体外仿生法研究牡蛎和蛤仔体内微量金属元素的生物可给性

采用体外全仿生消解方法,模拟人体的消化道环境,对牡蛎和蛤仔样品进行仿生消解,分析牡蛎和蛤仔体内微量元素的生物可给性.以原子吸收光谱法测定胃、肠仿生提取液中微量元素的含量.结果表明,牡蛎胃提取液中Fe,Cu,Zn,Cd的含量明显高于肠提取液中的含量,蛤仔胃提取液中Fe,Cu的含量与肠提取液中的含量没有明显差异,而Zn,Cd的含量远高于其在肠提取液中的含量.经全仿生消解后,牡蛎体Fe,Cu,Zn,Cd的可给性分别为60.2％,83.6％,83.1％,76.8％;蛤仔Fe,Cu,Zn,Cd的可给性分别为46.3％,86.3％,85.3％,87.7％.本研究结果为进一步研究牡蛎和蛤仔对金属元素的累积和迁移、生物可利用性,Cd等有害元素对食用者的健康风险评估,提供技术支持和理论依据.     

体积排阻高效液相色谱-电感耦合等离子体质谱测定印度芥菜中镉的形态

建立了体积排阻高效液相色谱-电感耦合等离子体质谱法(SEC-HPLC-ICP-MS)测定镉超积累植物印度芥菜中镉的形态分析方法.在镉胁迫下,诱导产生植物螯合肽(PCs).因此,在叶片和根部均检测到植物螯合肽(PC)3-Cd、植物螯合肽(PC)2-Cd、谷胱甘肽(GSH)-Cd,及半胱胺酸(Cys)-Cd 4种形态.研究结果证明,植物螯合肽的合成机制为先形成GSH-Cd而后形成植物螯合肽.在植物不同部位,Cd存在形态不同.叶片中主要以GSH-Cd存在,而在根部主要以PC2-Cd为主,结合不同镉刺激浓度条件下植物体内镉分布规律初步推断:根部PC2-Cd除了自身合成产生外,还有部分为叶部转移.为了防止巯基化合物氧化反应的发生,样品采取液氮保护并于-70 ℃保存,样品分析全流程用氮吹防氧化措施.     

广州市售四种贝类重金属含量分析及评价

采用电感耦合等离子体原子发射光谱法,对广州市售4种食用贝类体内Cd、Cr、Cu、Pb、As进行检测,分析其重金属污染状况,对其质量安全进行评价。结果表明,缢蛏、波纹巴非蛤、丽文蛤和菲律宾蛤仔,Cd、Cr、Cu、Pb含量均低于国家无公害标准,而As含量均超过国家无公害标准。分析认为,广州市售4种贝类已受到一定程度的As污染,应引起重视。     

应用体外仿生模型分析海藻水煎液中微量金属的形态和生物可给性

将体外"半仿生消化"和"全仿生消化"法分别应用于海藻分析前处理,即模拟人体消化环境,加入消化液所含有机物和无机物,模拟海藻(海带和紫菜)水煎液在胃肠中的吸收和转运机制.鉴于消化管和血管间的生物膜是类脂质膜,以单层脂质体为细胞生物膜模型考察海藻水煎液中微量金属在单层脂质体-水体系中的分配行为.以单层脂质体结合态、水溶态界定水煎液中微量金属的形态; 以单层脂质体结合态含量评价微量金属的生物可给性; 比较单层脂质体结合态金属在胃肠中浓度,确定微量金属的主要吸收部位.消化酶对海藻中微量元素的形态和生物可给性影响明显.水煎液全仿生消化后,海带和紫菜中的Fe均主要在胃被吸收,海带中的Mn和Zn主要在肠被吸收;紫菜中的Mn和Zn在胃与肠均有吸收.     

