Q1(h). AAS and ICP compared: accuracy, interferences, detection limit

Answer in brief

AAS: one element at a time, chemical and ionisation interference, detection limits µg L⁻¹ (flame) to sub-µg L⁻¹ (furnace). ICP: multi-element, spectral not chemical interference, wider linear range, down to ng L⁻¹ (ICP-MS).

Key points

• AAS: absorption of a hollow-cathode lamp line by ground-state atoms, one element at a time; ICP: emission or ions from argon plasma, many elements at once.
• Accuracy: flame AAS and ICP-OES about 1–2 % relative with matched standards; ICP more accurate for refractory elements and linear over 4–6 decades (AAS 2–3).
• AAS interferences: chemical (Ca with phosphate), ionisation (alkali metals) and background absorption; few spectral overlaps.
• ICP removes chemical interference almost completely but has many spectral interferences; in ICP-MS, polyatomic ions (⁴⁰Ar¹⁶O⁺ on ⁵⁶Fe⁺).
• Detection limit: flame AAS 1–100 µg L⁻¹; furnace AAS 0.01–1 µg L⁻¹; ICP-OES 0.1–10 µg L⁻¹; ICP-MS 0.001–0.1 µg L⁻¹.