Cation-exchange separation of metals in dimethyl sulphoxide-aqueous hydrochloric acid media

The behaviour of bismuth, cadmium, copper, lead, silver, tin and zinc on a cation-exchange resin in a solvent system consisting of dimethyl sulphoxide, hydrochloric acid and water was studied. The distribution coefficients of these metal ions between liquid and resin were determined as functions of the concentration of dimethyl sulphoxide and of hydrochloric acid. On the basis of the distribution coefficients found, predictions were made as to the possibilities of separating these metals from mixtures. Such separations were confirmed experimentally for bismuth from lead, bismuth from copper, zinc from lead, lead from cadmium, silver from copper, silver from lead, lead from cadmium from zinc, bismuth from lead from zinc, and bismuth from zinc from copper.     

Comparison of calculated and experimental flow velocities upstream from the sampling cone of an inductively coupled plasma mass spectrometer

Experimentally-determined flow velocities in the 6 mm upstream from the sampling cone of an inductively coupled plasma mass spectrometer were compared with velocities determined from a computer simulation of the flow and those calculated from a modified hemispherical sink model. The measured values and those from the simulation agreed within experimental error, but differed from the values calculated from the modified hemispherical sink model by as much as 30%. An empirical alternative to the modified hemispherical sink model is presented that allows for accurate calculation of flow properties upstream from the sampling cone under a range of plasma conditions.     

Chemical data: an essential tool in the regulation of drugs.

How the Bureau of Drugs laboratories and offices obtain chemical data from the scientific literature, from user complaints and product defect reporting systems, from the drug manufacturers, from analyses of drug samples collected from the market, and from analytical research are described. The chemical data thus educed have been used successfully in developing new analytical methods, in establishing better specifications of drug quality, in removing adulterated drugs from the marketplace, in successfully prosecuting purveyors of substandard drugs, and in general assuring that consumers are provided with safe and effective drugs of high quality.     

Chemiluminescence from polytetrafluoroethylene

The chemiluminescence emission from commercial samples of polytetrafluoroethylene, PTFE (Halon G-80 and Halon G-10), was studied at temperatures between 25 and 172°C. The emission intensity decreased on extended heating, removal of the surface layer, solvent extraction, or changing from an atmosphere of oxygen to an inert atmosphere. Films of PTFE deposited from the vapor phase showed comparatively little chemiluminescence under these conditions. Ozone-induced chemiluminescence was observed at 37°C from G-10 but not from G-80, or from films deposited from the vapor phase. The chemiluminescence intensity from ozone and G-10 was not reduced by solvent extraction.     

A Simple Synthesis of Methyl 7-Oxoheptanoate

Methyl 7-Oxoheptanoate has recently been used for the synthesis of 2-(6-methoxycarbonylhexyl)-cyclopent-2-en-l-one, a key intermediate for preparation of the pros tanoids! Several methods have been previously adop 3 ted to prepare the title compound: from cycloheptanone, from 1 -methoxycycloheptenef from suberic acid: from methyl 7-iodoheptanoate6,and from 6-bromohexanoic acid or 7 from E-caprolactone.     

The extraction of iridium and platinum from organic solvents by polyurethane foam

The feasibility of extracting iridium and platinum from organic solvents onto polyurethane foam was studied. Distribution ratios obtained were 1.1 x 10(4) for the extraction of iridium from ethyl acetate, 225 for the extraction of iridium from acetone and 4.8 x 1O(3) for the extraction of platinum from ethyl acetate. Capacities of about 16% w/w were obtained for extraction of iridium from ethyl acetate, and about 2.4% for extraction from acetone.     

Calculation of cryoscopic data

The accuracies of determinations of purity and freezing point based upon cryometric freezes suffer from the scatter of data, from the failure of systems ever to recover from the effects of supercooling, and from complex phenomena that elevate temperature during the later parts of runs. Methods are here proposed for decreasing the errors caused by scatter of data and failure to recover from supercooling. These methods utilize the optical projection of calculated curves upon the actual data and involve a new interpretation of the nature of recovery from supercooling.     

Effects of soluble fractions from untreated and SiO2-treated subcellular particles of macrophages on nucleic acid metabolism in isolated nuclei of experimental granulation tissue.

