AAShandout_000 - 1 Atomic Absorption Introduc A analysis w...

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Unformatted text preview: 1 Atomic Absorption Introduc A analysis w Agency ( as lead an the exact importan character has high selectivit analyzing In flame, fu of atoms exhibit li atoms lac absorptio Figure 1 Determin ction Atomic spect which is imp EPA) has se nd arsenic. t concentrati nt analyses in rization of pr sensitivity, o ty due to the g for multipl n atomic spe urnace, or pla are measure ine absorptio ck the many on spectrum : Atomic ab Atomic ation of C troscopy (abs portant for a et maximum The EPA cri ons of toxic nclude metal roteins in bi often exhibi presence of le elements s ectroscopy, a asma (a gas ed by absorp on and emiss rotational a for sodium i bsorption “l Absorpti alcium, M sorption and a variety of r allowable l iteria often r metals safe l impurities i ochemistry, ting detectio f extremely n simultaneou a substance i hot enough ption or emis sion spectra nd vibration in the visible line” spectr on Spectro Magnesium d emission) i easons. For imits for cer reflect the de for human c in pharmace and mineral on limits at th narrow spect usly and can is vaporized to contain io ssion of spec because elec nal states of m e region. a for sodium oscopy for m & Iron i is used to per example, th rtain heavy m etection limi consumption eutical and in l content of f he parts per tral lines. Th easily be aut and decomp ons and free cific wavelen ctronic trans molecules. F m in the visi r the in Multivit rform trace e he Environm metals in dri its of analyti n is unknown ndustrial pro foods. Atom trillion leve he technique tomated. posed into ga electrons). ngths of radi itions are qu Figure 1 sho ible region tamins elemental ental Protec nking water cal methods n. Other oducts, metal mic spectrosc l (ppt), and h e is capable aseous atom Concentratio iation. Atom uantized and ows the atom 2 ction such s as l copy high of s in a ons ms d ic 3 An instrument schematic for an atomic absorption spectrometer is shown in Figure 2 and the distinct differences from a UV-Vis spectrometer for molecular absorption in solution should be noted. The first difference is the light source. A “line” source must be used so that the narrow absorption band of the analyte is able to attenuate a measurable amount of the incident light. In addition, the bandwidth from the light source must be less than the bandwidth of the analyte so Beer’s Law is followed. Most typical monochromators are not capable generating bandwidths less than 0.01 nm, which is larger than the typical bandwidth of the analyte in the flame (~0.002 nm). Therefore, the light source commonly used is a hollow cathode lamp (HCL) which emits extremely narrow spectral lines of the metal cathode. The HCL is a tube filled with an inert gas such as Ne or Ar at pressure of 1-5 torr. Inside the tube, a high voltage (500 V) is applied between the anode and the cathode and the inert gas is ionized. The cations (Ne + or Ar + ) strike the metal cathode (negative electrode) with enough energy to eject metal atoms into the...
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This note was uploaded on 07/01/2011 for the course A 315 taught by Professor Arnold during the Fall '09 term at Indiana State University .

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AAShandout_000 - 1 Atomic Absorption Introduc A analysis w...

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