Determination of seventeen elements in edible oils and margarine by instrumental neutron activation analysis

Instrumental neutron activation analysis was used to determine the concentration of As, Ba, Ce, Co, Cr, Cs, Eu, Fe, Hg, K, Na, Rb, Sb, Sc, Se, Sr and Zn in almond, sunflower, peanut, sesame, linseed, soy, corn and olive oils, as well as in three margarine brands. The concentration of As, Ba, Ce, Cs, Eu, Hg, Rb, Se and Sr were below the system detection limit under the experiment conditions. Chromium was detected only in one of the margarine samples (171 μg/g); Sb only in corn oil (18 ng/g) and Sc only in linseed oil (19 ng/g). Cobalt, Fe, K, Na and Zn were detected in all oil and margarine samples investigated. The concentration ranges for Co, Fe, K, Na and Zn in oils were: 0.016–0.053; 4.45–19.1; 5.93–47.2; 2.44–12.9 and 0.48–1.54 μg/g, respectively. For margarine, the concentration ranges for Co, Fe, K, Na and Zn were 0.09–0.012; 4.53–10.6; 58.3–1140; 13.2–9870 and 0.38–0.47 μg/g, respectively. The elemental contents of the analyzed samples are within the ranges reported in the literature for edible oils and fats.     

Determination of oxygen and nitrogen in coal by instrumental neutron activation analysis

The purpose of this study was to measure oxygen and nitrogen in coals using instrumental neutron activation analysis. For six U.S. coals total oxygen ranged from 9.4 to 28.7% and total nitrogen varied from 0.72 to 1.61%. To obtain values of organic oxygen and nitrogen either a low-temperature-ashing method or an acid-treatment method was suitable for bituminous coals. The mean difference of the experimentally determined values (O_dmmf)_LTA ? (O_dmmf)_AT = ?0.82, s = 0.51, was found to be statistically significant at the 95% confidence level, but the comparable difference for nitrogen was not. By the LTA method oxygen and nitrogen on the dmmf basis for bituminous coals showed no statistically significant difference with calculated dmmf values. Nitrogen was detected in all the LTAs varying from 0.38 to 1.67%. Formation of insoluble CaF₂ in the acid-treatment method caused an interference in the nitrogen determination due to the ¹⁹F (n, 2n) ¹⁸F reaction but was correctable. In addition, recoil proton reactions on C and O leading to the formation of ¹³N must be accounted for in all nitrogen determinations in the coal matrix.     

Analysis of arsenic and bromine in marine and terrestrial oils

Samples of marine and terrestrial oils of both plant and animal origin have been analyzed for arsenic and bromine content. Two oil samples (cod liver oil and oil extracted from mackerel fillets) were fractionated on silica gel columns and bromine was determined in the different fractions. The results obtained indicate that lipid soluble bromine and arseno organic compounds are characteristic components of marine animal and marine plant oils (seaweed). The results also show that the bromine is not localized in any particular compound or type of compounds. The bromine-containing compounds seem to be relatively stable, but the arseno-containing compounds are not. When oils containing arsenic and bromine were saponified, some of the arsenic and bromine compounds were found in the fatty acid fraction while others appeared in the water soluble fraction.     

自动电位滴定仪测定PTA工厂废水中溴氯离子的含量

该方法主要通过大量的测试实验,并结合PTA工厂产生废水的特点,对溴氯量比在1:10~5:1的共沉淀问题以及解决方法进行了研究。经测试发现在pH=1.5的硝酸体系下进行PTA工厂废水的滴定,溴离子的RSDs在0.20%~0.41%,加标回收率在102%~106%;氯离子的RSDs在0.62%~0.67%,加标回收率在97%~101%;可以满足PTA工厂废水测试的要求。     

Determination of metallic impurities in high-purity type IIa diamond grown by high-pressure and high-temperature synthesis using neutron activation analysis

Metallic impurities in high-purity type IIa and conventional type Ib diamond single crystals grown by high-pressure and high-temperature (HPHT) synthesis were determined by neutron activation analysis using thermal neutrons. Metallic impurities of Fe, Co, Cr and other minor elements were detected in the high-purity type IIa diamond crystal. The typical quantities of these metallic impurities were a few ppb. The influence of these metallic impurities on the electrical properties of the type IIa diamond crystal was practically negligible compared with nitrogen and boron impurities behaving as a donor and an acceptor, respectively. In addition to the impurities detected in the type IIa diamond crystal, Ni impurities of several hundreds of ppb were detected in conventional type Ib diamond crystals. A difference in molten metal solvents used in the synthesis of each diamond crystal resulted in the difference in metallic impurities.     

