石墨炉原子吸收光谱法测定乳制品中铬的含量

本文主要开展了石墨炉原子吸收光谱法测定乳品中铬含量优化条件的研究.通过采用样品处理技术、基体改进剂、平台式横向加热石墨管、交流纵向塞曼效应背景校正技术相结合的技术及通过对仪器测定条件的优化可基本消除样品干扰问题,其测定灵敏度、检出限及精密度大幅提高.     

食品中铬（Ⅲ）与铬（Ⅵ）分析方法的探讨

研究了ＩＥ－ＡＡＳ法测定食品中痕量Ｃｒ（Ⅲ）和Ｃｒ（Ⅵ）的方法,讨论了原子化条件,样品预处理方法及Ｃｒ（Ⅲ）和Ｃｒ（Ⅵ）分别测定的条件选择与方法;确定了以酸浸提食品中的各种价态的铬的样品预处理方法;探讨了利用弱碱型阴离子交换树脂选择吸附Ｃｒ（Ⅵ）进而分别测定了Ｃｒ（Ⅲ）和Ｃｒ（Ⅵ）的条件与方法。     

潮州市食用明胶产品中铬含量的调查结果分析

对辖区内食用明胶销售摊点或企业进行摸底排查,了解食用明胶产品中的铬含量,为使用明胶作为原料的食品进行风险监测研究奠定基础.采用原子吸收光谱法对食用明胶进行样品预处理和含量测定.方法的线性良好,在线性范围0 mg/L～0.500 mg/L内,相关系数达0.999 6;测试样品的RSD值为1.32％～8.34％;回收率为8...     

浊点萃取-石墨炉原子吸收光谱法测定铬的形态

采用浊点萃取-石墨炉原子吸收光谱法(CPE-GFAAS)测定铬的形态。方法 以GFAAS为检测手段,TritonX-100为表面活性剂,8-羟基喹啉(8-HQ)为络合剂,考察pH和Triton X-100的用量、温度和时间等对浊点萃取Cr(Ⅲ)的影响。通过测定总铬和Cr(Ⅲ),计算出Cr(Ⅵ)的含量。结果 最佳浊点萃取条件为pH=9,1.0ml 3% Triton X-100,水浴95℃,20min。方法检出限为0.2μg/L,精密度RSD为4.1%,加标回收率在88%～98%之间。结论 本方法污染小、简便快速、准确灵敏、精密度好。     

原子吸收法快速检测自来水中铅、铬、镉的含量

目的建立一种快速、准确测定自来水中铅、铬、镉含量的石墨炉原子吸收法。方法样品硝酸浓度为1%,基体改进剂为10 g/L磷酸二氢铵,配制铅、铬、镉混合标准溶液,仪器固定体积自动配置曲线,采用外标法定量。结果该检测方法回收率范围:铅95.2%~106.0%,铬95.8%~102.4%,镉94.7%~110.7%;相对标准偏差(relative standard deviation,RSD)范围:铅0.91%~1.33%,铬0.81%~2.07%,镉0.98%~4.45%;检出限:铅0.1μg/L,铬0.1μg/L,镉0.03μg/L;定量限:铅0.3μg/L,铬0.3μg/L,镉0.09μg/L。结论该方法快速、准确、重复性好,可用于自来水中重金属铅、铬、镉的检测。     

分析纯元明粉中镍、铬、铁含量的测定

分析纯元明粉由于其纯度超高、杂质要求较苛刻。为提高产品的质量,通过大量实验确立了用原子吸收光谱法测定分析纯元明粉中镍、铬、铁含量的检测方法。此法快速准确、精密度高。实测样品中镍、铬、铁的回收率为分别为98.6%~102.75%、97.3%~103.4%、99.4%~101.25%,相对标准偏差(n=6)分别为3.23%、3.4%、2.28%。     

