Slide 1

1.1 Atomic Absorption Spectrometry (AAS) determination of elements not compounds needs radiation source high temperature for atomization Atomization a. Flame b. Electrothermal Slide 2 1.2 Flame atomizer for solutions 1. Desolvation: solvent evaporates to produce solid aerosol 2. Volatilization: form the gas molecules 3. Dissociation: produce atomic gas 4. {Ionization: ionize to form cations + electrons} 5. {Excitation: excited by heat of flame, emission} Slide 3 Fig. 8-9 (p.225) Samples are introduced into flames by a nebulizer Fig. 9-1 (p.231) Processes occurring during atomization Slide 4 Fig. 9-2 (p.231) Regions in a flame Fig. 9-3 (p.232) Temperature ( c) profile for a natural gas-air flame Slide 5 Flame structure a. Primary combustion zone: blue luminescence from emission of C 2, CH cool {thermal equilibrium not achieved) initial decomposition, molecular fragments b. Interzonal region: hottest (several cm) most free atoms, wildly used part c. Secondary combustion zone: cooler conversion of atoms to molecular oxides {then disperse to the surroundings} Flame temperatures FuelOxidanttemperature ( C) Natural gasAir1700 ~ 1900 H 2 O 2 2550 ~ 2700 AcetyleneO 2 3050 ~ 3000 60 metals or metalloids flameelectrothermal detection limit0.001-0.002 pm2x10 -6 -1 x10 -5 ppm relative error 1-2%5-"> 1.Quantitative determination of > 60 metals or metalloids flameelectrothermal detection limit0.001-0.002 pm2x10 -6 -1 x10 -5 ppm relative error 1-2%5-10% 2. Less suitable for weaker absorbers (forbidden transitions) non-metals (absorb in VUV) metal in low IP (alkali metals)