Recent advances in on-line coupling of capillary electrophoresis to atomic absorption and fluorescence spectrometry for speciation analysis and studies of metal-biomolecule interactions

Speciation information is vital for the understanding of the toxicity, mobility and bioavailability of elements in environmental or biological samples. Hyphenating high resolving power of separation techniques and element-selective detectors provides powerful tools for studying speciation of trace elements in environmental and biological systems. During the last five years several novel hybrid techniques based on capillary electrophoresis (CE) and atomic spectrometry have been developed for speciation analysis and metal-biomolecule interaction study in our laboratory. These techniques include CE on-line coupled with atomic fluorescence spectrometry (AFS), chip-CE on-line coupled with AFS, CE on-line coupled with flame heated quartz furnace atomic absorption spectrometry (FHF-AAS), and CE on-line coupled with electrothermal atomic absorption spectrometry (ETAAS). The necessity for the development of these techniques, their interface design, and applications in speciation analysis and metal-biomolecule interaction study are reviewed. The advantages and limitations of the developed hybrid techniques are critically discussed, and further development is also prospected.     

Trace element speciation by ICP-MS in large biomolecules and its potential for proteomics

Latest studies on the chemical association of trace elements to large biomolecules and their importance on the bioinorganic and clinical fields are examined. The complexity of the speciation of metal-biomolecules associations in various biological fluids is stressed. Analytical strategies to tackle speciation analysis and the-state-of-the-art of the instrumentation employed for this purpose are critically reviewed. Hyphenated techniques based on coupling chromatographic separation techniques with ICP-MS detection are now established as the most realistic and potent analytical tools available for real-life speciation analysis. Therefore, the status and potential of metal and semimetals elemental speciation in large biocompounds using ICP-MS detection is mainly focused here by reviewing reported metallo-complexes separations using size-exclusion (SEC), ion-exchange (IE), reverse phase chromatography (RP) and capillary electrophoresis (CE). Species of interest include coordination complexes of metals with larger proteins (e.g. in serum, breat milk, etc.) and metallothioneins (e.g. in cytosols from animals and plants) as well as selenoproteins (e.g. in nutritional supplements), DNA-cisplatin adducts and metal/semimetal binding to carbohydrates. An effort is made to assess the potential of present trace elements speciation knowledge and techniques for "heteroatom-tagged" (via ICP-MS) proteomics.     

Imaging surface spectroscopy for two- and three-dimensional characterization of materials

Secondary ion mass spectrometry (SIMS) exhibits a unique potential for the measurement of two-and three-dimensional distributions of trace elements in advanced materials, which is demonstrated on relevant technological problems. One example is the characterization of high purity iron. With this material segregation experiments have been performed and the initial and final distribution of the trace elements have been measured. Another example is the investigation of the corrosion behaviour of high purity chromium. Samples oxidized with (16)O and (18)O have been measured to explain the growing and adhesion of the oxide layer. All imaging techniques generate a vast quantitiy of data. In order to extract the important information the assistance of chemometric tools is essential. Detection of chemical phases by classification using neural networks or de-noising of scanning-SIMS images by wavelet-filtering demonstrates the increase of the performance of analytical imaging techniques.     

刺苞南蛇藤微量元素的测定

目的测定刺苞南蛇藤中微量元素的含量,为刺苞南蛇藤的生物活性和药理作用的进一步研究提供参考。方法将样品经过预处理、高压釜消解后,以~(45)Se、~(72)Ge、~(115)In、~(209)Bi为内标物质,采用ICP-MS法进行测定。结果首次测定了刺苞南蛇藤中48种微量元素的含量,结果表明,刺苞南蛇藤的临床用途和元素含量密切相关。结论刺苞南蛇藤中含有丰富的微量元素,具有较高的开发利用价值。     

Recent on-line processing procedures for biological samples for determination of trace elements by atomic spectrometric methods