微波消解-石墨炉原子吸收光谱法测定大米中铬

建立微波消解-石墨炉原子吸收光谱法测定大米中重金属铬含量的方法。采用微波消解法对样品进行消解,用石墨炉在波长357.9 nm处测定样品中铬的含量。结果表明,该方法线性关系良好,相关系数为0.999 7,检出限为0.006 mg/kg,定量限为0.02 mg/kg,回收率为81.6%～93.1%。该方法具有快速、简便、准确等优点,可用于大米中铬的含量测定。     

原子吸收光谱法测定四季感冒片铬含量

目的测定市场上四季感冒片铬含量,为制定四季感冒片标准提供参考数据。方法采用硝酸浸泡过夜,微波消解,石墨炉原子吸收光谱法测定。结果线性相关系数为0.9981,加样回收率96.9%,检出限0.41 ng/mL,重复性RSD为1.6%(n=6)。结论此法可用于四季感冒片质量控制,结果表明,市场上四季感冒片铬含量潜在风险较低。     

有机共沉淀一原子吸收法测定黄酒中铅

黄酒样品的硝酸一高氯酸消化液,在０．２ｍｏｌ／Ｌ硝酸介质中,加入吡咯啶二硫代甲酸铵,与铅作用形成难溶配合物和共沉淀一原子吸收法测定黄酒中铅离心除增清液,沉淀液用甲基异丁基甲酮溶解,将有机相引入空气一乙炔火焰中。     

食品中总铬和铬形态分析的前处理技术概述

铬既是一种人体必需的微量元素,又是已确认的致癌物质之一,且铬的毒性与摄入的铬总量及形态有关。本文主要综述了近年来食品中总铬及铬形态分析的前处理技术的研究现状。总铬样品的前处理技术有微波消解、干灰化法、高压消解、湿法消解等。铬形态分析的难点在于Cr(Ⅲ)与Cr(Ⅵ)的存在价态会发生改变,因此前处理技术必须保证铬形态分析过程中的稳定性,这对于检测结果的准确性来说十分关键。本文详细分析了超声消解、加速溶剂萃取、浊点萃取、固相萃取等铬形态提取和富集技术,并其优缺点进行了讨论。同时,总结了食品中总铬及铬形态分析前处理方法存在的主要问题以及发展方向。     

Development of a wet-chemical method for the speciation of iron in atmospheric aerosols

The ability to quantify the chemical and physical forms of transition metals in atmospheric particulate matter (PM) is essential in determining potential human health and ecological effects. A method for the speciation of iron in atmospheric PM has been adapted which involves extraction in a well-defined solution followed by oxidation state specific detection. The method was applied to a suite of environmental aerosols. Ambient atmospheric aerosols in an urban area of St. Louis (the St. Louis-Midwest Supersite) were collected on Teflon substrates and were leached in one of four different solutions: (1) >18.0 Momega water; (2) 140 microM NaCl solution; (3) pH = 7.4 NaHCO3 solution; and (4) pH = 4.3 acetate buffering system. Fe(ll) was determined directly using the Ferrozine method as adapted to liquid waveguide spectrophotometry using a 1 m path-length cell. Fe(lll) was determined similarly after reduction to Fe(ll). It was found that, at low ionic strength, pH exerted a major influence on Fe(ll) solubility with the greatest Fe(ll) concentration consistently found in the pH = 4.3 acetate buffer. Soluble Fe(lll) (as defined by a 0.2 microm filter) varied little with extractant, which implies that most of the Fe(lll) detected was colloidal. To characterize well-defined materials for future reference, NIST standard reference materials were also analyzed for soluble Fe(ll) and Fe(lll). For all SRMs tested, a maximum of 2.4% of the total iron (Urban Dust 1649a) was soluble in pH = 4.3 acetate buffer. For calibration curves covering the ranges of 0.5-20 microg/L Fe(ll), excellent linearity was observed in all leaching solutions with R2 values of > 0.999. Co-located filters were used to test the effect of storage time on iron oxidation state in the ambient particles as a function of time. On two samples, an average Fe(ll) decay rate of 0.89 and 0.57 ng Fe(ll) g(-1) PM day(-1) was determined from the slope of the regression, however this decrease was determined not to be significant over 3 months (95% confidence). As an application of this method to mobile source emissions, size-resolved PM10 samples were collected at the inlet and outlet of the Caldecott Motor Vehicle Tunnel in northern California. These samples indicate that the coarse fraction (PM10-PM2.5) contains almost 50% of the total soluble Fe(ll) in the aerosol.     

