Use of webcam in flow analysis to phosphorus determination in soil extract.

Knowing the level of available P in farmland is very important to manage the phosphorus supply by soils. Consequently, the accurate determination of phosphorus species in soils is essential. Use of the webcam presents a high potential for analysis in the visible region of the electromagnetic spectrum, and the proposed strategy constitutes itself in a promising alternative to traditional absorbance measurements relying on conventional equipment. In this work, a chemistry analysis system employing webcam as detector was applied to determine PO4 3- amounts in soil (Mehlich-I extract), by using procedure based on blue molybdenum method (AOAC, 1995) adapted to the flow system. The typical transient signal inherent to the flow system was obtained using a digital video and quantified by the ImageJ, freeware software. The dynamical concentration range for phosphorus determination were 0.5 - 4.0 mg L-1 P-PO4 3-, with R.S.D < 5%. Limit of detection and analytical frequencies was 0.08 mg L-1, and 52 h-1, respectively. The results obtained in the analyzes with the proposed system were in agreement with those obtained using spectrophotometric detection at a 95% confidence level. The use of the flow system associated with webcam detection (digital images) was shown to be a promising alternative for traditional absorbance measurements using conventional equipment in the determination of phosphorus in soil samples.