Few of the elements present in nature play a metabolic role in living organisms. According to their abundance, these elements are classified as macro-, micro- or trace elements, representing 93%, 5% and around 1% respectively, of the total body weight. The remaining percentage could be attributed to those elements with unknown biological functions, to others which are present only because of the exposure to polluted environment or to those intentionally introduced into the body for a special treatment. This review summarizes and discusses the most recent publications related to the on-line processing of biological samples for trace element determination using atomic spectrometry-based detectors. Preconcentration/separation procedures based on solid phase or cloud point extractions, electrochemical deposition, microdialysis, as well as chemical vapor generation are the common practice for improving the sensitivity and selectivity of the available atomic spectrometric techniques. The advantages of using isotope dilution mass spectrometry in speciation studies are also emphasized. Digestion or leaching in oxidizing acidic mixtures aided by heat or by ultrasound or microwave radiation, performed off- or on-line, is necessary to previous steps when processing solid biological samples. The most relevant analytical figures of merit such as detection limits, enrichment factors and sample throughput as well as some aspects related to the on-line system configurations and accuracy assessments are critically presented.     

Electrochemical methods for speciation of trace elements in marine waters. Dynamic aspects

The contribution of electrochemical methods to the knowledge of dynamic speciation of toxic trace elements in marine waters is critically reviewed. Due to the importance of dynamic considerations in the interpretation of the electrochemical signal, the principles and recent developments of kinetic features in the interconversion of metal complex species will be presented. As dynamic electrochemical methods, only stripping techniques (anodic stripping voltammetry and stripping chronopotentiometry) will be used because they are the most important for the determination of trace elements. Competitive ligand exchange-adsorptive cathodic stripping voltammetry, which should be considered an equilibrium technique rather than a dynamic method, will be also discussed because the complexing parameters may be affected by some kinetic limitations if equilibrium before analysis is not attained and/or the flux of the adsorbed complex is influenced by the lability of the natural complexes in the water sample. For a correct data interpretation and system characterization the comparison of results obtained from different techniques seems essential in the articulation of a serious discussion of their meaning.     

Applications of nuclear analytical techniques in environmental research. Plenary lecture.

Among nuclear analytical techniques, neutron activation analysis (NAA) is particularly useful for environmental studies. It affords low detection limits for many elements, high specificity and few sources of systematic error, which means that high accuracy is attainable. Neutron activation analysis is particularly useful for trace and ultra-trace analysis of environmental samples (water, soils, rocks and biological material). In trace element work associated with pollution, instrumental NAA is a powerful technique for multi-element surveys, in particular when combined with other spectroscopic techniques. Nuclear techniques, as with most analytical techniques, cannot be used to distinguish between different physico-chemical forms of an element per se. When used in combination with appropriate separation techniques, however, nuclear techniques can provide valuable information about trace element speciation in environmental and biological systems. From dynamic tracer experiments, i.e., addition of chemically well defined labelled compounds to environmental systems, valuable information can be obtained on the distribution of species and on microchemical processes influencing the physico-chemical forms. In these laboratories, speciation studies on trace elements in natural waters have been carried out by using instrumental NAA in combination with physical separation techniques, such as dialysis and ultrafiltration, in situ and in the laboratory. Dynamic radiotracer experiments have provided important information about processes influencing the speciation of trace elements in aquatic systems. Sequential extraction techniques have proved to be useful in studies on sediments and soils when combined with NAA. Sequential extractions also provide significant information about the physico-chemical behaviour of radionuclides supplied to natural soils from the Chernobyl accident.     

Schwermetalle in der Umwelt. Auf Ultra‐Spurensuche

The reliable determination of (ultra‐)trace elements is not a trivial task at all. Trace analyses of extremely clean environmental samples (ground water, snow, ice) require the cleanest sample collection and pre‐treatment procedures currently available, the most sensitive analysis techniques as well as highly motivated and well experienced lab personnel. It is only through the perfect interaction of all mentioned components that modern analysis strategies allow to answer succesfully questions of sociopolitical relevance. As such, looking back to ancient periods – through the analysis of ice cores – allows to put the current heavy metal pollution into perspective and to better predict future trends. Tap water or mineral water? What is better? Here too, modern ultra trace analysis opens news perspectives.     

Imaging surface spectroscopy for two- and three-dimensional characterization of materials

Secondary ion mass spectrometry (SIMS) exhibits a unique potential for the measurement of two-and three-dimensional distributions of trace elements in advanced materials, which is demonstrated on relevant technological problems. One example is the characterization of high purity iron. With this material segregation experiments have been performed and the initial and final distribution of the trace elements have been measured. Another example is the investigation of the corrosion behaviour of high purity chromium. Samples oxidized with ¹⁶O and ¹⁸O have been measured to explain the growing and adhesion of the oxide layer. All imaging techniques generate a vast quantitiy of data. In order to extract the important information the assistance of chemometric tools is essential. Detection of chemical phases by classification using neural networks or de-noising of scanning-SIMS images by wavelet-filtering demonstrates the increase of the performance of analytical imaging techniques.     

