Molecular dynamic simulation of the structure of liquid chlorobenzene, <Emphasis Type="Italic">ortho</Emphasis>-chlorotoluene,and their mixtures

The molecular dynamics method is used to simulate the structure of liquid chlorobenzene, ortho-chlorotoluene, and their mixtures with concentrations of 0.03 ppm, 0.05 ppm, 0.1 ppm, 0.5 ppm, and 0.95 ppm chlorobenzene. Radial angular distribution functions (RADFs) were found for the distances between benzene ring planes and the angle between them in pure components and solutions. The data obtained from RADFs indicate that in the nearest environment of molecules the parallel orientation of benzene rings is the dominant configuration, while the fraction of perpendicular contacts is relatively small. In a concentration range of 0.03 ppm, 0.05 ppm, and 0.95 ppm chlorobenzene, conglomerates form with structural characteristics close to those of the dissolved substance. At a concentration of 0.1 ppm chlorobenzene, solute molecules start to agglomerate. In a concentration range from 0.15 ppm to 0.9 ppm chlorobenzene, both agglomerates and conglomerates of the same size are present in the mixture. The radial distribution functions of chlorine-chlorine distances calculated in pure components and mixtures indicate the presence of chlorine aggregates. The results obtained are compared with molecular light scattering data.     

Determination of antimony in nail and hair by thermal neutron activation analysis

The concentration of antimony in nail and hair was determined by thermal neutron activation analysis. Samples were collected from the workers of an antimony refinery, inhabitants near the refinery, and residents in control area. They were irradiated by Kyoto University 5 000 kW Reactor for 1 h, and cooled for 30 to 100 days. After cooling, the concentration of Sb in nail and hair was estimated by measuring the intensity of gamma-ray from 124Sb of the samples, then the samples were washed by 0.1% aqueous solution of nonionic surface active agent in an ultrasonic cleaner. The gamma-ray spectrometry was done again (after washing). The concentration of Sb in nail before washing was 730 ppm for the workers, 2.46 ppm for habitants near the refinery, and 0.19 ppm for the control; after washing, it became 230 ppm for the workers, 0.63 ppm for habitants, and 0.09 ppm for the control. The concentration of Sb in hair before and after washing was 222 ppm and 196 ppm for the workers, and 0.21 ppm and 0.15 ppm for the control, respectively.     

Relationship among iodine, bromine and chlorine concentrations in cow's milk in Japan

In order to know the relationship among some elements in biological materials, iodine, bromine and chlorine concentrations in cow's milk samples in Japan were determined by the thermal neutron activation analysis using a low power research reactor and a Van de Graaff accelerator. The iodine contents in cow's milk samples ranged from 0.041 to 0.316 ppm with an average of 0.096 ppm. The bromine and chlorine in these samples ranged from 2.3 to 11.1 ppm and from 475 to 1650 ppm, respectively. The average concentration of the bromine was calculated to be 5.6 ppm and that of the chlorine was 853 ppm. The relationship among iodine, bromine and chlorine concentrations in cow's milk samples in Japan was studied with a regression analysis. It was suggested that the correlation has a power function as follows; Y = K(Z)-A where, Y is elemental concentration in ppm, Z is atomic weight [corrected] of element, A (= 7.4) is exponent and K (= 14.7) is a constant.     

Trace elements analysis in rice

Various rice species, marketed in Austria, were analyzed for their Se, Cr, Ni, Rb, Fe, Co, Cs, Ag and Hg contents by neutron activation analysis. The concentration values found for Se ranged between 0.023 and 0.265 ppm, for Cr 0.540–1.875 ppm, for Ni 0.359–0.965 ppm, for Rb 1.604–6.400 ppm, for Fe 24.3–139.8 ppm, for Co 0.026–0.055 ppm, for Cs 0.016–0.032 ppm, for Ag 0.0006–0.0034 ppm, for Hg 0.003–0.023 ppm. Statistical analysis showed in the majority of cases that there is a significant difference in Se, Cr, Ni, Rb, Fe, Co, Hg contents but not in Cs. Highest values of Se and Fe were found in rice from Belgium /long seed, super patna/, whereas the Cr concentration was the highest in rice from Thailand /siam patna/. Ni was highest in rice from Uncle Ben's, Rb in Kresto from USA.     

