I am studying photocatalysis of Polystyrene nanoplastics (22 nm) with TiO2 18 nm (%80 Anatase, %20 Rutile) under UVC in DI water (15 mL solution in 20 mL vials. Concentrations: 20 ppm PS, 20 ppm TiO2 and higher concentrations for TiO2). The problem is that TOC analyzer does not give proper results and after several tests I have figured that it may be due to TiO2 particles availability in solution and might accumulating in different parts of the device (TOC Apollo 9000) since they cannot be dissolved in water.
- Do you suggest any method for TOC analysis in this scenario?
- Should the sample be free of TiO2 for TOC analysis?
Thank you.
Of course, your samples must not contain TiO2 and be homogeneous!
You can use centrifugation to remove these particles
Thank you for the answer. I am trying to centrifuge it but still remains some TiO2 particles in supernatant maybe due to small dimensions. Any suggestions there?
I have tried 5, 10, 15 and 30 minutes at 4100 rpm for centrifuge, and clearly saw tio2 in the bottom after each centrifuge, however there still remains a little TiO2 in the supernatant. And actually I am afraid of doing centrifugation in higher times because it will increase the risk of PS sedimentation as well, will it not?
I also tried filtration with 0,22 micron in syringe which looks like even clears the tio2, seen the turbidity reduction by eye. However I still see anormal peaks in TOC signals in Millivolts which inrease drastically the TOC result (wrong).
Any recommendations in here? Thank tou.
To remove TiO2 nanoparticles, you can use first centrifugation. And then use a 33 mm diameter non-sterile syringe filter with a 0.22 µm pore size hydrophilic Polyethersulfone (PES) membrane.
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