Radioactivity measurements and radiation dose evaluation in tap waters of Central Italy

Consumption of drinking water is very important for human nutrition and its quality must be strictly controlled. A study of radioactivity content in tap water samples collected in the Central Italy was performed in order to check the compliance with recent European regulations. Gross alpha and beta activity, 226Ra, 238U and 234U concentrations were measured. Gross alpha and beta activities were determined by standard ISO 9696 and ISO 9697; for 226Ra determination liquid scintillation was used. 238U and 234U concentrations were determined by alpha spectrometry after separation from matrix by extraction chromatography and electroplating. Recommended WHO guideline activity concentrations for drinking water (0.1 and 1.0 Bq/L for gross alpha and gross beta activity, respectively) are exceeded in two cases for gross alpha activity and are not exceeded in any case for gross beta activity. The concentrations (mBq/L) of 226Ra, 238U and 234U ranged from <1.70 to 15.3, 0.65 to 48.8 and 0.780 to 51.5, respectively. Effective dose due to the uranium isotopes and radium was calculated for children and adults using the dose coefficients reported by EC Directive 96/29 EURATOM and annual water intake. For all class ages, the doses are quite similar and much lower than 0.1 mSv/year.     

食品及水体中碘形态分析研究进展

碘是人体必需的一种微量元素。但是由于碘在自然环境中的分布不均匀,不同地区人群的碘摄入会产生缺乏或过量的现象,进而引起一系列的疾病。我国是世界上碘缺乏最严重的国家之一,因此实施食品及相关水体中碘含量的监测是一项长期的基本任务。然而碘在自然环境中的存在形式复杂,不同形态碘的生物有效性及毒性差异很大,因此开展不同形态碘含量的监测对于科学、准确评估人群的碘摄入具有重要意义。本文总结了近十多年来碘形态分析技术的发展,比较了各种前处理技术及分离分析技术的优缺点及适用范围,以期为相关科研工作者开展进一步的工作提供参考。     

New combination of EXAFS spectroscopy and density fractionation for the speciation of chromium within an andosol

Studying speciation of heavy metals instead of their total concentration in a complex matrix such as soil is a scientific challenge that requires a combination of different analytical techniques. We compared the speciation of Cr within an andosol (island of Réunion) by using X-ray absorption spectroscopy (XAS) and sequential extraction. Contradictory results were obtained since the fraction of Cr bound to organic matter was detected only with the latter method. As bulk soil is rather complex, its fractionation by a densimetric method decreased its heterogeneity. We found that 60% Cr was within chromite-type primary minerals. Weathering of these phases led to Fe and Cr release, eventually resulting in either coprecipitation as mixed FeCr oxyhydroxide (16% total Cr) or precipitation of a Cr oxyhydroxide (5% total Cr). Our results also revealed that 13% Cr was bound to organic matter. The organic matter was complexed with mineral phases to form organomineral complexes with a density ranging from 1.9 to 2.6. The use of an original density fractionation-based sample preparation allowed identification of the role of organic matter in chromium speciation within an andosol and to overcome the difficulties of EXAFS to detect light elements in the vicinity of heavy elements.     

