Trace Element Speciation in Soils and Sediments Using Sequential Chemical Extraction Methods

Abstract

Several commonly used sequential chemical extraction procedures of heavy metals in soils and sediments are compared, and their advantages and disadvantages are discussed focusing on selected case studies. In particular, problems caused by handling of anoxic samples, and of specific phases (e.g. organic fractions and sulfides) are addressed.

Eventually, recommendations for the improvement of extraction selectivity as well as the reduction of readsorption effects are given.     

Comparison of Two Sequential Extraction Procedures for Trace Metal Partitioning in Sediments

Abstract

Two sequential extraction schemes (a modified Tessier procedure with five steps and a three steps protocol designed by BCR) are applied to four sediment samples with different heavy metal contents. The results obtained for Cd, Cr, Cu, Ni, Pb and Zn partitioning show that the metal distribution obtained with both procedures are significantly different. With the second procedure amounts of all the heavy metals are extracted with the oxidizing reagent (third fraction) whereas with the first one the non residual metals are distributed among the second, third and fourth fractions (acetic acid-acetate buffer (pH=5), reducing and oxidizing reagents respectively). The residual fraction obtained applying the three steps procedure is in general higher than that obtained using the five steps procedure, except for cadmium.     

Evaluation of Ammonium Oxalate for Fractionating Metallic Trace Elements in Soils by Sequential Extraction

Abstract

Ammonium oxalate is largely used to extract the trace elements bound to Mn-oxides, amorphous compounds and crystalline Fe-oxides. The objective of this work was to evaluate the selectivity and the efficiency of ammonium oxalate for extracting Cd, Cu, Ni, Pb and Zn by sequential extraction of soils. For this purpose, three schemes were selected and applied to three different soil samples of the Swiss Jura. Each extraction scheme consisted of six steps, where different reagents were used to extract Cd, Cu, Ni, Pb and Zn bound to the Mn and Fe compounds. The results showed that metallic trace elements extraction with ammonium oxalate are very dependant on the metal studied. The reason could be the capability of oxalate to form stable complexes with the metals considered which sometimes are only slightly soluble.     

微顺序注射-镉柱还原分光光度法测定海水中总氮

基于微顺序注射-阀上实验室,采用镉柱还原-偶氮染料染色分光光度法测定海水中总氮,对实验参数进行了优化,并进行了干扰因素实验。结果表明,海水中主要离子和盐度对本实验方法测定会产生干扰,采用一定盐度的国家标准海水作为溶剂制备系列标准溶液,可消除干扰。海水中总氮浓度在0.03~1.00 mg/L范围内与吸光度呈良好线性,线性相关系数r=0.9993;测定含氮浓度为0.2 mg/L的国家标准海水,相对标准偏差(RSD)为4.9％;方法的检出限为0.010 mg/L;样品加标回收率在99.5％~101.1％之间。经t检验分析,本方法与国标方法测定数据无显著性差异,可用于海水样品中总氮的测定。     

Application of a Sequential Extraction Procedure to Calcareous Soil Samples: Preliminary Studies

Abstract

The localization of trace metals in soils is usually performed by sequential extraction procedures. Our purpose was to study the fractioning of copper in calcareous soils, in order to predict its mobility, using the extraction procedure proposed by Tessier et al. This preliminary study is devoted to the improvements of this method applied to calcareous soil samples.

First, it was necessary to assess the experimental conditions allowing the complete solubilisation of the different compartments involved in the extraction procedure with their appropriate reagent (acetic acid-sodium acetate and carbonates, iron hydroxide and hydroxylamine, organic matter and hydrogen peroxide, fluorhydric-perchloric acid and residual fraction). The complete solubilisation of each compartment was tested by measuring the residual phase.

Secondly, it was necessary to study the analytical protocol for the determination of copper with electrothermal atomic absorption; an improvement of this determination was particularly necessary for the reagent used for the exchangeable fraction (sodium acetate at pH = 8.5).

According to the experimental results, the quality (repeatability, concordance of the sum of fractions with the total content of copper determined with independent measurement) of the proposed protocol seems to be quite good.

Some results of the fractioning of copper in calcareous soil samples are given; these samples are characterised by a high value of copper in the residual fraction corresponding to a poor availability of this element.     

