A Selective Colorimetric Method for the Determination of Penicillins and Cephalosporins with α-Aminoacyl Functions

ABSTRACT

A simple, sensitive and selective colorimetric method is described for the assay of ampicillin, amoxicillin, cephalexin, cefadroxil and cefaclor in their pharmaceutical preparations. The method is based on measuring the color obtained when the alkaline degradation products of these agents are allowed to react with ascorbic acid. The factors affecting the color generation and determination were studied and optimized. The reaction is selective to β-lactam antibiotics having amino acid side-chains with free amino functions and thus allow interference-free quantitation of some preparations containing these agents in combination with other β-lactam agents. The procedure is also successfully adopted as stability-indicating method for cephalosporins. A tentative mechanism of the color reaction is proposed.     

Lipophilicity study of eight cephalosporins by reversed‐phase thin‐layer chromatographic method

The lipophilicity (R_M0) and specific hydrophobic surface area for the representatives of four generation cephalosporins have been determined by reversed‐phase thin‐layer chromatography, and the effect of different mobile‐phase modifiers (such as methanol, acetonitrile, acetone, 1,4‐dioxane and 2‐propanol) on the retention has been studied. The compounds studied showed typical retention behavior; their R_M values decreased linearly with increasing concentration of the organic modifier in the eluent. The linear correlations between the volume fraction of the organic solvent and the R_M values over a limited range were established for each solute, resulting in high values of correlation coefficients (>0.95 in most cases). R_M values were determined by various concentrations of organic modifier, and the correlation obtained was extrapolated to 0% of organic modifier. Chromatographically established logP (R_M0) parameters were compared with computationally calculated partition coefficients values (AClogP, ALOGP, KOWWIN, ALOGPs, XLOGP2, MLOGP and XLOGP3) and experimental octanol–water logP values (measured by the shake flask method). The received results demonstrate that RP‐TLC may be a good alternative technique for analytics in describing the lipophilic nature of investigated cephalosporins as well as the activity. Copyright © 2015 John Wiley & Sons, Ltd.     

HPLC determination of cefotaxime and cephalexine residues in milk and cephalexine in veterinary formulation

An HPLC method was developed and validated for the determination of the cephalosporins cefotaxime and cephalexine in skimmed bovine milk. The analytical column, Kromasil C₁₈ (250 mm × 4.0 mm, 5 μm) was operated at ambient temperature. Mobile phase consisted of CH₃OH-acetate buffer (pH = 4.0) and it was delivered isocratically at a flow rate of 1.0 mL · min⁻¹. Total analysis time was less than 5 min. Caffeine was used as internal standard (5 ng · μL⁻¹). UV detection was performed at 265 nm. Method validation was performed by means of intra-day (n = 5) and inter-day accuracy and precision (n = 8), sensitivity and linearity. Limits of detection (LOD) and limits of quantification (LOQ) were 0.1 and 0.3 ng · μL⁻¹, respectively. The method was applied to the analysis of a veterinary drug (CEPOREX) containing cephalexine. The results were quite accurate with the relative error varying from −8.0 to −3.5%. Solid-phase extraction was applied to remove all matrix interference from milk samples. High extraction recoveries (average 84–121%) were achieved by using Abselut NEXUS cartridges with acetonitrile as eluent and a rinsing step with water and n-butanol. A pre-concentration step was necessary in a 1/10 level to reach the EU MRL concentration level (100 μg · kg⁻¹). RSD values were less than 7% for both cephalosporins. Correspondence: Ioannis N. Papadoyannis, Laboratory of Analytical Chemistry, Department of Chemistry, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece     

Chromatographic studies of some cephalosporins on thin layers of silica gel G–zinc ferrocyanide

A simple, selective and precise thin‐layer chromatographic method has been developed for the analysis of eight cephalosporin antibiotics, namely cephadroxil, cephalexin, cefixime, cefaclor, cefpodoxime proxetil, cefuroxime axetil, cefotaxime sodium and ceftriaxone sodium. The hR_F values of these cephalosporins were investigated on silica gel G–zinc ferrocyanide layers. Mixing of zinc ferrocyanide with silica gel G resulted in a decrease in hR_F values, removal of tailing and better resolutions. The influence of silica gel G–zinc ferrocyanide ratio and mobile phases on the chromatographic behavior of cephalosporins on thin layers was investigated. Cephalosporins were selectively separated in their binary and ternary synthetic mixtures and pharmaceutical formulations. Quantitative separations of cephalosporins from their synthetic mixtures were also achieved with good recoveries (97.8–100.3%). Copyright © 2010 John Wiley & Sons, Ltd.     

