Determination of iron in zeolite catalysts by a smartphone camera-based colorimetric analyzer

A colorimetric analyzer was improved to determine iron in zeolites prepared by incipient wetness impregnation. Software was installed in an Android smartphone for measuring red, green, and blue light intensities. The blue color was suitable for creating a calibration relationship for iron. The optimum distance from the smartphone camera to the sample holder was 5cm. The brightness was controlled by a table lamp with a 7W light emitting diode located at 25cm above the sample holder. Under these conditions, there was no influence from ambient light. A calibration equation was created from 0-1.2% (w/w) iron and stored in the program for analysis. The results agreed well with flame atomic absorption spectrophotometric measurements with a sample throughput exceeding 40h(-1). The relative standard deviation and the relative error were less than 1%. This method was convenient, rapid, simple, inexpensive, and easy with little chemical waste produced.