Inorganic trace analysis by mass spectrometry

Mass spectrometric methods for the trace analysis of inorganic materials with their ability to provide a very sensitive multielemental analysis have been established for the determination of trace and ultratrace elements in high-purity materials (metals, semiconductors and insulators), in different technical samples (e.g. alloys, pure chemicals, ceramics, thin films, ion-implanted semiconductors), in environmental samples (waters, soils, biological and medical materials) and geological samples. Whereas such techniques as spark source mass spectrometry (SSMS), laser ionization mass spectrometry (LIMS), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), glow discharge mass spectrometry (GDMS), secondary ion mass spectrometry (SIMS) and inductively coupled plasma mass spectrometry (ICP-MS) have multielemental capability, other methods such as thermal ionization mass spectrometry (TIMS), accelerator mass spectrometry (AMS) and resonance ionization mass spectrometry (RIMS) have been used for sensitive mono- or oligoelemental ultratrace analysis (and precise determination of isotopic ratios) in solid samples. The limits of detection for chemical elements using these mass spectrometric techniques are in the low ng g⁻¹ concentration range. The quantification of the analytical results of mass spectrometric methods is sometimes difficult due to a lack of matrix-fitted multielement standard reference materials (SRMs) for many solid samples. Therefore, owing to the simple quantification procedure of the aqueous solution, inductively coupled plasma mass spectrometry (ICP-MS) is being increasingly used for the characterization of solid samples after sample dissolution. ICP-MS is often combined with special sample introduction equipment (e.g. flow injection, hydride generation, high performance liquid chromatography (HPLC) or electrothermal vaporization) or an off-line matrix separation and enrichment of trace impurities (especially for characterization of high-purity materials and environmental samples) is used in order to improve the detection limits of trace elements. Furthermore, the determination of chemical elements in the trace and ultratrace concentration range is often difficult and can be disturbed through mass interferences of analyte ions by molecular ions at the same nominal mass. By applying double-focusing sector field mass spectrometry at the required mass resolution—by the mass spectrometric separation of molecular ions from the analyte ions—it is often possible to overcome these interference problems. Commercial instrumental equipment, the capability (detection limits, accuracy, precision) and the analytical application fields of mass spectrometric methods for the determination of trace and ultratrace elements and for surface analysis are discussed.     

Multidimensional approaches in biochemical speciation analysis

An understanding of the mechanisms controlling the essentiality and toxicity of trace elements in biological systems at the molecular level depends critically on the possibility of the identification, characterization, and quantification of chemical forms of these elements involved in life processes.Hyphenated techniques based on the combination of (electro)chromatography with ICP MS have become a routine tool for the analysis for metallospecies present in biological tissues. Finer analytical information on the true (down to individual species) speciation of trace elements in living organisms can be obtained by adding additional dimensions to the separation and detection steps, consisting of a sequential use of different HPLC separation mechanisms and capillary electrophoresis at the separation level, and of the use of electrospray MS, including collision induced dissociation MS, on the detection level. The value of the instrumental analytical data is decisively enhanced by the complementary use of molecular biology approaches involving gene identification, cloning and in vitro reproduction of the metal-controlled processes. A brief summary of the recent progress in biochemical speciation analysis is presented in the context of the latest research carried out in the authors' laboratory.     

