Matrix Modifiers

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Matrix Modifiers

• Used For Furnace Analyses

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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

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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?
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• 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

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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
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To solve problem

• Add excess NH4 NO3
• NaCl NH4NO3 ? NH4Cl NaNO3
• Both products volatilize at lower temps than NaCl

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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