1 / 16

ATOMIC ABSORPTION AND ATOMIC FLUORESCENCE SPECTROMETRY Chap 9 Source Modulation Interferences in Atomic Absorption Sp

ATOMIC ABSORPTION AND ATOMIC FLUORESCENCE SPECTROMETRY Chap 9 Source Modulation Interferences in Atomic Absorption Spectral Chemical Atomic Fluorescence Spectroscopy. AA Source Modulation. Need to eliminate emission from analyte atoms Source beam is chopped. Chopper placed here.

halil
Download Presentation

ATOMIC ABSORPTION AND ATOMIC FLUORESCENCE SPECTROMETRY Chap 9 Source Modulation Interferences in Atomic Absorption Sp

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ATOMIC ABSORPTION AND ATOMIC FLUORESCENCE SPECTROMETRY Chap 9 Source Modulation Interferences in Atomic Absorption Spectral Chemical Atomic Fluorescence Spectroscopy

  2. AA Source Modulation • Need to eliminate emission from analyte atoms • Source beam is chopped Chopper placed here

  3. Beam chopper for subtracting flame background emission • Lamp and flame • emission reach detector • Only flame • emission reaches • detector (c) Resulting signal

  4. ATOMIC ABSORPTION AND ATOMIC FLUORESCENCE SPECTROMETRY Chap 9 Source Modulation Interferences in Atomic Absorption Spectral Chemical Atomic Fluorescence Spectroscopy

  5. Spectral Interferences • 1) Undesired signals overlapping analyte signal • e.g., V at 308.11 nm near Al at 308.215 nm • ∴ use Al at 309.27 nm • 2) combustion products  broadband absorption • subtract signal from a blank • 3) matrix interferences (most serious) • use higher T • use radiation buffer • add excess of known interferent

  6. Other methods of correcting for matrix effects • Continuum Source (D2) Correction Method • D2 lamp provides continuum • UV abs. is subtracted from analyte signal • Fig. 9-14

  7. Fig 9-14Continuum-source background correction

  8. Other methods of correcting for matrix effects • Continuum Source (D2) Correction Method • D2 lamp provides continuum • UV abs. is subtracted from analyte signal • Fig. 9-14 • Zeeman Background Correction • based on splitting of absorption lines • by a magnetic field • lines absorb different polarizations

  9. Fig 9-14 Background correction by Zeeman effect • B field splits atomic absorption lines (Zeeman effect) • Line absorption differs with polarization of source

  10. Chemical interferences (very common) • 1) Certain components of the sample decrease • the extent of atomization • e.g., SO42- and PO43- hinder atomization of Ca2+ • Add releasing agent: Sr+, La3+, etc. • Add protecting agent: EDTA, hydroxyquinoline • Ionization interference • Occurs when O2 or N2O is oxidant • Analyte ionizes and releases electrons at high T • M ⇌ M+ + e-

  11. Table 9-2 Degree of Ionization with temperature • Add ionization supressor: K, Rb, Cs salts • Provides high concentration of electrons to flame • M ⇌ M+ + e- shifted to the left

  12. Fig 9-17 Effect of K as ionization suppressor for Ca

  13. Table 9-3 Detection limits (ppb) for selected elements

  14. ATOMIC ABSORPTION AND ATOMIC FLUORESCENCE SPECTROMETRY Chap 9 Source Modulation Interferences in Atomic Absorption Spectral Chemical Atomic Fluorescence Spectroscopy

  15. Absorption and fluorescence by atoms in a flame

  16. Set-up for a Luminescence Experiment Fig. 7-1 (b) 90° • If source is at fixed λ and monochromator is scanned an emission spectrum results. • If source is scanned, and monochromator is at a fixed λ, an excitation spectrum results.

More Related