Heavy Metals in the Environment - Chapter 2 pot

2 Analytical Methods for Heavy Metals in the Environment: Quantitative Determination, Speciation, and Microscopic Analysis Richard Ortega University of Bordeaux, Gradignan, France 1. INTRODUCTION The aim of this chapter is to give an overview of the principal analytical methods used in environmental sciences for heavy metals determination. The monitoring of trace metals in the environment has been a subject of great concern over the last decade and will continue to be as there is an ever-increasing amount of metals that have to be found in the environment. Of the 92 naturally occurring elements, approximately 30 metals and metalloids are potentially toxic to humans, Be, B, Li, Al, Ti, V, Cr, Mn, Co, Ni, Cu, As, Se, Sr, Mo, Pd, Ag, Cd, Sn, Sb, Te, Cs, Ba, W, Pt, Au, Hg, Pb, and Bi. Analytical measurements are an integral part of environmental manage- ment. Quantitative determination techniques, described below, are required and must provide valid and affordable element analysis. They are used to assess health effects, which are important in prioritizing contaminants for regulation. Routine monitoring of regulated contaminants ensures compliance with allowed levels and can indicate a hazardous situation. In addition, cleanups of contaminated sites are driven by measurements indicating the location and extent of contamina- Copyright © 2002 Marcel Dekker, Inc. T ABLE 1 Some Useful Internet Links for Environmental Analysis http://www.who.int/peh/site map.htm World Health Organization Pro- tection of the Human Envi- ronment http://www.eea.eu.int/ European Environment Agency (EEA) http://www.epa.gov/ United States Environmental Pro- tection Agency (USEPA) http://www.epa.gov/epahome/index/sources.htm Sources of USEPA test methods http://clu-in.org/ The Hazardous Waste Clean-up Information Web Site. The site is managed by USEPA’s Tech- nology Innovation Office http://www.osha.gov/ Occupational Safety and Health Administration (OSHA) http://www.cdc.gov/niosh/homepage.html The National Institute for Occupa- tional Safety and Health (NIOSH) http://nvl.nist.gov/ National Institute of Standards and Technology (NIST) tion. Most of the new information about the environmental chemistry of heavy metals results from continuing improvements in trace element analytical research. This is particularly true in the fields of heavy metals speciation analysis and microscopic analysis, reviewed below. The problems associated with the collection, preservation, and storage of samples as well as sample preparation and pretreatment will not be detailed in this chapter. The reader is referred to specialized textbooks and monographs for heavy metals water analysis (1), soils and sediments analysis (2), and dust sam- pling (3). Finally, some Internet links on environmental analysis are given in Table 1, they provide valuable complementary information to this chapter. 2. HEAVY METALS QUANTITATIVE ANALYSIS This section will only focus on quantitative determination techniques. It could have been organized either by analytical methods, analytes, or matrices (air, wa- ter, soil, and sediments). In an effort of concision the first type of presentation has been selected as analytical methods used for heavy metals quantitative deter- mination are often multielemental and applicable to various type of matrices. The element-specific methodologies for individual determination of metals and metalloids, from lithium to transuranium elements, have been recently reviewed in the excellent textbook of Lobinski and Marczenko (4). The detailed description Copyright © 2002 Marcel Dekker, Inc. for individual analysis of heavy metals can also be found in other books (5,6), or monographs, such as for mercury determination in the environment (7), or for lead analysis (8). On the other hand, the very useful articles of Clement and Yang (9,10) reviewed the developments in applied environmental analytical chemistry in recent years, including inorganic analysis, ordered by matrix type: air, water, soil, and sediments. Detailed protocols depending on matrix type are also given in a number of books, for the examination of heavy metals in soils (2), water and wastewater (1), or workplace atmosphere (11). 