Oxidized haematoxylin,a new reagent for the spectrophotometric determination of penicillins and cephalosporins

Haematoxylin—Chloramine-T in phosphate buffer (pH 7.0) is proposed as a new reagent for spectrophotometric determination of penicillins and cephalosporins in pure samples and pharmaceutical preparations. The method is based on acid hydrolysis of penicillins and cephalosporins with 5M HCl and subsequent treatment with oxidized haematoxylin. The resulting colour exhibits maximum absorption at 555 nm.     

A Selective Fluorimetric Method for the Determination of Some β-Lactamic AntibioticsSupported by Natural Science Foundations of China and Shandong province

Abstract

Based on the reaction between acetylacetone-formaldehyde and β-lactamic antibiotics at pH=4.0, in which product can emit strong fluorescence, a selective simple fluorimetric method is described for the determination of both α-aminocephalosporins (namely cepharadine and cefalexin) and 6-aminopenicillanic acid (6-APA) in pure form and in pharmaceutical form. Other β-lactamic antibiotics free from α-amino group do not interfere with the assay. The linear ranges are 1.0×10^?4-8.0×10^?2 mg/ml, 2.0×10^?4-3.0×10^?2 mg/ml and 3.0×10^?4-2.0×10^?2mg/ml for cepharadine, cefalexin and 6-APA, respectively. Their detection limits (S/N=3) are 3.0×10^?5mg/ml, 4.0×10^?5mg/ml and 6.0×10^?5mg/ml.     

Efficient photocatalytic degradation of methyl violet with two metall–organic frameworks

Two metal–organic frameworks, [Co₂(L)(H₂O)₂(4,4′-bipy)]·3CH₃CN (1) and [Mn₂(L)(1,10-phen)(H₂O)]·H₂O (2) (H₄L = 5-[bis(4-carboxybenzyl)-amino]isophthalic acid; 4,4′-bipy = 4,4′-bipyridine, 1,10-phen = 1,10-phenanthroline), with two different N-donor ligands have been synthesized. The structures of both MOFs were determined using single-crystal X-ray diffraction technique. MOF 1 shows 3D uncommon (4,6,6)-c net with (4.5³.6²)₂(5⁷.6⁶.8²)(4².5⁴.6⁶.7².8) topology while in the case of 2, only L^4? ligands link Mn(II) ions into a 2D layer structure with chelating 1,10-phen ligand. The results demonstrate that variation in the N-donor ligands plays a pivotal role in deciding the framework of the two MOFs. Both MOFs have been exploited as photocatalyst materials for the degradation of MV. The photocatalysis results indicate that the two MOFs are stable and are prospective candidates for degradation of methyl violet under UV light irradiation. Additionally, 2 displayed superior photocatalytic activity in comparison to 1. The probable photocatalytic activity mechanism for both 1 and 2 against MV has been proposed using density of states (DOS) calculations.     

Ames Mutagenicity Tests of Three Acetanilide Herbicides During Their Alkaline Degradation

Abstract

Three acetanilide herbicides—propanil, propachlor and pronamide—were studied for alkaline degradation using the HPLC technique and found to be relatively stable for chemical degradation with the highest hydrolysis rate for pronamide (k _b = 0.4966 M^?1 hr^?1), followed by propachlor (k_b = 0.1466 M^?1 hr^?1) and propanil k_b = 0.0154 M^?1 hr^?1). Simultaneously, the Ames mutagenicity test for non-degraded and half-degraded acetanilides have been performed. Testing two types of samples (primary chemicals and mixtures of half-degraded primary chemicals with their degradation products, both in 10%-acetonitrile buffer; the ranges of concentrations were 2–400 mg l^?1 for propanil and propachlor and 2–50 mg l^?1 (for pronamide) have shown the increase in mutagenicity for propanil, the decrease for propachlor and almost the same dose-response curve for pronamide during their degradation. The preliminary results of the research indicate that some environmental problems related to the impact of pesticide degradation products can appear, not only to a pesticide itself.     

