Chiang Mai Journal of Science

     The method for iron determination by using the microvolume of chemicals coupled with employing natural reagent was proposed towards green analytical chemistry. A simple, portable, and economic digital microscope was used to magnify the drop of 30 μL of product, that was mixed between sample and guava leaf extract reagent, to monitor the analytical signal as primitive color, red/ green/blue or RGB. The optimum conditions for the reagent extraction and the RGB detection were investigated. The calibration graph with linearity in the range of 40-120 mg L^-1 Fe(III) was obtained with the detection limit at 10.8 mg L^-1. High precision was achieved with %RSD less than 1.8%. The developed method was successfully applied to the assay of iron in supplement samples and found to be in good agreement with the results obtained by the FAAS method at the 95% confidence level.