2.1 Atomic Absorption and Emission Spectrometry Atomic absorption spectrometry (AAS) and atomic emission spectrometry (AES) are the most widely used techniques for heavy metals quantitative analysis in environmental samples. These two techniques, and their environmental applica- tions, will be briefly described in this section. For greater depth description than is possible in this chapter, there are many books and articles on analytical atomic spectrometry and these should be consulted (12–14). AAS and AES are particu- larly applicable where the sample is in solution or readily solubilized. The U.S. EPA has published a sample preparation procedure for spectrochemical determi- nation of total recoverable elements, method 200.2 (15). This method provides sample preparation procedures for the determination of total recoverable analytes in groundwaters, surface waters, drinking waters, wastewaters, and in solid-type samples such as sediments, sludge, and soils. This method is applicable for the following analytes: Li, Be, B, Na, Mg, Al, P, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Sr, Mo, Ag, Cd, Sn, Sb, Ba, Hg, Tl, Pb, Th, and U. U.S. EPA method 200.3 describes sample preparation procedure for spectrochemical determination of total recoverable elements in biological tissues (16). 2.1.1 AAS AAS is one of the most valuable technique for environmental heavy metals analy- sis (for review see ref. 13). AAS is very simple to use, reliable, and cost effective. Although flame AAS has now largely been superseded by inductively coupled AES (see below), electrothermal (ET) AAS, hydride generation (HG) AAS, and cold vapor (CV) AAS, still present very interesting features for heavy metals analysis. Description. AAS involves the absorption of radiant energy produced by a special radiation source (lamp), by atoms in their electronic ground state. The lamp emits the atomic spectrum of the analyte elements, i.e., just the energy that can be absorbed in a resonance manner. The analyte elements are transformed in atoms in an atomizer. When light passes through the atom cloud, the atoms absorb ultraviolet or visible light and make transitions to higher electronic energy levels. A monochromator is used for selecting only one of the characteristic wave- Copyright © 2002 Marcel Dekker, Inc. lengths of the element being determined, and a detector, generally a photomulti- plier tube, measures the amount of absorption. The amount of light absorbed indicates the amount of analyte initially present. Since samples are usually liquids or solids, the analyte atoms or ions must be vaporized and atomized. Several AAS can be distinguished depending on the mode of sample introduction and atomization. Flame (FAAS), electrothermal at- omizers (ETAAS), hydride generation (HGAAS), and cold vapor (CVAAS) sys- tems have been described extensively (12,14,17). In FAAS, the liquid sample is pneumatically nebulized, the aerosol is mixed with acetylene, and then introduced in a flame atomizer. FAAS is applicable for quantitative analysis of nearly 70 elements. In ETAAS, which includes graphite furnace AAS (GFAAS), as the atoms are concentrated in a smaller volume than a flame, more light absorption takes place, resulting in detection limits approximately 100 times lower than those for FAAS. However, GFAAS generally requires time to heat the furnace, which makes it slower than flame AAS. ETAAS is applicable to nearly 60 elements. In HGAAS, the analyte is reduced to its volatile hydride (AsH 3 , SeH 2 , etc). The hydride is stripped-out from solution by an inert purge gas Ar and atomized in either a flame, an electrically heated tube, or a plasma. This technique is only applicable for the elements forming covalent gaseous hydrides, Ge, As, Se, Sn, Sb, Te, Bi, and Pb. Finally, CVAAS applies solely to Hg as it is the only analyte that has an appreciable atomic vapor pressure at room temperature. Multielement Capability. AAS is predominantly a single-element tech- nique. Although there is a potential for simultaneous multielement analysis (two to six elements), AAS is, however, seriously rivaled by other truly multielement techniques such as ICP-AES and ICP-MS. Detection Limits. FAAS Ͻ10 µg/L for Li, Be, Na, Mg, K, Ca, Mn, Cu, Zn, Ag, Cd 10–100 µg/L for Al, Ti, V, Fe, Co, Ni, As, Rb, Sr, Rh, Pd, Te, Cs, Au, Tl, Pb 100–1000 µg/L for Si, Sc, Cr, Ga, Ge, Se, Y, Ru, In, Sn, Sb, Ba, Ta, Os, Pt, Hg, Bi GFAAS Ͻ0.01 µg/L for Be, Mg, K, Cr, Mn, Fe, Cu, Co, Zn, Sr, Ag, Cd 0.01–0.1 µg/L for Li, Na, Al, Ca, Sc, Ni, Ga, Rb, Mo, In, Cs, Ba, Au, Tl, Pb, Bi 0.1–0.5 µg/L for B, Si, Ti, V, Ge, As, Se, Y, Zr, Nb, Tc, Ru, Rh, Pd, Sn, Sb, Te, La, Hf, Ta, W, Re, Os, Ir, Pt, Hg