冷焰ICP-MS法测定高纯稀土氧化物中铁和钙的研究

用冷焰技术对高纯稀土氧化物中Ｆｅ和Ｃａ的分析方法进行了研究。估算了测定范围和检出限,探讨了内标元素对基体影响的校正作用,测定了加标回收率,对半定量法（ＴＱ）和定量法（ＱＡ）的结果作了比较。表明冷焰条件下,痕量Ｆｅ的测定是可行的,但Ｃａ的测定结果仍不理想;ＱＡ法明显优于ＴＱ法。     

Applications of inductively coupled plasma mass spectrometry and laser ablation inductively coupled plasma mass spectrometry in materials science

Inductively coupled plasma mass spectrometry (ICP-MS) and laser ablation ICP-MS (LA-ICP-MS) have been applied as the most important inorganic mass spectrometric techniques having multielemental capability for the characterization of solid samples in materials science. ICP-MS is used for the sensitive determination of trace and ultratrace elements in digested solutions of solid samples or of process chemicals (ultrapure water, acids and organic solutions) for the semiconductor industry with detection limits down to sub-picogram per liter levels. Whereas ICP-MS on solid samples (e.g. high-purity ceramics) sometimes requires time-consuming sample preparation for its application in materials science, and the risk of contamination is a serious drawback, a fast, direct determination of trace elements in solid materials without any sample preparation by LA-ICP-MS is possible. The detection limits for the direct analysis of solid samples by LA-ICP-MS have been determined for many elements down to the nanogram per gram range. A deterioration of detection limits was observed for elements where interferences with polyatomic ions occur. The inherent interference problem can often be solved by applying a double-focusing sector field mass spectrometer at higher mass resolution or by collision-induced reactions of polyatomic ions with a collision gas using an ICP-MS fitted with collision cell. The main problem of LA-ICP-MS is quantification if no suitable standard reference materials with a similar matrix composition are available. The calibration problem in LA-ICP-MS can be solved using on-line solution-based calibration, and different procedures, such as external calibration and standard addition, have been discussed with respect to their application in materials science. The application of isotope dilution in solution-based calibration for trace metal determination in small amounts of noble metals has been developed as a new calibration strategy. This review discusses new analytical developments and possible applications of ICP-MS and LA-ICP-MS for the quantitative determination of trace elements and in surface analysis for materials science.     

Size fractionation techniques combined with INAA for speciation purposes

In natural waters trace elements, especially trace metals may be present in a variety of physicochemical forms. They may be associated with forms ranging from simple ions and molecules via hydrolysis products and colloids, pseudocolloids and organic or inorganic particles. The transition between categories is gradual. The presence of species differing in size, charge and density will influence on the transport, mobility and bioavailability of the trace element in question. Fractionation techniques which do not influence the distribution patterns are therefore required for speciation purposes. In the present work dialysis in situ and large membrane (hollow fibers) ultrafiltration are used for fractionation of low molecular weight species, colloids, pseudocolloids and particles. Due to the presence of foreign components transformation processes influence the distribution patterns of trace elements of interest. Sorption to foreign surfaces, complexation with agents present and aggregation of colloids (e.g., increasing ionic strength) result in a shift towards higher dimensions while desorption and dispersion processes mobilize the trace elements. Information on several components is therefore needed in speciation studies and a multielemental method of analysis having low determination limits must be applied. Instrumental neutron activation is appropriate to this kind of study because of its high sensitivity for simultaneous determination of a great-number of elements. Size fractionation techniques combined with INAA for the characterization of trace element species in natural waters will be discussed.     

Preconcentration techniques for uranium(VI) and thorium(IV) prior to analytical determination-an overview

The need for the preconcentration of trace and ultratrace amounts of uranium(VI) and thorium(IV) in conjunction with various detection techniques was clearly brought out in the introductory part. Subsequently, various off-line and on-line procedures developed for uranium(VI) and thorium(IV) prior to their analytical determination since 1990 were critically reviewed in terms of enrichment factor, retention/sorption capacity, validation using certified reference materials and application to complex real samples. The relative merits and demerits of various preconcentration and/or separation of uranium(VI) and thorium(IV) prior to quantitation by a plethora of analytical techniques are discussed in concluding part of the review article.     

Recent advances in removal of toxic elements from water using MOFs: A critical review

