Low-Cost Colorimetric Measurement of Phosphate Trace Levels in Water and in Soil Solutions by the Collinear Photothermal Beam Deflection Method

Abstract
The collinear photothermal beam deflection technique with a c.w. AlGaAs semi-conductor diode laser (790nm) and He-Ne laser (630 nm) used as the pump and probe beam, respectively, has been combined with the molybdenum blue colorimetry to measure the level of orthophosphate in water and in soil solutions. A detection sensitivity of 0.1 mmol/m3 of PO3- 4 has been achieved with the present set-up.