CHEM 315 Study Guide - Quiz Guide: Diffusion Flame, Noble Gas, Pyrophosphate

65 views4 pages
Atomization
Determination of Ca
1. Solution containing HCl: CaCl2 Easily volatilized
2. Solution contains SO42- or PO43-: Ca oxide (stable) and forms pyrophosphate (not
volatile)
Oxides forms in the flame, interfere with production of an atoms of analyte
Use higher flame temperature to break down the oxides
Refractory elements (~30 elements)
Also forms oxides, which diminishes the product yield
Require hotter flame to prevent this (Acetylene and N2O/O2)
Height in flame
Where atoms are generated must be manually optimized
So you can generate highest concentration of atoms
Different atoms form at different height of flame (factors are: element types, fuel/oxidizer
flow rate and nebulization speed)
Flame emits light
Flame also emits light which needs to be subtracted from the total signal
Air absorbs light
at ~190nm wavelength, high absorption
pick higher wavelength (less sensitive: > 230nm)
use argon/hydrogen diffusion flame
Furnaces
Uses electrically heated graphite tube to generate atoms
Pros
Less samples required (5-100 microliters)
More sensitive than flame
Due to high residence time (atoms forms cloud which is confined by the tube)
High reproducibility due to auto sampler
How atoms are generated?
Dry: solvent removal
Ash: matrix removal
Atomize: high temperature to form atom
Clean
Cool
Optimize (Drying step: splatter, Ash step: analyte loss instead of matrix)
Prevention of oxidation of graphite during ashing
Use Ar gas (noble gas, stable) through graphite tube
If Ar is purged, atomic cloud could be gone, decreasing residence time
Transversely heated graphite Furnaces
Center is 1000 degrees hotter than ends
Up to 60% of atoms diffuse to cooler ends and condense -> lost
find more resources at oneclass.com
find more resources at oneclass.com
Unlock document

This preview shows page 1 of the document.
Unlock all 4 pages and 3 million more documents.

Already have an account? Log in

Document Summary

3-: ca oxide (stable) and forms pyrophosphate (not volatile) Oxides forms in the flame, interfere with production of an atoms of analyte. Use higher flame temperature to break down the oxides. Also forms oxides, which diminishes the product yield. Require hotter flame to prevent this (acetylene and n2o/o2) Where atoms are generated must be manually optimized. So you can generate highest concentration of atoms. Different atoms form at different height of flame (factors are: element types, fuel/oxidizer flow rate and nebulization speed) Flame also emits light which needs to be subtracted from the total signal. At ~190nm wavelength, high absorption pick higher wavelength (less sensitive: > 230nm) use argon/hydrogen diffusion flame. Uses electrically heated graphite tube to generate atoms. Due to high residence time (atoms forms cloud which is confined by the tube) Optimize (drying step: splatter, ash step: analyte loss instead of matrix) Prevention of oxidation of graphite during ashing. Use ar gas (noble gas, stable) through graphite tube.