Determination of Total Phosphorus in Marine Sediments by Microwave Digestion-Phosphorus Vanadium Molybdenum Yellow Spectrophotometry

A new method to determine total phosphorus in marine sediments by phosphorus vanadium molybdenum yellow spectrophotometry with microwave digestion is presented in this paper. The working parameters of the microwave digestion instrument, including digestion reagent species and dosage, digestion time and temperature were optimized. The samples were dissolved by HNO₃ at the temperature of 190℃ for 15 min. The determination conditions including acidity for color-display and dilution factor were discussed to achieve a fast and accurate measurement for total phosphorus. The method has been validated by determination of total phosphorus in National Standard Reference materials GBW0731 and GBW07311. The results are in agreement with certified values and have a precision of 0.74% and the relative standard deviation (RSD, n=6) of 1.66%. Compared with the traditional digestion method, there is no significant difference between the two methods. However, the microwave digestion method is simple, rapid, accurate, low blank and contributes less pollution, compared to the National Standard method of GB 17378.5. Results of actual samples indicate that the method is suitable for the determination of total phosphorus in marine sediments.