巯基棉富集-表面活性剂增溶光度法测定茶叶中的汞

为了快速、高效、简便、准确的测定食品中的痕量汞,实验以龙井茶为材料,样品经过微波消解、巯基棉(SCF)分离富集后,以汞离子在酸性溶液和表面活性剂存在的条件下,可与硫代米蚩酮(TMK)形成胶束增溶配合物为基础,建立了微波消解-巯基棉分离富集—表面活性剂增溶分光光度法测定茶叶中痕量汞的方法。结果表明:微波消解功率400 W,消解时间5 min,p H值为4.5,表面活性剂十二烷基苯磺酸钠2 m L,硫代米蚩酮(TMK)2 m L时测定条件最佳;其线性方程为Y=0.037 2X+0.003 1,相关系数r=0.999,经检测龙井中汞的含量为0.013 9 mg/kg,加标回收率为99.91%,RSD为4.0%。     

螺旋藻预富集-FAAS测定干制品浸出液中的痕量铜

建立了螺旋藻预富集-火焰原子吸收光谱法测定干制品浸出液中的痕量铜的方法,讨论了螺旋藻的预处理方法、用量、颗粒大小、洗脱剂类型、洗脱剂浓度、洗脱流速、pH值等对干制品中痕量铜富集效果的影响。结果表明,在交换柱内径为0.8 cm、柱高为15 cm、螺旋藻用量为2 g、pH值6的条件下,干制品浸出液流速为10mL/min时,用0.6 mol/L HCl以6 mL/min的速度洗脱,可对Cu2+进行高效富集。用该方法测定几种干制品中的痕量铜,当n=6时,SD为0.000 02～0.000 09,RSD为2.5%～4.2%,特征浓度为0.059μg/L,加标回收率为97%～103%。     

预富集-氢化物发生原子吸收光谱法测定水产品中的痕量硒

研究了预富集-氢化物发生原子吸收光谱法测定水产品中的痕量硒的新方法。用吡咯烷二硫代氨基甲酸铵(APDC)作配位剂,在pH4.0～6.5的条件下,用固体硅胶捕集、膜滤纸抽滤分离Se-APDC配合物,然后用0.1moL/L盐酸从膜滤纸上洗下硅胶,得到能够直接用氢化物原子吸收光谱法测定的硒悬浊液。该法操作简便,富集速度快。100mL溶液,特征质量为1.5×10-11g/1%。在最佳条件下,用这个方法测定了水产品中的痕量硒,当n=6时,标准偏差为0.0027～0.0054,变异系数为0.012～0.028,样品的加标回收率在95.2%～104.6%之间,结果较为满意。     

APDC 和氧化铝富集-冷原子吸收光谱法测定水产品中的痕量汞

用吡咯烷二硫代氨基甲酸铵(APDC)作配位剂,在pH=5.0～6.0的条件下,用氧化铝捕集、膜滤纸抽滤分离Hg-APDC配合物.然后用0.1moL/L盐酸从膜滤纸上洗下氧化铝,得到能够直接用冷原子吸收光谱法测定汞的悬浊液.该法特征质量为2.1×10～11g/1%.在最佳条件下,用这个方法测定了5种水产品中的痕量汞,当测定次数n=6时,标准偏差SD为0.0314.0.136,相对标准偏差RSD为1.67%～2.87%,样品的加标回收率在94.2%～101%之间,结果较为满意.     

应用氢化物发生-原子荧光光谱法联合测定面粉中的砷和汞

研究了应用氢化物发生-原子荧光光谱法联合测定面粉中砷和汞,该方法灵敏度高、准确度好。在最佳条件下,以50g/L硫脲+50g/L抗坏血酸为预还原剂,荧光强度与砷浓度在0.0378ng.mL-1～100ng.mL-1范围内呈线性关系,检出限达0.0378 ng.mL-1,荧光强度与汞浓度在0.0227ng.mL-1～50ng.mL-1范围内呈线性关系,检出限达0.0227 ng.mL-1;测定8个面粉样品中砷、汞,相对标准偏差:砷为1.68以下,汞为1.82以下;回收率:砷为90.9%～113.2%,汞为92.4%～107.7%。     

海带预富集-石墨炉原子吸收光谱法测定饮料中的痕量铜

建立一种测定饮料中痕量铜的新方法.采用O.5 mol/mL HCI超声震荡清洗后的海带粉末,在pH值5～6的条件下捕集饮料中的痕量铜,经膜滤纸抽滤分离,用0.2 mol/mL的HCI洗涤,超声震荡离心后,经过离心得到富集了铜的离心液,再用GFAAS石墨炉原子吸收光谱法测定.在100 mL样品中,检测限为7.14×10-12g/mL,当n=6时,矿泉水等5种饮料中铜的含量为0.054～0.213 ng/mL,相对标准偏差为0.027～0.053,样品加标回收率为91.7%和103.1%.采用该方法测定饮料中的痕量铜具有较高的富集效率和准确度,分析结果较为满意.     