Determination of oxygen in certain gases : Improved winkler method

An improved method is described for the determination of micro-amounts of oxygen gas in argon, carbon dioxide, helium, hydrogen and nitrogen by the Winkler. procedure. The technique is such that a mean standard deviation of ± 0.33 ppm oxygen with a reproducibility of ± 0.67 is obtained for gases varying in oxygen content from 1 to 30 ppm. The results are reproducible on a day-to-day basis. The reagent blank is equivalent to about 2.5 ppm with a deviation of 0.2 ppm. The method can be used for oxygen gas determination from 1 to 1.50 ppm. The accuracy of the method is ± 0.1 ppm for the lower range of oxygen concentrations.The method may also be extended to higher oxygen-containing gases, except that the oxygen determination is made by titration and smaller gas samples are used.     

Spektrophotometrische Bestimmung von Nickel, Kobalt, Kupfer, Eisen und Zink in Niob

Zusammenfassung Nickel-, Kobalt-, Kupfer-, Eisen- und Zinkspuren werden als Diäthyldithiocarbamidatkomplexe durch Extraktion von Mob abgetrennt. Anschließend trennt man diese Elemente durch Anionenaustausch-Chromatographie voneinander und bestimmt sie in den einzelnen Fraktionen spektrophotometrisch. Die Nachweisgrenzen liegen für 0,5 g Einwaage bei 0,3 ppm Nickel, 0,1 ppm Kobalt, 0,3 ppm Kupfer, 0,3 ppm Eisen und 0,3 ppm Zink. Die Variationskoeffizienten der Bestimmungen schwanken in Abhängigkeit vom Spurengehalt bei den verschiedenen Elementen zwischen 4 und 24%.

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Summary Traces of nickel, cobalt, copper, iron and zinc are separated from niobium as diethyldithiocarbamidate complexes by extraction. Thereafter these elements are separated from each other by ion-exchange chromatography and determined spectrophotometrically. Amounts of 0.3 ppm of nickel, copper, iron and zinc and of 0.1 ppm of cobalt can be determined in 0.5 g of niobium. The relative standard deviations vary from 4 to 24% for the different elements in dependence of the contents of impurities.

     

Investigation of alpha emitters in fresh and powdered blood of fertile women: an in vitro application of CR-39 NTDs

Blood samples were acquired from 60 women aged 20–44 years having decreased fertility, infertile or with uterine tumors in the Iraqi Kurdistan region. The concentrations of α emitters in fresh blood ranged from 0.0029 to 0.0088 ppm, whereas those in powdered blood ranged from 0.0036 ppm in Eiskan to 0.0096 ppm in Halabjay–Kon in Sulaymania. The α emitter concentrations in fresh blood ranged from 0.0029 to 0.0139 ppm, whereas those in powdered blood ranged from 0.0031 ppm in Shorsh to 0.0146 ppm in Sedakan in the Erbil Governorate. However, the concentrations of α emitters in the blood of women with decreased fertility were higher in the North than women from South Iraq. The difference significantly p < 0.001 revealed higher means of track density of fresh and powder blood in Erbil compared to Sulaymania. α are more damaging to the living tissue and exposure of the gonads leads to decreased fertility in women, most of data have been significant therefore, the result shown the radiation effect on women fertility.     

INAA in the determination of the elemental constituents of a natural fluorite

A complementary use of the comparative and the semi-absolute variations of instrumental neutron activation analysis (INAA) has enabled us to determine 22 different elements in a sample of natural fluorite originating from the younger granite province of Nigeria. The mineral has a brownish purple appearance with some veinlets having a deep purple coloration. Of all the 22 elements measured, Fe (851.36 ppm), Sb (7.69 ppm), Ag (87.4 ppm), Hg (2.71 ppm) and Se (1.97 ppm) are found to be exclusive to the veinlets while Au (109.15 ppm), Co (2.15 ppm) and W (173.20 ppm) are concentrated in the main matrix of the fluorite. With the aid of the semi-absolute method, it was possible to measure the Au concentration in the IAEA Soil-7 reference material to be 56.83±5.87% ppm. A qualitative electron microprobe analysis (EMA) showed that the bulk of the matrix is composed mainly of Ca and F, as expected.     