Stereospecific analysis of triacyl-sn-glycerols in Docosahexaenoic acid-rich fish oils

This paper presents the positional distribution of fatty acids in docosahexaenoic acid (22∶6n-3)-rich fish oil triacyl-sn-glycerols (TG). Stereospecific analysis of TG was carried out by a nonenzymatic method. The TG of bonito head oil, obtained after a winterization process, contained 22∶6n-3 at concentrations of 28,7, and 49 mole % in thesn-1,sn-2, andsn-3 positions, respectively. In the TG of oil before the winterization process, 22∶6n-3 was concentrated in thesn-3 position, followed evenly by thesn-1 andsn-2 positions. Tuna orbital oil, obtained after winterization, showed the preferential association of 22∶6n-3 to thesn-3 position, followed by thesn-1 position. This distribution pattern was similar to that observed for seal oil TG rather than sardine oil TG. The bonito head and tuna orbital oils are useful as fish oils with characteristics different from those of common fish oils, such as menhaden, sardine, and herring oils.     

Separation of instrumental and chemical errors in the analysis of oils by gas chromatography—A collaborative evaluation

Thirty-five analysts studied the concept that, in the gas chromatographic (GC) analysis of fatty acid composition, errors can be separated into those caused by poor chromatograph optimization and those related to inefficient conversion of triacylglycerols (TAG) to fatty acid methyl esters (FAME). A primary standard mixture of FAME was used to determine how well the participants had optimized their chromatographs. A primary standard of the equivalent TAG was used to determine total error of analysis. “Chemistry error” was calculated as the difference between the absolute errors found for the FAME and the TAG standards. Grades of analysis were computed for the FAME and TAG results and for the chemistry errors calculated from these analyses. Only four analysts achieved grades of analysis for the FAME standard that can be considered excellent or good. These four analysts used different injector/column configurations, indicating that, when properly optimized, a GC with a flame ionization detector is an extremely accurate instrument. Conversely, it is evident that there is the potential for most analysts to improve their instrumental optimization. In agreement with published information, AOCS method Ce 2-66 and AOAC method 969.33 gave low chemistry grades, but a number of analysts used modifications of these methods, and some achieved much better grades. It would appear that many of the standard methods that are in common use are capable of producing improved results, but that critical parameters need to be better specified to ensure minimization of error. The concept of separating errors into those of instrument origin and those caused by the chemical component of the total method would appear to be a useful concept for the validation of analytical methods.     

Nd recovery from magnetic waste and its preliminary analysis by neutron activation analysis

The products of the new information and communication technologies (NTIC), whose life often not exceed three years, became consumables to the computer image and other waste that contains neodymium and praseodymium (rare earths); in this field of management, treatment, and recycling of waste, we propose the recovery of elements such as neodymium and praseodymium, from the super-magnet Nd–Fe–B. Our study provides a simple and inexpensive process. The implementation scheme of our project consists of a first step in developing a plan of experience that has been made specifically to perform the optimization of operating conditions of the precipitation process. This experimental design was inspired by a statistical technique advanced design of experiments known factorial design. The method begins by embrittlement in liquid nitrogen (?196°C), dissolution in an acidic solution and recovered by a unit operation of chemical engineering, we add an oxalic acid solution to precipitate Nd as neodymium oxalate, followed by purification of neodymium and praseodymium. For characterization we used the following techniques. The neutron radiography, the neutron activation analysis (NAA) and the scanning electron microscope coupled with EDX. The identification of the most intense peaks in the XRD spectrum shows the presence of a single compound which hydrated neodymium oxalate chemical formula Nd₂(C₂O₄)₃10H₂O. The counting of γ spectrum shows that the purity of the precipitate is higher than 99%. Then, the thermal decomposition transforms this powder to neodymium oxide. After the reduction we obtain pure neodymium, the analytical balance shows that this magnet contains 26% of neodymium.     

