Advanced Materials Research Vols. 781-784

Abstract: This document develops a new spectrophotometric method for the determination of palladium with 4-(5-bromo-2-pyridyl)-azo-1,3-diaminobenzene, in a medium of 1.80mol/L sulfuric acid, at the maximum wavelength of 566nm. Absorption spectra of reagent and complex, effect of acidity, composition of complex and heating time for color reaction are discussed. More than 30 kinds of interfering ions are determined. The interference of Pb²⁺, Ag⁺ and Cr⁶⁺ are eliminated effectively by the proposed method. Beers law is obeyed in the concentration ranges of 0-1.0mg/L for palladium, the molar absorption coefficient is 6.44×10⁴Lmol^-1cm^-1. The method is applied to the determination of palladium in general ores and palladium catalysts.

Abstract: The Dielectric Barrier Discharge plasma (DBD) plasma was used to treat Diisopropyl fluorophosphate (DFP, a stimulant of sarin) in the air. The influence factors of degradation efficiency, including power, carrier gas flow velocity and initial concentration of DFP were investigated. As a result, the degradation efficiency increased with the power increasing. The degradation efficiency increased fastly when the power less than 105W, but slowly when the power more than 105W. The degradation efficiency decreased obviously with the carrier gas flow velocity increasing, because the time of DFP stayed in plasma reactor decreased and the concentration of DFP increased. The degradation efficiency rose firstly and then fell with the initial DFP increasing, when the initial concentration was less than 80 mg/m³, but decreased with the the initial concentration increasing, when the initial concentration was more than 80 mg/m³. The main products were acetone, isopropanol, phosphoric acid, pyrophosphoric acid, carbon dioxide and water, analyzed by GC-MS. Reaction mechanism was discussed according to degradation products.

Abstract: H₂O₂ aerosol was used to oxidize dichlorvos vapor. 80.7% of dichlorvos, with the initial concentration of 90.9 mg/m³, was decontaminated when the H₂O₂ concentration kept in the range of 110~130 mg/m³ within 60 min. According to the oxidation products, analyzed by GC-MS, the decontamination reaction mechanism was discussed. Radical chain reaction is the main decontamination mechanism. H₂O₂ is dissociated to HOO^-, which can induce the formation of ·OH. The double bond in dichlorvos molecule is attacked by ·OH to form molecule radical, which is further oxidized to 1,1-dichloro ethoxy dimethyl phosphate, 1,1,1-trichloro-2-hydroxyl-ethyl dimethyl phosphate, dimethyl phosphite, dimethyl phosphate, trimethyl phosphate, methyl phosphate, dichloro acetaldehyde, oxalic acid, CH₂Cl₂, CHCl₃, parts of which are mineralized to phosphoric acid, CO₂, H₂O and chloridion.

Abstract: Analysis of the volatile components in Agrimonia pilosa Ledeb with heuristic evolving latent projections (HELP) was presented. After extracted with water distillation method, the volatile components were detected by GCMS. Then the qualitative and quantitative analysis of the volatile components was completed with HELP resolving two-dimensional original data into mass spectra and chromatograms. 62 of 83 separated constituents in the total ion chromatogram of the volatile components were identified and quantified, accounting for about 86.49% of the total content. The obtained information can provide foundation for further study of Agrimonia pilosa Ledeb. This developed method can also be used for quality control of Agrimonia pilosa Ledeb samples.

Abstract: A reversed phase HPLC method was developed and validated for analysis of roflumilast, its related substances and degradation products, using Ecosil C18 column (250×4.6 mm, 5 μm) with a flow rate of 1.0 ml/min and detection wavelength of 215nm. The mobile phase was a mixture of acetonitrile and 0.005mol·L^-1 ammonium dihydrogen phosphate buffer pH 3.5 in the ratio of 48:52 (v/v). The samples were analyzed using 20 μl injection volume and the column temperature was maintained at 30°C. The limit of detection and limit of quantitation were found to be 2.6 ng/ml and 8ng/ml, respectively. The stability-indicating capability of method was established by forced degradation studies and method demonstrated successful separation of drug, its related substances and degradation products. The method is sensitive, specific, accurate, precise and stability indicating for the quantitation of drug, its related substances and other degradation compounds.

