Flow injection sandwich technique applied to indirect visible spectrophotometric determinations. bromimetric and iodimetric determination of sulphite

Use of the flow injection sandwich technique is reviewed. A novel application to indirect determinations, in which an excess of a monitorand which is not the determinand is formed on-line and reacted on-line with the determinand, has been illustrated using the on-line spectrophotometric iodimetric and bromimetric determination of sulphite (> 5 × 10−6 M). The full (control) monitorand signal is obtained at one boundary and the signal in the presence of determinand is obtained at the other boundary. Compensation is made for refractive index effects.