Metal speciation in biological fluids — a review

Applications of ion chromatography in urine analysis: A review

Ion chromatography (IC) plays a crucial role in urine analysis for diverse medical diagnoses. This paper reviews a comprehensive investigation into urine pretreatment techniques, as well as the design and development of IC systems for the measurement of various chemicals. Prior to analysis, urine samples commonly undergo pretreatment procedures such as dilution, filtration, purification, and concentration. These steps effectively eliminate interfering factors and facilitate the accurate and sensitive analysis of ultra-trace components. To separate and quantify different chemical elements or ions present in urine, a range of homemade or commercially available columns coupled with various detectors were employed. This study focuses on the analysis of chemicals such as heavy metals, halogens, pesticides, drugs, and other essential or toxic substances by IC methods.

Trace Elements in Tears: Comparison of Rural and Urban Populations Using Particle Induced X-ray Emission

We aimed to evaluate the types and concentrations of trace elements in tears of individuals living in urban and rural environments using particle induced X-ray emission (PIXE) and the possible association with exposure to air pollution and suggest a novel method for tear-based biomonitoring studies. This cross-sectional pilot study comprised 42 healthy subjects, 28 living in a rural area and 14 in an industrial city. Tears were collected with Schirmer paper and characterized by PIXE. Trace element concentrations from both eyes were averaged together with environmental pollution data. Main outcome measures were between-group differences in types and concentrations of trace elements in tears and comparison to environmental data. The rural group included 12/28 men, mean age 45.2 ± 14.8 years. The urban group consisted of 11/14 men of mean age 27 ± 5.9 years. Six rural and all urban were active smokers. Air pollution data showed more toxic elements in the rural environment. On PIXE analysis, chlorine, sodium, and potassium were found in similar concentrations in all samples. Normalizing to chlorine yielded higher values of aluminum, iron, copper, and titanium in the rural group; aluminum was found only in the rural group. The higher levels of certain trace elements in the rural group may, in part, be a consequence of exposure to specific environmental conditions. No direct association was found with air pollution data. PIXE is useful to analyze trace elements in tears, which might serve as a marker for individual exposure to environmental pollutants in biomonitoring studies.

Quantitative trace metal determinations in cell culture media using LS-APGD-MS and ICP-OES with free/bound species differentiation following polymer fiber separations

Liquid sampling-atmospheric pressure glow discharge-mass spectrometry (LS-APGD-MS) and inductively coupled plasma-optical emission spectroscopy (ICP-OES) were employed for the quantification of trace metals in cell culture media and their capabilities compared. The LS-APGD is interfaced here to a compact mass spectrometer (Advion CMS) towards the development of an at-bioreactor process monitoring strategy. Both techniques have been previously employed for the quantification of trace metals in samples of various complexities, making them a natural choice for this application. They have also demonstrated comparable analytical figures of merit including limits of detection (LOD), matrix tolerance, etc. While cell culture media is a complex sample, the ICP-OES technique was unaffected by the matrix. However, the LS-APGD-MS suffered from increases in spectral background. Despite this, both techniques achieved appropriate LODs for all metals analyzed in this work (Cu, Fe, Zn, Co, Mn, Ni; LOD < 100 ng mL^-1), except for Mn and Ni via LS-APGD-MS. To overcome the increased background seen on the LS-APGD-MS, a capillary channeled polymer (C-CP) polypropylene (PPY) fiber stationary phase was employed as an on-line separation for the removal of organic components prior to sample introduction into the plasma. It was further determined that Ni was retained on the column, preventing the detection of this element via LS-APGD-MS, and insights into metal speciation were discussed. Following implementation of this on-line separation strategy, the agreement between the techniques was acceptable for all analytes, and was excellent for Cu, Fe, and Zn.

Exploring the pH dependent aqueous speciation of metal complexes through UV-Vis spectroscopy

Coordination chemistry is a major component of the undergraduate inorganic chemistry curriculum and yet the presentation of the material can be cumbersome due to the limitations of the course typically being taught in one semester. Also, because of the large scope of this branch of chemistry encompassing all of the elements, the course design has not been standardized. These factors result in some important coordination chemistry themes being given insufficient development. Herein we propose a novel activity to formally introduce metal complex aqueous speciation in a holistic active-learning manner that includes a lecture component and hands-on experience. This topic has real world relevance and contextualizes many important coordination concepts. It would extend student comprehension about the intricate factors that affect metal complexation in an aqueous solution environment by focusing on the influence of pH. The activity explores the pH dependent speciation of the well-characterized interaction between Fe(III) and 2,3-dihydroxynapthalene-6-sulfonate and reveals the colorful changes in species throughout the pH range of 0 to 13. Students learn how to generate speciation plots and to understand the ultraviolet-visible (UV-Vis) electronic absorption spectroscopy of transition metal compounds to be able to analyze the source of color that they observe. Assessment of the activity was conducted with 24 students who completed a Likert scale survey and responded to open-ended questions. The activity was then applied in actual course settings in which student comprehension was quantitatively evaluated. The activity can be easily adapted to students of different stages of academic development from elementary to college students.

