Matrix Modifiers - PowerPoint PPT Presentation

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Matrix Modifiers

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Matrix Modifiers Used For Furnace Analyses MATRIX MODIFIERS Help prevent loss of analyte in ashing stage They alter the behaviour of analyte or matrix May: - Render ... – PowerPoint PPT presentation

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Title: Matrix Modifiers


1
Matrix Modifiers
  • Used For Furnace Analyses

2
MATRIX MODIFIERS
  • Help prevent loss of analyte in ashing stage
  • They alter the behaviour of analyte or matrix
  • May
  • - Render analyte less volatile
  • - Help volatilise matrix
  • - Convert analyte to single compound

3
MATRIX MODIFIERS 1) Render analyte less volatile
e.g. (a) Pb Cl2 (NH4)2HPO4 ? PbHPO4
2NH4Cl Permits ashing to 850?C PbCl2
would be lost above 450?
4
  • e.g. (b) Palladium
  • Add Pd salt to sample soln
  • ? Pd? on heating
  • Cd Pd ? Cd-Pd Also for Pb, As
  • Many elements form stable alloys or other
    compounds with Pd? ? Can ash at a higher temp
  • Can also add reagents to help reduce Pd salt ? Pd
    metal

5
MATRIX MODIFIERS2) Help volatilize Interfering
Matrix
e.g. high NaCl Causes severe interference
excessive background absorption NaCl boils at
1400?C - would lose some analyte
6
To solve problem
  • Add excess NH4 NO3
  • NaCl NH4NO3 ? NH4Cl NaNO3
  • Both products volatilize at lower temps than NaCl

7
3) Convert analyte to single compound before
Atomisation
  • e.g.
  • PbCl2 Pb(NO)2 (NH4)2HPO4 ? PbHPO4
    salts Conversion During Ashing
  • Benefit - More Uniform
  • Volatilisation
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