HGAAS Ͻ0.1 µg/L for As and Se CVAAS ϳ0.02 µg/L for Hg Environmental Applications. AAS can be applied to a wide range of ele- ments, provided a suitable light source is available. In choosing among AAS techniques, FAAS should be considered first, or second if simultaneous ICP-AES is available, in the determination of Li, Na, Mg, Al, K, Ca, Mn, Fe, Ni, Cu, Zn, Copyright © 2002 Marcel Dekker, Inc. Cd, Ba, and Pb. FAAS has been widely used with adapters for flame gases and atom traps for the measurement of toxic metals such as Cd and Pb, with respective detection limits of 0.1 and 1 µg/L. U.S. EPA 7000 series methods detail FAAS protocols for 25 metals and metalloids (18). Owing to its better sensitivity, ETAAS is a technique of choice for the following elements: Be, Si, Cr, Co, Mo, Ag, In, Sn, Sb, Au, Tl, and Bi. It is probably the most commonly used technique for measuring ambient levels of chromium in environmental samples (19). U.S. EPA method 200.9 provides a procedure for the determination of dissolved and total recoverable elements by GFAAS in groundwater, surface water, drinking water, storm runoff, industrial and domestic wastewater, sludge, and soil (15). This method is applicable to the following elements: Be, Al, Cr, Mn, Fe, Co, Ni, Cu, As, Se, Ag, Cd, Sb, Sn, Tl, and Pb. HGAAS can be used to determine virtually all elements forming volatile hydrides, such as Ge, As, Se, Sn, Sb, Te, Bi, and Pb, to overcome problems associated with flame AAS determinations. CVAAS is the technique of choice for mercury with limits of detection down to 0.02 µg/L. U.S. EPA method 245.1 describes the determination of total mercury in drinking, surface, ground, sea, brackish waters, and industrial and domestic wastewater by CVAAS (15). U.S. EPA methods 245.5 and 245.6 describe the determination of mercury by CVAAS, respectively, in sediments, and tissues (16). 2.1.2 Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) Flame AAS was until recently the most widely used method for environmental trace metal analysis. However, it has now largely been superseded by ICP-AES (for review see ref. 20). Description. AES measures the optical emission from excited atoms to determine analyte concentration. High-temperature atomization sources are used to promote the atoms into high energy levels causing them to decay back to lower levels by emitting light. Inductively coupled plasma is a very high excitation source (7000–8000 K) that efficiently desolvates, vaporizes, excites, and ionizes atoms (21). The wavelengths of photons emitted are element specific. The inten- sity of emission is generally linearly proportional to the number of atoms of that element in the original sample. ICP-AES and the other atomic emission tech- niques simultaneously or sequentially measure the concentrations of 20 elements or more at sensitivities equivalent to those of AAS. A second advantage of ICP- AES is its broad dynamic range; ICP-AES calibration curves can be linear over several orders of magnitude. In addition, ICP-AES quantifies some nonmetals; phosphorus in particular is an example. Multielement Capability. Since all atoms in a sample are excited, they can be detected simultaneously, which is the major advantage of AES compared to AAS. Copyright © 2002 Marcel Dekker, Inc. Detection Limits. 0.1–10 µg/g (solids); 1–50 µg/L (aqueous). Environmental Applications. Environmental applications utilizing ICP- AES for metal determination encompass a wide range of materials, such as natu- ral waters, seawater, soils, sediments, biological tissues, and air particulate. Wa- ters, wastewaters, and solid samples should be prepared as described in U.S. EPA method 200.2 (15). U.S. EPA method 200.7 describes ICP-AES measurement of metals and some nonmetals (15). This method is applicable to the following ana- lytes: Li, Be, B, Na, Mg, Al, P, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Sr, Mo, Ag, Cd, Sn, Sb, Ba, Ce, Hg, Tl, and Pb. OSHA method ID-125G (11) describes ICP-AES analysis procedure for metal and metalloid particulate in workplace atmospheres. It is applicable for the quantitative analysis of 13 elements found in welding fume: Be, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Sb, Pb, and Bi. 2.2 Inductively Coupled Plasma–Mass Spectrometry (ICP-MS) Description. ICP-MS is the marriage of two well-established techniques, namely the inductively coupled plasma and mass