Hello,
Assuming I have a list of recorded numbers all measured in ppb, ppm and ppt and want to compare them to a drinking water quality standard which has all its items measured in mg/L. So would it be permissible to just have 1 ppm = 1 mg/L while actually we know in fact that there is a slight difference? What's the math here for all ppb, ppm and ppt measured numbers to place them next to this drinking water standard (mg/L)? Can you convert any side to make it look suitable for you like just convert for instance your ppm, ppt etc. to mg/L and then place them next to that standard?
The units ppm and ppb must not be used any more as they could have different meanings in different countries. In principle, you can assume 1 ppm = 1 mg/L for most water samples you have. Yet, please don’t use these two units anymore.
Here what I provide my students:
“Instead of ppm, ppb or ppt for liquids use mg/L, μg/L or ng/L. The Bureau International des Poids et Mesures (2019) recommends that “the terms ppb and ppt are best avoided” because “their meanings are language dependent” and therefore confusing. In addition, when used for water it is not clear if the “parts per” relates to the mass or the volume of the water. ISO 31-0 recommends avoiding the terms ppm, ppb and ppt at all. Therefore, it is recommended not to use any “part per” units for water.”
Christian Wolkersdorfer the reason for mentioning these units is that some Multi-parameter devices are designed to read with those units.
I know, the manufacturers are very likey slow in adjusting to the regulations of international organizations. Luckily, for most normal waters you can assume the ,quality of what I wrote above. Also look into the Gold Book and the ISO standard (31-0 or 80000).
Hello Christian,
As far as I know those ISO standards need to be paid for to be available for usage. Do you know of any free versions? Or at least if paid, which of those ISO guidelines/standards would be the ultimate best one to buy (also most updated) for chemicals present in drinking, surface and wastewater?
Ppm stands for parts per million and represents volume. Mg/L represents the mass of solute per liter of solution and is a mass based unit.
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