Hello,
I need to determine the total sediment concentration in g/L in some water samples. I have never worked with sediments before and wanted to ask what type of filter (polycarbonate or glassfiber) you all would recommend.
I would ideally like to have a retention of .45 microns for fine clays and would like to burn off the organics (I was thinking 4hrs at 400degC?). I was hoping to be able to use the GF/F filters we have around the lab but they only have a 0.7 micron retention size.
Thanks!
@ Astrid, so far I know the glassfiber filter can remove solid parts from water till 5 microns. Polycarbonate filter is normally using in electron microscopy.
It looks like you could use filter materials like MFI filter materials that are typically used for testing the mineral/colloid load of water produced by ATES wells . This resulting MFI value is used for prediction of well life time reduced by physical clogging. Use is made of 0.45micon filter membranes. http://www.akvoregia.eu/mfi/ It will be hard to separate filter and organic sediment.. For other purposes we used sheets of membrane from Schleicher&schuller that provided a range of different membranes.
May this help:
https://extensionpublications.unl.edu/assets/html/g1492/build/g1492.htm
Astrid,
How much sediment are you expecting to collect on the filters? If it is a lot, either because you have to filter a lot of water, or the water is particle-rich, you could use a surface filter (such as PES - PolyEtherSulfone) that you can get in nominal 0.2 micron pore size in various diameters, depending on the size of your filter holder. The great advantage these filters have is that they are very clean and you can wash off the accumulated particles with a bit of filtered water by letting it run over the particle-laden membrane (from a squirt bottle, for instance) while gently rubbing the folded filter with the sediment-laden sides facing each other between your gloved fingers. You can collect the particles in a clean container and freeze-dry them, or - if you are just interested in weighting the non-organic matter - combust them (450 degrees C for 12 hours). The added advantage of this approach is that you can do a lot more with the sediment particles than just weighting them. For instance, you could also characterize the particle size distribution, or the chemical composition.
If, in contrast, you expect to obtain very little material, a small-diameter depth filters such a GFF has advantages. Although the nominal pore size may be 0.7 micron, the more you filter the more pores get clogged, thereby reducing the effective particle size cutoff below 0.7 micron. You could double-filter a sample through the same filter, making sure you collect much of the finer fraction. If you pre-combust your GFF and weight the filters before you use them for filtration, all you need to do after the filtration is to dry them, combust them again, and take the weight afterwards to get, by difference, the non-combustable (non-organic) particle fraction.
The river sediment literature is rich in similar method descriptions.
Good luck,
Bernhard
Hi Astrid! GF-75s are glass fiber filters (so you can combust them) with a nominal pore size of 0.3 µm. I use them for microbial purposes, but perhaps they'd help here.
Dear Astrid, I would evaporate the water from a known quantity of sample so as to obtain the total clay content. Remember that heating samples containing organic matter and certain clay minerals results in their partial or complete decomposition, e. g., montmorillonite at 250 degrees C. Organic matter can dcompose at well below 80 degrees C. which creates problems with peats..
Stuart.
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