The Hach BioTector 7000i TOC-TP Online Analyser, or Total Phosphorous, Analyser is an additional analysis tool available from BioTector Analytical Systems. When the BioTector oxidises organic carbon compounds for TOC measurement, it also reduces phosphorus compounds (with the exception of poly-phosphates) to orthophosphates (PO4-). This phosphate is present as an ion in the oxidized sample fluid in the BioTector reactor.
When both TOC and TN analysis are complete, the sample fluid is reacted with a Vanadate-Molybdate reagent at 70°C to produce an acidic compound. The spectrophotometer then analyses this sample at the wavelengths applicable to ortho-phosphates. The result is displayed as Oxidized and Ortho-Phosphorus (OOP). For applications without any polyphosphates, the OOP is equal to TP.
For applications with significant polyphosphate concentrations, a further step is required to arrive at the TP result. The sample fluid undergoes an acid boiling at 100°C for 20 minutes, breaking down the polyphosphate bonds into ortho-phosphates. The result is displayed as Total Phosphorus (TP), which is measured using the procedure described above for OOP Analysis.