Nuclei isolated from proliferating granulation tissue were incubated with 20 000 g supernatants from untreated and SiO2-treated subcellular particles of rat peritoneal macrophages in the presence of radioactive nucleic acid precursors. The supernatant from SiO2-treated subcellular particles increased the incorporation of [3H]CTP into nuclear RNA maximally by 26% at 5 min, and that of [methyl-3H]dTTP into DNA by 16% at 20 min. The release of radioactivity from labeled DNA was suppressed simultaneously. An RNase preparation from rat peritoneal macrophages enhanced the release of radioactivity from labeled DNA similarly as the soluble fraction from untreated subcellular particles of macrophages. The results suggest that the effects of the soluble fractions upon DNA metabolism of granuloma cells are at least partly independent of the effects on RNA metabolism and that the soluble fraction from SiO2-treated subcellular particles of macrophages stabilizes DNA through inhibition of nuclease activity.     

Determination of molecular weight distribution for polypropylene by column fractionation and gel-permeation chromatography

Investigations on the molecular weight distribution of cyrstalline polypropylene were carried out by column fractionation and gel-permeation chromatography for the purpose of comparing the determination methods. Average molecular weight, standard deviation, skewness, and kurtosis were calculated as statistical parameters from the distribution curve of each, and the number-average and weight-average molecular weights were determined by osmometry and light scattering. The molecular weight distribution curves obtained from column fractionation were found to be narrower than those from gel-permeation chromatography, and it was confirmed that the molecular weight distribution curve obtained from GPC was more accurate and reliable than that from column fractionation by the fact that the average molecular weight from GPC agreed fairly well with that from the absolute methods. On the other hand, no clear difference between these determination methods was observed with respect to skewness and kurtosis of the data, while the standard deviation from GPC seemed to be greater than that from column fractionation.     

Traceability in perspective

Results that reference SI units rarely pose problems in chemical measurement because traceable standards, with uncertainties derived from a chain of calibrations from the SI, are readily available at the analyst??s bench. These uncertainties are nearly always far smaller than that required for fitness for purpose in the analytical result. Moreover, the greater part of the uncertainty in a typical result is not derived from primary measurements traceable to the SI but from recovery problems and matrix effects. Even so, the incidence of wildly inaccurate results stems not from this uncertainty but from ??blunders??, deviations from the correct procedure. Attention to traceability beyond that employed by any competent analyst therefore cannot reduce the uncertainty. Furthermore, there is no rational reason to reduce the uncertainty if the result is already fit for purpose. The current focus on traceability is distracting analysts from the more pressing task of eliminating blunders.     

Determination of ochratoxin A in wine and beer by immunoaffinity column cleanup and liquid chromatographic analysis with fluorometric detection: collaborative study.

The accuracy, repeatability, and reproducibility characteristics of a liquid chromatographic method for the determination of ochratoxin A (OTA) in white wine, red wine, and beer were established in a collaborative study involving 18 laboratories in 10 countries. Blind duplicates of blank, spiked, and naturally contaminated materials at levels ranging from < or =0.01 to 3.00 ng/mL were analyzed. Wine and beer samples were diluted with a solution containing polyethylene glycol and sodium hydrogen carbonate, and the diluted samples were filtered and cleaned up on an immunoaffinity column. OTA was eluted with methanol and quantified by reversed-phase liquid chromatography with fluorometric detection. Average recoveries from white wine, red wine, and beer ranged from 88.2 to 105.4% (at spiking levels ranging from 0.1 to 2.0 ng/mL), from 84.3 to 93.1% (at spiking levels ranging from 0.2 to 3.0 ng/mL), and from 87.0 to 95.0% (at spiking levels ranging from 0.2 to 1.5 ng/mL), respectively. Relative standard deviations for within-laboratory repeatability (RSDr) ranged from 6.6 to 10.8% for white wine, from 6.5 to 10.8% for red wine, and from 4.7 to 16.5% for beer. Relative standard deviations for between-laboratories reproducibility (RSDR) ranged from 13.1 to 15.9% for white wine, from 11.9 to 13.6% for red wine, and from 15.2 to 26.1% for beer. HORRAT values were < or =0.4 for the 3 matrixes.     