Two multifunctional organic-inorganic hybrid complexes based on polyoxometalates,BiEDTA and sodium linker: crystal structures,photochromic, and catalytic performances

Two 3-D organic–inorganic hybrid supermolecular complexes, Na(BiHEDTA·2H₂O)₃(PW₁₂O₄₀)·2H₃O (BiPW) and Na(BiHEDTA·2H₂O)₃(PMo₁₂O₄₀)·2H₃O·2H₂O (BiPMo) ethylenediamine tetraacetic acid (EDTA) have been synthesized by solution method and characterized by ultraviolet visible (UV–vis) spectroscopy, thermogravimetric-differential thermal analysis, photoluminescence, cyclic voltammetry, and single-crystal X-ray diffraction (XRD). XRD analysis reveals that BiPW and BiPMo are isostructural with 3-D architectures assembled by 2-D layer tetranuclear cation and a Keggin-type polyoxoanion. Although these two hybrids exhibit similar structures, the properties depend on the nature of polyoxoanion [PM₁₂O₄₀]^3? (M = W, Mo). Under UV irradiation, BiPW and BiPMo show fast response of reversible and irreversible photochromism, respectively. BiPW exhibits excellent photocatalytic activity in degradation of methyl orange dyes under irradiation of UV–visible light. It can be reused for at least six cycles without obvious loss of activity in the degradation experiments; BiPMo shows catalytic activity in elimination of methanol. The elimination rate of methanol reaches 56.9% when the concentration of methanol is 2.3 g·m^?3 and the flow velocity is 10 mL·min^?1 at 100 °C.     

Evaluation and Elimination of the Interference Effects of Three Cephalosporins on the Kinetic-Spectrophotometric Determination of Creatinine in Serum Using the Jaffe Reaction

Abstract

The cephalosporins studied, cefotaxime, cefazolin and cefoxitin react with alkaline picrate showing a complex kinetic behaviour which include a decomposition step in the case of cefotaxime and cefazolin. Cefoxitin does not conform strictly to pseudo-first order kinetics which seems to indicate that one or more intermediate reaction products might be formed before the final complex, or this might be unstable. The presence of the cephalosporins leads to results affected by systematic errors in the determination of creatinine in serum. This effect can be minimized for cefotaxime and cefazolin by choosing a specific time interval to process the analytical signal, δA. These intervals are 180–45 and 60–10s, respectively. The presence of cefoxitin requires the application of the generalized standard-addition method, which involves the simultaneus determination of creatinine and cefoxitin by measuring the δA for two different time intervals.     

Adsorption and redox chemistry of cis-RuLL'(SCN)2 with L=4,4′-dicarboxylic acid-2,2′-bipyridine and L'=4,4′-dinonyl-2,2′-bipyridine (Z907) at FTO and TiO2 electrode surfaces

The electrochemical and spectroelectrochemical properties of the sensitizer dye Z907 (cis-RuLL'(SCN)₂ with L=4,4′-dicarboxylic acid-2,2′-bipyridine and L'=4,4′-dinonyl-2,2′-bipyridine) adsorbed on fluorine-doped tin oxide (FTO) and TiO₂ surfaces have been investigated. Langmuirian binding constants for FTO and TiO₂ are estimated to be 3 × 10⁶ M⁻¹ and 4 × 10⁴ M⁻¹, respectively. The Ru(III/II) redox process is monitored by voltammetry and by spectroelectrochemistry. For Z907 adsorbed onto FTO, a slow EC-type electrochemical reaction is observed with a chemical rate constant of ca. k = 10⁻² s⁻¹ leading to Z907 dye degradation of a fraction of the FTO-adsorbed dye. The Z907 adsorption conditions affect the degradation process. No significant degradation was observed for TiO₂-adsorbed dye. Degradation of the Z907 dye affects the electron hopping conduction at the FTO–TiO₂ interface.     

Stability-indicating high performance thin layer chromatographic determination of sulfanilamide in human urine

A simple, sensitive, selective, precise and stability-indicating high-performance thin-layer chromatographic (HPTLC) method was developed and applied to human urine for the densitometric determination of sulfanilamide. A mixture of chloroform-ethyl acetate-xylene (2.5: 4.0: 1.0, v/v/v) was used as a mobile phase. The system was found to give compact spots for sulfanilamide (retardation factor, R _f = 0.21±0.02). The linear regression analysis data for the calibration plots showed good linear relationship with r ² = 0.9970 ± 0.0003 and r ² = 0.9947 ± 0.020 within the concentration range of 50–250 ng per spot and 100–1000 ng per spot with respect to peak area, respectively. The limit of detection (LOD) and quantification (LOQ) were 8 and 25 ng per spot, respectively. Sulfanilamide was subjected to acid and alkali hydrolysis, oxidation, dry heat and wet heat treatment. According to the International Conference on Harmonization (ICH) guidelines the method was validated for precision, recovery and robustness. The ultraviolet (UV) spectra of the degradation products which had different spectra from sulfanilamide were also recorded. The article is published in the original.     

