A smartphone-based dual-channel flame photometric platform and application in ratiometric determination of potassium ions †

Abstract

Herein, a smartphone-based dual-channel flame photometric platform was developed for the ratiometric determination of potassium ions, which can be potentially operated in an on-site mode. The test solution was introduced into an air-butane flame from a windproof lighter by a combination of a cosmetic ultrasonic nebulizer and T-glass tube assembly. With the help of a reflect mirror and two bandpass filters at central wavelengths of 760 and 850 nm, the images of flame atomic emission spectra of K (at 766 and 771 nm) and Cs (at 852 nm) were recorded by an external infrared camera controlled by a smartphone. The brightness of the K and Cs channels was measured for simultaneous determination of K+ and Cs+. In a ratiometric detection mode, 100 μM of Cs+ was added in the Cs-free samples and standard solutions. The brightness ratios betwwen K and Cs channels were used as the analytic signals, eliminating effectively the errors caused by the variation in the aerosol amount, combustion conditions of the flame and image detection area. Under optimal experimental conditions, the ratiometric brightness was in a linear relation with K+ concentration in the range from 2 to 200 μM, with the detection limit of 0.61 μM. The portable flame photometric device was used in the determination of K+ in water, juice, urine, and compound fertilizer samples, offering the advantages of good portability, low cost and high reliability.