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Editor's Notes

• #5: AbsorptionMatter can capture��electromagnetic radiation��and convert the energy of a photon to internal energy. This process is called absorption. Energy is transferred from the radiation field to the absorbing species. We describe the energy change of the absorber as a transition or an excitation from a lower energy level to a higher energy level. Since the energy levels of matter are quantized, only light of energy that can cause transitions from one level to another will be absorbed.The type of excitation depends on the��wavelength��of the light. Electrons are promoted to higher orbitals by ultraviolet or visible light, vibrations are excited by infrared light, and rotations are excited by microwaves.Absorption��spectroscopy��is one way to study the��energy levels��of the atoms, molecules, and solids. An absorption spectrum is the absorption of light as a function of wavelength. The spectrum of an atom or molecule depends on its energy-level structure, making absorption spectra useful for identifying compounds.Measuring the concentration of an absorbing species in a sample is accomplished by applying the��Beer-Lambert Law.
• #9: A cathode lamp (1), is a stable light source, which is necessary to emit the sharp characteristic spectrum of the element to be determined. A different cathode lamp is needed for each element, although there are some lamps that can be used to determine three or four different elements if the cathode contains all of them. Each time a lamp is changed, proper alignment is needed in order to get as much light as possible through the flame, where the analyte is being atomized, and into the monochromator.The atom cell (2), is the part with two major functions: nebulization of sample solution into a fine aerosol solution, and dissociation of the analyte elements into free gaseous ground state form. Not all the analyte goes through the flame, part of it is disposed.As the sample passes through the flame, the beam of light passes through it into the monochromator (3). The monochromator isolates the specific spectrum line emitted by the light source through spectral dispersion, and focuses it upon a photomultiplier detector (4), whose function is to convert the light signal into an electrical signal.The processing of electrical signal is fulfilled by a signal amplifier (5). The signal could be displayed for readout (6), or further fed into a data station (7) for printout by the requested format.
• #10: Gases mixture flame (1800 – 4500 º C): air-propane, air-acetylene etc. ; Atomic absorption spectrometry quantifies the absorption of ground state atoms in the gaseous state ; The atoms absorb ultraviolet or visible light and make transitions to higher electronic energy levels . The analyte concentration is determined from the amount of absorption.
• #11: Light sourceThe light source is usually a��hollow-cathode lamp��of the element that is being measured.��Lasers��are also used in research instruments. Since lasers are intense enough to excite atoms to higher energy levels, they allow AA and��atomic fluorescence��measurements in a single instrument. The disadvantage of these narrow-band light sources is that only one element is measurable at a time.AtomizerAA spectroscopy requires that the analyte atoms be in the gas phase. Ions or atoms in a sample must undergo desolvation and vaporization in a high-temperature source such as a flame or graphite furnace.
• #12: Flame AA uses a slot type burner to increase the path length, and therefore to increase the total absorbance (see��Beer-Lambert law). Sample solutions are usually aspirated with the gas flow into a nebulizing/mixing chamber to form small droplets before entering the flame.Flame AA can only analyze solutions
• #13: The graphite furnace has several advantages over a flame. It is a much more efficient atomizer than a flame and it can directly accept very small absolute quantities of sample. It also provides a reducing environment for easily oxidized elements. Samples are placed directly in the graphite furnace and the furnace is electrically heated in several steps to dry the sample, ash organic matter, and vaporize the analyte atoms.Graphite furnace AA can accept solutions, slurries, or solid samples.
• #14: Depending on the information required, total recoverable metals, dissolved metals, suspended metals, and total metals could be obtained from a certain environmental matrix. Table above lists the EPA method number for sample processing in terms of the environmental matrices and information required. For more detail information, readers could refer to EPA document SW-846 "Test methods for evaluating solid wastes".Appropriate acid digestion is employed in these methods. Hydrochloric acid digestion is not suitable for samples which will be analyzed by graphite furnace atomic absorption spectroscopy because it can cause interferences during furnace atomization.
• #16: Flame atomic absorption methods are referred to as direct aspiration determinations. They are normally completed as single element analyses and are relatively free of interelement spectral interferences. For some elements, the temperature or type of flame used is critical. If flame and analytical conditions are not properly used, chemical and ionization interferences can occur.Graphite furnace atomic absorption spectrometry replaces the flame with an electrically heated graphite furnace. The major advantage of this technique is that the detection limit can be extremely low. It is applicable for relatively clean samples, however, interferences could be a real problem. It is important for the analyst to establish a set of analytical protocol which is appropriate for the sample to be analyzed and for the information required. Table 3 lists the available method for different metal analysis provided in EPA manual SW-846.
• #18: A)��Spectral interferences are due to radiation overlapping that of the light source. The interference radiation may be an emission line of another element or compound, or general background radiation from the flame, solvent, or analytical sample. This usually occurs when using organic solvents, but can also happen when determining sodium with magnesium present, iron with copper or iron with nickel.B)��Formation of compounds that do not dissociate in the flame. The most common example is the formation of calcium and strontium phosphates.C)��Ionization of the analyte reduces the signal. This is commonly happens to barium, calcium, strontium, sodium and potassium.D)��Matrix interferences due to differences between surface tension and viscosity of test solutions and standards.
• #19: E)��Broadening of a spectral line, which can occur due to a number of factors. The most common linewidth broadening effects are:1. Doppler effectThis effect arises because atoms will have different components of velocity along the line of observation.2. Lorentz effectThis effect occurs as a result of the concentration of foreign atoms present in the environment of the emitting or absorbing atoms. The magnitude of the broadening varies with the pressure of the foreign gases and their physical properties.3. Quenching effectIn a low-pressure spectral source, quenching collision can occur in flames as the result of the presence of foreign gas molecules with vibrational levels very close to the excited state of the resonance line.4. Self absorption or self-reversal effectThe atoms of the same kind as that emitting radiation will absorb maximum radiation at the centre of the line than at the wings, resulting in the change of shape of the line as well as its intensity. This effect becomes serious if the vapour which is absorbing radiation is considerably cooler than that which is emitting radiation.
• #22: PerguruanTinggi Kimia IndustriDeperindag, Medan SUMUT, Telp : 061-4266383InstitutTeknologiSepuluhNopember Surabaya, Jurusan Kimia FMIPA.BBPOM JABAR BidangPengujian Jl. Pasteur Bandung 022-4200381BalaiBesarTekstil Bandung Telp. 08122030084InstitutTeknologi Bandung Lab. Kimia Jl. Ganesa No.10 BandungLembagaIlmuPengetahuan Indonesia PusatPenelitian Dan Pengembangan Kimia Terapan. (Jl. Sangkuriang no.21 Bandung ).PPTM Jl. Sudirman Bandung.Sucofindo Jl. SoekarnoHatta BandungUPI Jurusan Kimia Jl. Setia Budi Bandung.
• #24: 1. FESPropane-butane flame ( 2000 – 3000 º C);Optical filter is used to monitor for the selected emission wavelength produced by the analyte;Suitable for elements with low excitation energy (Na, K, Li, Rb and Ca).2. ICP - AESAtomic emission spectroscopy measures the intensity of light emitted by atoms or ions of the elements of interest at specific wavelengths;Inductively Coupled Plasma spectrometers use emission spectroscopy to detect and quantify elements in a sample; ICP-AES uses the argon plasma (6000-10000º C) for atomization and excitation of the sample atoms; ICP-AES determines approximately all of the elements except gases and some non-metals (C, N, F, O, H).