GC-MS analysis of aroma of Medemia argun (mama-n-khanen or mama-n-xanin), an ancient Egyptian fruit palm

The fruits of the edible and medicinal Egyptian palm, Medemia argun, were collected from Aswan in Egypt and the essential oil (EO) from fruits and headspace (HS) of the seeds and fleshy mesocarps were analyzed by GC and GC-MS. Results obtained by GC-MS analysis indicated a high variability in the oil and in the headspace from seeds and mesocarps. Sesquiterpene derivatives were the main group of volatiles in the EO from fruits and in the HS from seeds (45.0 and 64.0%, respectively), while oxygenated hydrocarbon derivatives were the main constituents in the HS obtained from fleshy mesocarps (96.5%). The different chemical composition of the headspace obtained from the seeds and mesocarps of M. argun can be correlated with the different roles that the different constituents play in the prevention of dehydration of the fruits in the desert region from where the plant was collected.     

Solution crystallization of nylon 6

Electron microscopy and x-ray diffraction data have been obtained on nylon 6 which has been crystallized from solutions in 1,6-hexanediol and 1,2,6-hexanetriol. Lamellar single crystals and spherulites of the γ form are obtained by crystallization from 1,2,6-hexanetriol. The morphology of the single crystals is different from that obtained from glycerine solutions. The spherulites of the γ form are composed of larger lamellae. Sheaflike crystals of the α form are obtained from both solvents. α-form and γ-form crystals both grow from 1,2,6-hexanetriol at appropriate crystallization temperatures. α-form crystals alone are obtained from 1,6-hexanediol solution at every crystallization temperature. The long periods measured by small-angle x-ray diffraction for the solution-grown crystals are in the range 56 to 66 Å. The melting behavior of the solution-grown crystals is examined and discussed. Effects of solvent on growth of the two crystalline forms from solution are investigated.     

宁夏枸杞甜菜碱提取物高效液相色谱指纹图谱研究

建立宁夏枸杞甜菜碱提取物高效液相色谱指纹图谱,为鉴别不同来源的宁夏枸杞提供依据。以10批宁夏不同产地的宁夏枸杞主栽品种"宁杞Ⅰ号"样品建立枸杞甜菜碱提取物指纹图谱共有模式,采用"中药色谱指纹图谱相似度评价系统"软件进行数据处理,对15批不同来源的枸杞样品进行了分析。结果表明:8个特征峰构成了宁夏枸杞甜菜碱提取物的色谱指纹图谱,不同产地、不同品种的枸杞样品甜菜碱提取物指纹图谱存在差异;建立的枸杞甜菜碱提取物高效液相色谱(HPLC)指纹图谱对不同产地、不同品种枸杞的鉴别有参考价值。     

Quality evaluation of traditional Chinese drug toad venom from different origins through a simultaneous determination of bufogenins and indole alkaloids by HPLC

A simple and efficient HPLC method has been developed to evaluate the quality of traditional Chinese medicine toad venoms. The major bioactive ingredients, including 10 bufogenins and 4 indole alkaloids in the drug, were separated and quantified on a phenyl-hexyl column with a UV detector. A total of 27 toad venom samples from two species, Bufo bufo gargarizans CANTOR and Bufo melanostictus SCHNEIDER, from the different drug production regions of China, were analyzed. The chromatograms showed significant differences with respect to the samples from different origins. These toad venom samples can be distinctly classified into 4 groups by cluster analysis using the contents of the 14 main constituents, including toad venom samples from B. bufo gargarizans from north China, median China and south China, and samples from B. melanostictus from south China. Toad venom samples from B. bufo gargarizans from median China were considered to be of the highest quality.     

Determination of fumonisins B1 and B2 in corn and corn flakes by liquid chromatography with immunoaffinity column cleanup: collaborative study.

A liquid chromatographic (LC) method for the determination of fumonisins B1 (FB1) and B2 (FB2) in corn and corn flakes was collaboratively studied by 23 laboratories, which analyzed 5 blind duplicate pairs of each matrix to establish the accuracy, repeatability, and reproducibility characteristics of the method. Fumonisin levels in the corn ranged from <0.05 (blank) to 1.41 microg/g for FB1 and from <0.05 to 0.56 microg/g for FB2, whereas in the corn flakes they ranged from <0.05 to 1.05 microg/g for FB1 and from <0.05 to 0.46 microg/g for FB2. The method involved double extraction with acetonitrile-methanol-water (25 + 25 + 50), cleanup through an immunoaffinity column, and LC determination of the fumonisins after derivatization with o-phthaldialdehyde. Relative standard deviations for the within-laboratory repeatability (RSDr) of the corn analyses ranged from 19 to 24% for FB1 and from 19 to 27% for FB2; for the corn flakes analyses, RSDr ranged from 9 to 21 % for FB1 and from 8 to 22% for FB2. Relative standard deviations for the between-laboratories reproducibility (RSDR) of the corn analyses ranged from 22 to 28% for FB1 and from 22 to 30% for the FB2; for corn flakes analyses, RSDR ranged from 27 to 32% for FB1 and from 26 to 35% for FB2. Mean recoveries of FB1 and FB2 from corn spiked with FB1 at 0.80 microg/g and with FB2 at 0.40 microg/g were 76 and 72%, respectively; for corn flakes spiked at the same levels recoveries were 110 and 97% for FB1 and FB2, respectively. HORRAT ratios for the analyses of corn ranged from 1.44 to 1.53 for FB1 and from 0.96 to 1.48 for FB2, whereas for corn flakes they ranged from 1.60 to 1.82 for FB1 and from 1.39 to 1.68 for FB2.     

