On-line automatic determination of orthophosphate in wastewater by flow injection spectrophotometry

An on-line automatic monitoring unit for determination of orthophosphate in wastewater was designed and developed in relation to GB/T6913-2008,based on flow injection analysis and spectrophotometry.The flow injection spectrophotometric method for on-line automatic determination of orthophosphate was established based on optimization of testing parameters including concentration of chromogenic agent,concentration of carrier solution,and length of sampling circle.The applicability of the device to determining orthophosphate in practical wastewater samples was investigated.It was found that within a concentration range of 0-15.0 mg/L,PO3-4 aqueous samples could be well detected on-line with good linear relationship between absorbancy and concentration and to a detection limit of 1.0 μg/L.When it was used to determine orthophosphate in rivers and wastewaters,a recovery of 99.4% and 106.2% was reached.In one word,the method is of low reagent consumption,rapid determination rate,high sensitivity,and strong endurance to interferences,and it can be satisfactorily used to determine orthophosphate in surface water and industrial wastewater.