Ion-exchange HPLC-ICP-MS: A new window to chromium speciation in biological tissues

The presented work proposes a novel analytical ICP-MS-based approach for the accurate and precise chromium speciation in biological tissues. The determination of total Cr(VI) and soluble Cr(III) species was carried out by alkaline EDTA extraction followed by their separation using ion-exchange high-performance liquid chromatography inductively coupled plasma mass spectrometry (IE-HPLC-ICP-MS). The developed method was validated according to the procedure given in the United States Food and Drug Administration guideline on the validation of bioanalytical methods. Validation parameters included limit of detection (≤ 0.03 μg g^-1), limit of quantification (≤ 0.08 μg g^-1), linearity (r ≥ 0.9998), intra-day and inter-day accuracy (86-110%) and precision (≤ 10%), extraction recovery (89-110%), carry-over effect and sensitivity. In addition, special attention was paid to the study of chromium species interconversion and the elimination of spectral interferences. Moreover, the validated ICP-MS method employing microwave acid digestion was used to determine the total Cr content in collected fractions. Finally, the whole ICP-MS-based methodology was applied to the analyses of two certified reference materials of hepatopancreas tissue. Obtained results indicated that the majority of chromium in biological tissues is bound to the solid residue, Cr(VI) was determined in none of the samples investigated. This is the first study focusing on soluble Cr(III), total Cr(VI), and total bound Cr species in biological tissues. It is characterized by efficient sample preparation and fast simultaneous analysis of Cr species with parallel total Cr analysis serving for chromium balance evaluation.

The role of chemical speciation, chemical fractionation and calcium disruption in manganese-induced developmental toxicity in zebrafish (Danio rerio) embryos

Manganese (Mn) is an essential nutrient that can be toxic in excess concentrations, especially during early development stages. The mechanisms of Mn toxicity is still unclear, and little information is available regarding the role of Mn speciation and fractionation in toxicology. We aimed to investigate the toxic effects of several chemical forms of Mn in embryos of Danio rerio exposed during different development stages, between 2 and 122h post fertilization. We found a stage-specific increase of lethality associated with hatching and removal of the chorion. Mn(II), ([Mn(H2O)6](2+)) appeared to be the most toxic species to embryos exposed for 48h, and Mn(II) citrate was most toxic to embryos exposed for 72 and/or 120h. Manganese toxicity was associated with calcium disruption, manganese speciation and metal fractionation, including bioaccumulation in tissue, granule fractions, organelles and denaturated proteins.

Characterization of metal profiles in serum during the progression of Alzheimer's disease

Metal dyshomeostasis is closely related to Alzheimer's disease, so the characterization of the metal profiles in these patients is of special interest for studying associated neurodegenerative processes and to discover potential markers of disease. An analytical approach, based on non-denaturing precipitation of proteins, has been optimized for the fractionation of high molecular mass (HMM) and low molecular mass (LMM) metal-species from serum, which were subjected to multielemental analysis by inductively coupled plasma mass spectrometry (ICP-MS). This methodology was applied to healthy controls, Alzheimer's disease (AD) and mild cognitive impairment (MCI) patients in order to study the progression of dementia. Thus, it was found that some metals, such as iron, copper, zinc and aluminium, suffer progressive changes along the advance of neurodegeneration, suggesting that these imbalances could be related to the decline of cognitive functions. On the other hand, elements such as manganese, lithium or vanadium allow discriminating between controls and diseased subjects, both AD and MCI, but no differences were found between these two clinical stages, so they could be considered as precursors in the early development of neurodegenerative failures. In addition, it should be noted the important role that low molecular mass fractions of iron, copper, aluminium and cobalt appear to play in pathogenesis of Alzheimer. Finally, correlation analysis indicated that these metal abnormalities can be interrelated, participating in common processes such as oxidative stress, altered homeostasis and uptake into brain, as well as impaired glucose metabolism.