Dioxidouranium isothiosemicarbazone coordination compounds: synthesis,characterization, crystal structure,and thermal behavior

Five uranium complexes with UO₂L′(solv) formula (L′: prepared by condensation reaction between 2-hydroxyacetophenon S-pentyl isothiosemicarbazone (H₂L) and 5-bromosalicylaldehyde (Sal); solv: ethanol (1), 2-propanol (2), 2-butanol (3), ethylene glycol (4), 1,2-propanediol (5)) were synthesized through template reactions between H₂L, Sal, and UO₂(CH₃COO)₂?2H₂O for 1 and recrystallization of 1 in appropriate solvents for the other complexes. The compounds are characterized by melting point, elemental analyses, FT-IR, ¹H NMR, ¹³C NMR, TGA, and X-ray crystallography. Molecular structures of the obtained crystals, determined by X-ray diffraction analysis, showed that the complexes have distorted pentagonal bipyramidal geometry. In all complexes, the bianionic tetradentate ligand (N₂O₂) with phenolic oxygens (O3, O4), thioamidic and azomethine nitrogen donor atoms is coordinated to the metal center in equatorial positions and the solv molecules occupied the fifth equatorial site and finally linear UO₂ is located in axial position. The thermal behavior of the complexes was studied with TGA and DTG data and the results revealed three weight loss stages. The Coats–Redfern method is used for all degradation steps to determine kinetic parameters.     

Preparation,characterization and photocatalytic properties of TiO<Subscript>2</Subscript> nanostructured spheres synthesized by the Sol–Gel method modified with ethylene glycol

Monodispersed nanostructured TiO₂ spheres were obtained by the Sol–Gel method modified with ethylene glycol. The sample morphology and surface textural properties were characterized by X-ray diffraction (XRD), N₂-physisorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and diffuse reflectance spectroscopy (DRS). The SEM image showed spheres with sizes ranging from 600 to 700 nm. In addition, HRTEM micrographs reveal hexagonal grains slightly elongated (20 nm). The powders present a BET surface area of 116 m² g⁻¹. Samples without thermal treatment and those treated at 400 °C both showed characteristic reflections of the anatase phase. The photocatalytic activity of the prepared TiO₂ spheres was determined by degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) in aqueous solution. Kinetics parameters have displayed than the nanostructured material present a reaction half-life time of 30 min and it was two times faster than commercial TiO₂ (P25).     

Phosphotungstic salt used as an efficient catalyst to rapidly remove RhB from water solution

Ag-modified polyoxometalate [Na(H₂O)]₂[Ag(bpf)]₃[PW₁₂O₄₀] (1) (bpf = 2,4-di(4-pyridyl)furan) was synthesized through a hydrothermal reaction. Single-crystal X-ray diffraction analysis revealed that 1 consists of a hybrid 3D MOF constructed from Keggin-type polyanionic [PW₁₂O₄₀]^3- and cationic Ag-bpf units. Ligand bpf in 1 was in situ transferred from 1,3-bis(4-pyridyl)propane under the higher temperature and pressure of hydrothermal conditions. Catalytic performance of 1 as a heterogeneous catalyst for degradation of organic dye Rhodamine B (RhB) was investigated. Experimental results showed that hybrid 1 was especially active to catalytically degrade RhB under room temperature and natural light. RhB-containing solution (5.0 mg·L^?1) could be quickly bleached in a short time, and the high removal efficiency (97%) could be reached in a mere 30 min. The degradation mechanism of RhB was discussed.     

Three Keggin-based complexes modified by an asymmetric ligand: structures,electrochemical, photocatalytic and fluorescence sensing properties

By using an asymmetric ligand with triazole and imidazole groups, three Keggin-based complexes were obtained, [Cu(HMET)₄(H₂O)₂](PMo₁₂O₄₀)₂·2H₂O (1), [Cu₃(HMET)₄Cl₂(H₂O)₂(XM₁₂O₄₀)₂]·4H₂O (X?=?Si, M?=?W 2, X?=?Ge, M?=?Mo 3) (MET?=?4-(2-imidazol-1-yl-ethyl)-4H-[1,3,4]triazole). Complex 1 contains discrete Keggin anions and mono-nuclear [Cu(MET)₄(H₂O)₂]²⁺ clusters. Complexes 2 and 3 are isostructural with tri-nuclear Cu clusters linked by Keggin anions to construct a 1D chain. The 1- to 3-CPEs show electrocatalytic properties and can also act as nitrite amperometric sensors. Complexes 1–3 exhibit photocatalytic activities for degradation of MB. Complexes 1–?3 own fluorescence sensing properties for detecting Hg²⁺ ions.