Determination of true iodine number of oils with conjugate unsaturation by use of hypochlorous acid reagent

Summary Hypochlorous acid reagent has conveniently been used for the determination of total unsaturation in oils containing conjugated double bonds. The use of 0.1 N HOCl reagent normally employed for oils with isolated double bonds leads to incomplete absorption, and the increase in concentration and reaction period gives desirable results in the presence of mercuric acetate catalyst. A 1-hr. reaction period with 0.3 N HOCl reagent in the presence of 2.5% solution of the catalyst is recommended. A sample size varying between 0.07–0.1 g. and a 300–400% excess reagent should be employed to obtain reliable results. This procedure can be effectively used for determining the total unsaturation of tung oil, isomerized fatty acids, and dehydrated castor oil and can be employed for detecting the adulteration in commercial samples of tung oil, which cannot be ordinarily detected by the determination of the partial iodine number with the help of conventional procedures.     

Diffusion of sulfuric acid solutions in Nylon 6,6 monitored by neutron activation analysis

Nylon 6,6 is an excellent material for the study of the diffusion mechanism and associated mechanical performance of polymers saturated with aqueous solutions of varying pH at different temperatures. The diffusion profile was studied for samples saturated at temperatures ranging from 20 to 90°C in solutions decreasing in pH from distilled water to 1.0M sulfuric acid. The presence of sulfuric acid molecules within the diffusing solutions acts to promote hydrolysis of the polyamide molecules. The degree of hydrolysis is dependent on saturation temperature and solution pH. The extent of degradation was evaluated via changes to mechanical performance and inherent viscosity and often results in a reduction of the stress at yield, flexural modulus, and inherent viscosity on increasing temperature and decreasing pH. The use of neutron activation analysis allowed for an evaluation of the sulfur content within the samples as a function of diffusing time. This demonstrated that although the mechanical performance decreases rapidly on initial exposure to the aqueous medium, this is likely due to plasticization. As diffusion time progresses, the sulfur content within the sample continues to rise to a level where the acid/water molar ratio is much higher in the sample than that of the bulk. This results in an enhancement of the degradation process as time progresses. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2476–2487, 2005     

从磷资源中回收粗碘脱氟除砷提纯碘的研究

采用钙铝混凝法对从磷资源生产过程富集的高氟碘吸收液中脱氟除砷去杂的机理进行了探讨。通过设计正交实验,找出了除氟的最佳工艺参数。脱氟处理后的碘吸收液再氧化得到的精碘中氟的质量分数降低到1×10-3%以下,脱氟率基本达到99%,并对提取得到的粗碘脱氟除砷制备医药级纯碘的精制工艺进行了试验研究。     

Volatilization of mercury,arsenic and selenium during underground coal gasification

Mercury, arsenic and selenium are trace elements well-known for their high volatility in underground coal gasification (UCG) which can lead to environmental and technical problems during gas utilization. In this paper, the volatilization of mercury, arsenic and selenium from coal in a seam during the process of UCG were investigated, based on comparison of their volatility during the transformation of coal to char and the conversion of char to ash. Three types of coal were involved in this study. The results indicate that the volatility of mercury, arsenic and selenium during UCG in the seam follows the sequence of Hg>Se>As. Mercury and selenium show volatility higher than 90% from coal to ash. The volatility of arsenic is lower than 60% as confirmed by arsenic enrichment in UCG ash. Arsenic volatilization during UCG is also enhanced by increasing temperature, which is different from the result during the combustion of crushed coal. Coal type has obvious effect on element volatilization. The higher the coal reactivity, the easier is the evaporation of the elements from coal in the seam. At the same time, thermodynamic equilibrium calculations using MTDATA program were performed to predict the possible species in UCG gas. With regard to UCG gas at the production well, mercury presents as Hg(g), H₂Se(g) is the main gaseous species of selenium, whereas arsenic occurs in condensed phase as As₂S₃ and As. The effect of the pressure on the equilibrium composition of the gas results in major changes of the proportions of the species. High pressure leads to the formation and enhancement of the reduced species and increases the condensation temperature of the volatile elements.     