Bacterial and mammalian cell response to poly(3-sulfopropyl methacrylate) brushes loaded with silver halide salts

This study investigates the antibacterial and cytotoxic effect of surfaces with sulphonate brushes containing silver salts. By using the same type of samples for both cytotoxicity and antibacterial studies, these two parameters could be compared in a controlled way. The silver was incorporated into the brush in four different forms to enable release of silver ions at different concentrations and different rates. It was found that although the surfaces displayed very good antibacterial properties in buffer solutions, this effect disappeared in systems with high protein content. Similarly, the silver-containing surfaces displayed cytotoxic effects in the absence of serum proteins but this effect was reduced in the presence of serum. The speciation of silver in the different solutions is discussed. Cytotoxic and antibacterial effects are compared at the different silver concentrations released. The implications of a concentration range where silver could be used to kill bacterial without harmful effects on mammalian cells are also discussed and questioned.

Determination of thallium in biological samples

Determination of thallium has become a major interest because of its high toxicity, especially as the monovalent cation. Thallium poisoning in the human body must be checked quickly by analysis of biological samples. This review highlights the development of highly sensitive detection techniques applied to the determination of thallium in biological samples, with or without pretreatment, based on the literature compiled in Analytical Abstracts from 1990.

Piezoelectric sensor functionalised by a self-assembled bipyridinium derivative: characterisation and preliminary applications in the detection of heavy metal ions

The synthesis of a molecule, 1-(11-dodecylsulfanyl-undecyl)-[4,4']bipyridinium bromide (1), suitable at the same time to form a covalent bond with gold electrodes of a piezoelectric quartz crystal and to interact with heavy metal ions in aqueous solutions, has been successfully accomplished. A commercial quartz crystal microbalance instrument has been modified in order to perform a Flow-Injection Analysis. The behaviour of the system follows the Kanazawa-Gordon equation as demonstrated by measurements with glucose solutions. The self-assembled layer of 1 onto a gold electrode has been characterised by Atomic Force Microscopy before and after the sensing tests. The sensing performances of the modified gold electrode were investigated by monitoring the frequency variation induced by the presence of heavy metal ions, such as lead, cadmium and mercury, in aqueous media. The explored concentrations ranged between 10(-4) and 10(-2) M and the corresponding frequency variations ranged between 10 and 50 Hz. All responses observed were fast, reproducible and reversible. In particular, the response to mercury appears significantly higher in comparison with the other analytes. To the best of our knowledge, this contribution represents the first example of sensing layer based on bipyridinium receptor showing reversible and, at some extent, differentiated response towards heavy metal ions.

Determination of selenium compounds in urine by high-performance liquid chromatography--inductively coupled plasma mass spectrometry

Selenium species, selenite, selenate, selenomethionine (Semet), seneloethionine (Seet) and trimethylselenonium ion (TmSe) were separated in aqueous solution using a gel-permeation (polyvinyl alcohol-based resin) GS-220 column by eluting with 25 mM tetramethylammonium hydroxide and 25 mM malonic acid at pH 7.9. The GS-220 column coupled with inductively coupled plasma mass spectrometry was used for the separation, identification, and quantification of selenium compounds present in certified reference material (CRM) No. 18 human urine from the National Institute for Environmental Studies in Japan (NIES). Spiking of the authentic standard to the urine and use of a silica-based LC-SCX cation-exchange column validated the peak of selenium compounds. High concentrations of chloride and bromide in the urine eluted from the GS-220 column formed molecular ions 40Ar37Cl+ and 81Br1H+ in the plasma, and these molecular ions created additional peaks in the chromatograms when 77Se and 82Se isotopes were monitored respectively. Thus, both the isotopes were selected concurrently for signal monitoring to eliminate the interfering signals. On the LC-SCX column, chloride and bromide were eluted with selenate and complicated its determination, but the peak of TmSe was baseline separated from rest of the Se compounds. Two unknown Se compounds were detected in both the columns. An additional Se compound having the same retention time as that of Semet was detected on the LC-SCX column. Peaks of selenite, selenate, TmSe and unknown selenium compounds in the urine were baseline separated on the GS-220 column, and were free from interferences. Therefore, the GS-220 column was used for the determination of selenium compounds in NIES CRM No. 18. Unknown Se compounds were the predominant selenium species followed by selenite, TmSe and selenate. The estimated value of TmSe as Se, by the standard additions method using the GS-220 column, was 3.42 +/- 0.17 microg l(-1) and was in good agreement with the LC-SCX value [3.38 +/- 0.21 (n=5) microg l(-1)].