离子交换富集ICP-AES法测定白酒中的痕量元素

探索了离子交换分离富集/ICP-MS法测定白酒中痕量元素的方法.采用734强酸性阳离子交换树脂,以中性白酒上柱,0.25～0.35 mol/L HCl洗脱,流速1.0 mL/min,高效富集了白酒中的Cu、Zn、Cd和Pb元素,富集效率达100～500倍甚至更高,用ICP-AES可测定白酒中ppb～ppt级的超痕量元素,RSD 1.89%～8.40%,加标回收率87.3%～106.8%.     

方波溶出伏安法测定茶叶中的痕量铅

研究提出了一种基于方波溶出伏安法的电化学传感器测定食品(茶)中痕量铅的快速测定新技术。优化了电极预镀汞膜的条件,最佳底液浓度及pH;最佳仪器条件参数等。实验结果表明,在优化条件下,溶出峰电流与铅浓度在0～6.7×102μg/L范围内呈现良好的线性关系,其回归方程为:Ip(μA)=-0.522-3.5642C(μg/L),相关系数为0.997,检出限为3.76μg/L。得出茶样中含铅的浓度为1.15mg/kg,且回收率达到89.9%～102.3%。由此可知,用研究出来的方波溶出伏安法电化学传感器测定茶叶中的痕量铅,具有快速、准确、简便、灵敏等优点。     

直接进样测汞法测定食品中总汞含量

建立了直接进样测汞法测定食品中总汞含量的方法。样品经高温灼烧及催化热解后,汞被还原成汞单质,用金汞齐富集带入检测器,在253.7 nm波长处进行原子吸收光谱测定。方法检出限为0.000 86 mg·kg^-1,加标回收率为70.3%～109.0%,精密度为0.93%～1.58%。方法操作简单,快速稳定,适合食品中微量汞的测定。     

用快速分离柱高效液相色谱法测定食品中的重金属元素的研究

研究了用固相萃取富集,快速分离柱高效液相色谱法测定食品中6种重金属元素:镍、铜、锡、铅、镉、汞的方法。食品样品用微波消化,样品消化液中的镍、铜、锡、铅、镉、汞用四-(邻氯苯基)-卟啉(T2CPP)柱前衍生,然后用ZORBAXRP1固相萃取小柱萃取富集镍、铜、锡、铅、镉、汞的T2-CPP络合物,富集8倍数为50倍;经富集后的络合物用甲醇-四氢呋喃(92/8)为流动相,ZORBAXStableBound(4.6×50mm,1.8μm)快速分离柱为固定相分离,用二极管矩阵检测器检测。镍、铜、锡、铅、镉、汞的检测限分别为:3、4、4、3、2、2ng/L,分离6种重金属元素络合物的时间只需2.0min。方法相对标准偏差为2.3%～2.8%,标准回收率为95%～105%。该方法用于测定食品中的痕量镍、铜、锡、铅、镉、汞,结果令人满意。     

Dry deposition fluxes and deposition velocities of trace metals in the Tokyo metropolitan area measured with a water surface sampler

Dry deposition fluxes and deposition velocities (=deposition flux/atmospheric concentration) for trace metals including Hg, Cd, Cu, Mn, Pb, and Zn in the Tokyo metropolitan area were measured using an improved water surface sampler. Mercury is deposited on the water surface in both gaseous (reactive gaseous mercury, RGM) and particulate (particulate mercury, Hg(p)) forms. The results based on 1 yr observations found that dry deposition plays a significant if not dominant role in trace metal deposition in this urban area, contributing fluxes ranging from 0.46 (Cd) to 3.0 (Zn) times those of concurrent wet deposition fluxes. The deposition velocities were found to be dependent on the deposition of coarse particles larger than approximately 5 microm in diameter on the basis of model calculations. Our analysis suggests that the 84.13% diameter is a more appropriate index for each deposited metal than the 50% diameter in the assumed undersize log-normal distribution, because larger particles are responsible for the flux. The deposition velocities for trace metals other than mercury increased exponentially with an increase in their 84.13% diameters. Using this regression equation, the deposition velocities for Hg(p) were estimated from its 84.13% diameter. The deposition fluxes for Hg(p) calculated from the estimated velocities tended to be close to the mercury fluxes measured with the water surface sampler during the study periods except during summer.     