Abstract: Monomer acid was the byproduct of preparing dimer acid from oleic acid in industry. Study its components and properties will contribute to the exploitation and application of it. First, we researched the physicochemical properties of monomer acid, such as iodine value, acid value, saponification value, and so on. The conclusion showed that the sample was a mixed fatty acid which contained longer chain of carbon and had high quality. Then, the chemical constituents of fatty acid in monomer acid were determined by GC/MS. After the sample was etherified via methanol, the chemical components and their relative contents of fatty acid from monomer acid were analyzed by GC/MS. Fifteen fatty acids predominated: myristic acid (12.16%), palmitic acid (8.51%), stearic acid (32.72%), and oleic acid (25.53%).

Abstract: A high performance liquid chromatography-tandem mass spectrometric method had been established for simultaneous determination of 25 sex hormones. The hormones were extracted by ethyl acetate and ethyl acetate-tert-butyl methyl ether (1/1, v/v) after enzymatic hydrolysis, followed by an LC-C18 cartridge for cleanup, then were quantified by HPLC-ESI MS/MS with internal standards. Limits of quantification were 1-2 μg.kg^-1, average recoveries were 92-113 %, and the R.S.D. was 6-10 %.

Abstract: Amygdalin was catalytic degraded by extracellular enzymes mixture from Aspergillus niger and a novel product, phenyl-(3,4,5-trihydroxy-6-methyl-tetrahydro-pyran-2-yloxy)-acetonitrile (PTMT), with high antitumor activity was identified and purified. To measured the Pharmacokinetic of amygdalin and its products, a simple and rapid SPE-HPLC method was set up. The analysis was performed on an Agilent HPLC system with a C18 ODS column (250 × 4.6 mm i.d.) by gradient elution with 0.05% formic acid in water and 0.05% formic acid in acetonitrile as the gradient mixtures. The flow rate was 1ml/min, the detection wavelength was 215 nm and the column temperature was kept at 25°C. The HPLC assay was carried out within 9 min. The retention times of amygdalin, mandelonitrile, prunasin, PTMT andbenzaldehyde were 3.14, 5.93, 6.82, 7.35 and 8.33 min, respectively. The mean absolute recoveries of three analysts were over 98%. The limit of detection and limit of quantification for were 0.02 and 0.04 μg/ml for amygdalin and benzaldehyde, 0.03 and 0.05 μg/ml for mandelonitrile, and 0.03 and 0.04 μg/ml for prunasin and PTMT.

Abstract: The poly-histidine (poly-HTD) film was prepared at glassy carbon electrode by electropolymerization, and its electrochemical behavior was investigated by cyclic voltammetry. Results show that the behavior of this poly-HTD film is in good agreement with quasi-reversible process characteristic. At low scan rates, the electronic transfer process of electrode reaction is controlled by surface process. At this poly-HTD film modified electrode, an excellent electrocatalytic ability towards the redox of hydroquinone (HQ) and catechol (CC) with decrease of the overpotential and improvement of the redox peak currents was found. Differential pulse voltammetry was used for the simultaneous determination of HQ and CC in their mixture, and the peak-to-peak separation ΔE_p for HQ and CC was 110 mV. Therefore, this polymer modified electrode can be used for the simultaneously selective determination of HQ and CC without interference with each other.

Abstract: A spectrophotometric method for the determination of ruthenium (III) is described, based on its catalytic effect on the oxidation reaction of switerland pigment with potassium periodate in 0.016 mol/L of hydrogen chloride medium and in the presence of OP emulsifier (p-iso-octyl phenoxy polyethoxy ethanol) at 100 °C. The above reaction is followed spectrophotometrically by measuring the decrease in the absorbance at 608 nm for the catalytic reaction of switerland pigment. The calibration curve for the recommended method was linear in the concentration range over 0.041.0 μg/L and the detection limit of the method for Ru (III) is 0.012 μg/L. The influence of the factors such as acidity, concentration of reactants, reaction time, temperature and co-existing ions on the reaction is discussed. The optimum conditions of reaction are established and some kinetic parameters are determined. The apparent activation energy of catalytic reaction is 100.48 kJ/mol. The relative standard deviation for the determination of ruthenium (III) at the concentration of 0.02 μg/25 mL is calculated to be 2.3 % (n=11). In combination with distilled separation, the method has been successfully applied for the determination of trace ruthenium (III) in some ores and metallurgy proucts with the relative standard deviations (RSD) over 2.9 %3.8 % and the recovery over 98.2 %-103.6 %.