spectrometry (for review see ref. 22). An ICP argon plasma is used as ion source, ensuring almost complete decomposition of the sample into its constituent atoms (21). The ionization condi- tions within ICP result in highly efficient ionization and importantly, these ions are almost exclusively singly charged. Mass analysis is simply a method of sepa- rating ions depending on their mass-to-charge ratio (m/z). Two types of mass analyzers are commonly employed for ICP-MS: the quadrupole and the magnetic sector. Quadrupoles are comprised of four metal rods, ideally hyperbolic cross section. A combination of radiofrequency (RF ) and direct-current (DC) voltages are applied to each rod, which creates an electric field within the region bounded by the rods. Depending on the RF/DC ratio, the electric field between the rods will allow ions in a narrow m/z range to pass, typically 0.8 m/z. Hence by chang- ing the RF/DC ratio in a controlled manner, the quadrupole can be scanned through the range allowing ions of consecutively higher m/z to pass through. Therefore, the quadrupole mass analyzer can only be operated in sequential mode, although the speed with which this can be achieved makes it seem almost like simultaneous mass analysis. The quadrupole mass analyzer has the advantage of being cheap, reliable, and compact, with mass resolution that is sufficient for elemental analysis. It is the most commonly used mass analyzer. However, if an extremely high degree of resolution or true simultaneous mass analysis is re- quired, then a magnetic sector must be used. Magnetic sector mass analyzers rely on the fact that ions are deflected by a magnetic field. In typical commercial instruments, the ions are accelerated after they are skimmed from the plasma, then travel through an electric sector, which acts as an energy filter. The ions Copyright © 2002 Marcel Dekker, Inc. are then deflected in a single plane by the magnetic field, with the degree of deflection increasing with increasing m/z. A mass spectrum can be generated by scanning the magnetic field. Alternatively, the magnetic and electric fields can be held constant and several detectors arranged in an array, thereby allowing truly simultaneous mass analysis. Magnetic mass analyzers are more expensive, less common, and less easy to operate than quadrupoles. Magnetic sectors cannot be scanned as rapidly as quadrupoles, and they are also capable of simultaneous operation for a limited number of masses. The main advantage of a magnetic sector is the high degree of resolution obtainable (R ϭ M/∆M). The resolution obtainable with quadrupoles used in ICP-MS is typically between 12 and 350, depending on m/z, which corresponds to peak width between 0.7 and 0.8. In comparison, magnetic sectors are capable of resolution exceeding 10,000. For most applications the resolution provided by quadrupoles is sufficient; however, for applications where spectroscopic interferences cause a major problem, the resolution afforded by magnetic sector may be desirable. For example, a particu- lar problem is the determination of arsenic, m/z ϭ 75, in a matrix that contains chloride because of interference with 40 Ar 35 Cl ϩ . Multielement Capability. If many elements must be determined in a sam- ple, ICP-MS is fast, many times faster than GFAAS and comparable to ICP- AES. A major advantage over any other spectrometric technique is the access to isotope determination. ICP-MS offers rapid multielement capability but suffers from a number of interferences. Spectroscopic interferences arise when an in- terfering species has the same nominal m/z as the analyte of interest. Detection Limits. Quadrupole 1–10 ng/L. Magnetic sector 0.01– 0.1 ng/L. ICP-MS is more sensitive than the GFAAS by more than one order of magnitude. By comparison with ICP-AES, it is more sensitive by almost three orders of magnitude. Environmental Applications. The applications of ICP-MS are broadly similar to those for ICP-AES, although the better sensitivity of the former has resulted in applications such as the determination of ultralow levels of trace ele- ments (23). ICP-MS technique has been employed to determine a large number of elements in environmental samples (for review see refs. 20,24), and it is espe- cially suited for heavy metals analysis in groundwater samples (25). U.S. EPA method 200.8 provides procedures for determination of dissolved elements in groundwaters, surface waters, and drinking water using a quadrupole mass ana- lyzer in scanning mode (15). It may also be used for determination of total recov- erable element concentrations in these waters as well as wastewaters, sludge, and soil samples. This method is applicable to the following elements: Be, Al, V, Cr, Copyright © 2002 Marcel Dekker, Inc. Mn, Co, Ni, Cu, Zn, As, Se, Mo, Ag, Cd, Sb, Ba, Tl, Pb, Th, and U. The major drawback of ICP-MS is its expense, and that is gradually reducing. 