Principal
Flame atomic absorption is a very common technique for detecting metals
and metalloids in environmental samples. The technique makes use of the
wavelengths of light specifically absorbed by an element. They correspond
to the energies needed to promote
electrons from one energy level to another, higher, energy level. Concentration measurements are determined from a working curve after calibrating the instrument with standards of a known concentration. The light source is a hollow-cathode lamp of the element that is being measured.
Fuel
-
Acetylene (C2H2): Minimum acceptable acetylene purity is 99.5 volume percent.
-
Hydrogen (H2): Argon/hydrogen/entrained air flames are often used for the analysis of arsenic, selenium and tin. Minimum acceptable hydrogen purity is 99.8 volume percent.
Oxidants
-
Air: The instrument requires an air supply. The ideal air supply is from an existing laboratory compressed air line; however, the air supply must be free of oil and condensed moisture.
-
Nitrous Oxide (N2O): Nitrous oxide-acetylene flames are used for the determination of the high melting refractory metals.
-
Argon (Ar): Argon is commonly used as a flame diluent with hydrogen when analysing elements which adsorb in the low UV region (e.g., As 194 nm, Se 196 nm).
Sensitivity
The analytical sensitivity or limit of detection of instrument FAAS Model
357 for various elements is shown in the following table.
Element
|
Limit
of detection (µg/ml or ppm) |
Element
|
Limit
of detection (µg/ml or ppm) |
| Aluminium (Al) | 0.4 |
Nickel (Ni) | 0.06 |
| Antinomy (Sb) | 0.2
|
Niobium (Nb) | 12 |
| Arsenic (As) | 0.4 |
Osmium (Os) | 1 |
| Barium (Ba) | 0.1 |
Palladium (Pd) | 0.14 |
| Beryllium (Be) | 0.01 |
Potassium (K) | 0.01 |
| Bismith (Bi) | 0.2 |
Phosphorous (P) | 250 |
| Boron (B) | 9 |
Platinum (Pt) | 1 |
| Cadmium (Cd) | 0.01 |
Praseodymium (Pr) | 20 |
| Calcium (Ca) | 0.05 |
Rhenium (Re) | 8 |
| Cesium (Cs) | 0.15 |
Rhodium (Rh) | 0.2 |
| Chromium (Cr) | 0.06 |
Rubidium (Rb) | 0.03 |
| Cobalt (Co) | 0.05 |
Ruthiem (Ru) | 0.8 |
| Copper (Cu) | 0.03 |
Samarium (Sm) | 3 |
| Dysprosium (Dy) | 0.6 |
Scandium (Sc) | 0.1 |
| Erbium (Er) | 0.04 |
Selenium (Se) | 0.4 |
| Europium (Eu) | 0.22 |
Silicon (Si) | 0.8 |
| Gallium (Ga) | 0.4 |
Silver (Ag) | 0.03 |
| Gadolium (Gd) | 13 |
Sodium (Na) | 0.001 |
| Germanium (Ge) | 0.8 |
Strontium (Sr) | 0.08 |
| Gold (Au) | 0.1 |
Tantalum (Ta) | 10 |
| Hafnium (Hf) | 14 |
Tellerium (Te) | 0.2 |
| Holium (Ho) | 0.66 |
Terbium (Tb) | 3.3 |
| Indium (In) | 0.18 |
Thallium (Tl) | 0.1 |
| Iridium (Ir) | 1.5 |
Thulium (Tm) | 0.3 |
| Iron (Fe) | 0.04 |
Tin (Sn) | 1.2 |
| Lanthanum (La) | 22 |
Titanium (Ti) | 0.9 |
| Lead (Pb) | 0.1 |
Tungsten (W) | 5 |
| Lithium (Li) | 0.016 |
Uranium (U) | 100 |
| Magnesium (Mg) | 0.003 |
Vanadium (V) | 0.6 |
| Manganese (Mn) | 0.02 |
Yttrium (Y) | 1.8 |
| Mercury (Hg) | 2.5 |
Ytterbium (Yb) | 0.08 |
| Molybdenum (Mo) | 0.2 |
Zinc (Zn) | 0.008 |
| Neodymium (Nd) | 5 |
Zirconium (Zr) | 10 |
Application
Current application of the instrument in ERI is to analyse the metals,
such as Cd, Cr, Co, Cu, Hg, Fe, Pb, Mg, Ni, Zn, etc for the assessment
of decontamination of aqueous medium by local natural or low-cost biosorbent
materials, e.g., seaweed, peat, bark, sawdust, crab carapace, etc.
