Efficacy of Shoebox Spectrophotometer Program Working on Smartphone to Measure Absorbance for Soil Phosphorus Analysis by Molybdenum Blue Colorimetric Method

Abstract

This trial compared an efficacy of handmade spectrophotometer using Shoebox Spectrophotometer program working on smartphone and standard spectrophotometer (Shimadzu Model UV2600) for absorbance measurement in soil phosphorus analysis by Molybdenum Blue colorimetric method. The standard phosphorus solution at concentration levels ranging from 0-1.0 mg/L was analyzed by Molybdenum Blue colorimetric method and measured the absorbance by a handmade and a standard spectrophotometer. Results showed simple linear regression with coefficient of determination (R2) at 0.997 and 0.998, respectively. The absorbance values given by a handmade spectrophotometer (x) were lower than those of standard spectrophotometer (y), but there was relationship in a positive linear correlation manner with high correlation coefficient at R = 0.998, and linear equation of y = 2.48x – 0.006. Available phosphorus in the soil was analyzed in five soil series; Bang Len, Nong Kae, Yang Talat, Khao Yoi and Lop Buri, by Molybdenum Blue colorimetric method and measured absorbance by a handmade (x) and a standard spectrophotometer (y). The results showed that there was relationship in a positive linear correlation with high correlation coefficient at R = 0.997 and linear equation of y = 0.649x + 3.787.