2.3 X-Ray Fluorescence Methods The English physicist H. G. J. Moseley discovered, in 1914, that the elements in any solid sample could be identified by measuring the spectrum of the second- ary X-ray they emit when excited with a X-ray source. This result was of the utmost significance because it gave the periodic classification of elements its definite form; moreover, this technique is now widely used as a method of nonde- structive analysis. When atoms are subjected to radiation of appropriate energy, provided by electrons, ions, or photons bombardment, electrons from the inner orbital shells are removed. The orbital vacancies formed are filled with outer orbital electrons producing X-ray radiation. The measurement of their energy and intensity forms the basis of X-ray fluorescence spectrometry. 2.3.1 X-Ray Fluorescence (XRF) Description. XRF spectrometry uses X-rays as primary excitation source, usually provided by X-ray tubes, or radioisotopes, which cause elements in the sample to emit secondary X-rays of a characteristic wavelength. The elements in the sample are identified by the wavelength/energy of the emitted X-rays while the concentrations are determined by the intensity of the X-rays. Two basic types of detectors are used to detect and analyze the secondary radiation. Wavelength- dispersive XRF spectrometry uses a crystal to diffract the X-rays, as the ranges of angular positions are scanned using a proportional detector. Energy-dispersive XRF spectrometry uses a solid-state detector from which peaks representing pulse-height distributions of the X-ray spectra can be analyzed. Usually, sample preparation required for XRF analysis is minimal compared to conventional ana- lytical techniques. However, for solid samples, since particle size, composition, and element form may affect the analysis, a homogeneous sample is usually pre- pared for quantitative analysis by fusion with a borate flux (2). Multielement Capability. XRF spectrometry allows simultaneous deter- mination of most elements with the exception of those with atomic number below 8. Detection Limits. 10–100 µg/g (soil); 0.5–10 mg/L (water). Environmental Applications. Energy-dispersive XRF has been success- fully applied to determine the major constituents of soils but its poor sensitivity makes it less suitable for analysis of minor and trace elements. Wavelength- dispersive XRF is therefore the technique most used in soil analysis (2). XRF can be applied for elemental and trace metals analysis of ambient air particles. OSHA method ID-185 describes a protocol for vanadium pentoxide determina- Copyright © 2002 Marcel Dekker, Inc. tion in workplace atmosphere using XRF analysis of PVC filters (26). Portable field X-ray fluorescence spectrometry is becoming a common analytical tech- nique for on-site screening and fast analysis of elements in hazardous waste sam- ples (for review see ref. 27). U.S. EPA has published a standard operating proce- dure for elemental analysis using a field X-ray fluorescence analyzer (28). Applications include the in situ analysis of metals in soil, sediments, air monitor- ing filters, and lead in paint. The portable energy-dispersive XRF instruments can be used for scanning the ground surface to determine the presence of metals without collecting a sample for analysis. However, portable XRF instruments are relatively limited in sensitivity and accuracy. 2.3.2 Particle-Induced X-Ray Emission (PIXE) Description. PIXE is a variant of the broad family of X-ray emission techniques; heavy charged particles, typically protons of 1–4 MeV, are used to produce the generated X-rays of the analyte in the sample. The emitted X-rays are virtually always measured with an energy-dispersive detector. For detailed information on the technique, the book of Johansson et al. (29) is highly recom- mended. An excellent review compares PIXE spectrometry to the other atomic and nuclear spectrometric techniques (30). Compared to conventional energy- dispersive XRF, PIXE offers detection limits that are often one order of magni- tude better, it is faster, and also allows analysis of a smaller sample mass. The microbeam variant of PIXE, the micro-PIXE, offers the possibility of spatially resolved analysis with micrometer resolution (cf. section 4.2). The major draw- backs of PIXE are that it requires a MeV particle accelerator and that commercial PIXE apparatus are not readily available. Multielement Capability. All elements from Na to U can in principle be measured simultaneously. Detection Limits. 