The detection limit for total phosphorus by Lianhua Instruments’ testing equipment is 0.01; when no detection is possible, the value 0.01ND is used. Where does this figure come from?
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When Lianhua instruments are used to measure total phosphorus in water, the reading shown is 0.003, which is lower than the instrument’s detection limit of 0.01; therefore, some people suggest using 0.01ND to represent this value. Where does this method of representation come from? So far, only the following information has been found: HJ/T 164-2004 \"Technical Specifications for Groundwater Environment Monitoring\", 6.7.5 – When the measurement result is above the detection limit of the analytical method, the actual measured value shall be reported ； When the test result is below the detection limit of the analytical method, the detection limit of the method used shall be reported, along with the flag “L”.
This post was last edited by sunshineda_VGMP on 2021-7-16 at 17:14. It has always been presented this way; I learned this convention and practice from my testing instructor, and at the time I didn’t think to ask where it came from or what the basis for it was. I have recently been using a water quality heavy metal detector to test for heavy metals in wastewater, and this issue has come up as well. Let’s see if anyone can help answer it.
Using the same national standard methods, the total phosphorus level detected by Lianhua’s analyzer is very low, while values obtained by third-party devices are higher – sometimes even by an order of magnitude. For example, for the same water sample after phosphorus removal, the value measured by Lianhua was 0.86, while one third-party device gave a value of 2.02 and another third-party device gave a value of 20.5. It’s not clear whether this difference is due to varying dilution factors