仿生消化-单层脂质体萃取在蕨类植物微量金属形态分析和生物可给性评价中的应用

依据化学仿生原理,将整体药物研究与分子药物研究法(以微量元素为指标)相结合,设计体外仿生消化法用于蕨类植物分析前处理。以单层脂质体为细胞膜模型,萃取分离食糜中微量元素形态(单层脂质体亲合态、水溶态);根据单层脂质体亲合态含量对微量元素的生物可给性和危险性进行评价。比较单层脂质体结合亲和态金属在胃、肠中浓度,可得金属主要吸收部位。沙椤茎、叶和蜈蚣草茎、叶成年人摄入安全剂量分别为210.4、153.5、828.2、367.5 g/day,最大摄入剂量分别为864.1、1208.8、2067.1、1977.3 g/day。     

准静态扫集胶束电动毛细管色谱法测定扇贝样品中的贝类毒素

采用准静态扫集胶束电动毛细管色谱(MEKC)法测定了扇贝样品中的2种贝类毒素。毛细管内首先充满含十二烷基硫酸钠(SDS)的缓冲溶液,调节缓冲溶液的pH值,使电渗流等于SDS胶束的电泳流速,电动进样时,带正电荷的贝类毒素离子被SDS扫集吸附,由于SDS在毛细管内处于准静止状态,可使进样时间延长至320 s。与常规电动进样MEKC相比,石房蛤毒素和软骨藻酸的检测灵敏度分别提高950和810倍。该方法对石房蛤毒素和软骨藻酸的检出限分别为0.05,0.12 ng/m L。方法可实现对扇贝样品中2种贝类毒素的快速、灵敏检测。     

镧(Ⅲ)离子对菲律宾蛤仔不同组织金属硫蛋白诱导的研究

稀土离子能否诱导海洋生物的金属硫蛋白(MT)合成,将影响到MT对海水重金属的指示作用。以菲律宾蛤仔(Ruditapes philippinarum)为试验动物,采用含镧(Ⅲ)离子(La3+)的人工海水对其进行暴露培养,测定得到蛤仔鳃部和内脏中MT含量随暴露浓度和时间的变化。结果表明,La3+能够促进蛤仔MT的诱导,当以1×102μg.L-1La3+对蛤仔暴露培养5 d时,鳃部和内脏MT含量均达到最高水平,分别为0.135±0.014μmol-SH/g和0.276±0.025μmol-SH/g;1×10-1~1×102μg.L-1的La3+对鳃部MT的诱导作用较大,继续增加La3+浓度,诱导作用有所降低;1×10-1~1×104μg.L-1的La3+对内脏MT均有较好诱导,并基本保持恒定,表明La3+对机体MT的诱导具有一定限度。值得注意的是,我国某些海域的海水稀土离子浓度已达到可诱导双壳类MT合成的水平。     

成都经济生态区大气降尘中镉赋存形态的研究

采用Tessier连续提取法对成都经济生态区不同区域的24个大气降尘样中镉的赋存形态进行了研究。研究结果表明,大气降尘中的镉主要以残留态形态存在;各形态镉在总镉中所占百分比含量由大到小排列顺序依次是:残留态,碳酸盐结合态,交换态,铁锰结合态,有机结合态;交换态镉、碳酸盐结合态镉这两种具有较高生物有效性的形态镉在总镉中所占的平均百分比含量分别是6.420%和8.917%;铁锰氧化物结合态、有机结合态、残留态镉这三种形态镉生物有效性很低,分别在总镉中所占的平均百分比含量分别是3.419%、2.365%和78.907%。通过分析可得出,汽油和煤的燃烧以及工厂排放镉能加大城市大气降尘的镉污染。     

纳米钛富集水样重金属镉-胶体金免疫层析法快速检测方法的建立

研究了纳米TiO2分离富集水样中痕量镉的最佳反应条件,应用自制抗Cd(Ⅱ)-iEDTA(Isothiocya-nobenzyi-EDTA)螯合物的单克隆抗体,建立了快速检测环境水样中重金属镉残留的胶体金免疫层析法。采用纳米钛富集水样中的痕量镉,用洗脱剂将吸附的镉离子洗脱后,再采用胶体金免疫层析法快速判断镉离子浓度,进而分析水样中的重金属镉含量。结果表明,pH 9.0时,Cd可被纳米TiO2定量富集,吸附于纳米TiO2上的镉离子可用0.1 mol/L的EDTA.2Na(乙二胺四乙酸二钠)溶液定量脱附。在优化实验条件下,纳米TiO2对Cd的吸附容量为14.7 mg/g,富集倍数可达50倍。制备了比色法判定结果的胶体金试纸条,并建立了纳米TiO2富集-胶体金试纸条联用检测方法。对实测样品的检测耗时约90 min,该方法对Cd的定量下限可达5μg/L,适用于环境水样的检测。     