Application of prompt activation analysis in the determination of fluorine in tea,in international geochemical standards,bones and teeth of experimental animals

By making use of the ¹⁹F(p,αγ)¹⁶O reaction the F-concentrations of different varieties of tea leaves, of some international geochemical reference materials, and of the bones and teeth of some experimental animals have been determined. The tea leaves from Ceylon (ordinary), Orange Pekoe (special Ceylon), China (ordinary black), Lapsang Souchong (special smoked Chinese) and Darjeeling (India) were found to contain 170 ppm, 170 ppm, 120 ppm, 160 ppm and 100 ppm of fluorine, respectively, The F-concentrations of established geochemical reference materials, NIM-D, NIM-N, NIM-P and NIM-S, from the National Institute of Metallurgy, South Africa were determined to be 60 ppm, 120 ppm, 130 ppm and 190 ppm, respectively. The bones of rabbits, who were given fluoridated water, were found to contain much higher amount of fluorine than the bones of the control rabbit. Furthermore, the rabbits who were kept on fluoridated water for 45 days, had almost double the amount of F in their bones than the rabbits who were given fluoridated water for only 15 days. Similarly, the teeth of grown-up monkeys who were given fluoridated water since birth had double the amount of fluorine than those of the control monkey.     

Validation of scanning electron microscope (SEM), energy dispersive X-ray (EDX) and gamma spectrometry to verify source nuclear material for safeguards purposes

Ten ore samples, two unpurified yellow cake samples and natural uranyl nitrate hexahydrate sample were analyzed by Scanning Electron Microscope (SEM) and Energy Dispersive X-ray (EDX) method to verify source nuclear material. Samples represent source nuclear material as possible. All samples were scanned at ideal conditions; working distance = 10 mm, voltage = 30 kV, magnification value = × 100, spot size = 50 to screen samples for the presence of uranium and thorium, Also Hyper pure germanium (HPGe) gamma spectrometers were applied to estimate the uranium and thorium contents in Bq/kg (ppm). For the ore samples uranium-238 ranges from 1,049.23 Bq/kg (85.30 ppm) to 2,096.06 Bq/kg (170.41 ppm), uranium-235 ranges from 47.51 to 105.61 Bq/kg and thorium-232 ranges from 22.84 Bq/kg (5.65 ppm) to 41.78 Bq/kg (10.34 ppm). For the yellow cake samples and uranyl nitrate hexahydrate uranium-238 ranges from 42.99 Bq/kg (3.50 ppm) to 71,887.2 Bq/kg (5,844.49 ppm) and thorium-232 is 4.78 Bq/kg (1.83 ppm) and the other two samples are lower than the detection limit.     

Screening nitrate in forages with a test strip: collaborative study

A collaborative study was conducted for screening nitrate in forages with a commercially available test strip. The method involves extracting a finely ground sample with deionized water. The test strip is dipped in the sample extract. The color of the reaction zone on the test strip changes from white to pink or purple depending on the nitrate concentration in sample extract. The nitrate present in the extract is determined by comparing the color of the test strip to the color scale on the test strip container. Six blind quintuplicates of forage samples were analyzed by 20 collaborators. Nitrate concentrations in forage samples tested ranged from < 1000 ppm nitrate to > 10,000 ppm nitrate on dry matter basis. Each collaborator was asked to assign each sample to one of the 4 following nitrate concentration ranges: (1) < 1000 ppm, (2) 1000 to 5000 ppm, (3) > 5000 ppm to 10,000 ppm, and (4) > 10,000 ppm. Nineteen of 20 collaborators reported results. Results from 2 laboratories were rejected as outliers by inspection and chi 2 test. Sensitivity rates (p+) ranged from 0.965 to 0.998, with standard errors of 0.006 to 0.16. Specificity rates (p-) ranged from 0.991 to 0.997 for the 4 ranges, with standard errors of 0.003 to 0.006. False-positive rates (pf+) ranged from 0.006 to 0.046, with standard errors of 0.006 to 0.025. False-negative rates (pf-) ranged from 0.003 to 0.007, with standard errors of 0.003 to 0.006. Screening nitrate in forages with a test strip has been adopted first action by AOAC INTERNATIONAL.     

Bemerkung zur Formaldehydbestimmung unter Verwendung von komplex gebundenem Schwefeldioxid

Zusammenfassung Arbeitsweisen zur Bestimmung von HCHO-Spuren werden angegeben. Die Bestimmungsgrenze ist 0,0128 ppm, die Standardabweichung für Konzentrationen von 0,0128 bis 0,20 ist 0,00513, für Konzentrationen von 0,40 bis 2,0 beträgt sie 0,0139 ppm HCHO.

