Partial Energy Level Diagrams 460 nm 323 nm 610 nm 330 nm 819 nm 404 nm 694 nm 671 nm 589 / 590 nm 767 / 769 nm Lithium Sodium Potassium
Gas Mixtures Maximum Temperatures, C Air-Coal Gas 1825 Air-Propane 1725 Air-Hydrogen 2045 Air-Acetylene 2250 Oxygen-Hydrogen 2677 Oxygen-Acetylene 3060 Nitrous Oxide- Acetylene Argon-Hydrogen- Entrained Air 2955 1577
surrounding air interconal zone secondary combustion zone primary combustion zone preheat zone
Maxwell-Boltzmann Equation: N 1 N 0 g 1 g 0 e (E 1 E 0)/kT (nm) Energy (ev) N 1 /N 0 g 1 /g 0 2000 K 3000 K 4000 K Cs 852.1 1.46 2 4.44 X10-4 7.24 X10-3 2.98 X10-2 Na 589.0 2.11 2 9.86 X10-6 5.88 X10-4 4.44 X10-3 Ca 422.7 2.93 3 1.21 X10-7 3.69 X10-5 6.04 X10-4 Zn 213.8 5.80 3 7.29 X10-15 5.38 X10-10 1.48 X10-6
The 228.8 nm line of Cadmium corresponds to the 1 S 0-1 S 1 transition. N 1 Calculate the ratio of in air/ N 0 C 2 H 2 The temperature is 2250 C or 2523 K Degeneracy ratio of the two levels is: g 1 /g 0 = [2(1)+1]/[2(0)+1] =3/1
N 1 N 0 g 1 g 0 e (E 1 E 0 )/kt First find the frequency of light at 228 nm so that the energy difference can be calculated from E = h c 2.998 10 10 cm sec -1 2.288 10 5 cm 1.310 10 15 sec 1
N 1 N 0 g 1 g 0 e (E 1 E 0 )/kt Find the energy difference between the levels: E 1 E 0 h (6.626 10 27 erg - sec)(1.310 10 15 sec 1 ) 8.682 10 12 erg
Find the ratio: N 1 N 0 g 1 g 0 e (E 1 E 0 )/kt 3 8.682 10 12 erg 1 e[ (1.3805 10 16 erg K -1 )(2523 K) ] 3e 24.93 4.5 10 11
SI Units 1 Joule = 10 7 ergs
SOLUTION NEBULIZATION LARGE AND SMALL DROPLETS DRAIN FLAME COMPOUND FORMATION MO THERMAL EXCITATION M + X M* DISSOCIATION MX M + + e - IONIZATION Desolvation RADIATIONAL EXCITATION M + hv EMISSION OR FLUORESCENCE
Types of Interferences chemical ionization spectral background excitation
chemical - formation of stable compounds - hotter flame, releasing agent, separation ionization - ionization suppressant spectral - atomic and molecular - improve spectral resolution of spectrometer background - flame gas or matrix emission -matrix match, resolve spectrally, modulation excitation- temp. change by matrix or solvent - standard addition, matrix match
analyte, aluminum ionizes in flame Al Al e ionization suppressant sodium at 100-1000 g l 1 Na Na e forces equilibrium of Al to left
C B A
Photographic plate -UV spectrum 302 nm 310 nm Iron Aluminum Magnesium Lead Steel C e T i A g Z n Z r Nickel Beryllium ore N i C u C u Fe Al Be Na Be
Emission ce f Q L h 0 A 21 (g 1 g 2 )e E 21 kt f, g c = concentration, L = path length h 0 = energy of photon A 21 = Einstein coefficient = rate of sample introduction = efficiency of sample introduction = efficiency of atomization
Emission ce f Q L h 0 A 21 ( g 1 g 2 )e Q = flow rate of flame gases E 21 kt f, g e f = increased volume on combustion = solid angle of light collection = wavelength g = efficiency of detector
BURNER HEADS ATOMIC ABSORPTION EMISSION OR FLUORESCENCE
Advantages of graphite furnace long residence time compared to flame micro samples electrically heated
Features of graphite furnace matrix modifiers L vov platform size: 20-30 mm x 6-8 mm blackbody radiation rapid heating absolute analysis
electrode light path electrode light path
magnetic field OFF magnetic field ON absorption absorption profile absorption source emission profile - analytical wavelength
S-5 S-4 Absolute Sensitivity ma / W S-5 RCA IP28 S-1 RCA 7102 S-4 RCA IP21 S-1 Wavelength, nm
I 0 light source Absorption Cell b I detector Transmittance T= I I 0 %T= I I0 x 100
Fraction of light transmitted decays exponentially with both path length: T k is a constant I I 0 10 kb and concentration: T I I 0 10 k ' c
or: lgt lg I I 0 kb and: lgt lg I I 0 k' c combination of these two: lgt lg I I 0 abc
define: Absorbance, A = - lg T which results in Beer s law: A lg T lg I 0 I abc and: A 2.00 log%t
Instrumental Limitations of Beer s law Stray Light A lg I 0 I lg 1 10 A 0 - fraction of light that is not absorbable A 0 - true or ideal absorbance
2.0 Deviations due to 0% 0.2% 1% A 1.0 5% (%) 0 Concentration
Effect of Instrumental noise on precision of analyses 100 instrumental noise limit %T T T c 0 10 c concentration limit caused by exponent T 10 k'c
Effect of Instrumental noise on precision of analyses relative concentration uncertainty, % c C 100 6 5 4 3 2 1 best precision: 0.2-0.7 absorbance 0 absorbance 1.0 transmittance 100 0
Differentially pumped region from nebulizer argon in ICP ion lenses channel electron multiplier detector ICP RF supply quadrupole mass filter computer control mechanical pump cryogenic pump quad RF supply
Quadrupole Mass Spectromter ion with unstable trajectory to electron multiplier ions from ICP ion with stable trajectory dc and rf voltages
Atomic mass units (Daltons)
SPECTRAL INTERFERENCES in ICP-MS Polyatomic ions from mineral acids Diatomic ions from plasma and carrier gases Oxides of matrix elements
ICP-MS interferences Acid Ion m/z Overlap HNO3 N+ 14 ArN+ 54 54 Fe+ 54 Cr+ HClO4 Cl+ 35.37 ClO+ 51 51 Y+ 53 53 Cr+ H2SO4 S+ 32,33, 34 SO+ 48 48 Ti+ 49 49 Ti+ 50 50 Cr+
ICP-MS interferences plasma ion m/z Overlap N2+ 28 28 Si+ NO+ 30 30 Si+ O 2 + 32 32 S+ 34 34 S+ ArO+ 52 52 Cr+ 54 54 Cr+ 54 54 Fe+ Ar 2 + 72 72 Ge+ 74 74 Se+
ICP-MS interferences Analyte ion m/z Interferant Ni+ 58 42 Ca 16 O 60 44 Ca 16 O 61 44 Ca 16 OH Cu+ 63 46 Ca 16 OH Co+ 59 43 Ca 16 O Zn+ 64 48 Ca 16 O Cd+ 111 94 Zr 16 OH Sb+ 123 91 Zr 16 O 2
This is a new slide This is to test for conversion from ppt v3.0 to ppt v4.0