中草药龙胆中微量元素的形态分析

采用传统煎煮法对丽水当地中草药龙胆中钙、锌、铁、铜、锰、铅、镉和铬等8种元素进行提取,并用微孔滤膜分离提取液中可溶态与悬浮态;利用大孔吸附树脂分离可溶态中有机态与无机态;采用正辛醇/水分配体系模拟水煎液中这8种微量元素在人体胃肠中分配情况,再用火焰原子吸收光谱法(FAAS)测定了各种形态中的8种元素。研究结果显示:龙胆中8种元素的提取率在34.25%～74.53%,浸留比在49.58%～371.1%,悬浮态颗粒吸附率在6.5%～29.8%,该法对各元素的加标回收率在91.3%～108.5%;相对标准偏差小于3.5%;锌、铁、铜、锰在正辛醇/水分配体系中溶出性受酸碱性影响大些。     

Speciation of heavy metal binding non-protein thiols in Agropyron elongatum by size-exclusion HPLC-ICP-MS

An analytical approach based on the coupling of size-exclusion HPLC with ICP-MS was used for studying the speciation of heavy metal binding non-protein thiols (NPTs) in extracts of Agropyron elongatum. A non-oxidizing (N₂) preparation environment and a −85 °C preservation condition were employed to avoid the oxidation of sulfhydryl groups and corresponding decomposition of the heavy metal binding NPTs. The accumulated free heavy metal ions on the column were cleaned by a 10 mmol/l 2-mercaptoethanol eluate so as to avoid these free heavy metal ions in exchanging with the metals from NPT complexes. When these precautions were taken, the on-line size-exclusion HPLC-ICP-MS method allowed very low levels of procedural blanks for Cd, Cu and Zn, and the limits of detection were 0.4, 2.1 and 2.3 μg/l for Cd, Cu and Zn, respectively. Then, the method was applied to the study of heavy metal binding NPTs in roots of Agropyron elongatum. Results showed that the nutrient heavy metals (Cu and Zn) were bound to GSH and Cysteine both under Cd stress and in the control. Under Cd stress, phytochelatins (PCs) were induced, but, these PCs induced by Cd were not only bound to Cd, but also to Cu. Interestingly, neither GSH-Cd nor Cysteine-Cd, which was presumed to be the precursors of the PC-Cd, was detected in the extracts. This leads to the question about GSH-Cd or Cysteine-Cd as precursors of PCs, which warrants further investigation.     

Application of high-performance liquid chromatography--inductively coupled plasma mass spectrometry to the investigation of cadmium speciation in pig kidney following cooking and in vitro gastro-intestinal digestion

The speciation of cadmium in retail pig kidney has been examined by size-exclusion chromatography (SEC) coupled directly to inductively coupled plasma mass spectrometry (ICP-MS). Approximately 35% of the cadmium from uncooked kidney was soluble after aqueous extraction at pH 8 and SEC - ICP-MS revealed three discrete peaks whose retention times corresponded to estimated relative molecular masses of 1.2 x 10(6), 7.0 x 10(4) and 6 x 10(3)-9 x 10(3). In the cooked kidney, 35% of the Cd was soluble and was all associated with a peak of a relative molecular mass (Mr) of 6 x 10(3)-9 x 10(3). After simulated gastric digestion of cooked pig kidney at pH 2.5, 60% of the cadmium was solubilised and associated with a species of Mr less than 1 x 10(3). When the digest was also subjected to simulated intestinal digestion at pH 6.8, a single peak, which corresponded to 20% of the original cadmium, was eluted. This peak co-eluted with the single peak extracted at pH 8.0 from the cooked kidney. It was also of similar estimated Mr to the single broad peak observed after simulated gastro-intestinal digestion of equine renal metallothionein (Mr = 1.1 x 10(4]. The results suggest that the majority of soluble cadmium in retail pig kidney is associated with a metallothionein-like protein that survives both cooking and simulated in vitro gastro-intestinal digestion.     

