A semi-automated method for the determination of inorganic, organic and total phosphate in sediments

A simple, rapid and semi-automated method for the determination of inorganic, organic and total phosphorus in lake and river sediments is described. Total phosphorus is extracted from sediments with 1 N hydrochloric acid after ignition at a high temperature (550 °C) or by digestion with sulphuric acid-potassium persulphate at 135 °C in a sealed PTFE-lined Parr bomb. Organic phosphorus is determined by the difference in phosphorus content of the 1 N hydrochloric acid extract measured before and after ignition of the dry sediments at 550 °C. In all instances the orthophosphate is determined by using standard Technicon AutoAnalyzer II techniques. The interferences caused by silica and variable acid concentrations on the determination of phosphorus have been studied. Freedom from interferences under the chosen experimental conditions as well as the good results obtained for recovery and precision indicate that the methods are suitable for monitoring inorganic, organic and total phosphorus in sediments.