Indirect determination of chloride and carbonate by reversed flow-injection analysis coupled with atomic-absorption spectrometry and in-line preconcentration by precipitation

Chloride and carbonate are determined indirectly by reversed flow-injection analysis with preconcentration by precipitation. The anions are precipitated in a Tygon tube containing glass beads and connected to an atomic-absorption spectrophotometer, and are then dissolved by suitable reagents. Chloride is precipitated as silver chloride, which is then dissolved with ammonia, sodium thiosulphate or potassium cyanide solution. Carbonate is precipitated as calcium carbonate, which is dissolved with hydrochloric acid. The response of the system has been optimized with respect to concentration, precipitation time, solution flow-rate and other AAS variables. Detection limits are 3 × 10 −7 and 5 × 10 −7 M for chloride and carbonate, respectively, with thiosulphate and hydrochloric acid as the dissolution agents.