Synchrotron-based XANES speciation of chromium in the oxy-fuel fly ash collected from lab-scale drop-tube furnace

Speciation of chromium (Cr) in the fly ash collected from oxy-firing of Victorian brown coal has been reported for the first time to address the potential formation of toxic Cr(VI) and the variation of the quantities of Cr(III)-bearing species with flue gas composition. Synchrotron-based X-ray absorption near-edge structure (XANES) was employed for Cr speciation. Apart from a pure O(2)/CO(2) mixture (27/73, v/v) versus air, the O(2)/CO(2) mixtures doped with SO(2), HCl, and steam individually or together to simulate real flue gas have also been tested. Under all of the conditions tested here, the fractions of Cr(VI) in the fly ashes are insignificant, constituting no more than 5% of the total Cr. The test of Cr-doped brown coal in pyrolysis further confirmed that the Cr(VI) formation preferentially occurred through a local oxidation of Cr(III) at the oxygen-containing functions sites within coal matrix, rather than through an oxidation by external bulk O(2). This reaction is also highly temperature-dependent and slower than the interaction between Cr(III) and other metals such as iron oxide. Increasing temperature to 1000 °C inhibited the oxidation of Cr(IIII) to Cr(VI). Shifting the combustion gas from air to O(2)/CO(2) exerted little effect on the Cr(VI) formation. Instead, the formation of iron chromite (FeCr(2)O(4)) was facilitated in O(2)/CO(2), probably due to a strong reducing microenvironment formed by the CO(2) gasification reaction within the char matrix. The accumulation of HCl in flue gas favored the vaporization of chromium as gaseous chloride/oxychloride, as expected. The coexistence of SO(2) inhibited this phenomenon by promoting the formation of sulfate. The presence of steam was even beneficial for the inhibition of water-soluble Cr sulfate through stabilizing the majority of Cr into alumino-silicate which is in the slagging phase.     

Bioaccessibility of trace elements and chromium speciation in commonly consumed cereals and pulses

Copper, manganese, and chromium content and their bioaccessibility were determined in commonly consumed cereals and pulses. Copper, manganese, and chromium concentration of these grains ranged from 0.19 to 1.22, 0.46 to 8.12, and 0.02 to 0.11 mg/100 g, respectively. Bioaccessibility of these minerals from the grains ranged from 6.6 to 32.5% (copper), 15.5 to 43.5% (manganese), and 2.66 to 36.4% (chromium). In terms of bioaccessibility of these minerals, pulses provided more than cereals. Speciation analysis of chromium by selective alkaline method demonstrated the presence of the toxic hexavalent chromium in lower concentration than trivalent form.     

Cloud-point extraction and preconcentration of cyanobacterial toxins (microcystins) from natural waters using a cationic surfactant

A new cloud-point extraction and preconcentration method using a cationic surfactant, Aliquat-336 (tricaprylylmethylammonium chloride), has been developed for the determination of cyanobacterial toxins, microcystins, in natural waters. Sodium sulfate was used to induce phase separation at 25 degrees C. The phase behavior of Aliquat-336 with respect to concentration of Na2SO4 was studied. The cloud-point system revealed a very high phase volume ratio compared to other established systems of nonionic, anionic, and cationic surfactants. At pH 6-7, it showed an outstanding selectivity in analyte extraction for anionic species. Only MC-LR and MC-YR, which are known to be predominantly anionic, were extracted (with averaged recoveries of 113.9 +/- 9% and 87.1 +/- 7%, respectively). MC-RR, which is likely to be amphoteric at the above pH range, was not detectable in the extract. Coupled to HPLC/UV separation and detection, the cloud-point extraction method (with 2.5 mM Aliquat-336 and 75 mM Na2SO4 at 25 degrees C) offered detection limits of 150 +/- 7 and 470 +/- 72 pg/mL for MC-LR and MC-YR, respectively, in 25 mL of deionized water. Repeatability of the method was 7.6% for MC-LR and 7.3% for MC-YR. The cloud-point extraction process can be completed within 10-15 min with no cleanup steps required. Applicability of the new method to the determination of microcystins in real samples was demonstrated using natural surface waters collected from a local river and a local duck pond spiked with realistic concentrations of microcystins. Effects of salinity and organic matter (TOC) content in the water sample on the extraction efficiency were also studied.