The standard provides flame atomic absorption spectrophotometry for the determination of copper and zinc in soil. The detection limit for copper and zinc is respectively 1mg/kg and 0.5mg/kg (calculated by 0.5g sample, digest and make the solvent to 50ml). When the digested soil solvent contains more than 100mg/L iron, absorption of zinc will be suppressed. Lanthanum nitrate can be added to remove the interference of other coexisting components. High concentration of salts often leads to non characteristic absorption, which could be overcome by background correction.

Soil quality-Determination of copper, Zinc-Flame atomic absorption spectrophotometry (GB/T17138-1997)