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 MODIFIERS1) 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