Automation of molecular emission cavity analysis. Determination of phosphorus

Abstract

The molecular emission cavity analysis (MECA) technique has been fully automated and the new instrument was used for the determination of phosphorus anions in inorganic samples after a rapid batch ion-exchange process. The system consists of an automatic sample dispenser and a microprocessor-controlled timer, which, via a moveable cavity device attachment, controls the movement and the residence time of the cavity in a hydrogen-nitrogen-air flame (where the green HPO emission is monitored at 528 nm) and the cooling time of the cavity outside the flame between successive injections. The relative standard deviation for phosphates is improved from 4.5% for the manual MECA method to 0.9% for the automatic method (using peak-height measurements) and the detection limit is 2.5 ng of phosphorus.