Graphical abstract

By using an asymmetric ligand three POM-based complexes were constructed. The 1– to 3–CPEs exhibit good electrocatalytic activities and can be used as nitrite amperometric sensors. The title complexes show good photocatalytic activities for degradation of MB. Moreover, complexes 1–3 can act as fluorescence sensors to selectively detect Hg²⁺.

     

Thermo-XRD investigation of monoionic montmorillonites mechanochemically treated with urea

Montmorillonite (M) saturated with H⁺,Li⁺,Na⁺,K⁺,Rb⁺,Cs⁺,NH₄ ⁺,Mg²⁺,Ca²⁺,Sr²⁺,Ba²⁺,Mn²⁺,Co²⁺,Cu²⁺,Al³⁺ and Fe³⁺ were dry-ground with urea (U) in mass ratios U/M between 0.1 and 2.0 in an agate mortar and diffracted by X-ray. Extensive swellings occurred with H-, Li-, Na-, di-and trivalent cation-clays, suggesting the formation of urea-montmorillonite intercalation complexes. Mechanochemically treated samples were heated at different temperatures up to 375°C. The rise in temperature was accompanied by a decrease in the basal spacing. There was a correlation between the results of the thermo-XRD-analysis and the fine structures of the urea-montmorillonite complexes described in the literature. Five stages in the basal spacing vs. temperature curves were identified. In the first stage (at 150°C) the decrease was due to dehydration. In the second stage (175°C) this dehydration was accompanied by some thermal intercalation of excess urea. The other stages (at 225, 325 and 375°C) were associated with the degradation of urea and the condensation of the degraded species to polymeric products. At 375°C Li-, Na-, K-NH₄-, Mh-, Co- and Cu-montmorillonite collapsed, indicating that urea was evolved. The other urea-clay complexes did not collapse due to intercalated polymers formed by the degradation products of urea.     

Structures and photocatalytic performance of two d10 metal-based coordination polymers containing mixed building units

The linker 1,4-bis(2-methyl-imidazole-yl)-butane (bib) was used to construct two coordination polymers, specifically [Cd(bib)(ipa)]_n (1) and [Zn(bib)(tpa)]_n (2), in the presence of isophthalic acid (H₂ipa) and terephthalic acid (H₂tpa), respectively, under solvothermal conditions. Topological analyses reveal that the crystal of complex 1 consists of a 3D threefold interpenetrating network with Schläfli symbol {6⁵.8}, while complex 2 possesses a 2D wavelike layer structure with Schläfli symbol {6⁶}. The photocatalytic properties of both complexes for the degradation of methyl violet have been explored, revealing that complex 2 is a better photocatalyst than 1. A mechanism for the photocatalytic properties of the complexes is proposed, based on the results of density of states (DOS) and partial DOS calculations.

     

Phase transformation in a nanostructured M300 maraging steel obtained by SPS of mechanically alloyed powders

New complexes of type [Cu(HTBG)₂]Cl₂ (1), [Cu(TBG)₂]·3H₂O (2) and [CuL]·nH₂O (3) L:L¹, n = 2 and (4) L:L², n = 1 (HTBG: 2-tolylbiguanide, L¹ and L²: ligands resulted from 2-tolylbiguanide, ammonia/hydrazine and formaldehyde one pot condensation) were synthesised and characterised. The features of complexes have been assigned from microanalytical, IR and UV–Vis data. Redox behaviour was established by cyclic voltammetry. The in vitro qualitative and quantitative antimicrobial activity assays showed that the complexes exhibited variable antimicrobial activity against Gram-negative and Gram-positive strains isolated from the hospital environment. The thermal analyses have evidenced the thermal intervals of stability and also the thermodynamic effects that accompany them. After water elimination, complexes have a similar thermal behaviour. Processes as water elimination, melting, chloride anion removal as well as oxidative degradation of the organic ligands were observed. The final product of decomposition was copper (II) oxide.     

Hydrogen-bonded assemblies of a new polyoxometalate-based 3-D supramolecular architecture

A new hydrogen-bonded 3-D supramolecular architecture [Ni(2,2′-bpy)₃]_1.5[AsW^VI ₁₀W^V ₂O₄₀Ni(2,2′-bpy)₂(H₂O)]·0.5H₂O (2,2′-bpy?=?2,2′-bipyridine) (1) has been hydrothermally synthesized and characterized by single-crystal X-ray diffraction analysis, PXRD, elemental analysis, XPS, and IR spectrum. Compound 1 exhibits photocatalytic activity for methylene blue degradation under visible-light irradiation and shows good stability toward visible-light photocatalysis. Luminescence of 1 is also reported.