Procedure to obtain total dissolved solids
For this measurement you need an accurate scale that measures at least to the 1/100 of a gram. This measurement also needs to be done both in the field and in the lab, and can be done over the course of a couple of days.
- Put on protective gloves and goggles.
- Collect a sample into a clean, clear high-density polyethylene (HDPE - #2 plastic) or glass jar, using either the TERC water pump (for samples from depth) or the sample collection method described below (for surface samples). Bring the sample to the lab.
- Filter the sample using rough student-grade filter paper, to remove all organic debris.
- Using an accurate scale, weigh a clean evaporation dish. Use tongs to handle the dish, because even the oils from your hands will affect the reading. Write down the weight of the dish in your Journal.
- Measure 30 mL of the filtered sample. Using a clean dropper, put the sample onto the evaporation dish.
- Use tongs to put the dish into an oven or over a heating source, being careful not to spill the sample. Do not disturb the dish until all the sample has evaporated.
- Use tongs to place the dish onto the scale. Weigh the dish again after all the sample has evaporated. There should be a small increase in the weight from before. That difference is all of the dissolved materials in the water.
- Subtract the initial weight of the dish from the final weight of the dish, and then divide by 30, using the equation below. This gives you the amount of total dissolved solids in units of grams/mL.
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