A study of the compositional variation of the essential oil of ylang-ylang (Cananga odorata Hook Fil. et Thomson,formagenuina) during flower development

Volatile secondary metabolites from Colombian ylang-ylang flowers were obtained by combined steam distillation - solvent extraction. The samples were analyzed by high resolution gas chromatography with flame ionization, nitrogen/phosphorus, or mass spectrometric detection. The chemical composition of the oils extracted from flowers at different stages of development differed both qualitatively and quantitatively. The generation of total volatile metabolites, light oxygenated compounds in particular, increased markedly during flower maturation. In this work the quality of the ylang-ylang essential oils was studied as a function of flower maturity.     

Calorimetric study of liquid gadolinium-based alloys

The enthalpies of mixing of liquid Gd-Si (1770±5 K) and Al-Gd (1760±5 K) alloys have been measured by high-temperature isoperibolic calorimetry. The calorimetric study of the gadolinium-based liquid alloys demonstrates the great negative enthalpies of mixing, which is associated with the contribution of GdSi and GdAl₂ intermetallides into the liquid-state thermodynamics. The comparison of obtained results with literature data has been performed. This revised version was published online in August 2006 with corrections to the Cover Date.     

A Stability-Indicating LC Method for Candesartan Cilexetil

An isocratic reversed-phase liquid chromatographic method has been developed for quantitative determination of candesartan cilexetil, used to treat hypertension, in the bulk drug and in pharmaceutical dosage forms. The method is also applicable to analysis of related substances. Chromatographic separation was achieved on a 250 mm × 4.6 mm, 5 μm particle, CN column with a 50:50 (v/v) mixture of phosphate buffer, pH 3.0, and acetonitrile as mobile phase. The flow rate was 1.0 mL min⁻¹ and the detection wavelength was 210 nm. Resolution of candesartan cilexetil and six potential impurities was greater than 2.0 for all pairs of compounds. The drug was subjected to hydrolytic, oxidative, photolytic, and thermal stress and substantial degradation occurred in alkaline and acidic media and under oxidative and hydrolytic stress conditions. The major product obtained as a result of basic hydrolysis was different from that produced by acid hydrolysis and aqueous hydrolysis. The stress samples were assayed against a reference standard and the mass balance was found to be close to 99.6%. The method was validated for linearity, accuracy, precision, and robustness.     

Supported liquid membrane separation of amine and amino acid derivatives with chiral esters of phosphoric acids as carriers

Studies on the possible use of phosphate and phosphonate esters bearing chiral menthol or nopol moieties as carriers for the transport of amines, amino acids, and amino acid esters through supported liquid membranes (SLM) are presented. Additionally, the enantioselectivity of the SLM transport of alkyl esters of aromatic amino acids and a non‐protein amino acid was also evaluated. It could be concluded that the extent of transport strongly depends on the hydrophobicity of the amino compound. Moreover, the carrier structure also influences the transport of those compounds through SLM: chiral phosphate and phosphonate esters appear to be poor or moderate carriers for enantioselective SLM transport of amino acids and their esters. The transport efficiency and selectivity is strongly dependent on the structure of both the transported compounds and the carrier. However, no meaningful relationship exists between these structural features and transportation or enantioselectivity.     

Eco-friendly synthesis of high silica zeolite Y with choline as green and innocent structure-directing agent

Zeolite synthesis in contemporary chemical industries is predominantly conducted using organic structure-directing agents (OSDAs), which are chronically hazardous to humans and the environment. It is a growing trend to develop an eco-friendly and nuisanceless OSDA for zeolite synthesis. Herein, choline is employed as a non-toxic and green OSDA to synthesize high silica Y zeolite with SiO₂/Al₂O₃ ratios of 6.5–6.8. The prepared Y zeolite samples exhibited outstanding (hydro)thermal stability at ultrahigh temperature owing to the higher SiO₂/Al₂O₃ ratio. The XRF, SEM, ²⁹Si-NMR and ¹³Na+ results suggested that choline plays a structure-directing role in the synthesis of Y zeolite, while the feed molar fraction of Na⁺ is a crucial determinant for the framework SiO₂/Al₂O₃ ratio and the crystal morphology.     

New products

Summary An efficient and economical GC method for rapid determination of FAMEs in rapeseed-mustard is described. The seeds were transmethylated with acetylchloride, using microwave heating and separation achieved on a 3 m column packed with a mixture of 2% SP-2300 and 3% SP-2310 on Chromosorb ‘W’. The method is compared with the conventional heating method and extended efficiently for half-seed analysis. The fatty acid composition of the FAMEs mixtures prepared by both methods was similar with highly significant correlation coefficients (P<0.001).     

HPLC of amino acids and oligopeptides by pre-column fluorescence derivatization with N-hydroxysuccinimidyl-α-(9-phenanthrene)-acetate

Summary A sensitive LC method for the detection of amino acids and oligopeptides with pre-column fluorescence derivatization has been developed. Glycine, glycylglycine, triglycine, glutathione, glutamic acid, and cysteine were separated on a reversed-phase C₁₈ column with methanol-water-triethylamine eluent, derivatization and chromatographic conditions were optimized. The six derivatives were eluted in 20 min with good reproducibility. The relative standard derviations (n=6) at an analytical concentration of 2×10⁻⁶ M are <5%. Detection limits (signal-to-noise ratio=3) for the six derivatives are 23–68 fmol.     

SFE of rosemary oil: Assessment of the influence of process variables and extract characterization

The effects of temperature and solvent density on the characteristics of the extracts obtained from supercritical fluid extraction (SFE) of the volatile compounds from Brazilian rosemary (Rosamarinus officianalis L., Labiatae) using carbon dioxide (CO₂) as solvent were investigated. The experiments were performed in a semi-batch laboratory scale home-made unit at two temperatures, viz. 310.15 and 320.15 K, over the pressure range of 100-160 bar. This study allowed to determine the crossover point and the maximum solubility of the oil. The products were analyzed by HRGC-MS, and compounds grouped in three different classes according to their molecular mass distribution in order to evaluate the influence of the variables studied on the characteristics of the extracts. The model proposed by Sovová was adopted in an attempt to interpret the mass transfer phenomena in the extraction process.     

TLC resolution of enantiomeric mixtures of amino acids

Summary Resolution of enantiomeric mixtures of DL-amino acids (Nine) using silica gel layers impregnated with (-)-bruncine is reported. The solvent system used was Butanol: Acetic acid: Chloroform (3∶1∶4). The diastereomers were formed and hydrolysed, by dilute HCl spray, on the chromatogram only and the amino acids thus resolved were located by ninhydrin spray. The cross resolution possibilities of enantiomers were also calculated.