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Summary Procedures are given for determining traces of formaldehyde. The determination limit is 0.0128 ppm, the standard deviation is 0.00513 for concentrations from 0.0128 to 0.20, and 0.0139 ppm formaldehyde for concentrations from 0.40 to 2.0.

     

Dechlorination of PCB contaminated transformer oils by extraction with acetone

Neutron activation analysis was used to study the dechlorination of transformer oils containing 2000 ppm of polychlorinated biphenyls by solvent extraction with acetone. The distribution coefficients of PCBs between acetone and oil have been measured and they vary from 1.25 to 1.45. The concentration of PCBs in the oil can be reduced from 2000 ppm to less than 25 ppm in five extraction cycles.     

Determination of site-specific (deuterium/hydrogen) ratios in vanillin by 2H-nuclear magnetic resonance spectrometry: collaborative study

The results of collaborative study are reported for a method that determines the site-specific isotope ratios of deuterium/hydrogen (D/H)i in vanillin by deuterium-nuclear magnetic resonance (2H-NMR) spectrometry. This method allows characterization of all the main commercial sources of commercial vanillin and detection of undeclared mixtures. It is based on the fact that the amounts of deuterium at various positions in the vanillin molecule are significantly different from one source to another. Vanillin is dissolved in acetonitrile and analyzed with a high-field NMR spectrometer fitted with a deuterium probe and a fluorine lock. The proportions of isotopomers monodeuterated at each hydrogen position of the molecule are recorded, and the corresponding (D/H) ratios are determined by using a calibrated reference. Nine laboratories analyzed 5 materials supplied as blind duplicates (1 natural vanillin from vanilla beans, 2 synthetic vanillins from guaiacol, 1 semisynthetic vanillin from lignin, and a mixture of natural and synthetic vanillins). The precision of the method for measuring site-specific ratios was as follows: for (D/H)1 the within-laboratory standard deviation (Sr) values ranged from 2.2 to 5.8 ppm, and the among-laboratories standard deviation (sR) values ranged from 3.6 to 5.1 ppm; for (D/H)3 the Sr values ranged from 1.7 to 3.2 ppm, and the SR values ranged from 2.4 to 3.7 ppm; for (D/H)4 the Sr values ranged from 2.3 to 6.2 ppm, and the SR values ranged from 2.4 to 6.4 ppm; for (D/H)5 the Sr values ranged from 0.8 to 2.7 ppm, and the SR values ranged from 0.9 to 2.3 ppm. It was shown that these values allow a satisfactory discrimination between vanillin sources. Therefore, the Study Director recommends the method for adoption as a First Action Official Method by AOAC INTERNATIONAL.     

Determination of Cyclohexylamine in Water by Solid Phase Extraction and Quantitative High Performance Thin Layer Chromatography

Abstract

Cyclohexylamine (CHA) was isolated from water by solid phase extraction on a C₁₈ microcolumn. The CHA in the column eluate was chromatographed on a high performance preadsorbent silica gel layer, detected with ninhydrin reagent and exposure to UV light, and quantified by reflectance scanning. Recovery from fortified distilled water samples at 10 ppm averaged 95.0% and at 1 ppm averaged 94.9%. Quantitative recoveries from tap water at 10 ppm and from lake water at 1 ppm were also demonstrated. Other boiler water additives permitted by FDA do not interfere.     

Accumulation and distribution of elements in rice /seed,brand layer,husk/ by neutron activation analysis

Various rice samples /seed, brand layer, husk/ from Vietnam were analyzed for Se, Hg, Cr, Ni, Sc, Rb, Fe, Zn and Co by neutron activation analysis. The concentration values found /seed/ were the following: Se 0.04–0.07 ppm, Hg 0.02–0.07 ppm, Cr 2.13–8.65 ppm, Ni 1.56–4.95 ppm, Sc 0.02–0.06 ppm, Rb 0.84–2.71 ppm, Fe 26.31–96.07 ppm, Zn 10.65–27.39 ppm and Co 0.02–0.15 ppm. The values were reported in ppm /dry weight/. Statistical analysis /t-test, t=0.05/ showed that the content of elements varies between sorts of rice; the content of Rb, Fe, Ni, Cr of rice husk was significantly higher than in rice seed and brand layer.     