Vancomycin-resistant enterococci in shellfish,unchlorinated waters,and chicken

Vancomycin-resistant enterococci (VRE) have been a cause of increasing concern chiefly regarding the infection of hospital patients. There is suspicion, but limited evidence, that food and environmental spread may be important. Biomonitoring by examination of bivalve shellfish was used to assess the occurrence of VRE entering the environment. Using pre-enrichment and Lewisham and Slanetz and Bartley agars, 2/125 (1.6%) of shellfish were found to contain enterococci resistant to high levels of vancomycin. Lewisham agar allows relatively rapid identification of VRE. In a second phase of the work using pre-enrichment and Slanetz and Bartley agar, 4/151 (2.7%) shellfish and 5/27 (18.5%) raw chickens contained VRE. Using filtration and pre-enrichment, no VRE were found in 54 unchlorinated water samples. The study shows that environmental prevalence of VRE is low, and that raw chickens are frequently contaminated.     

Novel polymeric chelating fibers for selective removal of mercury and cesium from water

We report here the synthesis and characterization of two new classes of chelating fibers, namely, (1) polymercaptopropylsilsesquioxane (PMPS) and (2) copper(II) ferrocyanide complexed with poly[1-(2-aminoethyl)-3-aminopropyl]silsesquioxane (Cu-FC-PAEAPS) fibers. These fibers were evaluated for selective removal of trace amount of mercury and cesium ions respectively in the presence of competing metal ions from water. The PMPS and Cu-FC-PAEAPS fibers were prepared by coating their corresponding soluble prepolymers, which are derived from mercaptopropyltrimethoxysilane and [1-(2-aminoethyl)-3-aminopropyl]trimethoxysilane monomers, respectively, on a glass fiber substrate, followed by a cross-linking step at 120 degrees C. The fibers were characterized through infrared spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). These novel materials are extremely efficient in removing low concentrations of mercury and cesium ions from water in the presence of high concentrations of sodium or potassium ions. They were shown to remove trace mercury and cesium contaminants effectively to well below parts per billion concentrations under a variety of conditions.     

微波消解-氢化物发生双道原子荧光光谱法同时测定糖蜜中的砷和汞

建立了微波消解-氢化物发生双道原子荧光光谱法同时测定糖蜜样品中砷和汞的分析方法。实验探索了酸的种类比例、固液比、微波强度、消解时间等各种微波消解条件,并对工作条件进行了优化。仪表检出限为砷0.0704μg/L,汞0.0089μg/L;精密度为砷1.13%,汞0.49%;样品加标回收率为砷96.1%～107.6%,汞102.3%～105.1%。应用该方法对广西某制糖集团下属公司的糖蜜中砷和汞的含量进行了分析,结果令人满意。     

Assay of Total Mercury in Commercial Food Supplements of Marine Origin by Means of DLLME/ICP-AES

In this work, we have developed a sensitive and cost-effective preconcentration and quantification methodology for total mercury (Hg) at trace levels in food supplements of marine origin. Dispersive liquid–liquid microextraction was successfully employed for the preconcentration of mercury at trace levels prior to inductively coupled plasma atomic emission spectrometry. The mercury was extracted as mercury-1, 5-diphenyl-3-formazathiol complex, at pH 1.0 mediated by multidroplet formation of microextraction solvent assisted by disperser solvent. The lower limit of detection obtained under the optimal conditions was 0.24 μg L⁻¹. The calibration graphs were linear up to 500 μg L⁻¹. The precision of the method in terms of relative standard deviation was 4.8% for the concentration of 100 μg L⁻¹. In order to validate the proposed method, a certified reference material RTC-QCI-049 was analyzed with the proposed procedure. Moreover, potential interference by 20 species was also evaluated.     