化学提取方法快速评估污染土壤中生物可消化性铅

为建立一种简单的方法鉴定污染土壤中的铅在消化系统中被人体消化吸收的潜力（即生物可消化性或生物可接受性）,采用连续提取法和7种单一化学提取法比较研究了13个污染土壤中铅的化学形态及其可提取性,以模拟胃液提取法为参比,选择和比较了7种化学提取剂,包括：CaCl2稀盐、NH4OAc、DTPA—TEA、Mehlich Ⅰ、Mehlich Ⅲ、草酸铵缓冲液和盐酸羟铵溶液。结果表明,土壤中铅的平均提取率由高至低依次为：草酸铵缓冲液,盐酸羟铵溶液,MehlichⅠ、MehlichⅢ,DTPA—TEA,NH4OAc,CaCl2相关分析表明,氧化物结合态铅是污染土壤中生物可消化铅的主要组分,用盐酸羟铵溶液提取的铅可很好地表征污染土壤中铅的生物可消化性,其提取量与模拟胃液提取的铅接近,两者之间具有显著的相关性。     

提取脂质的改良干柱法

报道了一种提取脂质的改良干柱法。用低毒溶剂正己烷/异丙醇(3∶2,V/V)作洗脱剂代替干柱法中毒性较强的二氯甲烷/甲醇,通过对重要提取条件的考察,建立了改良干柱法提取脂质的最佳条件,并对干柱法提取机理进行了探讨。使用7.5cm×27mmi.d.玻璃层析柱,内装2.0gCaHPO4·2H2O/Celite545(1∶9),再装入样品、无水Na2SO4、Celite545混合物制备干柱。用40mL正己烷/异丙醇(3∶2,V/V)进行洗脱,可在40min内洗脱完毕。测定了6种肉制品的脂质含量,并做了脂肪酸分析,结果与传统的氯仿/甲醇法一致,统计检验表明,两方法间不存在显著性差异,但改良干柱法洗脱剂毒性更低、试剂用量更少。     

Improvement of Analytical Measurements within the BCR-Programme: Single and Sequential Extraction Procedures Applied to Soil and Sediment Analysis

Abstract

The determination of extractable trace metal contents in soil and sediment, using respectively single and sequential extraction procedures, is currently performed in many laboratories to assess the bioavailable metal fraction (and related phyto-toxic effects) and the accessability to the environment (e.g. contamination of ground waters).

Owing to the need for validation of the extraction schemes used and of the analytical techniques, the Community Bureau of Reference (BCR) decided to organize a project for the improvement of the quality of determinations of extractable trace metal contents in soil and sediment. The implementation of this project follows a stepwise approach involving feasibility studies, intercomparisons to detect and remove sources of errors in the application of the analytical methods, and the certification of the extractable compounds. This paper describes the organization of the work completed so far (feasibility studies and first intercomparison) and discusses its further development.     

New Approaches to the Extraction of Arsenic Species from Soils

Arsenic extraction in natural and spiked soil samples was studied using two main types of extractants. The extractants were phosphoric acid used alone and with the addition of reducing agents (ascorbic acid and hydroxylammonium hydrochloride). The stability of arsenite (As(III)), arsenate (As(V)), monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) in the extracts over time and under different storing conditions was assessed by means of LC-HG-AFS. A protocol was devised to extract arsenic species from soils. The protocol assures the stability of the original sample species in the extract proposed by using an extraction solution of phosphoric acid with ascorbic acid and by purging the extracts after microwave extraction. The total As, Mn and Fe content in aqua regia and in phosphoric extracts was also measured by ICP-AES in order to perform the mass balance.     

氨基硅胶毛细管整体柱萃取谷氨酸

采用溶胶-凝胶技术,以四乙氧基硅烷(TEOS)和N-(β-氨乙基)-γ-氨丙基三乙氧基硅烷(AEAPTES)为反应物,制备了含氨基的硅胶整体柱,并将其应用于谷氨酸(Glu)的萃取.在优化的条件下,一段长4 cm、内径250 μm的毛细管萃取柱的柱容量为2.5 ng.     

Sequential Extraction of Copper and Zinc from Sewage Sludges. Use of Organic Solvents

Abstract

Sequential extraction procedures were used to evaluate the bioavailability of metals from two sewage sludges after application in soils. Organic solvents were used prior to sequential extraction to evaluate the influence of oil and waxes on heavy metals extractability.

The preliminary results showed that a extraction of oil and waxes present in the sewage sludges by n-hexane followed by acetone increased the accessibility of Cu and Zn and did not remove substantial metal amounts.     