Spectrophotometric determination of traces of metallic ions and their mixtures with 3-methyl-1,2-cyclopentanodione dithiosemicarbazone: I. Zinc,cadmium, and mercury

The properties of zinc, cadmium, and mercury complexes of 3-methyl-1,2-cyclopentanodione dithiosemicarbazone and the optimal conditions for their formation are described. The complexes were used with success in the photometric determination of traces of zinc, cadmium, and mercury. Seven procedures are proposed for the accurate analysis of Zn(II)-Cd(II), Zn(II)-Hg(II), Zn(II)-Bi(III), Cd(II)-Hg(II), Cd(II)-Bi(III), Hg(II)-Bi(III), and Zn(II)-Cd(II)-Hg(II) mixtures. Satisfactory results were obtained.     

火焰原子吸收光谱法分析中药中锌的形态

采取正辛醇水分配体系模拟中药水煎液中锌在人体胃肠中的分配情况，用原子吸收光谱法测定了十二味中药药材及其水剪液中锌的含量，水煎液中水溶态锌、醇溶态锌的含量。实验结果表明，中药中锌的水煮溶出率较氏，中药中锌的形态与中药成分，配伍情况及作用靶位（胃肠）的酸度有关，酸度及配伍对中药中锌的溶出率及水煎液中锌的形态影响较大。     

Speciation analysis of antimony in marine biota by HPLC-(UV)-HG-AFS: Extraction procedures and stability of antimony species

Speciation analysis of antimony in marine biota is not well documented, and no specific extraction procedure of antimony species from algae and mollusk samples can be found in the literature. This work presents a suitable methodology for the speciation of antimony in marine biota (algae and mollusk samples). The extraction efficiency of total antimony and the stability of Sb(III), Sb(V) and trimethylantimony(V) in different extraction media (water at 25 and 90 °C, methanol, EDTA and citric acid) were evaluated by analyzing the algae Macrosystis integrifolia (0.55 ± 0.04 μg Sb g⁻¹) and the mollusk Mytilus edulis (0.23 ± 0.01 μg Sb g⁻¹). The speciation analysis was performed by anion exchange liquid chromatography (post-column photo-oxidation) and hydride generation atomic fluorescence spectrometry as detection system (HPLC-(UV)-HG-AFS). Results demonstrated that, based on the extraction yield and the stability, EDTA proved to be the best extracting solution for the speciation analysis of antimony in these matrices. The selected procedure was applied to antimony speciation in different algae samples collected from the Chilean coast. Only the inorganic Sb(V) and Sb(III) species were detected in the extracts. In all analyzed algae the sum of total antimony extracted (determined in the extracts after digestion) and the antimony present in the residue was in good agreement with the total antimony concentration determined by HG-AFS. However, in some extracts the sum of antimony species detected was lower than the total extracted, revealing the presence of unknown antimony species, possibly retained on the column or not detected by HPLC-(UV)-HG-AFS. Further work must be carried out to elucidate the identity of these unknown species of antimony.     