原子荧光光谱法测定败酱草中痕量硒

采用原子荧光光谱法测定了败酱草中硒的含量。研究了酸度、还原剂等条件对测定方法的影响,并建立了测定硒元素的方法。结果表明,硒元素的荧光强度在0～70 ng/m L浓度范围与浓度呈线性关系,检出限为1. 12 ng/m L。测得败酱草中硒的含量为43. 97 ng/g。该方法操作简便,检出限低,线性关系好,灵敏度高,准确性高。     

Determination of mixtures in vegetable oils and milk fat by analysis of sterol fraction by gas chromatography

A rapid gas-chromatographic (GC) procedure was developed for the analysis of the total sterol fraction of vegetable oils, milk fat or mixtures, to detect possible admixtures of sunflower with olive oil and the addition of vegetable oils to milk fat. The method, which employs alkali-catalyzed transesterification with KOH/methanol, was compared with saponification procedures with and without transformation of sterols into silyl derivatives prior to analysis. Repeatability of the method was assessed, and the coefficient of variation was 6.0 and 8.0% for β-sitosterol in olive and sunflower oils, respectively. Recovery of β-sitosterol ranged from 92.6 to 95.8 for both oils. The GC method assayed in this work requires little analysis time and eliminates the need for saponification, extraction, and derivatization steps. It offers good repeatability and recovery and is thus well suited to routine use.     

食品添加剂中微量砷的吸光光度测定

在１：１的盐酸介质中,以ＣｕＳＯ４为催化剂,Ｃａ（Ｈ２ＰＯ２）２为还原剂,将砷还原为肉桂色单质胶体砷,砷在０～２０ｕｇ／２０ｍｌ范围内符合比耳定律。该方法应用于食品添加剂碳酸钠、碳酸氢钠和碳酸氢铵中微量砷的测定,结果良好。     

Instrumental neutron activation analysis of archaeological ceramics: scale and interpretation

Instrumental neutron activation analysis has become a standard technique for the study of the production and distributional patterns of archaeological pottery. Questions once framed within the context of long distance exchange are now focused on issues of subregional and even intrasite levels. The increasing specificity at which these questions are poised requires a high level of analytical precision as we seek to observe statistically and archaeologically significant differences among groups of pottery produced from geographically closely spaced resources or the compositional differences that arise from production behaviors of the producers of the pottery.     

四溴苯酐酸值及游离溴含量和铁含量的测定

介绍了化学法测定四溴苯酐酸值、游离溴含量和铁含量的原理、所用仪器和试剂、试验过程与步骤、试验结果与计算方法,并对结果进行了讨论。其酸值(KOH)X1按式X1=(V0-V)c×56.11/m计算;游离溴含量X2(μg/g)按式X2=(V0-V)c×79.9×1000/m计算;样品中的铁含量X3采用标准曲线上查出的所测试液的铁含量(m1),按式X3=m1/m计算。该试验方法简单易行,重复性较好。检测结果与其对应的指标基本相符。     

采用ICP-OES测定二次盐水中的碘

阐述了用全谱ICP—OES测定二次精制盐水中碘含量的实验条件及准确性,比较了在用ICP—OES测量碘时采用生成挥发物进样技术和普通液体进样技术的2种方法,探讨了采用普通液体进样技术的仪器配置要求、气流参数和高频发生器功率的选择、碘测定谱线的选择等。最后用优化好的条件进行二次盐水中碘含量的测定,并通过实验验证了方法的可行性和稳定性。该法解决了传统方法检验时间长、准确性差的问题。