Impurity analysis of 1,4-dioxane in nonionic surfactants and cosmetics using headspace solid-phase microextraction coupled with gas chromatography and gas chromatography-mass spectrometry

1,4-Dioxane impurity in nonionic surfactants and cosmetics were analyzed using solid-phase microextraction (SPME) coupled with gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Experimental results show that there is no significant difference using SPME-GC and SPME-GC-MS for analysis of 1,4-dioxane in three types of nonionic surfactants at the 95% confidence level. The relative standard deviation (R.S.D.) values of each analytical method were smaller than 3%. The amount of 1,4-dioxane was found to vary from 11.6 +/- 0.3 ppm to 73.5 +/- 0.5 ppm in 30% of nonionic surfactants from manufacturers in Taiwan. These methods were linear over the studied range of 3-150 ppm with correlation coefficients higher than 0.995. The recoveries of 1,4-dioxane for these nonionic surfactants following SPME were all higher than 96 +/- 1% (n = 3). The detection limits of 1,4-dioxane for these nonionic surfactants following SPME were from 0.06 ppm to 0.51 ppm. The experimentally determined level of 1,4-dioxane in cosmetics from manufacturers in Taiwan varied from 4.2 +/- 0.1 ppm to 41.1 +/- 0.6 ppm in 22% of daily used cosmetics following SPME coupled with GC and GC-MS. Conventional solvent extraction takes around 1 h for extraction and reconcentration but SPME takes only around 10 min. SPME provides better analyses of 1,4-dioxane in nonionic surfactants and cosmetics than conventional solvent extraction and head space pretreatments in term of simplicity, speed, precision, detection limit, and solvent consumption.     

~(19)F-NMR研究镍系催化丁二烯聚合中氟的存在状态

<正> Ziegler-Natta型Ni(naph)_2-Al(i-Bu)_3-BF_3OEt_2(简称Ni-Al-B)催化体系在丁二烯(Bd)聚合过程中,活性中心络合物上氟的状态和数量控制着单体配位、引发、增长和链转移等步骤。文献[1—6]曾指出该体系显高催化活性的Al/B(mol比)范围在0.5—1.0之间,即F/Al=6—3.Al/B>1或F/Al<3时,聚合活性显著降低。最近,我们采用了添加酸、醇、酚和酯类等方法来改进体系中B组分的分散及氟的反应性,Al/B显著拓宽为0.3—3,氟的利用率得到提高。在此基础上,本文将讨论用~(19)F-NMR法研究氟     

Radiofrequency spark source mass spectrometric analysis of oxygen in undoped silicon crystals and of carbon in undoped and carbon doped gallium arsenide crystals

Radiofrequency spark source mass spectrometry is a reliable and precise analytical method to measure the amount of oxygen in silicon grown by the Czochralski technique from SiO₂ crucibles in the common range from 2ppm(atomic) to 20ppm(atomic) and in silicon grown by the floating zone technique below 0.1ppm(atomic). The technique is also excellent for the measurement of the amount of carbon in semi-insulating gallium arsenide grown under low and high pressure N₂ ambient gas by the B₂O₃ encapsulated Czochralski technique from pyrolytic BN crucibles in the common range from 0.02ppm(atomic) to 0.4ppm(atomic). The results are in rather good agreement with concentrations measured by charged particle activation analysis and consistent with those obtained using other methods.     

Pervaporation separation of aqueous chlorophenols by a novel polyurethane urea–poly (methyl methacrylate) interpenetrating network membrane

A novel polymer membrane system consisting of interpenetrating network (IPN) of hydroxy terminated polybutadiene (HTPB) based polyurethane urea (PUU)–poly (methyl methacrylate) (PMMA) has been designed and developed as highly permselective membrane for pervaporation separation of toxic p-chlorophenol and 2,4-dichlorophenol from their dilute aqueous solutions. It was observed that 3 ppm 2,4-dichlorophenol in water could be reduced to 0.3 ppm 2,4-dichlorophenol using a PUU–PMMA IPN membrane of 28 cm² area and 150 μm thickness. This membrane has shown high selectivity towards p-chlorophenol and 2,4-dichlorophenol at very low concentration in feed. Feed concentration of p-chlorophenol was varied from 1000 to 7000 ppm and that of 2,4-dichlorophenol was varied from 3 to 4000 ppm. Fifty seven percent 2,4-dichlorophenol in permeate was obtained from 3 ppm concentration in feed compared to 87% 2,4-dichlorophenol in permeate from 1000 ppm in feed. Pervaporation studies were carried out by varying the temperature of feed, membrane thickness and PMMA content in the membrane. The results of this investigation have revealed that these membranes would be suitable for separation of chlorophenols from industrial effluents.