0.1–10 µg/g. Environmental Applications. The major part of PIXE applications in en- vironmental sciences are related to heavy metals measurement in aerosols and in biological samples (31–33). 2.3.3 Total-Reflection X-Ray Fluorescence (TXRF) Description. The principle of TXRF is the use of the total reflection of the exciting beam from conventional radiation sources at a flat support (for review see ref. 34). TXRF analysis requires excitation with a very narrow beam at an angular divergence of less than 1 mrad. Due to a remarkable improvement of the signal-to-background ratio, absolute detection limits can be two or three orders of magnitude lower than that of conventional X-ray fluorescence techniques. For liquid samples, the classical sample preparation technique consists in deposition Copyright © 2002 Marcel Dekker, Inc. of a droplet of solution on a pure substrate, after evaporation of the solvent, the residue can be irradiated and analyzed. Multielement Capability. Yes. Detection Limits. 0.1 µg/L (water). Environmental Applications. TXRF has been increasingly applied for multielement analysis in a wide range of environmental and biological materials. These specimens ranged from river water, seawater, rain, ice, and to a number of solid materials such as airborne particles, aerosols, biopsy samples, food, and humic substances (for review see refs. 34,35). 2.4 Neutron Activation Analysis (NAA) Description. NAA is a highly sensitive procedure for determining the concentrations of chemical elements in the most varied substances (for review see ref. 36). NAA is based on conversion of stable nuclei of atoms into radioactive ones and subsequent measurement of characteristic nuclear radiation emitted by the radioactive nuclei. When a nuclear reaction results at a radioactive nucleus, the process is denoted as activation. The incident neutrons required for activation can be obtained by various means; fast neutrons with energies of several MeV can be produced with a neutron generator or in an isotopic neutron source. The produced radionuclide decays to a stable atomic nucleus under emission of char- acteristic radiation (often gamma-radiation). By determining the energy of the gamma-radiation and using the decay schemes, the emitting radionuclide can be identified as well as the nature of the activated element. Quantitative activation analysis is based on measurement of the intensity of the radiation. The radioactiv- ity is proportional to the number of target nuclei in the irradiated sample. NAA has the advantage of requiring little, if any, pretreatment of the sample. The main drawback of NAA is probably the high cost and limited access to the facilities. When the sensitivity of instrumental activation analysis is insufficient, ra- diochemical neutron activation analysis may be used. In this case, the radio- nuclides corresponding to the elements of interest are chemically separated post- irradiation. Various separation techniques can be used including ion exchange, chromatography, precipitation, electrolysis, and distillation. The separation schemes are specific not only for the elements to be measured, but also for the matrix composition of the material. Generally, the schemes cover a few elements in which the radionuclides are grouped in such a way that they can be determined without mutual interference (37). Multielement Capability. Most elements can be determined with some limitations such as for Pb. Interferences occur when radionuclides emit gamma- rays of similar energy. Copyright © 2002 Marcel Dekker, Inc. [...]