超临界流体萃取-硅胶柱收集联用提取蓬莪术中有效成分

采用超临界流体CO2萃取和硅胶柱收集在线联用,提取蓬莪术中的挥发油,随后分别用正己烷、乙醇和乙醚对硅胶柱进行选择性洗脱,从而使蓬莪术挥发油中有效成分莪术二酮的相对含量由原来单一萃取的10．7％提高到34．7％。     

Speciation of Heavy Metals in Soils and Sediments. An Account of the Improvement and Harmonization of Extraction Techniques Undertaken Under the Auspices of the BCR of the Commission of the European Communities

Abstract

An account is presented of a series of investigations and collaborative studies, initiated by BCR, on current methods of metal speciation by extraction of soils and sediments with chemical reagents. It was established by extensive consultation with European experts that the diverse procedures used could be harmonized into agreed methods. These methods, including both single extractant and sequential extraction procedures were subjected to collaborative, interlaboratory trials and the results, presented briefly here, showed that it was both possible and desirable that reference soils and sediments, characterised by certified values for extractable contents, be prepared. As a consequence of these studies two soils have been prepared and will shortly be the subject of interlaboratory analysis with a view to certification of their EDTA and acetic acid extractable contents of some heavy metals. Following this workshop a feasibility study of the agreed sequential extraction procedure will, it is believed, shortly lead to certification of sediments for contents extractable by a defined sequential extraction procedure.     

食品中46种禁限用合成色素的分级提取净化体系研究

建立了46种禁限用合成色素的分级提取净化体系,采用反相液相色谱多波长检测对该体系的效果进行了评价。提取净化体系的第一级采用正己烷振荡提取、凝胶渗透色谱净化,实现了对苏丹类染料的有效提取分离,回收率均大于80%;第二级采用水振荡提取,乙腈辅助提取的手段,实现了对大多数水溶性合成色素及工业染料的提取分离,回收率均大于60%;第三级采用甲醇-氨水振荡提取,可实现对少数极性较强染料的提取分离,回收率均大于55%。经过第二、三级提取后的样品,无需再净化,即可直接进行高效液相色谱分析,提高了分析效率。采用此体系对样品进行合成色素的测定分析,结果表明,本方法对含蛋白质、脂肪类食品基质具有较强的适用性。     

电渗泵在顺序注射萃取法测定酚中的应用

电渗泵是一种液流驱动泵,具有装置简单、载流无脉动、流量范围大和驱动电压适中等优点。用含1mmol/L三乙醇胺和0.1mmol/L四丁基溴化铵的乙醇溶液作泵载流,采用顺序注射萃取-分光光度法,对水样挥发酚进行了测定。有机载流可避免产生界面,减小检测干扰。载流添加剂可提高泵流量,改善流量稳定性。另外,还研究了酚的各种萃取条件。水中酚的检出限为7цg/L(3a,n=11);回收率为92%-94%。方法证明了电动流动分析系统可用于溶剂萃取和有机分析。     

不同方法提取菟丝子微量元素Fe，Mn和Mg的比较研究

为比较不同提取方法对菟丝子中微量元素含量的影响,采用酸式提取法、碱式提取法、沸水提取法及超声提取法对中药菟丝子中的微量元素进行提取,用原子吸收分光光度法测定了提取液中微量元素铁、锰和镁的含量并进行了比较。结果表明,4种提取方法对微量元素的溶出率由高到低顺序为：铁-酸提,超提,碱提,沸提;锰-酸提,超提,沸提,碱提。镁酸提,沸提,超提,碱提。     

提取方式对信阳山茶油品质影响与评价研究

采用超临界CO2法、超声波辅助提取法和索氏提取法提取山茶籽油,对它的理化指标、脂肪酸组成进行测定,并对茶粕有效成分进行分析。研究表明,超临界CO2法和超声波法提油率高,环保安全性和工艺效率好;索氏法提取的油茶籽油酸值过大;从茶粕有效成分含量来看,超声波辅助提取法更优。综合考虑3种提取方法,超声波辅助提取山茶油品质最优。     

大肠杆菌代谢物组测定中抽提方法的比较分析

代谢物组学作为一种重要的功能基因组学工具,已经在微生物性状改良等方面得到了应用。实施代谢物组学研究需要定性和定量分析细胞内的全部代谢物。所以,必须有一种能够提供良好的重复性和相对抽提效率较高的细胞内代谢物抽提方法。本研究以特定厌氧条件下培养的大肠杆菌为研究对象,以电喷雾质谱直接进样测定为评价标准,比较并分析了冰甲醇、热乙醇和碱抽提3种抽提方法。结果显示,冰甲醇抽提的样品在电喷雾质谱实验中表现出良好的重复性和最高的峰强度,并能够同时检测到超过20种不同的胞内代谢物。