Synthesis and X-ray crystal structure of an organometallic phosphonate [η6-1,2-C6H4(OCH3)(P(O)(OCH2CH3)2)]Cr(CO)3

The chiral, racemic, arene phosphonate complex, [t⁶-1,2-C₆H₄(OCH₃t)(P(O)(OCH²CH₃t)²)t] Cr(CO)₃ (1), was prepared via the reaction of 1,2-C₆H₄(OCH₃)(P(O)(OCH²CH₃)²) with Cr(CO)₆ in refluxing dioxane/THF. The title complex crystallized in P1 with the cell dimensions: a = 8.4893(4) Å, b = 11.0638(9) Å, c = 11.2135(8) Å, and = 62.151(8), = 105.154(5), = 112.426(6), giving a volume of 856.34(10) ų. The conformation of 1 is described as eclipsed (E) in which the methoxy substituent eclipses a carbonyl ligand of the tripod, and the phosphonate substituent is staggered.     

Fluctuating charge normal modes: An algorithm for implementing molecular dynamics simulations with polarizable potentials

A new method for performing molecular dynamics simulations with fluctuating charge polarizable potentials is introduced. In fluctuating charge models, polarizability is treated by allowing the partial charges to be variables, with values that are coupled to charges on the same molecule as well as those on other molecules. The charges can be efficiently propagated in a molecular dynamics simulation using extended Lagrangian dynamics. By making a coordinate change from the charge variables to a set of normal mode charge coordinates for each molecule, a new method is constructed in which the normal mode charge variables uncouple from those on the same molecule. The method is applied to the TIP4P-FQ model of water and compared to other methods for implementing the dynamics. The methods are compared using different molecular dynamics time steps.     

Determination of furosine in milk samples by ion-pair reversed phase liquid chromatography

Summary An ion-pair, reversed-phase, liquid chromatographic procedure using UV detection for quantitation of furosine is described. The standard plot was linear (r>0.999) over a 5 ng range. An authentic synthesised sample of furosine was used for calibration. Commerical milk samples were analyzed by the described procedure.     

Rapid Separation on Activated Charcoal of High Oligosaccharides in Honey

A novel, simple and rapid stability-indicating high-performance liquid chromatographic (HPLC) method for pravastatin sodium (PRA) was successfully developed and validated for the assay of in tablets. Chromatographic separation was achieved isocratically on a C₁₈ column (150 mm × 4.6 mm) utilizing a mobile phase of methanol-phosphate buffer (pH 7; 0.02 M) (57:43, v/v) at a flow rate of 1.0 mL min⁻¹ with UV detection at 238 nm. A linear response (r = 0.9999) was observed in the range of 1–5 μg mL⁻¹. The method showed good recoveries (100.50%) and the relative standard deviation of intra and inter-day were 1.40%. The method can be used for both quality control assay of pravastatin in tablets and for stability studies as the method separates pravastatin from its degradation products and tablet excipients.An erratum to this article can be found at     

Determination of Oligosaccharides by Conventional High-Resolution Gas Chromatography

This paper describes a simple gas chromatographic method for the analysis of (higher) oligosaccharides without needing a high-temperature procedure. The newly developed method used an ordinary capillary column and a temperature program with 360 °C as the maximum temperature. Sample preparation consisted of the oxymation and silyation of the sugars. Oligosaccharides with degrees of polymerisation of up to 7 could be determined with good repeatability (variation coefficient < 7.5%), reproducibility (variation coefficient < 11.8%) and accuracy (mean recovery 103.9%). Analysis of oligosaccharide-enriched food products demonstrated that this cheap and easy procedure could be a valuable and reliable tool for the quantitative determination of oligosaccharides in foodstuffs.     

A Reliable Gas Capillary Chromatographic Determination of Lactulose in Dairy Samples

The rhizome of Polygonum cuspidatum is an important Chinese medicine used against infectious hepatitis, leucorrhagia, pruritus vulvae of the dampness-heat type, burns, snake bite, carbunculosis, amenorrhea, dysmenorrhea, trauma with blood stasis, and rheumatism, etc. Emodin, resveratrol, and polydatin are main active components of the rhizome. We report a simple densitometric HPTLC method for quantification of these compounds. The method was validated for precision, repeatability, and accuracy. The method was found to be precise, with RSD of 0.23, 0.25, and 0.32 (interday) and 0.45, 0.57, and 0.48 (intraday) for different concentrations of emodin, resveratrol, and polydatin, respectively. Instrument precision was 0.25, 0.23, and 0.34 (%CV) for emodin, resveratrol, and polydatin, respectively. The accuracy of the method was checked by measuring the recovery of the three compounds at three different levels; the average recoveries were 102.56%, 100.21%, and 100.27%, respectively. The amounts of emodin, resveratrol and polydatin in Polygonum cuspidatum, as estimated by the proposed method, were 4.96 mg g^–1, 1.81 mg g^–1, and 13.02 mg g^–1. The HPTLC method proposed for estimation of emodin, resveratrol and polydatin was found to be simple, precise, specific, sensitive, and accurate and can be used for quality control of Polygonum cuspidatum.     

Analysis of free carbohydrates in milk using micropacked columns

Summary A gas chromatographic method using a micropacked column is described for the analysis of lactose, galactose, lactulose and epilactose in processed milks. The method is evaluated for precision and accuracy using phenyl-β-glucoside as an internal standard. Recoveries near 100% were found for lactulose concentrations higher than 0.1 mgml⁻¹, showing coefficients of variation from 5.9 to 9.4%.     

Structural study of amorphous Al0.20As0.50Te0.30, Al0.10As0.40Te0.50 and Al0.10As0.20Te0.70 by x-ray diffraction (I)

An analysis of the atomic radial distribution function of Al_0.20As_0.30Te_0.30, Al_0.10As_0.40Te_0.50 and Al_0.10As_0.20Te_0.70 amorphous alloys obtained from quenching of the molten mixture of the elements was performed. A structure in which all the Al atoms are tetrahedrally bonded to the other types of atoms in the material, would satisfy the requirements of the experimental curve. Tetrahedral groups might be linked to each other by As and Te atoms, or directly through a Te or As atom belonging to more than one tetrahedra.