When testing pollutants in water, users may inevitably encounter factors that affect the accuracy of the detection data. Therefore, it is essential to pay attention to certain issues during the testing process! In this chapter, we will discuss several key points to consider when detecting total phosphorus in wastewater using the Modi–Tech TP-9000 Total Phosphorus Online Analyzer.
1.During the testing process, if the total phosphorus concentration in the water sample does not exceed 0.5 mg/L, directly take an 8 ml sample and follow the instructions for testing.
2.If the total phosphorus concentration in the water exceeds 0.5 mg/L, it is necessary to dilute the sample before proceeding with the testing steps. The specific dilution ratio depends on the total phosphorus concentration in the water.
During testing, if the total phosphorus concentration exceeds 0.5 mg/L and there are interferences from pollutants such as arsenic, chromium, and sulfur under acidic conditions, these interferences should be diluted if they are significant. This ensures that the measurement results do not become turbid, allowing the water quality analyzer to accurately detect the total phosphorus in the water in real time.
Additional reminders:
During the measurement of total phosphorus, the presence of substances such as arsenic and chromium requires the addition of potassium persulfate reagent, which may cause turbidity. This can render the water sample invalid and lead to inaccurate data. So, what dilution multiples should be applied? For the same water sample, dilution multiples may include fivefold, tenfold, twentyfold, fiftyfold, hundredfold, or higher. After adding potassium persulfate, observe which dilution multiple does not cause turbidity. Then, continue heating for digestion and check which dilution multiple remains non-turbid.
Dilution methods for total phosphorus:
– For a fivefold dilution, use a 20 ml volumetric pipette to measure 20 ml of the wastewater sample, dilute it to the mark in a 100 ml volumetric flask, and mix well with distilled water.
– For a tenfold dilution, use a 10 ml volumetric pipette to measure 10 ml of the wastewater sample, dilute it to the mark in a 100 ml volumetric flask, and mix well with distilled water.