Hg L3 XANES study of mercury methylation in shredded Eichhornia crassipes

Eichhornia crassipes (water hyacinth) is a non-native plant found in abundance in the Sacramento-San Joaquin River Delta (hereafter called Delta). This species has become a problem, clogging waterways and wetlands. Water hyacinth are also known to accumulate mercury. Recent attempts to curb its proliferation have included shredding with specialized boats. The purpose of this research is to better understand the ability of water hyacinth to phytoremediate mercury and to determine the effect of shredding and anoxic conditions on mercury speciation in plant tissue. In the field assessment, total mercury levels in sediment from the Dow Wetlands in the Delta were found to be 0.273 +/- 0.070 ppm Hg, and levels in hyacinth roots and shoots from this site were 1.17 +/- 0.08 ppm and 1.03 +/- 0.52 ppm, respectively, indicating bioaccumulation of mercury. Plant samples collected at this site were also grown in nutrient solution with 1 ppm HgCl2 under (1) aerobic conditions, (2) anaerobic conditions, and (3)with shredded plant material only. The greatest accumulation was found in the roots of whole plants. Plants grown in these conditions were also analyzed at Stanford Synchrotron Radiation Laboratory using Hg L3 X-ray Absorption Near Edge Spectroscopy (XANES), a method to examine speciation that is element-specific and noninvasive. Least-squares fitting of the XANES data to methylated and inorganic mercury(II) model compounds revealed that in plants grown live and aerobically, 5 +/- 3% of the mercury was in the form of methylmercury, in a form similar to methylmercury cysteine. This percentage increased to 16 +/- 4% in live plants grown anaerobically and to 22 +/- 6% in shredded anaerobic plants. We conclude that shredding of the hyacinth plants and, in fact, subjection of plants to anaerobic conditions (e.g., as in normal decay, or in crowded growth conditions) increases mercury methylation. Mechanical removal of the entire plant is significantly more expensive than shredding, but it may be necessary to avoid increased biomagnification of mercury in infested areas.     

Monitoring the content and intake of trace elements from food in Denmark

The content of cadmium, lead, nickel, mercury and selenium in 83 foods was monitored from 1993 to 1997. In comparison with similar results from 1988 to 1992, a general decrease in lead levels had occurred, whereas the contents of cadmium, nickel, mercury and selenium were stable or declined only slightly. The distribution in dietary intake of the five trace elements was estimated by combining the mean trace element concentrations with food consumption data from 1837 Danes aged 15-80 years. The lead intake for 1993-97 showed a decrease in comparison with similar estimates from the previous monitoring cycles: 1983-87 and 1988-92. The intake of cadmium and mercury decreased to a lesser extent, whereas the intake of selenium and nickel remained unchanged in the same period. The dietary intake of trace elements was compared with the provisional tolerable weekly intake (PTWI). The 95th percentile of the distribution in cadmium intake amounts to 34% of PTWI, which is relatively high, and therefore calls for a more detailed future risk assessment. The intakes of lead and mercury were 11% of PTWI and, like the intake of nickel, did not cause any health concern in the adult population. The Danes ingest close to 100% of the Nordic Nutrition Recommendation for selenium at 50 μg day -1 , and no individuals had an intake less than the lower limit of 20 μg day -1 .     

阳极溶出伏安法测定天然水和罐头食品中的痕量铊

<正> 铊是一种十分有用而稀少的金属,但在植物、动物和人体中含量超过一定量时,会出现中毒现象。铊中毒可能引起高血压及秃发症。天然水中铊的含量很低,已有的分光光度法、原子吸收法、中子活化法等测定痕量铊,有灵敏度低,分析手续烦长、仪器复杂而昂贵等弱点。阳极溶出伏安法测定铊,检测下限可达3.5×10~(-10)M。所以,近年来有人用微分脉冲伏安法测定铊,但干扰严重,必须预先用离子交换树脂或氢氧化镁共沉淀分离、富     

阳极溶出伏安法测定天然水和食品中痕量锑

本文提出测定天然水和食品中痕量锑的汞膜电极上阳极溶出伏安法,并对其共存元素的干扰情况进行探索。在0.3M盐酸—乙醇溶液中测定了天然水和食品中的痕量锑,得到满意的结果。     

催化动力学光度法测定茶叶中硒浸出率

在盐酸介质中,硒(Ⅳ)能强烈催化溴酸钾氧化亚甲基蓝使之褪色,据此建立测定痕量硒(Ⅳ)的催化动力学光度法,在选定的条件下,硒(Ⅳ)的测定线性范围为0～0.6μg/50mL,检出限3.63×10-10g/mL。本实验通过催化动力学光度法可测出茶叶中原茶及冲泡后硒(Ⅳ)含量,计算可得茶叶中硒(Ⅳ)浸出率。通过对铁观音、绿茶、红茶进行测定,其浸出率分别为24.7%、25.3%、22.7%,结果令人满意。