Oxygen Generation of Schiff Base Substituted Novel Silicon Phthalocyanines by Sonophotochemical and Photochemical Applications

Although the sonophotodynamic method has an effective therapeutic outcome for anticancer treatment compared with the photodynamic method, there are not enough related studies in the literature and this study aims to contribute to the development of sonophotodynamic studies. For this purpose, the Schiff base substituted silicon phthalocyanines were designed and synthesized as effective sensitizer candidates and the photophysicochemical and sonophotochemical features of the phthalocyanines were examined to increase singlet oxygen efficiency. The calculated Φ_Δ values indicate that the contribution of substituent groups improved the production of singlet oxygen compared with silicon (IV) phthalocyanine dichloride (SiPcCI₂) and also the sonophotochemical applications increased the singlet oxygen yields. The Φ_Δ values (Φ_Δ = 0.76 for axially bis-{4-[(E)-(pyridin-3-ylimino)methyl]phenol} substituted silicon (IV) phthalocyanine ( 2a ), 0.68 for axially bis-4-[(E)-{[(pyridin-3-yl)methyl]imino}methyl]phenol substituted silicon (IV) phthalocyanine ( 2b ) in photochemical study) reached to Φ_Δ = 0.98 for 2a , 0.94 for 2b in sonophotochemical study. This article will enrich the literature on increasing singlet oxygen yield.     

RNA-sensitive N-isopropylacrylamide/vinylphenylboronic acid random copolymer

Random copolymers of N-isopropylacrylamide (NIPA) and 4-vinylphenylboronic acid (VPBA) were obtained by solution polymerization using 2,2′-azobisizobutyronitrile as the initiator in ethanol at 65 °C. NIPA-co-VPBA copolymer exhibited both temperature- and pH-sensitivity. Thermally reversible phase transitions were observed both in the acidic and alkaline pH region for the copolymers produced with different VPBA/NIPA feed ratios. The pH dependency of the lower critical solution temperature (LCST) was stronger for the copolymers produced with higher VPBA feed concentrations. RNA was selected as a model biomolecule having vicinal-diol and amino groups that were potentially reactive with the boronic acid groups of NIPA-co-VPBA copolymer. The effect of RNA concentration on the LCST of NIPA-co-VPBA copolymer was investigated in aqueous media at different pHs. Although no significant effect was observed at pH 4, 7 or 10.5, the LCST decreased linearly with increasing RNA concentration at a pH approximately equal to the pK_a of boronic acid. This behavior was explained by considering the binding of RNA onto the copolymer chains to occur via two types of complex formation. For the formation of these complexes, the amino and vicinal-diol groups of RNA should react with the boronic acid groups of the copolymer in the tetrahedral anionic form. The results indicated that NIPA-co-VPBA copolymer could be utilized as a new reagent for the determination of RNA concentration in aqueous media. The proposed method was valid for the RNA concentration range of 0–4 g · mL⁻¹.

The schematical representation of the possible interactions between NIPA-co-VPBA copolymer and RNA. (A) A typical structure of single-stranded RNA. (B) Tetrahedral anionic form of boronic acid groups. (C) The interaction between the amino groups of the unpaired bases of RNA and the boronic acid groups of the copolymer. (D) Cyclic borate ester formation by the interaction between vicinal diol groups located at the 3′-end of RNA and boronic acid groups of the copolymer.     

Ion‐exchanger synthesis using reversible addition‐fragmentation chain transfer polymerization

An ion‐exchanger with polyanionic molecular brushes was synthesized by a “grafting from” route based on “surface‐controlled reversible addition‐fragmentation chain transfer polymerization” (RAFT). The RAFT agent, PhC(S)SMgBr was covalently attached to monodisperse‐porous poly(dihydroxypropyl methacrylate‐co‐ethylene dimethacrylate), poly(DHPM‐co‐EDM) particles 5.8 μm in size. The monomer, 3‐sulfopropyl methacrylate (SPM), was grafted from the surface of poly(DHPM‐co‐EDM) particles with an immobilized chain transfer agent by the proposed RAFT protocol. The degree of polymerization of SPM (i. e. the molecular length of the polyanionic ligand) on the particles was controlled by varying the molar ratio of monomer/RAFT agent. The particles carrying polyanionic molecular brushes with different lengths were tested as packing material in the separation of proteins by ion exchange chromatography. The columns packed with the particles carrying relatively longer polyanionic ligands exhibited higher separation efficiency in the separation of four proteins. Plate heights between 130–200 μm were obtained. The ion‐exchanger having poly‐(SPM) ligand with lower degree of polymerization provided better peak‐resolutions on applying a salt gradient with higher slope. The molecular length and the ion‐exchanger group content of polyionic ligand were adjusted by controlling the degree of polymerization and the grafting density, respectively. This property allowed control of the separation performance of the ion‐exchanger packing.     

Towards dual photodynamic and antiangiogenic agents: design and synthesis of a phthalocyanine-chalcone conjugate

A phthalocyanine-chalcone conjugate has been designed to combine the vascular disrupting effect of chalcones with the photodynamic effect of phthalocyanines. This potential dual photodynamic and antiangiogenic agent was obtained by the condensation of a tetrahydroxylated non-peripherally substituted Zn(ii) phthalocyanine with an amino chalcone converted into the corresponding activated isocyanate. The conjugate was fully characterized.     

Source apportionment of trace elements in the Eastern Mediterranean atmosphere

Concentrations of elements and ions, measured in aerosol samples collected during 1993 were investigated to identify sources and source composition of aerosols in the Eastern Mediterranean atmosphere. The factor analysis have shown that Eastern Mediterranean aerosol is a four-component system, including a crustal component, long-range transported pollution component, a marine component and a local pollution component. Main anthropogenic component, which reaches to the region by long-range transport accounts for 70%-90% of the concentrations of Zn, Se, NO_3-, nss-SO₄ ^2-, NH₄ ⁺ and smaller fractions of V, Sb, Cr and Mn concentrations. According to the quantitative analysis of local and Saharan dust components, the most promising marker elements to distinguish Saharan dust from local soil were found to be Cr, Nd, Mg and Cs as they have significantly different compositions in the local soil and Saharan dust.