Assessment of total arsenic and arsenic species stability in alga samples and their aqueous extracts

In order to achieve reliable information on speciation analysis, it is necessary to assess previously the species stability in the sample to analyse. Furthermore, in those cases where the sample treatment for species extraction is time-consuming, an assessment of the species integrity in the extracts is of paramount importance. Thus, the present paper reports total arsenic and arsenic species stability in alga samples (Sargassum fulvellum and Hizikia fusiformis), as well as in their aqueous extracts, which were stored in amber glass and polystyrene containers at different temperatures. Total arsenic determination was carried out by inductively coupled plasma atomic emission spectroscopy (ICP-AES), after sample acid digestion in a microwave oven, while arsenic speciation was conducted by anion exchange high performance liquid chromatography on-line coupled to ICP-AES, with and without sample introduction by hydride generation (HPLC-ICP-AES and HPLC-HG-ICP-AES), after aqueous microwave-assisted extraction. The results obtained for solid alga samples showed that total arsenic (for Hijiki alga) and arsenic species present (As(V) for Hijiki and NIES No. 9 Sargasso) are stable for at least 12 months when samples are stored in polystyrene containers at +20 degrees C. On the other hand, a different behaviour was observed in the stability of total arsenic and As(V) species in aqueous extracts for both samples, being the best storage conditions for Sargasso extracts a temperature of -18 degrees C and polystyrene containers, under which they are stable for at least 15 days, while Hijiki extracts must be stored in polystyrene containers at +4 degrees C in order to ensure the stability for 10 days.     

Sequential extraction procedure for speciation of inorganic cadmium in emissions and working areas

A sequential extraction procedure for separating and concentrating soluble Cd(II) salts, CdO, Cd(0), CdS, CdSe and cadmium-aluminosilicates, has been developed for the cadmium speciation in samples such as particulate matter in emissions and working areas. The proposed procedure has been tested first on synthetic samples prepared in a laboratory with the different cadmium salts, then also in the presence of atmospherical particulate matter sampled in a laboratory of the Department of Analytical Chemistry, previously checked for the absence of cadmium. Finally the speciation was tested on particulate matter collected near the emission of a power plant fed by coal, after emission's treatment by electrostatic precipitator: matrix spiking and recovery analyses have been evaluated and the repeatability of the cadmium speciation was assessed by performing multiple analyses of the spiked samples. Quantitative determinations have been made by FAAS and GFAAS through the standard additions method.     

Identification of a metallothionein in Synechococcus by capillary electrophoresis hyphenated with inductively coupled plasma mass spectrometry.

A home-made system hyphenating capillary electrophoresis with an inductively coupled plasma mass spectrometer (CE-ICP-MS) for cadmium speciation of protein-binding and free cadmium ions in solution is presented. The CE-ICP-MS interface consisted of an acrylic block with an internal volume ca. 20 microL in which a platinum electrode, a capillary column, and a connection to an ICP nebulizer were inserted. A make-up electrolyte solution containing 50 mmol L(-1) Tris-HCl buffer solution (pH 9.0) was continuously flowed through the interface to the ICP nebulizer. The separation of free Cd ions, Cd-cysteine, and Cd bounded to metallothionein (MT) isoforms from rabbit liver was carried out by capillary electrophoresis, and the analytes were detected by ICP-MS. The feasibility to isolate metallothionein compounds extracted from the cyanobacterium Synechococcus PCC7942 was demonstrated. The Cd binding proteins were induced in Synechococcus PCC7942 and further analyzed by CE ICP-MS.     

Stability of total selenium and selenium species in lyophilised oysters and in their enzymatic extracts

To obtain reliable information on speciation analysis it is necessary to previously evaluate the stability of the species in the sample of interest. Furthermore, in those cases in which sample treatment to extract the species is time-consuming, an evaluation of how to maintain species integrity in the extracts is paramount. Thus, the present paper reports the stability of total Se, SeMet and TMSe+ in freeze-dried oyster and in the enzymatic extracts stored in Pyrex and polyethylene containers at different temperatures (-18, 4 and 20 degrees C). Total selenium determinations and Se speciation were carried out by HG-AAS after acid digestion in a microwave oven and by on-line coupling of cation exchange HPLC-ICP-MS after enzymatic hydrolysis, respectively.The results obtained for the freeze-dried sample showed that total Se and the selenium species evaluated are stable for at least 12 months, under all the conditions tested. However, Se species in the enzymatic extracts are only stable for 10 days if stored at 4 degrees C in Pyrex containers. These results show that the extracts do not necessarily have to be analysed just after sample treatment.