ATOMIC-ABSORPTION SPECTROPHOTOMETRIC DETERMINATION OF TOTAL PHOSPHORUS AND ORTHO-PHOSPHATE IN WATER AND ITS APPLICATION TO UNDERGROUND WATER

A simple and sensitive method for the determination of total phosphorus and orthophosphate in water was established by using atomic absorption spectrophotometry with a graphite furnace atomizer, and the method was applied to underground water samples. The proposed method is based on the atomic absorption spectrophotometric determination of molybdenum in a chelate complex produced by the reaction of orthophosphate with the molybdate reagent used in a spectrophotometric method. When the recoveries and coefficient values were estimated by applying this method to potassium dihydrogenphosphate as a standard compound in various kinds of water, they were within the range of 96.7-109.0% and below 6.1%, respectively, which are satisfactory. Since the proposed method is highly sensitive (detection limit: 0.0005 mg/l), a time-consuming concentration procedure of water samples could be omitted. When the proposed method and the spectrophotometric method described in the Official Gazette were applied to various kinds of water, a highly significant correlation (r = 0.999) was observed between the two. The assayed values of total phosphorus in samples of underground water obtained from 77 stations situated in the southern area of Hyogo prefecture in Japan were distributed between 0.001 and 2.318 mg/l. The concentrations of total phosphorus in the underground water were confirmed to be influenced by the depth of the well, and there was a significant relationship between the concentration of total phosphorus in underground water and the degree of sewage diffusion.