Developed from the single channel model 410 with the objective of improving productivity and analytical performance of the laboratory when measuring Sodium and Potassium. The biggest improvement is dual channel operation, allowing both Sodium and Potassium to be calibrated, measured and displayed simultaneously. The model 420 retains many of the model 410’s attributes: ease of use, ease of maintenance and stable flame design but is enhanced with auto flame optimisation, internal standard referencing and on-board firmware to achieve significant improvement in sample throughput and precision. The time taken to set up and calibrate the instrument is much reduced; achieved by automatic ignition and optimisation of the flame conditions. The analytical performance is improved by the use of a Lithium Internal Standard signal which reduces fluctuation in flame conditions and dilution errors. The internal standard feature (Reference Mode) can be turned off if required.