Water pollution with potentially toxic trace elements (PTEs) has seriously threatened the environment and human health globally. Their widespread occurrence at varied toxic levels and in different chemical forms has made remediation measures a cumbersome task. Furthermore, recent trends of PTE release via natural and/or human sources have further portended numerous detrimental events. Hence, effective remediation of PTE-contaminated aqueous media is highly substantial. Among various adsorbents, metal–organic frameworks (MOFs) have been recently characterized and tested being versatile and highly effective adsorbents for remediating pollutant/PTE-contaminated aqueous media. Owing to their plethora of structures and numerous intrinsic characteristics (high adjustability, porosity, surface area, selectivity, reusability, and structural stability), MOFs have lately received an obvious consideration in environmental remediation and analytical chemistry. This review initially summarized the most recent data (2018–2022) about PTE water contamination (rivers, lakes, canals, groundwater, city, and industrial wastewater). Then the review comprehensively highlighted the effects of synthesis techniques/conditions and post-synthetic functionalization’s on MOF structural morphology by critically conferring the underlying mechanisms. Review summarizes MOF limitations apropos their large-scale industrial applications. The latest advancements regarding MOF syntheses and structural morphology to enhance their industrial applications have been updated and critically discussed. Likewise, the stability, selectivity, reusability, and multi-metal/pollutant removal potential of MOFs have been delineated using recent findings. Finally, the future perspectives have been put forth keeping in view the recent trends and potential research gaps. This review will act as guidelines for future studies of MOF-mediated PTE removal from wastewaters.     

电感耦合等离子体质谱法（ICP-MS）测定白砂糖中微量元素

目的 白砂糖是甘蔗糖业的主要产品,是人们日常生活中普遍食用的甜味剂.了解白砂糖中的微量元素营养成分,为健康吃糖提供科学依据.方法 采用硝酸和高氯酸消解法处理样品,用电感耦合等离子体质谱法（ICP-MS）测定白砂糖中的微量元素.结果 14种微量元素的检出限为0.336 1～11.63 μg·L-1,方法的准确度为95.0％～110.0％,方法精密度为1.30％～5.32％.结论 方法简便、快速、准确,可作为白砂糖中微量元素含量常规的测定方法.     

Simultaneous Determination of Cadmium,Cobalt, Copper,Lead, Mercury and Nickel in Zinc Sulfate Plant Electrolyte Using Liquid Chromatography with Electrochemical and Spectrophotometric Detection

Abstract

The current efficiency (cost) of electrolytic production of high purity metallic zinc from zinc sulfate plant electrolyte is critically dependent on the concentration of a number of trace elements. The matrix, containing a very large concentration excess of zinc sulfate in concentrated sulfuric acid presents difficulties for determining low concentrations of other metals with many analytical methods. In this work it is shown that Cd, Co, Cu, Pb, Hg and Ni impurities may be simultaneously determined at concentrations less than or equal to 1 ppm using a combination of solvent extraction, high performance liquid chromatography and electrochemical or spectrophotometrie detection. Solvent extraction utilizes the formation of pyrrolidine dithiocarbamate complexes, which after removal of zinc complexes and excess ligand on an anion exchange column can be separated on a C-18 reverse phase chromatographic column and detected by UV/Visible spectrophotometrie or electrochemical detection. Other combinations of chromatographic and detection procedures were thwarted by the very large concentration excess of zinc and other problems.     

ICP-MS分析马莲花中的10种元素

目的 对马莲花中的微量元素进行分析.方法 采用微波消解法处理样品,利用电感耦合等离子体质谱法（ICP-MS）对马莲花中钾、钠、钙、镁、铜、铁、锌、锰、钼、镍等10种元素进行测定.所测元素校准方程的相关系数均大于0.999 0,回收率范围为90.2％ ～107.0％,相对标准偏差为1.54％～7.57％.结果 马莲花中含有丰富的钾、钙、镁等元素.结论 该法简便、快速、准确,灵敏度高,可用于马莲花中10种元素的同时测定.     

Study on chemical species of inorganic elements in some marine algae by neutron activation analysis combined with chemical and biochemical separation techniques

The compositional changes of inorganic elements on freshwater leaching of 35 species of Chinese algae were studied by the determination of the element contents in marine algae using instrumental neutron activation analysis. It was found that alkali metals and chlorine mainly exist as ions in algae, in which, water-soluble K and Na exist as chlorides. While, other elements exist as the states of both ions and organic combination in which the water leaching ratios of alkaline earth metals are the lowest. The combination of trace elements with various organic macromolecules inSargassum kjellmanianum was also studied using neutron activation analysis combined with chemical and biochemical separation techniques. The results indicate that the concentration of many trace elements, such as Zn, Fe, Sc, Th are earths in protein are quite high, and some trace elements can also be combined by pigment and polyphenol. Alkaline earth metal mainly bind with alginic acid inSargassum kjellmanianum.