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- Posts: 26
- Joined: Wed Jun 05, 2019 3:57 pm
There are two analysts in my work that are disagreeing on how to process HPLC data. I'm not sure with which way to go.
We are analysing an impurity in a solution of various components - acids, methanol etc. Our goal is to determine if the solution contains <1,000ppm of impurity and if so, it's good to be used.
We pipette 0.1ml into a 10ml volumetric flask, record the actual weight of the sample and make up to the mark with ultrapure water and then obtain a ppm result from the HPLC.
Parameters:
Dilution factor: 100
Example sample weight (0.1ml sample): 0.1016g
Example Machine ppm result: 2.41
One of our analysts is saying that all we should do is multiply the PPM result by the 100 dilution factor and report this result as ppm:
- [machine ppm (2.41) * dilution factor (100)] = 241ppm
The other analyst is saying we should account for weight of test sample and apply a correction to bring it per constant weight (0.1g) (?) and report as mg/kg:
- [Correcting to 0.1g (0.1) / sample weight(g) (0.1016) ] = 0.9843
- [0.9843 * machine ppm (2.41)] = 2.3721ppm
- [2.371ppm * dilution factor (100)] = 237 mg/kg
What is the difference between ppm and mg/kg? Can anybody offer any input into clarifying the calculation or how they would go about this?
Thank you.