... group Metals in solution are generally detected by measuring the conductivity of the solution Postcolumn reactions can be employed to enhance the specificity and selectivity of the detection, 4-( 2- pyridyzalo)resorcinol (PAR) being the preferred reagent for most metal ions (40) The lack of selectivity control limits the versatility of IC methods, particularly if there is interest in trace metals eluting in. .. ratios in chromium-contaminated soils (54) On the other hand, EXAFS spectra contain structural information such as the central atom-neighbors’ atom distance, the nature of the neighbors, the local disorder, and the number of neighbors EXAFS have been applied to direct determination of heavy metals speciation in various type of matrices The molecular-level speciation analysis of arsenic and lead in mine... Adsorptive stripping voltammetry is used in seawater analysis for the measurement of metal ions such as Al 3ϩ, Ti 4ϩ, V 5ϩ, Mn 2 , Fe 2 , Fe 3ϩ, Cu 2 , Zn 2 , Se 4ϩ, Se 6ϩ, and Mo 6ϩ; adsorptive stripping potentiometry for Co 2 , Ni 2 , and Zn 2 ; potentiometric stripping analysis for Cd 2 and Copyright © 20 02 Marcel Dekker, Inc Pb 2 ; anodic stripping voltammetry for Hg 2 ; and differential pulse polarography... region commences The fine structure is caused by the interference of the outgoing photoelectric wavefront with the waves backscattered from neighboring atoms From the fine structure, the interatomic distances and coordination numbers around the absorbing atom can be determined As such, the XAFS is a very important structural investigation method for studying noncrystalline materials Because of the requirement... Irgolic In: RA Meyers, ed Encyclopedia of Environmental Analysis and Remediation New York: John Wiley & Sons, 1998, pp 4 02 413 ´ 77 N Molenat, A Astruc, M Holeman, G Maury, R Pinel Analusis 27 :795–803, 1999 Copyright © 20 02 Marcel Dekker, Inc 78 LW Reiter US EPA Research plan for arsenic in drinking water Cincinnatti: US EPA, EPA/600/R698/0 42, 1998 79 I Drabaek In: Hazardous Metals in the Environment. .. Environment Techniques and Instrumentation in Analytical Chemistry Amsterdam: Elsevier, 19 92, pp 25 7 28 6 80 SJ Hill In: Hazardous Metals in the Environment Techniques and Instrumentation in Analytical Chemistry Amsterdam: Elsevier, 19 92, pp 23 1 25 5 81 MJC Taylor In: RA Meyers, ed Encyclopedia of Environmental Analysis and Remediation New York: John Wiley & Sons, 1998, pp 4978–4989 82 KJ Reddy In: RA Meyers, ed... example, particles containing lead and bromine were linked to car exhaust emission, lead-to-silicon ratios were linked to soil, and lead-to-potassium ratios were linked to refuse burning (3) To ensure the statistical relevance of the results, a large number of particles need to be analyzed and this makes individual particle analysis time consuming Computer-controlled EPXMA is the most advanced example... Werner Nucl Instrum Meth B 109/110: 26 6 26 9, 1996 73 J Kotas, Z Stasicka Environ Pollut 107 :26 3 28 3, 20 00 74 JC Petura, BR James, RJ Vitale In: RA Meyers, ed Encyclopedia of Environmental Analysis and Remediation New York: John Wiley & Sons, 1998, pp 11 42 1158 75 KI Irgolic In: Hazardous Metals in the Environment Techniques and Instrumentation in Analytical Chemistry Amsterdam: Elsevier, 19 92, pp 28 7–350... sensitive element-selective detectors are the main hyphenated techniques developed in a number of laboratories With the exception of one instrument, a GC-microwave-induced plasma (MIP)-AES, there are no commercial instruments available for on-line speciation analysis of organometallic compounds Hyphenated techniques are therefore usually developed in experienced analytical laboratories Finally, if the sensitivity... resolution The following section gives an overview of the analytical principle, performance, and environmental applications for the main microanalytical techniques that can be used for heavy metals determination (summarized in Table 2) Microbeam techniques have been used in environmental studies essentially for single-particle analysis These techniques are very valuable as a complement to the more conventional . INTRODUCTION The aim of this chapter is to give an overview of the principal analytical methods used in environmental sciences for heavy metals determination. The monitoring of trace metals in the environment. Al 3ϩ ,Ti 4ϩ ,V 5ϩ , Mn 2 ,Fe 2 ,Fe 3ϩ ,Cu 2 ,Zn 2 ,Se 4ϩ ,Se 6ϩ , and Mo 6ϩ ; adsorptive stripping potenti- ometry for Co 2 ,Ni 2 , and Zn 2 ; potentiometric stripping analysis for Cd 2 and Copyright © 20 02. (28 ). Applications include the in situ analysis of metals in soil, sediments, air monitor- ing filters, and lead in paint. The portable energy-dispersive XRF instruments can be used for scanning the ground