Guidelines for analysis of human milk for environmental chemicals

When analyzing human milk for environmental chemicals, in either a monitoring or research project, researchers must ensure that the technique used for measuring the target analytes complies with certain analytical criteria and that a quality control/quality assurance program is in place. In this report, these analytical criteria and the accompanying quality assurance program are elaborated in more detail. Examples of representative methods are also given for the determination of a number of classes of chemicals of environmental concern, such as polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, polychlorinated biphenyls, volatile organics, and halogenated flame retardants. Most of these techniques are physical/chemical in nature, but the possibility of the use of bioassays for screening of analytes in human milk is noted. The described methods are not exclusive, but any laboratory undertaking the analysis of human milk should demonstrate proficiency in their execution. This is usually accomplished by producing reliable data in interlaboratory studies. Human milk is an ideal matrix for estimating exposure to certain environmental chemicals, and researchers must ensure that the techniques used to determine these compounds adhere to known and accepted analytical requirements.

[Biological monitoring: concepts and applications in public health]

This study provides an overview of the theoretical discussion on potential uses for biological monitoring of exposure to chemical substances as related to human health, considering different concepts: definitions, uses, and limitations of internal dose and biological effect indicators and their availability for the substances to be quantified; knowledge of reference values, action levels, and limits based on health and negotiated patterns in biological monitoring interpretation and perspectives; and ethical and social problems in practice and within different preventive practices and their use in public health. Biological monitoring is the result of an exposure situation with conclusions based on scientific and consensus values, rules, and legislation. Biological monitoring as a continuous process and related to actually observed cases has helped establish technological exposure reference values and consensus levels as indicators for improving the environment and the workplace. As a step in the decision-making process in risk analysis, biological monitoring needs to be critically assessed as to its ethical aspects in light of the end use of results and values, which are references for application of this methodology.

Separation and identification of organic and organometallic compounds by use of a liquid chromatography–particle beam-glow discharge mass spectrometry combination

Evaluation of the particle beam glow discharge mass spectrometry (PB-GDMS) system as a detector for liquid chromatography (LC) is described for the analysis of polycyclic aromatic hydrocarbons, steroids, selenoamino acids, and alkyllead compounds. A particle beam interface is used to introduce analyte species from the LC into a glow discharge source for subsequent vaporization and ionization. Mass spectra display classic EI fragmentation patterns for the organic compounds, as well as elemental and molecular information for the organometallic compounds. Chromatographic separations display good temporal correlation between UV and PB-GDMS detection modes. Detection limits for Pb in lead nitrate, triethyllead, and triphenyllead fall in the sub-ppb (ng) range.

Speciation of ionic alkyllead compounds in human urine by gas chromatography-mass spectrometry after butylation through a Grignard reaction

One analytical procedure for the determination of ionic alkyllead in human urine has been studied. The system consists of the extraction of Me3Pb+, Et3Pb+ and Pb2+ at pH 9.0 with diethyldithiocarbamate to an organic phase. Then, the ionic compounds are butylated with BuMgCl and the final organic solution is analyzed by GC-MS-SIM. The elimination of both foam and gels in the extraction step and the general procedure for the urine are discussed. The recovery of compounds ranges from 105.1% for Me3Pb+ to 97.2% for Et3Pb+ using hexane as extracting agent and detection limits are 18.4 pg/ml of Me3Pb+ and 19.2 pg/ml of Et3Pb+ in urine. The speciation of ionic alkylleads in the urine of a petrol station worker showed a value of 27.9 pg/ml of Me3Pb+ in urine and Et3Pb+ was below the detection limit.

Chromatographic and hyphenated methods for elemental speciation analysis in environmental media

This review discusses chromatographic techniques that permit the analysis of speciated metals in the environment using conventional detectors, such as UV, and element-specific detectors, such as flame atomic absorption spectrometry, electrothermal atomic absorption spectrometry and inductively coupled plasma mass spectrometry. The importance of determining precise elemental forms in hazardous waste-contaminated soil, water and biota in terms of toxicity is outlined. Previous reviews on this subject are described and recent research on this subject is discussed. Most of the work cited has been performed in the 1990s and a table summarizing the chromatographic method and the detector system used, including brief comments on the work, is included to enable quick reference.