Determination of oxytetracycline and doxycycline in pharmaceutical compounds, urine and honey by derivative spectrophotometry

Derivative spectrophotometric methods have been developed for determining oxytetracycline and doxycycline and for resolving their binary mixtures. Oxytetracycline and doxycycline were determined in pharmaceutical samples, urine and honey without any pre-treatment of the samples. In all instances, first-derivative spectra were used.     

Syntheses of Bile Pigments. Part 18. Synthesis and conformational studies of oxa- and thia-deaza-biliverdin analogues

Following the conventional methodology used for the synthesis of bile pigments, some oxa- and thia-deazabiliverdin analogues were synthetized for the first time. Both UV/VIS spectroscopic and ¹H{¹H}-NOE difference studies reveal that the oxa-deaza-biliverdin analogue 8a occurs in apolar solvents in a partly ‘stretched’ conformation, whereas the corresponding thia derivative 8b behaves rather like a genuine bile pigment. Unexpectedly, the helical-shaped conformation is also preponderant in a trioxa-trideaza-biliverdin analogue, which could be only characterized in its protonated form 14 .     

Synthesis and properties of a new class of nitrogen-rich multinuclear[m.n] ferrocenophanes

The synthesis of the first tetraaza[3,3]ferrocenophane, from the previously unreported 1,1'-bis(triphenylphosphoranylidenamino)ferrocene and its conversion into a nitrogen-rich [2,2]bis[3,3]ferrocenophane is described. The electronic behaviour of these multinuclear ferrocenophanes indicates a strong electronic coupling between the iron centers.     

An Enzyme Immunoassay for Determining Immunoreactive Trypsinogen (IRT) in Dried Blood Spots on Filter Paper Using an Ultra-Microanalytical System

Cystic fibrosis (CF) is a severe autosomal recessive disorder. It is caused by mutations in the CF transmembrane conductance regulator gene. Early diagnosis of CF can be carried out by determining high immunoreactive trypsinogen (IRT) blood values in newborns. A simple sandwich-type ultramicroELISA assay (UMELISA®) has been developed for the measurement of IRT in dried blood spots on filter paper. Strips coated with a high affinity monoclonal antibody directed against IRT are used as solid phase, to ensure the specificity of the assay. The assay is carried out within 20 h. The useful rank of the curve is 0–500 ng/mL, and the lowest detectable concentration is 4.8 ng/mL. Intra- and inter-assay coefficients of variation were lower than 10%. The recovery mean value was 100.3 ± 11.2%. Cross-reactivity with proteins structurally related to IRT (α2-macroglobulin, α1-antitrypsin, and human chymotrypsin) was lower than the detection limit of the assay. Four thousand four hundred six newborn samples from the Cuban Newborn Screening Program were analyzed, and the mean IRT concentration was 12.8 ng/mL. Higher IRT values were obtained when samples were eluted overnight. Regression analysis showed a good correlation with the commercially available AutoDELFIA® Neonatal IRT kit (n?=?3948, r =?0.885, ??=?0.976, p?<?0.01). The analytical performance characteristics of our UMELISA® TIR Neonatal suggest that it can be used for the neonatal screening of CF.     

The radiochemical and chemical characterization of marine sediments taken up from Cuba's northern and southern littoral

Journal of Radioanalytical and Nuclear Chemistry - Radioactive contamination factor (RCF) has been proposed as a suitable unit to measure the magnitude of radioactive contamination at global scale,...     

Manganese Catalyzed Hydrogenation of Organic Carbonates to Methanol and Alcohols

The first example of a homogeneous catalyst based on an earth‐abundant metal for the hydrogenation of organic carbonates to methanol and alcohols is reported. Based on the mechanistic investigation, which indicates metal‐ligand cooperation between the manganese center and the N?H group of the pincer ligand, we propose that the hydrogenation of organic carbonates to methanol occurs via formate and aldehyde intermediates. The reaction offers an indirect route for the conversion of CO₂ to methanol, which coupled with the use of an earth abundant catalyst, makes the overall process environmentally benign and sustainable.     

[(1,4,8,11‐Tetraazacyclotetradeca‐1,4,8,11‐tetrayl)tetraacetamide‐κ6N1,N4,N8,N11,O1,O8]copper(II) sulfate 4.5‐hydrate

The crystal structure of the title copper(II) complex, [Cu(C₁₈H₃₆N₈O₄)]SO₄·4.5H₂O, formed with the tetra­amide cyclam derivative 2‐(4,8,11‐triscarbamoyl­methyl‐1,4,8,11‐tetra­aza­cyclo­tetradec‐1‐yl)­acet­amide (TETAM), is described. The macrocycle lies on an inversion centre occupied by the hexacoordinated Cu atom. The four macrocyclic tertiary amines form the equatorial plane of an axially Jahn–Teller elongated octahedron. Two O atoms belonging to two diagonally opposite amide groups occupy the apical positions, giving rise to a trans‐III stereochemistry, while both the remaining pendant side arms extend outwards from the macrocyclic cavity and are engaged in hydrogen bonds with sulfate anions and co‐crystallized water mol­ecules.     

Salicylaldehyde guanylhydrazone as an analytical reagent for spectrophotometric estimation of iron

The properties and analytical possibilities of salicylaldehyde guanylhydrazone as spectrophotometric reagent have been examined. A new method for the determination of iron has been developed. Iron can be determined in the presence of the oxalate, tartrate, citrate, aluminum, and others.