Use of chemometric and geostatistical methods to evaluate pesticide pollution in the irrigation and drainage channels of the Ebro river delta during the rice-growing season

Data sets obtained from quantitative analysis of seventeen pesticides in water samples from a network of irrigation and drainage channels in the Ebro river delta (Catalonia, NE Spain) have been analysed by chemometric and geostatistical methods. Samples were taken at fourteen locations during the main rice-growing season, from May to August 2005. Principal-component analysis enabled investigation of the spatial and temporal distribution of the main pollution patterns caused by application of pesticides in the region under study. A first pesticide-contamination pattern from the Ebro river was differentiated from a second more specific pattern from the water-drainage channels of the delta, collected from the rice fields. The seasonal peak in this more specific rice pesticide source was observed in July. Coupling the results from chemometric data analysis with use of geostatistical methods was shown to be a useful procedure for discovery of the most significant spatial and monthly variations of the main pesticide-contamination patterns, taking into account the particular geographical structure of the area under study.     

Reflectance spectra of pigmented and nonpigmented skin in the UV spectral region

We present measurements of reflectance spectra from human skin in vivo in the spectral range from 250 to 700 nm. These measurements show that the reflectance from strongly pigmented skin is higher than that from weakly pigmented skin at wavelengths shorter than approximately 300 nm. We simulate the measured results using a new radiative transfer model developed to study light propagation in skin tissue. Our simulations mimic the measured spectra when scattering from melanosomes, and fragmented melanosomes are taken into account. Scattering from microstructures with high relative refractive indices plays a major role in tissue optics. Our results show that scattering from melanosomes and fragmented melanosomes is of particular significance.     

Pyrolysis—gas chromatography of normal human cells and amniotic fluid

Human cells derived from tissues and biological fluids have been characterized by pyrochromatography. Normal cells from the brain, kidney, liver and spleen of given individuals have been differentiated by their pyrochromatograms. Pyrochromatograms, are presented for cells from cultured skin fibroblasts which were obtained from cystic fibrotic individuals as well as those taken from disease-free individuals. Characteristic pyrochromatograms were also obtained from amniotic fluid.     

In vitro pH-dependent drug release from N4-(4-carboxybutyryl)-1-beta-D-arabinofuranosylcytosine and its conjugate with poly-L-lysine or decylenediamine-dextran T70

N4-(4-Carboxybutyryl)-1-beta-D-arabinofuranosylcytosine (glu-ara-C), the conjugate of glu-ara-C and poly-L-lysine (PLL), (PLL-glu-ara-C), and the conjugate of glu-ara-C and decylenediamine-dextran T70 (T70-C10), (T70-C10-glu-ara-C), were prepared. Drug regeneration from glu-ara-C and the conjugates was investigated in buffered solutions of pH 4,5,7,7.4 and 8. The character of the drug release from the conjugates was different from that from glu-ara-C. Namely, the release of 1-beta-D-arabinofuranosylcytosine (ara-C) from glu-ara-C was accelerated under both weakly acidic and weakly basic conditions, while it was accelerated only under weakly basic conditions from the conjugates. Overall, the drug release profiles from the conjugates showed similar patterns. However, under neutral and weakly basic conditions, ara-C was regenerated more rapidly from PLL-glu-ara-C than from T70-C10-glu-ara-C. During the incubation of glu-ara-C and the conjugates under weakly acidic conditions, 1-beta-D-arabinofuranosyluracil (ara-U) was detected and its amount increased with time to similar extents.